PD-1-BINDING MOLECULES AND METHODS OF USE THEREOF

Technical FieldPD-1 binding molecules that comprise the PD-1-binding domain of selected anti-PD-1 antibodies capable of binding to both cynomolgus monkey PD-1 and to human PD-1: PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15 are disclosed but not claimed herein. PD-1 binding molecules that are humanized or chimeric versions of such antibodies, or that comprise PD-1 binding-fragments of such anti-PD-1 antibodies (especially immunocongugates, diabodies, BiTEs, bispecific antibodies,etc.)are disclosed but not claimed herein. PD-1-binding molecules that are additionally capable of binding an epitope of a molecule involved in regulating an immune check point that is present on the surface of an immune cell are disclosed but not claimed herein. The present invention pertains to PD-1 binding molecules of the invention, as defined by claims 1-6, for use in methods to stimulate an immune response. In particular, the present invention pertains to PD-1 binding molecules of the invention, as defined by claims 1-6, for use in methods of combination therapy in which a PD-1-binding molecule that comprises one or more PD-1-binding domain(s) of such selected anti-PD-1 antibodies is administered in combination with one or more additional molecules that are effective in stimulating an immune response and/or in combination with one or more additional molecules that specifically bind a cancer antigen.Background Of The InventionI. Cell Mediated Immune ResponsesThe immune system of humans and other mammals is responsible for providing protection against infection and disease. Such protection is provided both by a humoral immune response and by a cell-mediated immune response. The humoral response results in the production of antibodies and other biomolecules that are capable of recognizing and neutralizing foreign targets (antigens). In contrast, the cell-mediated immune response involves the activation of macrophages, Natural Killer cells (NK), and antigen specific cytotoxic T-lymphocytes by T-cells, and the release of various cytokines in response to the recognition of an antigen (Dong, C. et al. (2003) "Immune Regulation by Novel Costimulatory Molecules," Immunolog. Res. 28(1):39-48).The ability of T-cells to optimally mediate an immune response against an antigen requires two distinct signaling interactions (Viglietta, V. et al. (2007) "Modulating CoStimulation," Neurotherapeutics 4:666-675;Korman, A.J. et al. (2007) "Checkpoint Blockade in Cancer Immunotherapy," Adv. Immunol. 90:297-339). First, antigen that has been arrayed on the surface of Antigen-Presenting Cells(APC)must be presented to an antigen-specific naive CD4+T-cell. Such presentation delivers a signal via the T-Cell Receptor(TCR)that directs the T-cell to initiate an immune response that will be specific to the presented antigen. Second, a series of costimulatory and inhibitory signals, mediated through interactions between the APC and distinct T-cell surface molecules, triggers first the activation and proliferation of the T-cells and ultimately their inhibition. Thus, the first signal confers specificity to the immune response whereas the second signal serves to determine the nature, magnitude and duration of the response.The immune system is tightly controlled by costimulatory and co-inhibitory ligands and receptors. These molecules provide the second signal for T-cell activation and provide a balanced network of positive and negative signals to maximize immune responses against infection while limiting immunity to self (Wang, L. et al. (March 7, 2011) "VISTA, A Novel Mouse Ig Superfamily Ligand That Negatively Regulates T-Cell Responses," J. Exp. Med. 10.1084/jem.20100619:1-16;Lepenies, B. et al. (2008) "The Role Of Negative Costimulators During Parasitic Infections," Endocrine, Metabolic& Immune Disorders - Drug Targets 8:279-288). Of particular importance is binding between the B7.1 (CD80) and B7.2 (CD86) ligands of the Antigen-Presenting Cell and the CD28 and CTLA-4 receptors of the CD4+ Tlymphocyte (Sharpe, A.H. et al. (2002) "The B7-CD28 Superfamily," Nature Rev. Immunol. 2:116-126;Dong, C. et al. (2003) "Immune Regulation by Novel Costimulatory Molecules," Immunolog. Res. 28(1):39-48;Lindley, P.S. et al. (2009) "The Clinical Utility Of Inhibiting CD28Mediated Costimulation," Immunol. Rev. 229:307-321). Binding of B7.1 or of B7.2 to CD28 stimulates T-cell activation; binding of B7.1 or B7.2 to CTLA-4 inhibits such activation (Dong, C. et al. (2003) "Immune Regulation by Novel Costimulatory Molecules," Immunolog. Res. 28(1):39-48;Lindley, P.S. etal. (2009) "The Clinical Utility Of Inhibiting CD28Mediated Costimulation," Immunol. Rev. 229:307-321;Greenwald, R.J. et al. (2005) "The B7 Family Revisited," Ann. Rev. Immunol. 23:515-548). CD28 is constitutively expressed on the surface of T-cells (Gross, J., et al. (1992) "Identification And Distribution Of The Costimulatory Receptor CD28 In The Mouse," J. Immunol. 149:380-388), whereas CTLA-4 expression is rapidly upregulated following T-cell activation (Linsley, P. et al. (1996) "Intracellular Trafficking Of CTLA4 And Focal Localization Towards Sites Of TCR Engagement," Immunity 4:535-543). Since CTLA-4 is the higher affinity receptor (Sharpe, A.H. et al. (2002) "The B7-CD28 Superfamily," Nature Rev. Immunol. 2:116-126), binding first initiates T-cell proliferation (via CD28) and then inhibits it (via nascent expression of CTLA-4), thereby dampening the effect when proliferation is no longer needed.Further investigations into the ligands of the CD28 receptor have led to the identification and characterization of a set of related B7 molecules (the "B7 Superfamily") (Coyle, A.J. et al. (2001) "The Expanding B7 Superfamily: Increasing Complexity In Costimulatory Signals Regulating T-Cell Function," Nature Immunol. 2(3):203-209;Sharpe, A.H. et al. (2002) "The B7-CD28 Superfamily," Nature Rev. Immunol. 2:116-126;Greenwald, R.J. et al. (2005) "The B7 Family Revisited," Ann. Rev. Immunol. 23:515-548;Collins, M. et al. (2005) "The B7 Family Of Immune-Regulatory Ligands," Genome Biol. 6:223.1-223.7;Loke, P. et al. (2004) "Emerging Mechanisms Of Immune Regulation: The Extended B 7 Family And Regulatory T-Cells." Arthritis Res. Ther.6:208-214;Korman, A.J. et al. (2007) "Checkpoint Blockade in Cancer Immunotherapy," Adv. Immunol. 90:297-339;Flies, D.B. et al. (2007) "The New B7s: Playing a Pivotal Role in Tumor Immunity," J. Immunother. 30(3):251-260;Agarwal, A. et al. (2008) "The Role Of Positive Costimulatory Molecules In Transplantation And Tolerance," Curr. Opin. Organ Transplant. 13:366-372;Lenschow, D.J. et al. (1996) "CD28/B7 System of T-Cell Costimulation," Ann. Rev. Immunol. 14:233-258;Wang, S. et al. (2004) "Co-Signaling Molecules Of The B7-CD28 Family In Positive And Negative Regulation Of T Lymphocyte Responses," Microbes Infect. 6:759-766). There arecurrently several known members of the family: B7.1 (CD80), B7.2 (CD86), the inducible costimulator ligand (ICOS-L), the programmed death-1 ligand (PD-L1; B7-H1), the programmed death-2 ligand (PD-L2; B7-DC), B7-H3, B7-H4 and B7-H6 (Collins, M. et al. (2005) "The B7 Family Of Immune-Regulatory Ligands," Genome Biol. 6:223.1-223.7;Flajnik, M.F. et al. (2012) "Evolution Of The B7 Family: Co-Evolution Of B7H6 And Nkp30, Identification Of A New B7 Family Member, B7H7, And Of B7's Historical Relationship With The MHC," Immunogenetics epub doi.org/10.1007/s00251-012-0616-2).II. Programmed Death-1 ("PD-1")Programmed Death-1 ("PD-1," also known as "CD279") is an approximately 31 kD type I membrane protein member of the extended CD28/CTLA-4 family of T-cell regulators that broadly negatively regulates immune responses (Ishida, Y. et al. (1992) "Induced Expression Of PD-1, A Novel Member Of The Immunoglobulin Gene Superfamily, Upon Programmed Cell Death," EMBO J. 11:3887-3895;United States Patent Application Publication No. 2007/0202100;2008/0311117;2009/00110667;United States Patents Nos. 6,808,710;7,101,550;7,488,802;7,635,757;7,722,868;PCT Publication No. WO 01/14557).PD-1 is expressed on activated T-cells, B-cells, and monocytes (Agata, Y. et al. (1996) "Expression Of The PD-1 Antigen On The Surface Of Stimulated Mouse T And B Lymphocytes," Int. Immunol. 8(5):765-772;Yamazaki, T. et al. (2002) "Expression Of Programmed Death 1 Ligands By Murine T-Cells And APC," J. Immunol. 169:5538-5545) and at low levels in natural killer (NK) T-cells (Nishimura, H. et al. (2000) "Facilitation Of Beta Selection And Modification Of Positive Selection In The Thymus Of PD-1-Deficient Mice," J. Exp. Med. 191:891-898;Martin-Orozco, N. et al. (2007) "Inhibitory Costimulation And AntiTumor Immunity," Semin. Cancer Biol. 17(4):288-298).The extracellular region of PD-1 consists of a single immunoglobulin (Ig)V domainwith 23% identity to the equivalent domain in CTLA-4 (Martin-Orozco, N. et al. (2007) "Inhibitory Costimulation And Anti-Tumor Immunity," Semin. Cancer Biol. 17(4):288-298). The extracellular IgV domain is followed by a transmembrane region and an intracellular tail. The intracellular tail contains two phosphorylation sites located in an immunoreceptor tyrosine-based inhibitory motif and an immunoreceptor tyrosine-based switch motif, which suggests that PD-1 negatively regulates TCR signals (Ishida, Y. et al. (1992) "Induced Expression Of PD-1, A Novel Member Of The Immunoglobulin Gene Superfamily, Upon Programmed Cell Death," EMBO J. 11:3887-3895;Blank, C. et al. (2006) "Contribution Of The PD-L1/PD-1Pathway To T-Cell Exhaustion: An Update On Implications For Chronic Infections And Tumor Evasion Cancer," Immunol. Immunother. 56(5):739-745).PD-1 mediates its inhibition of the immune system by binding to B7-H1 and B7-DC (Flies, D.B. et al. (2007) "The New B7s: Playing a Pivotal Role in Tumor Immunity," J. Immunother. 30(3):251-260;United States Patents Nos. 6,803,192;7,794,710;United States Patent Application Publication Nos. 2005/0059051;2009/0055944;2009/0274666;2009/0313687;PCT Publication Nos. WO 01/39722;WO 02/086083).B7-H1 and B7-DC are broadly expressed on the surfaces of human and murine tissues, such as heart, placenta, muscle, fetal liver, spleen, lymph nodes, and thymus as well as murine liver, lung, kidney, islets cells of the pancreas and small intestine (Martin-Orozco, N. et al. (2007) "Inhibitory Costimulation And Anti-Tumor Immunity," Semin. Cancer Biol. 17(4):288-298). In humans, B7-H1 protein expression has been found in human endothelial cells (Chen, Y. et al. (2005) "Expression of B7-H1 in Inflammatory Renal Tubular Epithelial Cells," Nephron. Exp. Nephrol. 102:e81-e92;de Haij, S. et al. (2005) "Renal Tubular Epithelial Cells Modulate T-Cell Responses Via ICOS L And B7-H1" Kidney Int. 68:2091-2102;Mazanet, M.M. et al. (2002) "B7-H1 Is Expressed By Human Endothelial Cells And Suppresses T-Cell Cytokine Synthesis," J. Immunol. 169:3581-3588), myocardium (Brown, J.A. et al. (2003) "Blockade Of Programmed Death-1 Ligands On Dendritic Cells Enhances T-Cell Activation And Cytokine Production," J. Immunol. 170:1257-1266), syncyciotrophoblasts (Petroff, M.G. et al. (2002) "B7 Family Molecules: Novel Immunomodulators At The Maternal-Fetal Interface," Placenta 23:S95-S101). The molecules are also expressed by resident macrophages of some tissues, by macrophages that have been activated with interferon (IFN)-γ or tumor necrosis factor (TNF)-α (Latchman, Y. et al. (2001) "PD-L2 Is A Second Ligand For PD-1 And Inhibits T-Cell Activation," Nat. Immunol 2:261-268), and in tumors (Dong, H. (2003) "B7-H1 Pathway And Its Role In The Evasion Of Tumor Immunity," J. Mol. Med. 81:281-287).The interaction between B7-H1 and PD-1 has been found to provide a crucial negative costimulatory signal to T and B-cells (Martin-Orozco, N. et al. (2007) "Inhibitory Costimulation And Anti-Tumor Immunity," Semin. Cancer Biol. 17(4):288-298) and functions as a cell death inducer (Ishida, Y. et al. (1992) "Induced Expression Of PD-1, A Novel Member Of The Immunoglobulin Gene Superfamily, Upon Programmed Cell Death," EMBO J. 11:3887-3895;Subudhi, S.K. etal. (2005) "The Balance Of Immune Responses: CostimulationVerse Coinhibition," J. Molec. Med. 83:193-202). More specifically, interaction between low concentrations of the PD-1 receptor and the B7-H1 ligand has been found to result in the transmission of an inhibitory signal that strongly inhibits the proliferation of antigen-specific CD8+T-cells; at higher concentrations the interactions with PD-1 do not inhibit T-cell proliferation but markedly reduce the production of multiple cytokines (Sharpe, A.H. et al. (2002) "The B7-CD28 Superfamily," Nature Rev. Immunol. 2:116-126). T-cell proliferation and cytokine production by both resting and previously activated CD4 and CD8 T-cells, and even naive T-cells from umbilical-cord blood, have been found to be inhibited by soluble B7-H1-Fc fusion proteins (Freeman, G.J. et al. (2000) "Engagement Of The PD-1 Immunoinhibitory Receptor By A Novel B7 Family Member Leads To Negative Regulation Of Lymphocyte Activation," J. Exp. Med. 192:1-9;Latchman, Y. etal. (2001) "PD-L2 Is A Second Ligand For PD-1 And Inhibits T-Cell Activation," Nature Immunol. 2:261-268;Carter, L. et al. (2002) "PD-1:PD-L Inhibitory Pathway Affects Both CD4(+) and CD8(+) T-cells And Is Overcome By IL-2," Eur. J. Immunol. 32(3):634-643;Sharpe, A.H. et al. (2002) "The B7-CD28 Superfamily," Nature Rev. Immunol. 2:116-126).The role of B7-H1 and PD-1 in inhibiting T-cell activation and proliferation has suggested that these biomolecules might serve as therapeutic targets for treatments of inflammation and cancer. Thus, the use of anti-PD-1 antibodies to treat infections and tumors and up-modulate an adaptive immune response has been proposed (see,United States Patent Application Publication Nos. 2010/0040614;2010/0028330;2004/0241745;2008/0311117;2009/0217401;United States Patents Nos. 7,521,051;7,563,869;7,595,048;PCT Publications Nos. WO 2004/056875;WO 2008/083174). Antibodies capable of specifically binding to PD-1 have been reported byAgata, T. et al. (1996) "Expression Of The PD-1 Antigen On The Surface Of Stimulated Mouse T And B Lymphocytes," Int. Immunol. 8(5):765-772; andBerger, R. et al. (2008) "Phase I Safety And Pharmacokinetic Study Of CT-011, A Humanized Antibody Interacting With PD-1, In Patients With Advanced Hematologic Malignancies," Clin. Cancer Res. 14(10):3044-3051(see, also,United States Patent Nos. 8,008,449and8,552,154;US Patent Publication Nos. 2007/0166281;2012/0114648;2012/0114649;2013/0017199;2013/0230514and2014/0044738; andPCT Patent Publication Nos. WO 2003/099196;WO 2004/004771;WO 2004/056875;WO 2004/072286;WO 2006/121168;WO 2007/005874;WO 2008/083174;WO 2009/014708;WO 2009/073533;WO 2012/135408,WO 2012/145549; andWO 2013/014668).However, despite all such prior advances, a need remains for improved compositions capable of more vigorously directing the body's immune system to attack cancer cells or pathogen-infected cells, especially at lower therapeutic concentrations. For although the adaptive immune system can be a potent defense mechanism against cancer and disease, it is often hampered by immune suppressive mechanisms in the tumor microenvironment, such as the expression of PD-1. Furthermore, co-inhibitory molecules expressed by tumor cells, immune cells, and stromal cells in the tumor milieu can dominantly attenuate T-cell responses against cancer cells. Thus, a need remains for potent PD-1-binding molecules. In particular, a need exists for potent PD-1-binding molecules having a desirable binding kinetic profile and that antagonize the PD-1/PD-L1 axis by blocking the PD-1/PD-L1 interaction, which could provide improved therapeutic value to patients suffering from cancer or other diseases and conditions.WO 2014194302relates to compositions and methods relating to or derived from anti-PD-1 antibodies.WO 2014179664relates to an isolated immunoglobulin heavy chain polypeptide and an isolated immunoglobulin light chain polypeptide that bind to a programmed death-1 (PD-1) protein.Summary Of The InventionThe present invention is directed to an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO: 147, and said Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO: 153 for use in combination with one or more additional molecules that are effective in stimulating an immune response, wherein said one or more additional molecules are antibodies, in stimulating a T-cell mediated immune response of a subject in need thereof.The present invention is also directed to one or more molecules that are effective in stimulating an immune response, wherein said one or more molecules are antibodies, for use in combination with an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO: 147, andsaid Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO:153, in stimulating a T-cell mediated immune response of a subject in need thereof.The present invention is further directed to a combination of an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO:147, and said Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO: 153, and one or more additional molecules that are effective in stimulating an immune response, wherein said one or more additional molecules are antibodies, for use in stimulating a T-cell mediated immune response of a subject in need thereof.The present invention is directed to an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO: 147, and said Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO: 153 for use in combination with another anti-cancer agent, and/or one or more additional molecules that specifically bind a cancer antigen, in the treatment of cancer.The present invention is also directed to an anti-cancer agent, and/or one or more molecules that specifically bind a cancer antigen, for use in combination with an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO:147, and said Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO: 153, in the treatment of cancer.The present invention is further directed to a combination of an anti-human PD-1-binding monospecific monoclonal antibody that comprises a Variable Heavy Chain Domain and a Variable Light Chain Domain, wherein: said Variable Heavy Chain Domain comprises the amino acid sequence of SEQ ID NO:147, and said Variable Light Chain Domain comprises the amino acid sequence of SEQ ID NO: 153, and an anti-cancer agent and/or one or more additional molecules that specifically bind a cancer antigen, for use in the treatment of cancer.The invention is defined by the claims and any other aspects, configurations, instances or embodiments set forth herein not falling within the scope of the claims are for information only.Any references in the description to methods of treatment (or diagnosis) refer to the compounds, pharmaceutical compositions and medicaments of the present invention for use in a method of treatment of the human (or animal) body by therapy (or for diagnosis).PD-1 binding molecules that comprise the PD-1-binding domain of selected anti-PD-1 antibodies capable of binding to both cynomolgus monkey PD-1 and to human PD-1: PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15 are disclosed but not claimed herein. PD-1 binding molecules that are humanized or chimeric versions of such antibodies, or that comprise PD-1 binding-fragments of such anti-PD-1 antibodies (especially immunocongugates, diabodies, BiTEs, bispecific antibodies,etc.)are disclosed but not claimed herein. PD-1-binding molecules that are additionally capable of binding an epitope of a molecule involved in regulating an immune check point that is present on the surface of an immune cell are disclosed but not claimed herein. The present invention pertains to PD-1 binding molecules of the invention, as defined by claims 1-6, for use in methods to stimulate an immune response. In particular, the present invention pertains to PD-1 binding molecules of the invention, as defined by claims 1-6, for use in methods of combination therapy in which a PD-1-binding molecule that comprises one or more PD-1-binding domain(s) of such selected anti-PD-1 antibodies is administered in combination with one or more additional molecules that are effective in stimulating an immune response and/or in combination with one or more additional molecules that specifically bind a cancer antigen.In detail, the invention provides an anti-human PD-1-binding molecule, as defined by and for use in accordance with claims 1-6, that comprises the three Heavy Chain CDR Domains, CDRH1, CDRH2 and CDRH3 and the three Light Chain CDR Domains, CDRL1, CDRL2, and CDRL3, wherein:(1) the CDRH1 Domain, CDRH2 Domain, and CDRH3 Domain are the Heavy Chain CDRs of hPD-1 mAb 7(1.2), and respectively have the amino acid sequences:SEQ ID NO:139,SEQ ID NO:140, andSEQ ID NO:141; and(2) the CDRL1 Domain, CDRL2 Domain, and CDRL3 Domain are the Light Chain CDRs of hPD-1 mAb 7(1.2), and, respectively have the amino acid sequences:SEQ ID NO:157,SEQ ID NO:145, andSEQ ID NO:146;The anti-human PD-1-binding molecule, as defined by and for use in accordance with claims 1-6, is a humanized antibody.The anti-human PD-1-binding molecule as defined by and for use in accordance with claims 1-6, comprises a Heavy Chain Variable Domain that has the amino acid sequence ofSEQ ID NO: 147.The anti-human PD-1-binding molecule, as defined by and for use in accordance with claims 1-6, comprises a Light Chain Variable Domain that has the amino acid sequence ofSEQ ID NO:153.The invention further concerns the embodiments of such anti-human PD-1-binding molecules, as defined by and for use in accordance with claims 1-6, wherein the molecule comprises an Fc Region, and wherein the Fc Region is a variant Fc Region that comprises one or more amino acid modifications that reduces the affinity of the variant Fc Region for an FcγR and/or enhances the serum half-life, and more particularly, wherein the modifications comprise at least one amino acid substitution selected from the group consisting of:(1) L234A; L235A;(2) L234A and L235A;(3) M252Y; M252Y and S254T;(4) M252Y and T256E;(5) M252Y, S254T and T256E; or(6) K288D and H435K;wherein the numbering is that of the EU index as in Kabat.The invention further concerns the embodiments in which any of the above-described PD-1-binding molecules, as defined by and for use in accordance with claims 1-6, is used to stimulate a T-cell mediate immune response. The invention additionally concerns the embodiments in which any of the above-described PD-1-binding molecules is for use in the treatment of a disease or condition associated with a suppressed immune system, especially cancer or an infection.The invention particularly concerns such use in the treatment or diagnosis or prognosis of cancer, wherein the cancer is characterized by the presence of a cancer cell selected from the group consisting of a cell of: an adrenal gland tumor, an AIDS-associated cancer, an alveolar soft part sarcoma, an astrocytic tumor, bladder cancer, bone cancer, a brain and spinal cord cancer, a metastatic brain tumor, a breast cancer, a carotid body tumors, a cervical cancer, a chondrosarcoma, a chordoma, a chromophobe renal cell carcinoma, a clear cell carcinoma, a colon cancer, a colorectal cancer, a cutaneous benign fibrous histiocytoma, a desmoplastic small round cell tumor, an ependymoma, a Ewing's tumor, an extraskeletal myxoid chondrosarcoma, a fibrogenesis imperfecta ossium, a fibrous dysplasia of the bone, a gallbladder or bile duct cancer, gastric cancer, a gestational trophoblastic disease, a germ cell tumor, a head and neck cancer, hepatocellular carcinoma, an islet cell tumor, a Kaposi's Sarcoma, a kidney cancer, a leukemia, a lipoma/benign lipomatous tumor, a liposarcoma/malignant lipomatous tumor, a liver cancer, a lymphoma, a lung cancer, a medulloblastoma, a melanoma, a meningioma, a multiple endocrine neoplasia, a multiple myeloma, a myelodysplastic syndrome, a neuroblastoma, a neuroendocrine tumors, an ovarian cancer, a pancreatic cancer, a papillary thyroid carcinoma, a parathyroid tumor, a pediatric cancer, a peripheral nerve sheath tumor, a phaeochromocytoma, a pituitary tumor, a prostate cancer, a posterious uveal melanoma, a rare hematologic disorder, a renal metastatic cancer, a rhabdoid tumor, a rhabdomysarcoma, a sarcoma, a skin cancer, a soft-tissue sarcoma, a squamous cell cancer, a stomach cancer, a synovial sarcoma, a testicular cancer, a thymic carcinoma, a thymoma, a thyroid metastatic cancer, and a uterine cancer.The invention particularly concerns such use in the treatment or diagnosis or prognosis of cancer, wherein the cancer is colorectal cancer, hepatocellular carcinoma, glioma,kidney cancer, breast cancer, multiple myeloma, bladder cancer, neuroblastoma; sarcoma, non-Hodgkin's lymphoma, non-small cell lung cancer, ovarian cancer, pancreatic cancer, a rectal cancer, acute myeloid leukemia (AML), chronic myelogenous leukemia (CML), acute B lymphoblastic leukemia (B-ALL), chronic lymphocytic leukemia (CLL), hairy cell leukemia (HCL), blastic plasmacytoid dendritic cell neoplasm (BPDCN), non-Hodgkin's lymphomas (NHL), including mantel cell leukemia (MCL), and small lymphocytic lymphoma (SLL), Hodgkin's lymphoma, systemic mastocytosis, or Burkitt's lymphoma.Any of the above-described PD-1-binding molecules may be detectably labeled and used in the detection of PD-1.Brief Description of the DrawingsFigure 1provides a schematic of a representative covalently bonded diabody having two epitope-binding sites composed of two polypeptide chains, each having an E-coil or K-coil Heterodimer-Promoting Domain. A cysteine residue may be present in a linker and/or in the Heterodimer-Promoting Domain as shown inFigure 3B.VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern.Figure 2provides a schematic of a representative covalently bonded diabody molecule having two epitope-binding sites composed of two polypeptide chains, each having a CH2 and CH3 Domain, such that the associated chains form all or part of an Fc Region. VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern.Figures 3A-3Cprovide schematics showing representative tetravalent diabodies having four epitope-binding sites composed of two pairs of polypeptide chains(i.e.,four polypeptide chains in all). One polypeptide of each pair possesses a CH2 and CH3 Domain, such that the associated chains form all or part of an Fc Region. VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern. The two pairs of polypeptide chains may be same. When the VL and VH Domains recognize different epitopes (as shown inFigures 3A-3C),the resulting molecule possesses four epitope-binding sites and is bispecific and bivalent with respect to each bound epitope. When the VL and VH Domains recognize the same epitope (e.g., the same VL Domain CDRs and the same VH Domain CDRs are used on both chains), the resulting molecule possesses four epitope-binding sites and is monospecific and tetravalent with respect to a single epitope. Alternatively, the two pairs ofpolypeptides may be different. When the VL and VH Domains of each pair of polypeptides recognize different epitopes (as shown inFigures 3A-3C),the resulting molecule possesses four epitope-binding sites and is tetraspecific and monovalent with respect to each bound epitope.Figure 3Ashows an Fc diabody which contains a peptide Heterodimer-Promoting Domain comprising a cysteine residue.Figure 3Bshows an Fc Region-containing diabody, which contains E-coil and K-coil Heterodimer-Promoting Domains comprising a cysteine residue and a linker (with an optional cysteine residue).Figure 3C,shows an Fc-Region-Containing diabody, which contains antibody CH1 and CL domains.Figures 4Aand4Bprovide schematics of a representative covalently bonded diabody molecule having two epitope-binding sites composed of three polypeptide chains. Two of the polypeptide chains possess a CH2 and CH3 Domain, such that the associated chains form all or part of an Fc Region. The polypeptide chains comprising the VL and VH Domain further comprise a Heterodimer-Promoting Domain. VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern.Figure 5provides the schematics of a representative covalently bonded diabody molecule having four epitope-binding sites composed of five polypeptide chains. Two of the polypeptide chains possess a CH2 and CH3 Domain, such that the associated chains form an Fc Region that comprises all or part of an Fc Region. The polypeptide chains comprising the linked VL and VH Domains further comprise a Heterodimer-Promoting Domain. VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern.Figures 6A-6Fprovide schematics of representative Fc Region-containing trivalent binding molecules having three epitope-binding sites.Figures 6Aand6B,respectively, illustrate schematically the domains of trivalent binding molecules comprising two diabody-type binding domains and a Fab-type binding domain having different domain orientations in which the diabody-type binding domains are N-terminal or C-terminal to an Fc Region. The molecules inFigures 6Aand6Bcomprise four chains.Figures 6Cand6D,respectively, illustrate schematically the domains of trivalent binding molecules comprising two diabody-type binding domains N-terminal to an FcRegion, and a Fab-type binding domain in which the light chain and heavy chain are inked via a polypeptide spacer, or an scFv-type binding domain. The trivalent binding molecules inFigures 6Eand6F,respectively illustrate schematically the domains of trivalent binding molecules comprising two diabody-type binding domains C-terminal to an Fc Region, and a linked Fab-type binding domain, or an scFv-type bindingdomain in which the diabody-type binding domains are. The trivalent binding molecules inFigures 6C-6Fcomprise three chains. VL and VH Domains that recognize the same epitope are shown using the same shading or fill pattern.Figures 7A-7Dshows that the anti-PD-1 antibodies PD-1 mAb 1-15 bind to human PD-1. Binding curves for binding to shPD-1-His are shown inFigure 7A(PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 4 and PD-1 mAb 9),Figure 7B(PD-1 mAb 5, PD-1 mAb 6, and PD-1 mAb 7), andFigure 7C(PD-1 mAb 3, PD-1 mAb 8, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15). Binding curves for binding to shPD-1-human Fc are shown inFigure 7D(PD-1 mAb 3, PD-1 mAb 8, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15).Figures 8A-8Cshows that the anti-PD-1 antibodies PD-1 mAb 1-15 bind to cynomolgus monkey PD-1. Binding curves for binding to scynoPD-1-hFc are shown inFigure 8A(PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7),Figure 8B(PD-1 mAb 9), andFigure 8C(PD-1 mAb 3, PD-1 mAb 8, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15).Figures 9A-9Dshow the ability of the anti-PD-1 antibodies PD-1 mAb 1-15 to block the binding of human PD-L1 to human PD-1. Inhibition curves are shown inFigure 9A(PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 15, and PD-1 mAb A),Figure 9B(PD-1 mAb 4),Figure 9C(PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, and PD-1 mAb A), andFigure 9D(PD-1 mAb 3, PD-1 mAb 8, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, PD-1 mAb 15, and PD-1 mAb A).Figures 10A-10Bshow the tissue specificity of the anti-human PD-1 antibody PD-1 mAb 7.Figure 10Ashows histological stains of normal colon (Panels iandvii), liver (Panels iiandviii), lung (Panels iiiandix), pancreas (Panels ivandx), kidney(Panels vandxi) and heart (Panels viandxii) tissue.Figure 10A, Panels i-vishow the results of tissue incubated with labeled PD-1 mAb 7 (0.313 µg/mL).Figure 10A, Panels vii-xiishow the results of tissue incubated with labeled isotype control mAb (0.314 µg/mL).Figure 10Bshows histological stains of skin (Panels iandiv), tonsils (Panels iiandv), and NSO cells expressing PD-1 (Panels iiiandvi).Figure 10B, Panels i-iiishow the results of tissue incubated with labeled PD-1 mAb 7 (0.313 µg/mL).Figure 11shows the binding profiles of humanized anti-human PD-1 antibodies hPD-1 mAb 2, hPD-1 mAb 7(1.1), hPD-1 mAb 7(1.2), hPD-1 mAb 9(1.1), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B having IgG1 (AA) or IgG4 (P) for binding to cell surface PD-1.Figures 12A-12Bshow the ability of humanized anti-PD antibodies hPD-1 mAb 2, hPD-1 mAb 7(1.1), hPD-1 mAb 7(1.2), hPD-1 mAb 9(1.1), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B, having IgG1 (AA) or IgG4 (P) to block the binding of soluble human PD-L1(Figure 12A)and soluble human PD-L2(Figure 12B)to cell surface human PD-1.Figure 13shows the ability of humanized anti-PD antibodies hPD-1 mAb 2, hPD-1 mAb 7(1.1), hPD-1 mAb 7(1.2), hPD-1 mAb 9(1.1), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B, having IgG1 (AA) or IgG4 (P) to antagonize the PD-1/PD-L1 axis by blocking the PD-1/PD-L1 interaction and preventing down-regulation of T-cell responses in a Jurkat-luc-NFAT / CHO-PD-L1 luciferase reporter assay.Figure 14shows that PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9 and PD-1 mAb 15 are able to stimulate cytokine production to levels comparable or higher than the referenced anti-PD-1 antibodies (PD-1 mAb A and PD-1 mAb B) and that treatment with PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9 and PD-1 mAb 15 in combination with LAG-3 mAb 1 provided the largest enhancement of cytokine release. IFNγ secretion profiles fromStaphylococcalenterotoxin B (SEB)-stimulated PBMCs treated with anti-PD-1 and anti-LAG-3 antibodies alone and in combination.Figures 15A-15Bshow the ability of humanized anti-PD antibodies hPD-1 mAb 2, hPD-1 mAb 7(1.2), hPD-1 mAb 9(1.1), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B, having IgG1 (AA) or IgG4 (P) to stimulate cytokine production. IFNγ (Figure 15A) and TNFα (Figure 15B), secretion profiles from SEB-stimulated PBMCs treated with anti-PD-1 antibodies.Figures 16A-16Bshow that the PD-1 x LAG-3 bispecific diabody constructs DART A, DART D, DART E, DART F, DART G and DART H, are able to stimulate cytokine production to levels comparable or higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A + LAG-3 mAb A), and that the PD-1 x LAG-3 bispecific diabody constructs DART A, DART D, DART E, DARTF and DART G provided the largest enhancement of cytokine release. IFNγ secretion profiles of PBMCs stimulated with a low concentration of SEB (0.2 ng/mL treated with PD-1 x LAG-3 bispecific diabodies, or anti-PD-1 and anti-LAG-3 antibodies alone and in combination are plotted. The results using PBMCs from two representative donors are shown inFigure 16AandFigure 16B.Figures 17A-17Bshow that the PD-1 x LAG-3 bispecific diabody constructs DART A, DART B and DART C are able to stimulate cytokine production to levels higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A + LAG-3 mAb A). IFNγ secretion profiles of PBMCs from two representative donors, stimulated with a high concentration of SEB (85 ng/mL) treated with PD-1 x LAG-3 bispecific diabodies, or anti-PD-1 and anti-LAG-3 antibodies alone and in combination are plotted. The results using PBMCs from two representative donors are shown inFigure 17AandFigure 17B.Figures 18A-18Bshow that the PD-1 x LAG-3 bispecific diabody constructs DART A, DART B and DART C are able to stimulate cytokine production to levels higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A + LAG-3 mAb A). IFNγ secretion profiles of PBMCs from two representative donors, stimulated with a middle concentration of SEB (0.5 ng/mL) treated with PD-1 x LAG-3 bispecific diabodies, or anti-PD-1 and anti-LAG-3 antibodies alone and in combination are plotted. The results using PBMCs from two representative donors are shown inFigure 18AandFigure 18B.Figure 19shows that the PD-1 x LAG-3 bispecific diabody constructs DART D and DART H are able to stimulate cytokine production to levels comparable or higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A + LAG-3 mAb A), and that DART D provided the largest enhancement of cytokine release. IL-2 secretion profiles of PBMCs from a representative donor stimulated with a high concentration of SEB (85 ng/mL) treated with PD-1 x LAG-3 bispecific diabodies, or anti-PD-1 and anti-LAG-3 antibodies alone and in combination are plotted.Figure 20shows that the PD-1 x LAG-3 bispecific diabody constructs DART B and DART I are able to stimulate cytokine production to levels higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A+ LAG-3 mAb A, hPD-1 mAb 7(1.2) + hLAG-3 mAb 1(1.4), hPD-1 mAb 7(1.2) + hLAG-3 mAb 6(1.1)). IFNγ secretion profiles of PBMCs from a representative donor, stimulated with a middle concentration of SEB (0.5 ng/mL) treated with PD-1 x LAG-3 bispecific diabodies, or anti-PD-1 and anti-LAG-3 antibodies alone and in combination are plotted.Figures 21A-21Dshow that the that the PD-1 x LAG-3 bispecific diabody DART I is able to stimulate cytokine production to levels higher than that observed upon the administration of the combination of an anti-PD-1 mAb + an anti-LAG-3 mAb (PD-1 mAb A + LAG-3 mAb A). IFNγ(Figures 21Aand21C)and IL-2(Figures 21Band21D)secretion profiles of CD4 memory cells from two representative donors, stimulated with tetanus toxoid (5 µg/mL) treated with the PD-1 × LAG-3 bispecific diabody DART-I, anti-PD-1 and anti-LAG-3 antibodies in combination, or an isotype control are plotted. The results at day 7 using CD4 memory T cells from two representative donors are shown inFigures 21A-BandFigures 21C-D.Figure 22shows that the the pharmacokinetics of the PD-1 × LAG-3 bispecific molecule, DART I are comparable to those of the anti-PD-1 antibody, PD-1 mAb A IgG4 (P) in cynomolgus monkey. The lines indicate the mean serum concentration of DART I (solid) and PD-1 mAb A (dashed). The individual values for the male (filled) and female (open) monkeys are plotted for DART I (triangles) and PD-1 mAb A (circles).Figures 23A-23Cshow serum antibody concentrations and percentage of bound PD-1 on the surface of CD4+ or CD8+ T cells over time in animals following treatment with different anti-PD-1 antibodies. The percentage of bound PD 1 on the surface of CD4+ or CD8+ T cells following anti-PD 1 mAb treatment is plotted on the right y-axes; symbols represent % bound PD 1 on T cells for each individual animal and dashed lines represent the mean values. Serum mAb concentrations are plotted on the left y-axes; symbols represent serum levels for each individual animal and solid lines represent nonlinear fits of the data. Each panel presents data for animals (n = 1/sex/group) administered 10 mg/kg hPD-1 mAb 7 (1.2) IgG4 (P)(Figure 23A),PD-1 mAb A IgG4 (P)(Figure 23B),or PD-1 mAb B IgG4 (P)(Figure 23B)by IV infusion on Day 1.Detailed Description of the InventionPD-1-binding molecules that comprise the PD-1-binding domain of selected anti-PD-1 antibodies capable of binding to both cynomolgus monkey PD-1 and to human PD-1:PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15 are disclosed but not claimed herein. The invention concerns PD-1-binding molecules that are humanized antibodies, wherein the anti-human PD-1 binding monospecific monoclonal antibody comprises a Variable Heavy Chain Domain that comprises the amino acid sequence of SEQ ID NO: 147 and a Variable Light Chain Domain that comprises the amino acid sequence of SEQ ID NO: 153 for use in accordance with claims 1-6. The present invention is directed to such PD-1-binding molecules for use in methods of stimulating an immune response. In particular,the present invention is directed to such PD-1-binding molecules for use in methods of combination therapy in which a PD-1-binding molecule that comprises one or more PD-1-binding domain(s) of such selected anti-PD-1 antibodies, as defined by and for use in accordance with claims 1-6, is administered in combination with one or more additional molecules that are effective in stimulating an immune response and/or in combination with one or more additional molecules that specifically bind a cancer antigen.I. Antibodies and Their Binding DomainsAntibodies are immunoglobulin molecules capable of specific binding to a target, such as a carbohydrate, polynucleotide, lipid, polypeptide,etc.,through at least one antigen recognition site, located in the Variable Domain of the immunoglobulin molecule. As used herein, the terms"antibody"and"antibodies"refer to monoclonal antibodies, multispecific antibodies, human antibodies, humanized antibodies, synthetic antibodies, chimeric antibodies, polyclonal antibodies, camelized antibodies, single-chain Fvs (scFv), single-chain antibodies, Fab fragments, F(ab') fragments, disulfide-linked bispecific Fvs (sdFv), intrabodies, and epitope-binding fragments of any of the above. In particular, antibodies include immunoglobulin molecules and immunologically active fragments of immunoglobulin molecules,i.e.,molecules that contain an antigen-binding site. Immunoglobulin molecules can be of any type(e.g.,IgG, IgE, IgM, IgD, IgA and IgY), class(e.g.,IgG1, IgG2, IgG3, IgG4, IgA1and IgA2) or subclass. In addition to their known uses in diagnostics, antibodies have been shown to be useful as therapeutic agents. Antibodies are capable of immunospecifically binding to a polypeptide or protein or a non-protein molecule due to the presence on such molecule of a particular domain or moiety or conformation (an"epitope"). An epitopecontaining molecule may have immunogenic activity, such that it elicits an antibody production response in an animal; such molecules are termed"antigens"). The last few decades have seena revival of interest in the therapeutic potential of antibodies, and antibodies have become one of the leading classes of biotechnology-derived drugs (Chan, C.E. et al. (2009) "The Use Of Antibodies In The Treatment Of Infectious Diseases," Singapore Med. J. 50(7):663-666). Over 200 antibody-based drugs have been approved for use or are under development.The term"monoclonal antibody"refers to a homogeneous antibody population wherein the monoclonal antibody is comprised of amino acids (naturally occurring and nonnaturally occurring) that are involved in the selective binding of an antigen. Monoclonal antibodies are highly specific, being directed against a single epitope (or antigenic site). The term "monoclonal antibody" encompasses not only intact monoclonal antibodies and fulllength monoclonal antibodies, but also fragments thereof (such as Fab, Fab', F(ab')2Fv), single-chain (scFv), mutants thereof, fusion proteins comprising an antibody portion, humanized monoclonal antibodies, chimeric monoclonal antibodies, and any other modified configuration of the immunoglobulin molecule that comprises an antigen recognition site of the required specificity and the ability to bind to an antigen. It is not intended to be limited as regards to the source of the antibody or the manner in which it is made (e.g., by hybridoma, phage selection, recombinant expression, transgenic animals,etc.). The term includes whole immunoglobulins as well as the fragmentsetc.described above under the definition of "antibody." Methods of making monoclonal antibodies are known in the art. One method which may be employed is the method ofKohler, G. et al. (1975) "Continuous Cultures Of Fused Cells Secreting Antibody Of Predefined Specificity," Nature 256:495-497or a modification thereof. Typically, monoclonal antibodies are developed in mice, rats or rabbits. The antibodies are produced by immunizing an animal with an immunogenic amount of cells, cell extracts, or protein preparations that contain the desired epitope. The immunogen can be, but is not limited to, primary cells, cultured cell lines, cancerous cells, proteins, peptides, nucleic acids, or tissue. Cells used for immunization may be cultured for a period of time (e.g., at least 24 hours) prior to their use as an immunogen. Cells may be used as immunogens by themselves or in combination with a non-denaturing adjuvant, such as Ribi (see,e.g.,Jennings, V.M. (1995) "Review of Selected Adjuvants Used in Antibody Production," ILAR J. 37(3): 119-125). In general, cells should be kept intact and preferably viable when used as immunogens. Intact cells may allow antigens to be better detected than ruptured cells by the immunized animal. Use of denaturing or harsh adjuvants,e.g.,Freud's adjuvant, may rupture cells and therefore is discouraged. The immunogen may be administered multiple times at periodic intervals such as, bi-weekly, or weekly, or may be administered in such a way as to maintainviability in the animal (e.g.,in a tissue recombinant). Alternatively, existing monoclonal antibodies and any other equivalent antibodies that are immunospecific for a desired pathogenic epitope can be sequenced and produced recombinantly by any means known in the art. An antibody may be sequenced and the polynucleotide sequence is then cloned into a vector for expression or propagation. The sequence encoding the antibody of interest may be maintained in a vector in a host cell and the host cell can then be expanded and frozen for future use. The polynucleotide sequence of such antibodies may be used for genetic manipulation to generate the monospecific molecules of the invention, as defined by and for use in accordance with claims 1-6, as well as an affinity optimized, a chimeric antibody, a humanized antibody, and/or a caninized antibody, to improve the affinity, or other characteristics of the antibody. The general principle in humanizing an antibody involves retaining the basic sequence of the antigen-binding portion of the antibody, while swapping the non-human remainder of the antibody with human antibody sequences.Natural antibodies (such as IgG antibodies) are composed of twoLight Chainscomplexed with twoHeavy Chains.Each light chain contains a Variable Domain(VL)and a Constant Domain(CL).Each heavy chain contains a Variable Domain(VH),three Constant Domains(CH1, CH2andCH3),and a hinge domain located between theCH1andCH2Domains. The basic structural unit of naturally occurring immunoglobulins (e.g., IgG) is thus a tetramer having two light chains and two heavy chains, usually expressed as a glycoprotein of about 150,000 Da. The amino-terminal ("N-terminal") portion of each chain includes a Variable Domain of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The carboxy-terminal ("C-terminal") portion of each chain defines a constant region, with light chains having a single Constant Domain and heavy chains usually having three Constant Domains and a Hinge Domain. Thus, the structure of the light chains of an IgG molecule is n-VL-CL-c and the structure of the IgG heavy chains is n-VH-CH1-H-CH2-CH3-c (where H is the hinge domain, and n and c represent, respectively, the N-terminus and the C-terminus of the polypeptide). The Variable Domains of an IgG molecule consist of the complementarity determining regions(CDR),which contain the residues in contact with epitope, and non-CDR segments, referred to as framework segments(FR),which in general maintain the structure and determine the positioning of the CDR loops so as to permit such contacting (although certain framework residues may also contact antigen). Thus, the VL and VH Domains have the structure n-FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4-c. Polypeptides that are (or may serve as) the first, second and third CDR of an antibody Light Chain are hereinrespectively designatedCDRL1 Domain, CDRL2 Domain,andCDRL3 Domain.Similarly, polypeptides that are (or may serve as) the first, second and third CDR of an antibody heavy chain are herein respectively designatedCDRH1 Domain, CDRH2 Domain,andCDRH3 Domain.Thus, the terms CDRL1 Domain, CDRL2 Domain, CDRL3 Domain, CDRH1 Domain, CDRH2 Domain, and CDRH3 Domain are directed to polypeptides that when incorporated into a protein cause that protein to be able to bind to a specific epitope regardless of whether such protein is an antibody having light and heavy chains or a diabody or a single-chain binding molecule (e.g.,an scFv, a BiTe,etc.), or is another type of protein. Accordingly, as used herein, the term"epitope-binding fragment"means a fragment of an antibody capable of immunospecifically binding to an epitope, and the term"epitope-binding site"refers to that portion of a molecule comprising an epitope-binding fragment that is responsible for epitope binding. An epitope-binding site may contain 1, 2, 3, 4, 5 or all 6 of the CDR Domains of such antibody and, although capable of immunospecifically binding to such epitope, may exhibit an immunospecificity, affinity or selectivity toward such epitope that differs from that of such antibody. Preferably, however, an epitope-binding fragment will contain all 6 of the CDR Domains of such antibody. An epitope-binding fragment of an antibody may be a single polypeptide chain (e.g.,an scFv), or may comprise two or more polypeptide chains, each having an amino terminus and a carboxy terminus (e.g.,a diabody, a Fab fragment, an F(ab')2fragment,etc.).Single-chain Variable Domain fragments are made by linking Light and/or Heavy chain Variable Domain by using a short linking peptide.Bird et al. (1988) ("Single-Chain Antigen-Binding Proteins," Science 242:423-426) describes example of linking peptides which bridge approximately 3.5 nm between the carboxy terminus of one Variable Domain and the amino terminus of the other Variable Domain. Linkers of other sequences have been designed and used (Bird et al. (1988) "Single-Chain Antigen-Binding Proteins," Science 242:423-426). Linkers can in turn be modified for additional functions, such as attachment of drugs or attachment to solid supports. The single-chain variants can be produced either recombinantly or synthetically. For synthetic production of scFv, an automated synthesizer can be used. For recombinant production of scFv, a suitable plasmid containing polynucleotide that encodes the scFv can be introduced into a suitable host cell, either eukaryotic, such as yeast, plant, insect or mammalian cells, or prokaryotic, such as E. coli. Polynucleotides encoding the scFv of interest can be made by routine manipulations such as ligation of polynucleotides. The resultant scFv can be isolated using standard protein purification techniques known in the art.The term"humanized"antibody refers to a chimeric molecule, generally prepared using recombinant techniques, having an antigen-binding site of an immunoglobulin from a non-human species and a remaining immunoglobulin structure of the molecule that is based upon the structure and /or sequence of a human immunoglobulin. Anti-human PD-1 antibodies include humanized, chimeric or caninized variants of antibodies PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15. The polynucleotide sequence of the variable domains of such antibodies may be used for genetic manipulation to generate such derivatives and to improve the affinity, or other characteristics of such antibodies. The general principle in humanizing an antibody involves retaining the basic sequence of the antigen-binding portion of the antibody, while swapping the non-human remainder of the antibody with human antibody sequences. There are four general steps to humanize a monoclonal antibody. These are: (1) determining the nucleotide and predicted amino acid sequence of the starting antibody light and heavy variable domains (2) designing the humanized antibody or caninized antibody,i.e., deciding which antibody framework region to use during the humanizing or canonizing process (3) the actual humanizing or caninizing methodologies/techniques and (4) the transfection and expression of the humanized antibody. See, for example,U.S. Patents Nos. 4,816,567;5,807,715;5,866,692; and6,331,415.The antigen-binding site may comprise either a complete Variable Domain fused to a Constant Domain or only the complementarity determining regions (CDRs) of such Variable Domain grafted to appropriate framework regions. Antigen-binding sites may be wild-type or modified by one or more amino acid substitutions. This eliminates the constant region as an immunogen in human individuals, but the possibility of an immune response to the foreign variable domain remains (LoBuglio, A.F. et al. (1989) "Mouse/Human Chimeric Monoclonal Antibody In Man: Kinetics And Immune Response," Proc. Natl. Acad. Sci. (U.S.A.) 86:4220-4224). Another approach focuses not only on providing human-derived constant regions, but modifying the variable domains as well so as to reshape them as closely as possible to human form. It is known that the variable domains of both heavy and light chains contain three complementarity determining regions (CDRs) which vary in response to the antigens in question and determine binding capability, flanked by four framework regions (FRs) which are relatively conserved in a given species and which putatively provide a scaffolding for the CDRs. When non-human antibodies are prepared with respect to a particular antigen, thevariable domains can be "reshaped" or "humanized" by grafting CDRs derived from nonhuman antibody on the FRs present in the human antibody to be modified. Application of this approach to various antibodies has been reported bySato, K. et al. (1993) Cancer Res 53:851-856.Riechmann, L. et al. (1988) "Reshaping Human Antibodies for Therapy," Nature 332:323-327;Verhoeyen, M. et al. (1988) "Reshaping Human Antibodies: Grafting An Antilysozyme Activity," Science 239:1534-1536;Kettleborough, C. A. et al. (1991) "Humanization Of A Mouse Monoclonal Antibody By CDR-Grafting: The Importance Of Framework Residues On Loop Conformation," Protein Engineering 4:773-3783;Maeda, H. et al. (1991) "Construction Of Reshaped Human Antibodies With HIV-Neutralizing Activity," Human Antibodies Hybridoma 2:124-134;Gorman, S. D. et al. (1991) "Reshaping A Therapeutic CD4 Antibody," Proc. Natl. Acad. Sci. (U.S.A.) 88:4181-4185;Tempest, P.R. et al. (1991) "Reshaping A Human Monoclonal Antibody To Inhibit Human Respiratory Syncytial Virus Infection in vivo," Bio/Technology 9:266-271;Co, M. S. et al. (1991) "Humanized Antibodies For Antiviral Therapy," Proc. Natl. Acad. Sci. (U.S.A.) 88:2869-2873;Carter, P. etal. (1992) "Humanization Of An Antipl85her2 Antibody For Human Cancer Therapy," Proc. Natl. Acad. Sci. (U.S.A.) 89:4285-4289; andCo, M.S. et al. (1992) "Chimeric And Humanized Antibodies With Specificity For The CD33 Antigen," J. Immunol. 148:1149-1154. Humanized antibodies may preserve all CDR sequences (for example, a humanized mouse antibody which contains all six CDRs from the mouse antibodies). Alternatively, humanized antibodies may have one or more CDRs (one, two, three, four, five, or six) which differ in sequence relative to the original antibody.A number of "humanized" antibody molecules comprising an antigen-binding site derived from a non-human immunoglobulin have been described, including chimeric antibodies having rodent or modified rodent Variable Domain and their associated complementarity determining regions (CDRs) fused to human Constant Domains (see, for example,Winter et al. (1991) "Man-made Antibodies," Nature 349:293-299;Lobuglio et al. (1989) "Mouse/Human Chimeric Monoclonal Antibody In Man: Kinetics And Immune Response," Proc. Natl. Acad. Sci. (U.S.A.) 86:4220-4224 (1989),Shaw et al. (1987) "Characterization Of A Mouse/Human Chimeric Monoclonal Antibody (17-1A) To A Colon Cancer Tumor Associated Antigen," J. Immunol. 138:4534-4538, andBrown et al. (1987) "Tumor-Specific Genetically Engineered Murine/Human Chimeric Monoclonal Antibody," Cancer Res. 47:3577-3583). Other references describe rodent CDRs grafted into a human supporting framework region (FR) prior to fusion with an appropriate human antibodyConstant Domain (see, for example,Riechmann, L. et al. (1988) "Reshaping Human Antibodies for Therapy," Nature 332:323-327;Verhoeyen, M. et al. (1988) "Reshaping Human Antibodies: Grafting An Antilysozyme Activity," Science 239:1534-1536; andJones et al. (1986) "Replacing The Complementarity-Determining Regions In A Human Antibody With Those From A Mouse," Nature 321:522-525). Another reference describes rodent CDRs supported by recombinantly veneered rodent framework regions. See, for example,European Patent Publication No. 519,596. These "humanized" molecules are designed to minimize unwanted immunological response towards rodent anti-human antibody molecules, which limits the duration and effectiveness of therapeutic applications of those moieties in human recipients. Other methods of humanizing antibodies that may also be utilized are disclosed byDaugherty et al. (1991) "Polymerase Chain Reaction Facilitates The Cloning, CDR-Grafting, And Rapid Expression Of A Murine Monoclonal Antibody Directed Against The CD18 Component Of Leukocyte Integrins," Nucl. Acids Res. 19:2471-2476and inU.S. Patents Nos. 6,180,377;6,054,297;5,997,867; and5,866,692.II. Fcγ Receptors (FcγRs)The CH2 and CH3 Domains of the two heavy chains interact to form theFc Region,which is a domain that is recognized by cellularFc Receptors,including but not limited to Fc gamma Receptors(FcγRs).As used herein, the term "Fc Region" is used to define a C-terminal region of an IgG heavy chain. The amino acid sequence of the CH2-CH3 Domain of an exemplary human IgG1 is(SEQ ID NO:1):as numbered by the EU index as set forth in Kabat, wherein, x is a lysine (K) or is absent.The amino acid sequence of the CH2-CH3 Domain of an exemplary human IgG2 is(SEQ ID NO:2):as numbered by the EU index as set forth in Kabat, wherein, x is a lysine (K) or is absent.The amino acid sequence of the CH2-CH3 Domain of an exemplary human IgG3 is(SEQ ID NO:3):as numbered by the EU index as set forth in Kabat, wherein, x is a lysine (K) or is absent.The amino acid sequence of the CH2-CH3 Domain of an exemplary human IgG4 is(SEQ ID NO:4):as numbered by the EU index as set forth in Kabat, wherein, x is a lysine (K) or is absent.Throughout the present specification, the numbering of the residues in the constant region of an IgG heavy chain is that of the EU index as inKabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, NH1, MD (1991) ("Kabat"), expressly. The term "EU index as in Kabat" refers to the numbering of the human IgG1 EU antibody. Amino acids from the Variable Domains of the mature heavy and light chains of immunoglobulins are designated by the position of an amino acid in the chain. Kabat described numerous amino acid sequences for antibodies, identified an amino acid consensus sequence for each subgroup, and assigned a residue number to each amino acid, and the CDRs are identified as defined by Kabat (it will be understood that CDRH1 as defined byChothia, C. & Lesk, A. M. ((1987) "Canonical structures for the hypervariable regions of immunoglobulins,". J. Mol. Biol. 196:901-917) begins five residues earlier). Kabat's numbering scheme is extendible to antibodies not included in his compendium by aligning the antibody in question with one of the consensus sequences in Kabat by reference to conserved amino acids. This method for assigning residue numbers has become standard in the field and readily identifies amino acids at equivalent positions in different antibodies, including chimeric or humanized variants. For example, an amino acid at position 50 of a human antibody light chain occupies the equivalent position to an amino acid at position 50 of a mouse antibody light chain.Polymorphisms have been observed at a number of different positions within antibody constant regions (e.g.,CH1 positions, including but not limited to positions 192, 193, and 214; Fc positions, including but not limited to positions 270, 272, 312, 315, 356, and 358 as numbered by the EU index as set forth in Kabat), and thus slight differences between the presented sequence and sequences in the prior art can exist. Polymorphic forms of human immunoglobulins have been well-characterized. At present, 18 Gm allotypes are known: G1m (1, 2, 3, 17) or G1m (a, x, f, z), G2m (23) or G2m (n), G3m (5, 6, 10, 11, 13, 14, 15, 16, 21, 24, 26, 27, 28) or G3m (b1, c3, b3, b0, b3, b4, s, t, g1, c5, u, v, g5) (Lefranc, et al., "The Human IgG Subclasses: Molecular Analysis Of Structure, Function And Regulation." Pergamon, Oxford, pp. 43-78 (1990);Lefranc, G. et al., 1979, Hum. Genet.: 50, 199-211). It is specifically contemplated that the antibodies of the present invention, as defined by and for use in accordance with claims 1-6, may incorporate any allotype, isoallotype, or haplotype of any immunoglobulin gene, and are not limited to the allotype, isoallotype or haplotype of the sequences provided herein. Furthermore, in some expression systems the C-terminal amino acid residue (bolded above) of the CH3 Domain may be post-translationally removed. Accordingly, the C-terminal residue of the CH3 Domain is an optional amino acid residue in the PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6. Specifically encompassed by the instant invention are PD-1-binding molecules lacking the C-terminal residue of the CH3 Domain. Also specifically encompassed by the instant invention are such constructs comprising the C-terminal lysine residue of the CH3 Domain.Activating and inhibitory signals are transduced through the ligation of an Fc region to a cellular Fc gamma Receptor (FcyR). The ability of such ligation to result in diametrically opposing functions results from structural differences among the different FcyRs. Two distinct domains within the cytoplasmic signaling domains of the receptor called immunoreceptor tyrosine-based activation motifs (ITAMs) and immunoreceptor tyrosine-based inhibitory motifs (ITIMS) account for the different responses. The recruitment of different cytoplasmic enzymes to these structures dictates the outcome of the FcyR-mediated cellular responses. ITAM-containing FcyR complexes include FcyRI, FcyRIIA, FcγRIIIA, whereas ITIM-containing complexes only include FcγRIIB. Human neutrophils express the FcγRIIA gene. FcyRIIA clustering via immune complexes or specific antibody cross-linking serves to aggregate ITAMs along with receptor-associated kinases which facilitate ITAM phosphorylation. ITAM phosphorylation serves as a docking site for Syk kinase, activation ofwhich results in activation of downstream substrates (e.g.,PI3K). Cellular activation leads to release of proinflammatory mediators. The FcγRIIB gene is expressed on B lymphocytes; its extracellular domain is 96% identical to FcyRIIA and binds IgG complexes in an indistinguishable manner. The presence of an ITIM in the cytoplasmic domain of FcγRIIB defines this inhibitory subclass of FcyR. Recently the molecular basis of this inhibition was established. When co-ligated along with an activating FcyR, the ITIM in FcγRIIB becomes phosphorylated and attracts the SH2 domain of the inositol polyphosphate 5'-phosphatase (SHIP), which hydrolyzes phosphoinositol messengers released as a consequence of ITAM-containing FcyR- mediated tyrosine kinase activation, consequently preventing the influx of intracellular Ca++. Thus cross-linking of FcγRIIB dampens the activating response to FcyR ligation and inhibits cellular responsiveness. B-cell activation, B-cell proliferation and antibody secretion is thus aborted.The ability of an antibody to bind an epitope of an antigen depends upon the presence and amino acid sequence of the antibody's VL and VH Domains. Interaction of an antibody light chain and an antibody heavy chain and, in particular, interaction of its VL and VH Domains forms one of the two epitope-binding sites of a natural antibody. Natural antibodies are capable of binding to only one epitope species (i.e.,they are monospecific), although they can bind multiple copies of that species (i.e.,exhibiting bivalency or multivalency).The binding domains ofan antibody bind to epitopes in an"immunospecific"manner. As used herein, an antibody, diabody or other epitope-binding molecule is said to"immunospecifically"bind a region of another molecule (i.e.,an epitope) if it reacts or associates more frequently, more rapidly, with greater duration and/or with greater affinity with that epitope relative to alternative epitopes. For example, an antibody that immunospecifically binds to a viral epitope is an antibody that binds this viral epitope with greater affinity, avidity, more readily, and/or with greater duration than it immunospecifically binds to other viral epitopes or non-viral epitopes. It is also understood by reading this definition that, for example, an antibody (or moiety or epitope) that immunospecifically binds to a first target may or may not specifically or preferentially bind to a second target. As such, "immunospecific binding" does not necessarily require (although it can include) exclusive binding. Generally, but not necessarily, reference to binding means "specific" binding. Two molecules are said to becapable of binding to one another in a"physiospecific"manner, if such binding exhibits the specificity with which receptors bind to their respective ligands.The functionality of antibodies can be enhanced by generating multispecific antibody-based molecules that can simultaneously bind two separate and distinct antigens (or different epitopes of the same antigen) and/or by generating antibody-based molecule having higher valency(i.e.,more than two binding sites) for the same epitope and/or antigen.In order to provide molecules having greater capability than natural antibodies, a wide variety of recombinant bispecific antibody formats have been developed (see,e.g.,PCT Publication Nos. WO 2008/003116,WO 2009/132876,WO 2008/003103,WO 2007/146968,WO 2009/018386,WO 2012/009544,WO 2013/070565), most of which use linker peptides either to fuse a further epitope-binding fragment (e.g.,an scFv, VL, VH,etc.)to, or within the antibody core (IgA, IgD, IgE, IgG or IgM), or to fuse multiple epitope-binding fragments (e.g.,two Fab fragments or scFvs). Alternative formats use linker peptides to fuse an epitope-binding fragment (e.g.,an scFv, VL, VH,etc.) to an a dimerization domain such as the CH2-CH3 Domain or alternative polypeptides (WO 2005/070966,WO 2006/107786AWO 2006/107617A,WO 2007/046893). Typically, such approaches involve compromises and trade-offs. For example,PCT Publications Nos. WO 2013/174873,WO 2011/133886andWO 2010/136172disclose that the use of linkers may cause problems in therapeutic settings, and teaches a trispecific antibody in which the CL and CH1 Domains are switched from their respective natural positions and the VL and VH Domains have been diversified (WO 2008/027236;WO 2010/108127) to allow them to bind to more than one antigen. Thus, the molecules disclosed in these documents trade binding specificity for the ability to bind additional antigen species.PCT Publications Nos. WO 2013/163427andWO 2013/119903disclose modifying the CH2 Domain to contain a fusion protein adduct comprising a binding domain. The document notes that the CH2 Domain likely plays only a minimal role in mediating effector function.PCT Publications Nos. WO 2010/028797,WO2010028796andWO 2010/028795disclose recombinant antibodies whose Fc Regions have been replaced with additional VL and VH Domains, so as to form trivalent bindingmolecules.PCT Publications Nos. WO 2003/025018andWO2003012069disclose recombinant diabodies whose individual chains contain scFv Domains.PCT Publications No. WO 2013/006544discloses multivalent Fab molecules that are synthesized as a single polypeptide chain and then subjected to proteolysis to yield heterodimeric structures. Thus, the molecules disclosed in these documentstrade all or some of the capability of mediating effector function for the ability to bind additional antigen species.PCT Publications Nos. WO 2014/022540,WO 2013/003652,WO 2012/162583,WO 2012/156430,WO 2011/086091,WO 2008/024188,WO 2007/024715,WO 2007/075270,WO 1998/002463,WO 1992/022583andWO 1991/003493disclose adding additional binding domains or functional groups to an antibody or an antibody portion (e.g., adding a diabody to the antibody's light chain, or adding additional VL and VH Domains to the antibody's light and heavy chains, or adding a heterologous fusion protein or chaining multiple Fab Domains to one another). Thus, the molecules disclosed in these documents trade native antibody structure for the ability to bind additional antigen species.The art has additionally noted the capability to produce diabodies that differ from such natural antibodies in being capable of binding two or more different epitope species (i.e.,exhibiting bispecificity or multi specificity in addition to bivalency or multivalency) (see,e.g.,Holliger et al. (1993) "'Diabodies': Small Bivalent And Bispecific Antibody Fragments," Proc. Natl. Acad. Sci. (U.S.A.) 90:6444-6448;US 2004/0058400 (Hollinger et al.);US 2004/0220388/WO 02/02781 (Mertens et al.);Alt et al. (1999) FEBS Lett. 454(1-2):90-94;Lu, D. et al. (2005) "A Fully Human Recombinant IgG-Like Bispecific Antibody To Both The Epidermal Growth Factor Receptor And The Insulin-Like Growth Factor Receptor For Enhanced Antitumor Activity," J. Biol. Chem. 280(20):19665-19672;WO 02/02781 (Mertens et al.);Olafsen, T. et al. (2004) "Covalent Disulfide-Linked Anti-CEA Diabody Allows Site-Specific Conjugation And Radiolabeling For Tumor Targeting Applications," Protein Eng. Des. Sel. 17(1):21-27;Wu, A. et al. (2001) "Multimerization Of A Chimeric Anti-CD20 Single Chain Fv-Fv Fusion Protein Is Mediated Through Variable Domain Exchange," Protein Engineering 14(2):1025-1033;Asano et al. (2004) "A Diabody For Cancer Immunotherapy And Its Functional Enhancement By Fusion Of Human Fc Domain," Abstract 3P-683, J. Biochem. 76(8):992;Takemura, S. et al. (2000) "Construction Of A Diabody (Small Recombinant Bispecific Antibody) Using A Refolding System," Protein Eng. 13(8):583-588;Baeuerle, P.A. et al. (2009) "Bispecific T-Cell Engaging Antibodies For Cancer Therapy," Cancer Res. 69(12):4941-4944).The design of a diabody is based on the antibody derivative known as a single-chain Variable Domain fragment (scFv). Such molecules are made by linking Light and/ or Heavy chain Variable Domains by using a short linking peptide.Bird et al. (1988) ("Single-Chain Antigen-Binding Proteins," Science 242:423-426) describes example of linking peptides whichbridge approximately 3.5 nm between the carboxy terminus of one Variable Domain and the amino terminus of the other Variable Domain. Linkers of other sequences have been designed and used (Bird et al. (1988) "Single-Chain Antigen-Binding Proteins," Science 242:423-426). Linkers can in turn be modified for additional functions, such as attachment of drugs or attachment to solid supports. The single-chain variants can be produced either recombinantly or synthetically. For synthetic production of scFv, an automated synthesizer can be used. For recombinant production of scFv, a suitable plasmid containing polynucleotide that encodes the scFv can be introduced into a suitable host cell, either eukaryotic, such as yeast, plant, insect or mammalian cells, or prokaryotic, such asE. coli.Polynucleotides encoding the scFv of interest can be made by routine manipulations such as ligation of polynucleotides. The resultant scFv can be isolated using standard protein purification techniques known in the art.The provision of non-monospecific diabodies provides a significant advantage over antibodies, including but not limited to, the capacity to co-ligate and co-localize cells that express different epitopes. Bispecific diabodies thus have wide-ranging applications including therapy and immunodiagnosis. Bispecificity allows for great flexibility in the design and engineering of the diabody in various applications, providing enhanced avidity to multimeric antigens, the cross-linking of differing antigens, and directed targeting to specific cell types relying on the presence of both target antigens. Due to their increased valency, low dissociation rates and rapid clearance from the circulation (for diabodies of small size, at or below ~50 kDa), diabody molecules known in the art have also shown particular use in the field of tumor imaging (Fitzgerald et al. (1997) "Improved Tumour Targeting By Disulphide Stabilized Diabodies Expressed In Pichia pastoris, " Protein Eng. 10:1221).The bispecificity of diabodies has led to their use for co-ligating differing cells, for example, the cross-linking of cytotoxic T-cells to tumor cells (Staerz et al. (1985) "Hybrid Antibodies Can Target Sites For Attack By T Cells, " Nature 314:628-631, andHolliger et al. (1996) "Specific Killing Of Lymphoma Cells By Cytotoxic T-Cells Mediated By A Bispecific Diabody, " Protein Eng. 9:299-305;Marvin et al. (2005) "Recombinant Approaches To IgG-Like Bispecific Antibodies," Acta Pharmacol. Sin. 26:649-658). Alternatively, or additionally, bispecific diabodies can be used to co-ligate receptors on the surface of different cells or on a single cell. Co-ligation of different cells and/or receptors is useful to modulation effector functions and/or immune cell signaling. Multispecific molecules (e.g., bispecific diabodies) comprising epitope-binding sites may be directed to a surface determinant of any immune cellsuch as B7-H3 (CD276), B7-H4 (VTCN1), BTLA (CD272), CD3, CD8, CD16, CD27, CD32, CD40, CD40L, CD47, CD64, CD70 (CD27L), CD80 (B7-1), CD86 (B7-2), CD94 (KLRD1), CD137 (4-1BB), CD137L (4-1BBL), CD226, CTLA-4 (CD152), Galectin-9, GITR, GITRL, HHA2, ICOS (CD278), ICOSL (CD275), Killer Activation Receptor (KIR), LAG-3 (CD223), LIGHT (TNFSF14, CD258), MHC class I or II, NKG2a, NKG2d, OX40 (CD134), OX40L (CD134L), PD1H, PD-1 (CD279), PD-L1 (B7-H1, CD274), PD-L2 (B7-CD, CD273), PVR (NECL5, CD155), SIRPa, TCR, TIGIT, TIM-3 (HAVCR2), and/or VISTA (PD-1H), which are expressed on T lymphocytes, Natural Killer (NK) cells, Antigen-presenting cells or other mononuclear cell. In particular, epitope-binding sites directed to a cell surface receptor that is involved in regulating an immune checkpoint (or the ligand thereof) are useful in the generation of bispecific or multispecific binding molecules which antagonize or block the inhibitory signaling of immune checkpoint molecules and thereby stimulate, upregulate or enhance, immune responses in a subject. Molecules involved in regulating immune checkpoints include, but are not limited to B7-H3, B7-H4, BTLA, CD40, CD40L, CD47, CD70, CD80, CD86, CD94, CD137, CD137L, CD226, CTLA-4, Galectin-9, GITR, GITRL, HHLA2, ICOS, ICOSL, KIR, LAG-3, LIGHT, MHC class I or II, NKG2a, NKG2d, OX40, OX40L, PD1H, PD-1, PD-L1, PD-L2, PVR, SIRPa, TCR, TIGIT, TIM-3 and/or VISTA.However, the above advantages come at a salient cost. The formation of such non-monospecific diabodies requires the successful assembly of two or more distinct and different polypeptides (i.e., such formation requires that the diabodies be formed through the heterodimerization of different polypeptide chain species). This fact is in contrast to monospecific diabodies, which are formed through the homodimerization of identical polypeptide chains. Because at least two dissimilar polypeptides (i.e.,two polypeptide species) must be provided in order to form a non-monospecific diabody, and because homodimerization of such polypeptides leads to inactive molecules (Takemura, S. et al. (2000) "Construction Of A Diabody (Small Recombinant Bispecific Antibody) Using A Refolding System," Protein Eng. 13(8):583-588), the production of such polypeptides must be accomplished in such a way as to prevent covalent bonding between polypeptides of the same species(i.e.,so as to prevent homodimerization) (Takemura, S. et al. (2000) "Construction Of A Diabody (Small Recombinant Bispecific Antibody) Using A Refolding System," Protein Eng. 13(8):583-588). The art has therefore taught the non-covalent association of such polypeptides (see,e.g.,Olafsen et al. (2004) "Covalent Disulfide-Linked Anti-CEA Diabody Allows Site-Specific Conjugation And Radiolabeling For Tumor Targeting Applications, " Prot. Engr. Des. Sel.17:21-27;Asano et al. (2004) "A Diabody For Cancer Immunotherapy And Its Functional Enhancement By Fusion Of Human Fc Domain," Abstract 3P-683, J. Biochem. 76(8):992;Takemura, S. et al. (2000) "Construction Of A Diabody (Small Recombinant Bispecific Antibody) Using A Refolding System," Protein Eng. 13(8):583-588;Lu, D. et al. (2005) "A Fully Human Recombinant IgG-Like Bispecific Antibody To Both The Epidermal Growth Factor Receptor And The Insulin-Like Growth Factor Receptor For Enhanced Antitumor Activity," J. Biol. Chem. 280(20):19665-19672).However, the art has recognized that bispecific diabodies composed of noncovalently associated polypeptides are unstable and readily dissociate into non-functional monomers (see,e.g.,Lu, D. et al. (2005) "A Fully Human Recombinant IgG-Like Bispecific Antibody To Both The Epidermal Growth Factor Receptor And The Insulin-Like Growth Factor Receptor For Enhanced Antitumor Activity," J. Biol. Chem. 280(20):19665-19672).In the face of this challenge, the art has succeeded in developing stable, covalently bonded heterodimeric non-monospecific diabodies, termedDART®(DualAffinityReTargetingReagents) diabodies; see,e.g.,United States Patent Publications No. 2013-0295121;2010-0174053and2009-0060910; European Patent Publication No.EP 2714079;EP 2601216;EP 2376109;EP 2158221andPCT Publications No. WO 2012/162068;WO 2012/018687;WO 2010/080538; andSloan, D.D. et al. (2015) "Targeting HIV Reservoir in Infected CD4 T Cells by Dual-Affinity Re-targeting Molecules (DARTs) that Bind HIV Envelope and Recruit Cytotoxic T Cells," PLoS Pathog. 11(11):e1005233. doi: 10.1371/journal.ppat. 1005233;Al Hussaini, M. et al. (2015) "Targeting CD123 In AML Using A T-Cell Directed Dual-Affinity Re-Targeting (DART®) Platform," Blood pii: blood-2014-05-575704;Chichili, G.R. et al. (2015) "A CD3xCD123 Bispecific DART For Redirecting Host T Cells To Myelogenous Leukemia: Preclinical Activity And Safety In Nonhuman Primates," Sci. Transl. Med. 7(289):289ra82;Moore, P.A. et al. (2011) "Application Of Dual Affinity Retargeting Molecules To Achieve Optimal Redirected T-Cell Killing Of B-Cell Lymphoma," Blood 117(17):4542-4551;Veri, M.C. et al. (2010) "Therapeutic Control Of B Cell Activation Via Recruitment Of Fcgamma Receptor IIb (CD32B) Inhibitory Function With A Novel Bispecific Antibody Scaffold," Arthritis Rheum. 62(7):1933-1943;Johnson, S. et al. (2010) "Effector Cell Recruitment With Novel Fv-BasedDual-Affinity Re-Targeting Protein Leads To Potent Tumor Cytolysis And in vivo B-Cell Depletion," J. Mol. Biol. 399(3):436-449). Such diabodies comprise two or more covalently complexed polypeptides and involve engineeringone or more cysteine residues into each of the employed polypeptide species that permit disulfide bonds to form and thereby covalently bond two polypeptide chains. For example, the addition of a cysteine residue to the C-terminus of such constructs has been shown to allow disulfide bonding between the polypeptide chains, stabilizing the resulting heterodimer without interfering with the binding characteristics of the bivalent molecule.Each of the two polypeptides of the simplest bispecificDART®diabody comprises three domains. The first polypeptide comprises (in the N-terminal to C-terminal direction): (i) a First Domain that comprises a binding region of a Light Chain Variable Domain of a first immunoglobulin (VL1), (ii) a Second Domain that comprises a binding region of a Heavy Chain Variable Domain of a second immunoglobulin (VH2), and (iii) a Third Domain that contains a cysteine residue (or a cysteine-containing domain) and a Heterodimer-Promoting Domain that serves to promote heterodimerization with the second polypeptide of the diabody and to covalently bond the diabody's first and second polypeptides to one another. The second polypeptide contains (in the N-terminal to C-terminal direction): (i) a First Domain that comprises a binding region of a Light Chain Variable Domain of the second immunoglobulin (VL2), (ii) a Second Domain that comprises a binding region of a Heavy Chain Variable Domain of the first immunoglobulin (VH1), and (iii) a Third Domain that contains a cysteine residue (or a cysteine-containing domain) and a complementary Heterodimer-Promoting Domain that complexes with the Heterodimer-Promoting Domain of the first polypeptide chain in order to promote heterodimerization with the first polypeptide chain. The cysteine residue (or a cysteine-containing domain) of the third domain of the second polypeptide chain serves to promote the covalent bonding of the second polypeptide chain to the first polypeptide chain of the diabody. Such molecules are stable, potent and have the ability to simultaneously bind two or more antigens. The Third Domains of the first and second polypeptides each contain a cysteine residue, which serves to bind the polypeptides together via a disulfide bond.Figure 1provides a schematic of such a diabody, which utilizes E-coil/K-coil Heterodimer-Promoting domains and a cysteine containing linker for covalent bonding. As provided inFigure 2andFigures 3A-3C,one or both of the polypeptides may additionally possesses the sequence of a CH2-CH3 Domain, such that complexing between the two diabody polypeptides forms an Fc Region that is capable of binding to the Fc receptor of cells (such as B lymphocytes, dendritic cells, natural killer cells, macrophages, neutrophils, eosinophils, basophils and mast cells). As provided in more detail below, the CH2 and/or CH3 Domains of such polypeptide chains neednot be identical in sequence, and advantageously are modified to foster complexing between the two polypeptide chains.Many variations of such molecules have been described (see, e.g.,United States Patent Publications No. 2015/0175697;2014/0255407;2014/0099318;2013/0295121;2010/0174053and2009/0060910; European Patent Publication No.EP 2714079;EP 2601216;EP 2376109;EP 2158221andPCT Publications No. WO 2012/162068;WO 2012/018687;WO 2010/080538). These Fc Region-containingDART®diabodies may comprise two pairs of polypeptide chains. The first polypeptide chain comprises (in the N-terminal to C-terminal direction): (i) a First Domain that comprises a binding region of a Light Chain Variable Domain of a first immunoglobulin (VL1), (ii) a Second Domain that comprises a binding region of a Heavy Chain Variable Domain of a second immunoglobulin (VH2), (iii) a Third Domain that contains a cysteine residue (or a cysteine-containing domain) and a serves to promote heterodimerization with the second polypeptide of the diabody and to covalently bond the diabody's first and second polypeptides to one another, and (iv) a CH2-CH3 Domain. The second polypeptide contains (in the N-terminal to C-terminal direction): (i) a First Domain that comprises a binding region of a Light Chain Variable Domain of the second immunoglobulin (VL2), (ii) a Second Domain that comprises a binding region of a Heavy Chain Variable Domain of the first immunoglobulin (VH1), and (iii) ) a Third Domain that contains a cysteine residue (or a cysteine-containing domain) and a Heterodimer-Promoting Domain that promotes heterodimerization with the first polypeptide chain. Here two first polypeptides complex with each other to form an Fc Region.Figures 3A-3Cprovide schematics of three variations of such diabodies utilizing different Heterodimer-Promoting Domains.Other Fc-Region-containing DART®diabodies may comprise three polypeptide chains. The first polypeptide of such DART®diabodies contains three domains: (i) a VL1-containing Domain, (ii) a VH2-containing Domain and (iii) a Domain containing a CH2-CH3 sequence. The second polypeptide of such DART®diabodies contains: (i) a VL2-containing Domain, (ii) a VH1-containing Domain and (iii) a Domain that promotes heterodimerization and covalent bonding with the diabody's first polypeptide chain. The third polypeptide of such DART®diabodies comprises a CH2-CH3 sequence. Thus, the first and second polypeptide chains of such DART®diabodies associate together to form a VL1/VH1 binding site that is capable of binding to the epitope, as well as a VL2/VH2 binding site that is capable of binding to the second epitope. Such more complex DART®molecules also possess cysteine-containingdomains which function to form a covalently bonded complex. Thus, the first and second polypeptides are bonded to one another through a disulfide bond involving cysteine residues in their respective Third Domains. Notably, the first and third polypeptide chains complex with one another to form an Fc Region that is stabilized via a disulfide bond.Figures 4A-4Bprovide schematics of such diabodies comprising three polypeptide chains.Still other Fc-Region-containing DART®diabodies may comprise five polypeptide chains which may comprise the binding regions from the Light and Heavy Chain Variable Domains of up to three different immunoglobulins (referred to as VL1/VH1, VL2/VH2 and VL3/VH3). For example, the first polypeptide chain of such diabodies may contain: (i) a VH1-containing domain, (ii) a CH1-containing domain, and (iii) a Domain containing a CH2-CH3 sequence. The second and fifth polypeptide chains of such diabodies may contain: (i) a VL1-containing domain, and (ii) a CL-containing domain. The third polypeptide chain of such diabodies may contain: (i) a VH1-containing domain, (ii) a CH1-containing domain, (iii) a Domain containing a CH2-CH3 sequence, (iv) a VL2-containing Domain, (v) a VH3-containing Domain and (vi) a Heterodimer-Promoting Domain, where the Heterodimer-Promoting Domains promote the dimerization of the third chain with the fourth chain. The fourth polypeptide of such diabodies may contain: (i) a VL3-containing Domain, (ii) a VH2-containing Domain and (iii) a Domain that promotes heterodimerization and covalent bonding with the diabody's third polypeptide chain. Here the first and third polypeptides complex with each other to form an Fc Region. Such more complex DART®molecules also possess cysteine-containing domains which function to form a covalently bonded complex, such that each polypeptide chain is bonded to at least one addition polypeptide chain through a disulfide bond involving cysteine residues. Preferably, such domains are ordered in the N-terminal to C-terminal direction.Figure 5provides schematics of such diabodies comprising five polypeptide chains.Alternative constructs are known in the art for applications where a tetravalent molecule is desirable but an Fc is not required including, but not limited to, tetravalent tandem antibodies, also referred to as"TandAbs"(see,e.g.United States Patent Publications Nos. 2005-0079170,2007-0031436,2010-0099853,2011-0206672013-0189263; European Patent Publication Nos.EP 1078004,EP 2371866,EP 2361936andEP 1293514;PCT Publications Nos. WO 1999/057150,WO 2003/025018, andWO 2013/013700) which are formed by thehomo-dimerization of two identical chains each possessing a VH1, VL2, VH2, and VL2 Domain.Recently, trivalent structures incorporating two diabody-type binding domains and one non-diabody-type domain and an Fc Region have been described (see,e.g., PCT Application No:PCT/US 15/33076, titled "Tri-Specific Binding Molecules and Methods of Use Thereof," filed May 29, 2015; andPCT/US15/33081, titled "Tri-Specific Binding Molecules That Specifically Bind to Multiple Cancer Antigens and Methods of Use Thereof," filed May 29, 2015). Such trivalent molecules may be utilized to generate monospecific, bispecific or trispecific molecules.Figures 6A-6Fprovide schematics of such trivalent molecules comprising 3 or 4 polypeptide chains.IV. Anti-Human PD-1-Binding MoleculesPD-1-binding molecules include antibodies, diabodies, BiTEs,etc.and are capable of binding to a continuous or discontinuous (e.g., conformational) portion(epitope)of human PD-1 (CD279). PD-1-binding molecules preferably also exhibit the ability to bind to PD-1 molecules of one or more non-human species, in particular, primate species (and especially a primate species, such as cynomolgus monkey). A representative human PD-1 polypeptide (NCBI Sequence NP_005009.2; including a 20 amino acid residue signal sequence (shown underlined) and the 268 amino acid residue mature protein) has the amino acid sequence(SEQ ID NO:68):Anti-human PD-1-binding molecules may be characterized by any (one or more) of the following criteria:(1) specifically binds human PD-1 as endogenously expressed on the surface of a stimulated human T-cell;(2) specifically binds human PD-1 with an equilibrium binding constant (KD) of 40 nM or less;(3) specifically binds human PD-1 with an equilibrium binding constant (KD) of 5 nM or less;(4) specifically binds human PD-1 with an on rate (ka) of 1.5 × 104M-1min-1or more;(5) specifically binds human PD-1 with an on rate (ka) of 90.0 × 104M-1min-1or more;(6) specifically binds human PD-1 with an off rate (kd) of 7 µ 10-4min-1or less;(7) specifically binds human PD-1 with an off rate (kd) of 2 × 10-4min-1or less;(8) specifically binds non-human primate PD-1 (e.g., PD-1 of cynomolgus monkey);(9) inhibits (i.e., blocks or interferes with) the binding/the inhibitory activity)of PD-1 ligand (PD-L1/PD-L2) to PD-1;(10) stimulates an immune response; and/or(11) synergizes with an anti-human LAG-3 antibody to stimulate an antigen specific T-cell response.As used here the term "antigen specific T-cell response" refers to responses by a T-cell that result from stimulation of the T-cell with the antigen for which the T-cell is specific. Non-limiting examples of responses by a T-cell upon antigen specific stimulation include proliferation and cytokine production (e.g., TNF-α, IFN-γ production). The ability of a molecule to stimulate an antigen specific T-cell response may be determined, for example, using theStaphylococcus aureusEnterotoxin type B antigen("SEB")-stimulatedPBMC assay described herein.Anti-human PD-1-binding molecules disclosed but not claimed herein possess the VH and/or VL Domains of murine anti-human PD-1 monoclonal antibodies"PD-1 mAb 1," "PD-1 mAb 2," "PD-1 mAb 3,‴'PD-1 mAb 4," "PD-1 mAb 5," "PD-1 mAb 6," "PD-1 mAb 7," "PD-1 mAb 8," "PD-1 mAb 9," "PD-1 mAb 10," "PD-1 mAb 11," "PD-1 mAb 12," "PD-1 mAb 13," "PD-1 mAb 14," or "PD-1 mAb 15," and more preferably possess 1, 2 or all 3 of the CDRHs of the VH Domain and/or 1, 2 or all 3 of the CDRLs of the VL Domain of such anti-human PD-1 monoclonal antibodies. Such preferred anti-human PD-1-binding molecules include bispecific (or multispecific) antibodies, chimeric or humanized antibodies, BiTes, diabodies,etc,and such binding molecules having variant Fc Regions.The invention relates to PD-1-binding molecules, as defined by and for use in accordance with claims 1-6, comprising a PD-1 binding domain that possesses:(1) the three CDRHs of the VH Domain of PD-1 mAb 7 and the three CDRLs of the VL Domain of hPD-1 mAb 7 VL2;(2) the VH Domain of hPD-1 mAb 7 VH1;(3) the VL Domain of hPD-1 mAb 7 VL2; and(4) the VH and VL Domains of hPD-1 mAb 7(1.2).A. The Anti-Human PD-1 Antibody PD-1 mAb 11. Murine Anti-Human PD-1 Antibody PD-1 mAb 1The amino acid sequence of the VH Domain of PD-1 mAb 1(SEQ ID NO:69)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 1(SEQ ID NO:71):NDYAWNCDRH2 of PD-1 mAb 1(SEQ ID NO:72):HITYSGSTSYNPSLKSCDRH3 of PD-1 mAb 1(SEQ ID NO:73):DYGSGYPYTLDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 1 isSEQ ID NO:70(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 1(SEQ ID NO:74)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 1(SEQ ID NO:76):SATSIVSYVYCDRL2 of PD-1 mAb 1(SEQ ID NO:77):LTSNLASCDRL3 of PD-1 mAb 1(SEQ ID NO:78):QQWSDNPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 1 isSEQ ID NO:75(nucleotides encoding the CDRLresidues are shown underlined):2. Humanization of the Anti-Human PD-1 AntibodyPD-1 mAb 1 to Form "hPD-1 mAb 1"The above-described murine anti-human PD-1 antibody PD-1 mAb 1 was humanized and further deimmunized when antigenic epitopes were identified in order to demonstrate the capability of humanizing an anti-human PD-1 antibody so as to decrease its antigenicity upon administration to a human recipient. The humanization yielded one humanized VH Domain, designated herein as "hPD-1 mAb 1 VH1," and one humanized VL Domain designated herein as "hPD-1 mAb 1 VL1." Accordingly, an antibody comprising the humanized VL Domains paired with the humanized VH Domain is referred to as "hPD-1 mAb 1."The amino acid sequence of the VH Domain of hPD-1 mAb 1 VH1 (SEQIDNO:79) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 1 VH1 isSEQ ID NO:80(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 1 VL1(SEQ ID NO:81)is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 1 VL1 isSEQ ID NO:82(nucleotides encoding the CDRHresidues are shown underlined):B. The Anti-Human PD-1 Antibody PD-1 mAb 21. Murine Anti-Human PD-1 Antibody PD-1 mAb 2The amino acid sequence of the VH Domain of PD-1 mAb 2(SEQ ID NO:83)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 2(SEQ ID NO:85):SFGMHCDRH2 of PD-1 mAb 2(SEQ ID NO:86):YISSGSMSISYADTVKGCDRH3 of PD-1 mAb 2(SEQ ID NO:87):LSDYFDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 2 isSEQ ID NO:84(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 2(SEQ ID NO:88)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 2(SEQ ID NO:90):RSSQSLVHSTGNTYLHCDRL2 of PD-1 mAb 2(SEQ ID NO:91):RVSNRFSCDRL3 of PD-1 mAb 2(SEQ ID NO:92):SQTTHVPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 2 isSEQ ID NO:89(nucleotides encoding the CDRLresidues are shown underlined):2. Humanization of the Anti-Human PD-1 AntibodyPD-1 mAb 2 to Form "hPD-1 mAb 2"The above-described murine anti-human PD-1 antibody PD-1 mAb 2 was humanized and further deimmunized when antigenic epitopes were identified in order to demonstrate the capability of humanizing an anti-human PD-1 antibody so as to decrease its antigenicity upon administration to a human recipient. The humanization yielded one humanized VH Domain, designated herein as"hPD-1 mAb 2 VH1,"and one humanized VL Domains designated herein as"hPD-1 mAb 1 VL1."Accordingly, any antibody comprising the humanized VL Domains paired with the humanized VH Domain is referred to as"hPD-1 mAb 2."The amino acid sequence of the VH Domain of hPD-1 mAb 2 VH1(SEQ ID NO:93is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 2 VH1 isSEQ ID NO:94(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 2 VL1(SEQ ID NO:95is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 2 VL1 isSEQ ID NO:96(nucleotides encoding the CDRHresidues are shown underlined):C. Murine Anti-Human PD-1 Antibody PD-1 mAb 3The amino acid sequence of the VH Domain of PD-1 mAb 3(SEQ ID NO:97)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 3(SEQ ID NO:99):DYVMHCDRH2 of PD-1 mAb 3(SEQ ID NO:100):TIDPETGGTAYNQKFKGCDRH3 of PD-1 mAb 3(SEQ ID NO:101):EKITTIVEGTYWYFDVAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 3 isSEQ ID NO:98(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 3 (SEQ ID NO:102) is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 3(SEQ ID NO:104):RSSQNIVHSNGDTYLECDRL2 of PD-1 mAb 3(SEQ ID NO:105):KVSNRFSCDRL3 of PD-1 mAb 3(SEQ ID NO:106):FQGSHLPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 3 isSEQ ID NO:103(nucleotides encoding the CDRLresidues are shown underlined):D. Murine Anti-Human PD-1 Antibody PD-1 mAb 4The amino acid sequence of the VH Domain of PD-1 mAb 4 (SEQ ID NO:107) is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 4(SEQ ID NO:109):SFGMHCDRH2 of PD-1 mAb 4(SEQ ID NO:110):YISSGSMSISYADTVKGCDRH3 of PD-1 mAb 4(SEQ ID NO:111):LTDYFDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 4 isSEQ ID NO:108(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 4(SEQ ID NO:112)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 4(SEQ ID NO:114):RSSQSLVHSTGNTYFHCDRL2 of PD-1 mAb 4(SEQ ID NO:115):RVSNRFSCDRL3 of PD-1 mAb 4(SEQ ID NO:116):SQTTHVPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 4 isSEQ ID NO:113(nucleotides encoding the CDRLresidues are shown underlined):E. Murine Anti-Human PD-1 Antibody PD-1 mAb 5The amino acid sequence of the VH Domain of PD-1 mAb 5(SEQ ID NO:117)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 5(SEQ ID NO:119):AYWMNCDRH2 of PD-1 mAb 5(SEQ ID NO:120):VIHPSDSETWLNQKFKDCDRH3 of PD-1 mAb 5(SEQ ID NO:121):EHYGSSPFAYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 5 isSEQ ID NO:118(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 5(SEQ ID NO:122)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 5(SEQ ID NO:124):RANESVDNYGMSFMNCDRL2 of PD-1 mAb 5(SEQ ID NO:125):AASNQGSCDRL3 of PD-1 mAb 5(SEQ ID NO:126):QQSKEVPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 5 isSEQ ID NO:123(nucleotides encoding the CDRLresidues are shown underlined):F. Murine Anti-Human PD-1 Antibody PD-1 mAb 6The amino acid sequence of the VH Domain of PD-1 mAb 6 (SEQ ID NO:127) is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 6 (SEQ ID NO:129):SYGMSCDRH2 of PD-1 mAb 6 (SEQ ID NO:130):TISGGGSDTYYPDSVKGCDRH3 of PD-1 mAb 6 (SEQ ID NO:131):QKATTWFAYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 6 isSEQ ID NO:128(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 6(SEQ ID NO:132)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 6 (SEQ ID NO:134):RASESVDNYGISFMNCDRL2 of PD-1 mAb 6 (SEQ ID NO:135):PASNQGSCDRL3 of PD-1 mAb 6 (SEQ ID NO:136):QQSKEVPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 6 isSEQ ID NO:133(nucleotides encoding the CDRLresidues are shown underlined):G. The Anti-Human PD-1 Antibody PD-1 mAb 71. Murine Anti-Human PD-1 Antibody PD-1 mAb 7The amino acid sequence of the VH Domain of PD-1 mAb 7 (SEQ ID NO:137) is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 7 (SEQ ID NO:139):SYWMNCDRH2 of PD-1 mAb 7 (SEQ ID NO:140):VIHPSDSETWLDQKFKDCDRH3 of PD-1 mAb 7 (SEQ ID NO:141):EHYGTSPFAYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 7 isSEQ ID NO:138(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 7(SEQ ID NO:142)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 7(SEQ ID NO:144):RANESVDNYGMSFMNCDRL2 of PD-1 mAb 7(SEQ ID NO:145):AASNQGSCDRL3 of PD-1 mAb 7(SEQ ID NO:146):QQSKEVPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 7 isSEQ ID NO:143(nucleotides encoding the CDRLresidues are shown underlined):2. Humanization of the Anti-Human PD-1 Antibody PD-1 mAb 7 to Form "hPD-1 mAb 7"The above-described murine anti-human PD-1 antibody PD-1 mAb 7 was humanized and further deimmunized when antigenic epitopes were identified in order to demonstrate the capability of humanizing an anti-human PD-1 antibody so as to decrease its antigenicity upon administration to a human recipient. The humanization yielded two humanized VH Domains, designated herein as"hPD-1 mAb 7 VH1,"and"hPD-1 mAb 7 VH2,"and three humanized VL Domains designated herein as"hPD-1 mAb 7 VL1," "hPD-1mAb7VL2,"and"hPD-1 mAb 7 VL3."Any of the humanized VL Domains may be paired with either of the humanized VH Domains. Accordingly, any antibody comprising one of the humanized VL Domains paired with the humanized VH Domain is referred to generically as"hPD-1 mAb 7,"and particular combinations of humanized VH/VL Domains are referred to by reference to the specific VH/VL Domains, for example a humanized antibody comprising hPD-1 mAb 7 VH1 and hPD-1 mAb 1 VL2 is specifically referred to as"hPD-1 mAb 7(1.2)."The amino acid sequence of the VH Domain of hPD-1 mAb 7 VH1 (SEQ ID NO:147) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 7 VH1 isSEQ ID NO:148(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VH Domain of hPD-1 mAb 7 VH2 (SEQ ID NO:149) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 7 VH2 isSEQ ID NO:150(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 7 VL1 (SEQ ID NO:151) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 7 VL1 isSEQ ID NO:152(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 7 VL2 (SEQ ID NO:153) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 7 VL2 isSEQ ID NO:154(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 7 VL3 (SEQ ID NO:155) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 7 VL3 isSEQ ID NO:156(nucleotides encoding the CDRHresidues are shown underlined):The CDRL1 of the VL Domain of both hPD-1 mAb 7 VL2 and hPD-1 mAb 7 VL3 comprises an asparagine to serine amino acid substitution and has the amino acid sequence: RASESVDNYGMSFMN((SEQ ID NO:157),the substituted serine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the PD-1 mAb 7 CDRL1 Domains described above.In addition, the CDRL2 of the VL Domain of hPD-1 mAb 7 VL3 comprises a glutamine to arginine amino acid substitution and has the amino acid sequence: AASNRGS ((SEQ ID NO:158), the substituted arginine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the PD-1 mAb 7 CDRL2 Domains described above.H. Murine Anti-Human PD-1 Antibody PD-1 mAb 8The amino acid sequence of the VH Domain of PD-1 mAb 8(SEQ ID NO:159)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 8(SEQ ID NO:161):DYYMNCDRH2 of PD-1 mAb 8(SEQ ID NO:162):DINPKNGDTHYNQKFKGCDRH3 of PD-1 mAb 8(SEQ ID NO:163):DFDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 8 isSEQ ID NO:160(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 8 (SEQ ID NO:164) is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 8(SEQ ID NO:166):RSSQTLVYSNGNTYLNCDRL2 of PD-1 mAb 8(SEQ ID NO:167):KVSNRFSCDRL3 of PD-1 mAb 8(SEQ ID NO:168):SQSTHVPFTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 8 isSEQ ID NO:165(nucleotides encoding the CDRLresidues are shown underlined):I. The Anti-Human PD-1 Antibody PD-1 mAb 91. Murine Anti-Human PD-1 Antibody PD-1 mAb 9The amino acid sequence of the VH Domain of PD-1 mAb 9(SEQ ID NO:169)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 9(SEQ ID NO:171):SYLVSCDRH2 of PD-1 mAb 9(SEQ ID NO:172):TISGGGGNTYYSDSVKGCDRH3 of PD-1 mAb 9(SEQ ID NO:173):YGFDGAWFAYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 9 isSEQ ID NO:170(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 9 (SEQ ID NO:174) is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 9(SEQ ID NO:176):RASENIYSYLACDRL2 of PD-1 mAb 9(SEQ ID NO:177):NAKTLAACDRL3 of PD-1 mAb 9(SEQ ID NO:178):QHHYAVPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 9 isSEQ ID NO:175(nucleotides encoding the CDRLresidues are shown underlined):2. Humanization of the Anti-Human PD-1 Antibody PD-1 mAb 9 to Form "hPD-1 mAb 9"The above-described murine anti-human PD-1 antibody PD-1 mAb 9 was humanized and further deimmunized when antigenic epitopes were identified in order to demonstrate the capability of humanizing an anti-human PD-1 antibody so as to decrease its antigenicity upon administration to a human recipient. The humanization yielded two humanized VH Domains, designated herein as"hPD-1 mAb 9 VH1,"and"hPD-1 mAb 9 VH2,"and two humanized VL Domains designated herein as"hPD-1 mAb 9 VL1,"and"hPD-1 mAb 9 VL2."Any of the humanized VL Domains may be paired with the humanized VH Domains. Accordingly, any antibody comprising one of the humanized VL Domains paired with the humanized VH Domain is referred to generically as"hPD-1 mAb 9,"and particular combinations of humanized VH/VL Domains are referred to by reference to the specific VH/VL Domains, for example a humanized antibody comprising hPD-1 mAb 9 VH1 and hPD-1 mAb 9 VL2 is specifically referred to as"hPD-1 mAb 9(1.2)."The amino acid sequence of the VH Domain of hPD-1 mAb 9 VH1(SEQ ID NO:179) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 9 VH1 isSEQ ID NO:180(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VH Domain of hPD-1 mAb 9 VH2(SEQ ID NO:181) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 9 VH2 isSEQ ID NO:182(nucleotides encoding the CDRHresidues are shown underlined):The CDRH1 of the VH Domain of hPD-1 mAb 9 VH2 comprises a serine to glycine amino acid substitution and has the amino acid sequence: SYLVG((SEQ ID NO:183),the substituted glycine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the PD-1 mAb 9 CDRH1 Domains described above.The amino acid sequence of the VL Domain of hPD-1 mAb 9 VL1(SEQ ID NO:184) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 9 VL1 isSEQ ID NO:185(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of hPD-1 mAb 9 VL2(SEQ ID NO:186) is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 9 VL2 isSEQ ID NO:187(nucleotides encoding the CDRHresidues are shown underlined):The CDRL1 of the VL Domain of hPD-1 mAb 9 VL2 comprises a serine to asparagine amino acid substitution and has the amino acid sequence: RASENIYNYLA(SEQ ID NO:188),the substituted asparagine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the PD-1 mAb 9 CDRL1 Domains described above.The CDRL2 of the VL Domain of hPD-1 mAb 9 VL2 comprises an asparagine to aspartate amino acid substitution and has the amino acid sequence:DAKTLAA((SEQ ID NO:189), the substituted aspartate is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the PD-1 mAb 7 CDRL2 Domains described above.J. Murine Anti-Human PD-1 Antibody PD-1 mAb 10The amino acid sequence of the VH Domain of PD-1 mAb 10(SEQ ID NO:190)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 10(SEQ ID NO:192):NYLMSCDRH2 of PD-1 mAb 10(SEQ ID NO:193):SISGGGSNIYYPDSVKGCDRH3 of PD-1 mAb 10(SEQ ID NO:194):QELAFDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 10 isSEQ ID NO:191(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 10(SEQ ID NO:195)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 10(SEQ ID NO:197):RTSQDISNFLNCDRL2 of PD-1 mAb 10(SEQ ID NO:198):YTSRLHSCDRL3 of PD-1 mAb 10(SEQ ID NO:199):QQGSTLPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 10 isSEQ ID NO:196(nucleotides encoding the CDRLresidues are shown underlined):K. Murine Anti-Human PD-1 Antibody PD-1 mAb 11The amino acid sequence of the VH Domain of PD-1 mAb 11(SEQ ID NO:200)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 11(SEQ ID NO:202):GYWMHCDRH2 of PD-1 mAb 11(SEQ ID NO:203):AIYPGNSDTHYNQKFKGCDRH3 of PD-1 mAb 11(SEQ ID NO:204):GTYSYFDVAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 11 isSEQ ID NO:201(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 11(SEQ ID NO:205)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 11(SEQ ID NO:207):RASQSIGTSIHCDRL2 of PD-1 mAb 11(SEQ ID NO:208):YASESISCDRL3 of PD-1 mAb 11(SEQ ID NO:209):QQSNSWLTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 11 isSEQ ID NO:206(nucleotides encoding the CDRLresidues are shown underlined):L. Murine Anti-Human PD-1 Antibody PD-1 mAb 12The amino acid sequence of the VH Domain of PD-1 mAb 12(SEQ ID NO:210)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 12(SEQ ID NO:212):DYEMHCDRH2 of PD-1 mAb 12(SEQ ID NO:213):TIDPETGGTAYNQKFKGCDRH3 of PD-1 mAb 12(SEQ ID NO:214):ERITTVVEGAYWYFDVAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 12 isSEQ ID NO:211(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 4(SEQ ID NO:215)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 12(SEQ ID NO:217):RSSQNIVHSNGNTYLECDRL2 of PD-1 mAb 12(SEQ ID NO:218):KVSTRFSCDRL3 of PD-1 mAb 12(SEQ ID NO:219):FQGSHVPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 12 isSEQ ID NO:216(nucleotides encoding the CDRLresidues are shown underlined):M. Murine Anti-Human PD-1 Antibody PD-1 mAb 13The amino acid sequence of the VH Domain of PD-1 mAb 13(SEQ ID NO:220)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 13(SEQ ID NO:222):SHTMSCDRH2 of PD-1 mAb 13(SEQ ID NO:223):TISGGGSNIYYPDSVKGCDRH3 of PD-1 mAb 13(SEQ ID NO:224):QAYYGNYWYFDVAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 13 isSEQ ID NO:221(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 13(SEQ ID NO:225)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 13(SEQ ID NO:227):LASQTIGTWLACDRL2 of PD-1 mAb 13(SEQ ID NO:228):AATSLADCDRL3 of PD-1 mAb 13(SEQ ID NO:229):QQLDSIPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 13 isSEQ ID NO:226(nucleotides encoding the CDRLresidues are shown underlined):N. Murine Anti-Human PD-1 Antibody PD-1 mAb 14The amino acid sequence of the VH Domain of PD-1 mAb 14(SEQ ID NO:230)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 14(SEQ ID NO:232):SYWITCDRH2 of PD-1 mAb 14(SEQ ID NO:233):NIYPGTDGTTYNEKFKSCDRH3 of PD-1 mAb 14(SEQ ID NO:234):GLHWYFDVAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 14 isSEQ ID NO:231(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 14(SEQ ID NO:235)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 14(SEQ ID NO:237):KASQSVGTNVACDRL2 of PD-1 mAb 14(SEQ ID NO:238):SASSRFSCDRL3 of PD-1 mAb 14(SEQ ID NO:239):QQYNSYPYTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 14 isSEQ ID NO:236(nucleotides encoding the CDRLresidues are shown underlined):O. The Anti-Human PD-1 Antibody PD-1 mAb 151. Murine Anti-Human PD-1 Antibody PD-1 mAb 15The amino acid sequence of the VH Domain of PD-1 mAb 15(SEQ ID NO:240)is shown below (CDRHresidues are shown underlined).CDRH1 of PD-1 mAb 15(SEQ ID NO:242):SYLISCDRH2 of PD-1 mAb 15(SEQ ID NO:243):AISGGGADTYYADSVKGCDRH3 of PD-1 mAb 15(SEQ ID NO:244):RGTYAMDYAn exemplary polynucleotide that encodes the VH Domain of PD-1 mAb 15 isSEQ ID NO:241(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VL Domain of PD-1 mAb 15(SEQ ID NO:245)is shown below (CDRLresidues are shown underlined):CDRL1 of PD-1 mAb 15(SEQ ID NO:247):LASQTIGTWLACDRL2 of PD-1 mAb 15(SEQ ID NO:248):AATSLADCDRL3 of PD-1 mAb 15(SEQ ID NO:249):QQLYSIPWTAn exemplary polynucleotide that encodes the VL Domain of PD-1 mAb 15 isSEQ ID NO:246(nucleotides encoding the CDRLresidues are shown underlined):2. Humanization of the Anti-Human PD-1 Antibody PD-1 mAb 15 to Form "hPD-1 mAb 15"The above-described murine anti-human PD-1 antibody PD-1 mAb 15 was humanized and further deimmunized when antigenic epitopes were identified in order to demonstrate the capability of humanizing an anti-human PD-1 antibody so as to decrease its antigenicity upon administration to a human recipient. The humanization yielded onehumanized VH Domain, designated herein as"hPD-1 mAb 2 VH1," and one humanized VL Domains designated herein as "hPD-1 mAb 1 VL1." An antibody comprising the humanized VL Domain paired with the humanized VH Domain is referred to as"hPD-1 mAb 15."The amino acid sequence of the VH Domain of hPD-1 mAb 15 VH1(SEQ ID NO:250)is shown below (CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 15 VH1 isSEQ ID NO:251(nucleotides encoding the CDRHresidues are shown underlined):The amino acid sequence of the VH Domain of hPD-1 mAb 15 VL1(SEQ ID NO:252) is shown below CDRHresidues are shown underlined):An exemplary polynucleotide that encodes hPD-1 mAb 15 VL1 isSEQ ID NO:253(nucleotides encoding the CDRHresidues are shown underlined):V.Anti-Human PD-1 Antibodies PD-1 mAb 1-15, and Their Derivatives Having an Engineered Fc RegionIn traditional immune function, the interaction of antibody-antigen complexes with cells of the immune system results in a wide array of responses, ranging from effector functions such as antibody dependent cytotoxicity, mast cell degranulation, and phagocytosis toimmunomodulatory signals such as regulating lymphocyte proliferation and antibody secretion. All of these interactions are initiated through the binding of the Fc Region of antibodies or immune complexes to specialized cell surface receptors on hematopoietic cells. The diversity of cellular responses triggered by antibodies and immune complexes results from the structural heterogeneity of the three Fc receptors: FcyRI (CD64), FcyRII (CD32), and FcyRIII (CD16). FcyRI (CD64), FcyRIIA (CD32A) and FcyRIII (CD16) are activating (i.e.,immune system enhancing) receptors; FcyRIIB (CD32B) is an inhibiting(i.e.,immune system dampening) receptor. In addition, interaction with the neonatal Fc Receptor (FcRn) mediates the recycling of IgG molecules from the endosome to the cell surface and release into the blood. The amino acid sequence of exemplary wild-type IgG1 (SEQ ID NO:1), IgG2(SEQ ID NO:2),IgG3(SEQ ID NO:3),and IgG4(SEQ ID NO:4)are presented above.Modification of the Fc Region normally leads to an altered phenotype, for example altered serum half-life, altered stability, altered susceptibility to cellular enzymes or altered effector function. It may be desirable to modify an antibody or other binding molecule of the present invention, as defined by and for use in accordance with claims 1-6, with respect to effector function, for example, so as to enhance the effectiveness of such molecule in treating cancer. Reduction or elimination of effector function is desirable in certain cases, for example in the case of antibodies whose mechanism of action involves blocking or antagonism, but not killing of the cells bearing a target antigen. Increased effector function is generally desirable when directed to undesirable cells, such as tumor and foreign cells, where the FcyRs are expressed at low levels, for example, tumor-specific B cells with low levels of FcyRIIB(e.g.,non-Hodgkins lymphoma, CLL, and Burkitt's lymphoma). In said embodiments, molecules of the invention, as defined by and for use in accordance with claims 1-6, with conferred or altered effector function activity are useful for the treatment and/or prevention of a disease, disorder or infection where an enhanced efficacy of effector function activity is desired.In certain embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise an Fc Region that possesses one or more modifications (e.g., substitutions, deletions, or insertions) to the sequence of amino acids of a wild-type Fc Region(e.g.,SEQ ID NO:1),which reduce the affinity and avidity of the Fc Region and, thus, the molecule of the invention, for one or more FcyR receptors. In other embodiments, the molecules of the invention, as defined by and for use in accordance with claims 1-6, comprise an Fc Region that possesses one or more modifications to the aminoacids of the wild-type Fc Region, which increase the affinity and avidity of the Fc Region and, thus, the molecule of the invention, for one or more FcyR receptors. In other embodiments, the molecules comprise a variant Fc Region wherein said variant confers or mediates increased antibody dependent cell mediated cytotoxicity (ADCC) activity and/or an increased binding to FcyRIIA, relative to a molecule comprising no Fc Region or comprising a wild-type Fc Region. In alternate embodiments, the molecules comprise a variant Fc Region wherein said variant confers or mediates decreased ADCC activity (or other effector function) and/or an increased binding to FcyRIIB, relative to a molecule comprising no Fc Region or comprising a wild-type Fc Region. In some embodiments, the invention, as defined by and for use in accordance with claims 1-6, encompasses PD-1-binding molecules comprising a variant Fc Region, which variant Fc Region does not show a detectable binding to any FcyR, relative to a comparable molecule comprising the wild-type Fc Region. In other embodiments, the invention, as defined by and for use in accordance with claims 1-6, encompasses PD-1-binding molecules comprising a variant Fc Region, which variant Fc Region only binds a single FcyR, preferably one of FcyRIIA, FcyRIIB, or FcyRIIIA. Any such increased affinity and/or avidity is preferably assessed by measuringin vitrothe extent of detectable binding to the FcyR or FcγR-related activity in cells that express low levels of the FcyR when binding activity of the parent molecule (without the modified Fc Region) cannot be detected in the cells, or in cells which express non-FcyR receptor target antigens at a density of 30,000 to 20,000 molecules/cell, at a density of 20,000 to 10,000 molecules/cell, at a density of 10,000 to 5,000 molecules/cell, at a density of 5,000 to 1,000 molecules/cell, at a density of 1,000 to 200 molecules/cell or at a density of 200 molecules/cell or less (but at least 10, 50, 100 or 150 molecules/cell).The PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, may comprise a variant Fc Region having altered affinities for an activating and/or inhibitory Fcγ receptor. In one embodiment, the PD-1-binding molecule comprises a variant Fc Region that has increased affinityfor FcyRIIB and decreased affinity for FcyRIIIA and/or FcyRIIA, relative to a comparable molecule with a wild-type Fc Region. In another embodiment, the PD-1-binding molecule of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, which has decreased affinity for FcyRIIB and increased affinity for FcyRIIIA and/or FcyRIIA, relative to a comparable molecule with a wild-type Fc Region. In yet another embodiment, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region that has decreased affinity for FcyRIIB and decreasedaffinity for FcyRIIIA and/or FcyRIIA, relative to a comparable molecule with a wild-type Fc Region. In still another embodiment, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, which has unchanged affinity for FcyRIIB and decreased (or increased) affinity for FcyRIIIA and/or FcyRIIA, relative to a comparable molecule with a wild-type Fc Region.In certain embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region having an altered affinity for FcyRIIIA and/or FcyRIIA such that the immunoglobulin has an enhanced effector function. Non-limiting examples of effector cell functions include antibody dependent cell mediated cytotoxicity, antibody dependent phagocytosis, phagocytosis, opsonization, opsonophagocytosis, cell binding, resetting, C1q binding, and complement dependent cell mediated cytotoxicity.In a preferred embodiment, the alteration in affinity or effector function is at least 2-fold, preferably at least 4-fold, at least 5-fold, at least 6-fold, at least 7-fold, at least 8-fold, at least 9-fold, at least 10-fold, at least 50-fold, or at least 100-fold, relative to a comparable molecule comprising a wild-type Fc Region. In other embodiments of the invention, the variant Fc Region immunospecifically binds one or more FcRs with at least 65%, preferably at least 70%, 75%, 80%, 85%, 90%, 95%, 100%, 125%, 150%, 175%, 200%, 225%, or 250% greater affinity relative to a molecule comprising a wild-type Fc Region. Such measurements can be in vivo or in vitro assays, and in a preferred embodiment are in vitro assays such as ELISA or surface plasmon resonance assays.In different embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region wherein said variant agonizes at least one activity of an FcyR receptor, or antagonizes at least one activity of an FcyR receptor. In a preferred embodiment, the molecules comprise a variant that antagonizes one or more activities of FcyRIIB, for example, B-cell receptor-mediated signaling, activation of B-cells, B-cell proliferation, antibody production, intracellular calcium influx of B cells, cell cycle progression, FcyRIIB-mediated inhibition of FcεRI signaling, phosphorylation of FcyRIIB, SHIP recruitment, SHIP phosphorylation and association with She, or activity of one or more downstream molecules (e.g., MAP kinase, JNK, p38, or Akt) in the FcyRIIB signal transduction pathway. In another embodiment, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise avariant that agonizes one or more activities of FcεRI, for example, mast cell activation, calcium mobilization, degranulation, cytokine production, or serotonin release.In certain embodiments, the molecules comprise an Fc Region comprising regions from two or more IgG isotypes(e.g.,IgG1, IgG2, IgG3 and IgG4). As used herein, an Fc Region is said to be of a particular IgG isotype if its amino acid sequence is most homologous to that isotype relative to other IgG isotypes. The various IgG isotypes exhibit differing physical and functional properties including serum half-life, complement fixation, FcyR binding affinities and effector function activities(e.g.,ADCC, CDC,etc.)due to differences in the amino acid sequences of their hinge and/or Fc Regions, for example as described inFlesch and Neppert (1999) J. Clin. Lab. Anal. 14:141-156;Chappel et al. (1993) J. Biol. Chem. 33:25124-25131;Chappel et al. (1991) Proc. Natl. Acad. Sci. (U.S.A.) 88:9036-9040; orBrüggemann et al. (1987) J. Exp. Med 166:1351-1361. This type of variant Fc Region may be used alone, or in combination with an amino acid modification, to affect Fc-mediated effector function and/or binding activity. In combination, the amino acid modification and IgG hinge/Fc Region may display similar functionality (e.g., increased affinity for FcyRIIA) and may act additively or, more preferably, synergistically to modify the effector functionality in the molecule of the invention, relative to a molecule of the invention comprising a wild-type Fc Region. In other embodiments, the amino acid modification and IgG Fc Region may display opposite functionality (e.g., increased and decreased affinity for FcyRIIA, respectively) and may act to selectively temper or reduce a specific functionality in the molecule of the invention, relative to a molecule of the invention not comprising an Fc Region or comprising a wild-type Fc Region of the same isotype.In a preferred specific embodiment, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, wherein said variant Fc Region comprises at least one amino acid modification relative to a wild-type Fc Region, such that said molecule has an altered affinity for an FcR, provided that said variant Fc Region does not have a substitution at positions that make a direct contact with FcyR based on crystallographic and structural analysis of Fc-FcR interactions such as those disclosed bySondermann et al. (2000) Nature 406:267-73. Examples of positions within the Fc Region that make a direct contact with FcyR are amino acid residues 234-239, amino acid residues 265-269 (B/C loop), amino acid residues 297-299 (C'/E loop), and amino acid residues 327-332 (F/G loop). In some embodiments, the molecules of the invention, as definedby and for use in accordance with claims 1-6, comprise variant Fc Regions comprise modification of at least one residue that does not make a direct contact with an FcyR based on structural and crystallographic analysis,e.g., is not within the Fc-FcyR binding site.Variant Fc Regions are well known in the art, and any known variant Fc Region may be used in the present invention to confer or modify the effector function exhibited by a molecule of the invention comprising an Fc Region (or portion thereof) as functionally assayed,e.g., in an NK dependent or macrophage dependent assay. For example, Fc Region variants identified as altering effector function are disclosed inPCT Publications No. WO 04/063351;WO 06/088494;WO 07/024249;WO 06/113665;WO 07/021841;WO 07/106707; andWO 2008/140603, and any suitable variant disclosed therein may be used in the present molecules.In certain embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, having one or more amino acid modifications in one or more regions, which modification(s) alter (relative to a wild-type Fc Region) theRatio of Affinitiesof the variant Fc Region to an activating FcyR (such as FcyRIIA or FcyRIIIA) relative to an inhibiting FcyR (such as FcyRIIB):RatioofAffinities=Wild-TypetoVariantChangeinAffinitytoFcγRActivatingWild-TypetoVariantChangeinAffinitytoFcγRInhibitingParticularly preferred are PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, that possess a variant Fc Region (relative to the wild-type Fc Region) in which the variant Fc Region has a Ratio of Affinities greater than 1. Such molecules have particular use in providing a therapeutic or prophylactic treatment of a disease, disorder, or infection, or the amelioration of a symptom thereof, where an enhanced efficacy of effector cell function(e.g.,ADCC) mediated by FcyR is desired,e.g.,cancer or infectious disease. In contrast, a variant Fc Region having a Ratio of Affinities less than 1 mediates decreased efficacy of effector cell function.Table 1lists exemplary single, double, triple, quadruple and quintuple mutations by whether their Ratio of Affinities is greater than or less than 1.Table 1 Exemplary Single and Multiple Mutations Listed by Ratio of AffinitiesSingleDoubleTripleQuadrupleQuintupleRatio of Affinities > 1F243LF243L & R292PF243L, P247L & N421KL234F, F243L, R292P & Y300LL235V, F243L, R292P, Y300L & P396LD270EF243L & Y300LF243L, R292P & Y300LL235I, F243L, R292P & Y300LL235P, F243L, R292P, Y300L & P396LR292GF243L & P396LF243L, R292P & V305IL235Q, F243L, R292P & Y300LF243L, R292P, V305I, Y300L & P396LR292PD270E & P396LF243L, R292P & P396LF243L, P247L, D270E & N421KR292P & Y300LF243L, Y300L & P396LF243L, R255L, D270E & P396LR292P & V305IP247L, D270E & N421KF243L, D270E, G316D & R416GR292P & P396LR255L, D270E & P396LF243L, D270E, K392T & P396LY300L & P396LD270E, G316D & R416GF243L, D270E, P396L & Q419HP396L & Q419HD270E, K392T & P396LF243L, R292P, Y300L, & P396LD270E, P396L & Q419HF243L, R292P, V305I & P396LV284M, R292L & K370NP247L, D270E, Y300L & N421KR292P, Y300L & P396LR255L, D270E, R292G & P396LR255L, D270E, Y300L & P396LD270E, G316D, P396L & R416GRatio of Affinities<1Y300LF243L & P396LF243L, R292P & V305IP396LP247L & N421KR255L & P396LR292P & V305IK392T & P396LP396L & Q419HIn a specific embodiment, in variant Fc Regions, any amino acid modifications (e.g., substitutions) at any of positions 235, 240, 241, 243, 244, 247, 262, 263, 269, 298, 328, or 330and preferably one or more of the following residues: A240, I240, L241, L243, H244, N298, I328 or V330. In a different specific embodiment, in variant Fc Regions, any amino acid modifications (e.g., substitutions) at any of positions 268, 269, 270, 272, 276, 278, 283, 285, 286, 289, 292, 293, 301, 303, 305, 307, 309, 331, 333, 334, 335, 337, 338, 340, 360, 373, 376, 416, 419, 430, 434, 435, 437, 438 or 439 and preferably one or more of the following residues: H280, Q280, Y280, G290, S290, T290, Y290, N294, K295, P296, D298, N298, P298, V298, I300 or L300.In a preferred embodiment, in variant Fc Regions that bind an FcyR with an altered affinity, any amino acid modifications (e.g., substitutions) at any of positions 255, 256, 258, 267, 268, 269, 270, 272, 276, 278, 280,283, 285, 286, 289, 290, 292, 293, 294, 295, 296, 298, 300, 301, 303, 305, 307, 309, 312, 320, 322, 326, 329, 330, 332, 331, 333, 334, 335, 337, 338, 339, 340, 359, 360, 373, 376, 416, 419, 430, 434, 435, 437, 438 or 439. Preferably, the variant Fc Region has any of the following residues: A256, N268, Q272, D286, Q286, S286, A290, S290, A298, M301, A312, E320, M320, Q320, R320, E322, A326, D326, E326, N326, S326, K330, T339, A333, A334, E334, H334, L334, M334, Q334, V334, K335, Q335, A359, A360 or A430.In a different embodiment, in variant Fc Regions that bind an FcyR (via its Fc Region) with a reduced affinity, any amino acid modifications (e.g., substitutions) at any of positions 252, 254, 265, 268, 269, 270, 278, 289, 292, 293, 294, 295, 296, 298, 300, 301, 303, 322, 324, 327, 329, 333, 335, 338, 340, 373, 376, 382, 388, 389, 414, 416, 419, 434, 435, 437, 438 or 439.In a different embodiment, in variant Fc Regions that bind an FcyR (via its Fc Region) with an enhanced affinity, any amino acid modifications (e.g., substitutions) at any of positions 280, 283, 285, 286, 290, 294, 295, 298, 300, 301, 305, 307, 309, 312, 315, 331, 333, 334, 337, 340, 360, 378, 398 or 430. In a different embodiment, in variant Fc Regions that binds FcyRIIA with an enhanced affinity, any of the following residues: A255, A256, A258, A267, A268, N268, A272, Q272, A276, A280, A283, A285, A286, D286, Q286, S286, A290, S290, M301, E320, M320, Q320, R320, E322, A326, D326, E326, S326, K330, A331, Q335, A337 or A430.Preferred variants include one or more modifications at any of positions: 228, 230, 231, 232, 233, 234, 235, 239, 240, 241, 243, 244, 245, 247, 262, 263, 264, 265, 266, 271, 273, 275, 281, 284, 291, 296, 297, 298, 299, 302, 304, 305, 313, 323, 325, 326, 328, 330 or 332.Particularly preferred variants include one or more modifications selected from groups A-AI:A228E, 228K, 228Y or 228G;B230A, 230E, 230Y or 230G;C231E, 231K, 231Y, 231P or 231G;D232E, 232K, 232Y, 232G;E233D;F234I or 234F;G235D, 235Q, 235P, 235I or 235V;H239D, 239E, 239N or 239Q;I240A, 240I, 240M or 240T;J243R, 243, 243Y, 243L, 243Q, 243W, 243H or 243I;K244H;L245A;M247G, 247V or 247L;N262A, 262E, 262I, 262T, 262E or 262F;O263A, 263I, 263M or 263T;P264F, 264E, 264R, 264I, 264A, 264T or 264W;Q265F, 265Y, 265H, 265I, 265L, 265T, 265V, 265N or 265Q;R266A, 266I, 266M or 266T;S271D, 271E, 271N, 271Q, 271K, 271R, 271S, 271T, 271H, 271A, 271V, 271L, 2711, 271F, 271M, 271Y, 271W or 271G;T273I;U275L or 275W;V281D, 281K, 281Y or 281P;W284E, 284N, 284T, 284L, 284Y or284M;X291D, 291E, 291Q, 291T, 291H, 291I or 291G;Y299A, 299D, 299E, 299F, 299G, 299H, 299I, 299K, 299L, 299M, 299N, 299P, 299Q, 299R, 299S, 299V, 299W or 299Y;Z3021;AA304D, 304N, 304T, 304H or 304LAB3051;AC313F;AD323I;AE325A, 325D, 325E, 325G, 325H, 325I, 325L, 325K, 325R, 325S, 325F, 325M, 325T, 325V, 325Y, 325W or 325P;AF328D, 328Q, 328K, 328R, 328S, 328T, 328V, 328I, 328Y, 328W, 328P, 328G, 328A, 328E, 328F, 328H, 328M or 328N;AG330L, 330Y, 330I or 330V;AH332A, 332D, 332E, 332H, 332N, 332Q, 332T, 332K, 332R, 332S, 332V, 332L, 332F, 332M, 332W, 332P, 332G or 332Y; andAI336E, 336K or 336YStill more particularly preferred variants include one or more modifications selected from Groups 1-105:GroupVariantGroupVariant1A330L /I332E54S239D / D265L / N297D / I332E2D265F / N297E / I332E55S239D / D265T / N297D / I332E3D265Y / N297D / I332E56S239D / D265V / N297D / I332E4D265Y / N297D / T299L / I332E57S239D / D265Y / N297D / I332E5F241E / F243Q / V262T / V264F58S239D / I332D6F241E / F243Q / V262T / V264E / I332E59S239D / I332E7F241E / F243R / V262E / V264R60S239D / I332E / A330I8F241E / F243R / V262E / V264R / I332E61S239D / I332N9F241E / F243Y / V262T / V264R62S239D / I332Q10F241E / F243Y / V262T / V264R / I332E63S239D / N297D / I332E11F241L / F243L / V262I / V264I64S239D / N297D / I332E / A330Y12F241L / V262I65S239D / N297D / I332E / A330Y / F241S / F243H / V262T / V264T13F241R / F243Q / V262T / V264R66S239D / N297D / I332E / K326E14F241R / F243Q / V262T / V264R / I332E67S239D / N297D / I332E / L235D15F241W/F243W/V262A/ V264A68S239D / S298A / I332E16F241Y / F243Y / V262T / V264T69S239D / V264I / A330L / I332E17F241Y / F243Y / V262T / V264T / N297D / I332E70S239D / V264I / I332E18F243L / V262I / V264W71S239D / V264I / S298A / I332E19P243L / V264I72S239E / D265N20L328D / I332E73S239E / D265Q21L328E / I332E74S239E / I332D22L328H / I332E75S239E / I332E23L328I / I332E76S239E / I332N24L328M / I332E77S239E / I332Q25L328N / I332E78S239E / N297D / I332E26L328Q / I332E79S239E / V264I / A330Y / I332 E27L328T /I332E80S239E / V264I / I332 E28L328V / I332E81S239E / V264I / S298A / A330Y / I332E29N297D / A330Y / I332E82S239N / A330L / I332E30N297D / I332E83S239N / A330Y / I332E31N297D / I332E / S239D / A330L84S239N / I332D32N297D / S298A / A330Y / I 332E85S239N / I332E33N297D / T299L / I332E86S239N / I332N34N297D / T299F / I332E / N297D / T299H / I332E87S239N / I332Q35N297D / T299I / I332E88S239N1S298A / I332E36N297D / T299L / I332E89S239Q / I332D37N297D / T299V / I332E90S239Q / I332E38N297E / I332E91S239Q / I332N39N297S / I332E92S239Q / I332Q40P230A / E233D / I332E93S239Q / V264I / I332E41P244H / P245A / P247V94S298A / I332E42S239D / A330L / I332E95V264E / N297D / I332E43S239D / A330Y / I332E96V264I / A330L / I332E44S239D / A330Y / I332E / K326E97V264I / A330Y / I332E45S239D / A330Y / I332E / K326T98V264I / I332E46S239D / A330Y / I332E / L234I99V264I / S298A / I332E47S239D / A330Y / I332E / L235D100Y296D / N297D / I332E48S239D / A330Y / I332E / V240I101Y296E / N297D / I332 E49S239D / A330Y / I332E / V264T102Y296H / N297D / I332E50S239D / A330Y / I332E / V266I103Y296N / N297D / I332E51S239D / D265F / N297D / I332E104Y296Q / N297I / I332E52S239D / D265H / N297D / I332E105Y296T / N297D / I332E53S239D / D265I / N297D / I332EIn one embodiment, a PD-1-binding molecule of the invention, as defined by and for use in accordance with claims 1-6, will comprise a variant Fc Region having at least one modification in the Fc Region. In certain embodiments, the variant Fc Region comprises at least one substitution selected from the group consisting of L235V, F243L, R292P, Y300L, V305I, and P396L.In a specific embodiment, the variant Fc Region comprises:(A) at least one substitution selected from the group consisting of F243L, R292P, Y300L, V305I, and P396L;(B) at least two substitutions selected from the group consisting of:(1) F243L and P396L;(2) F243L and R292P; and(3) R292P and V305I;(C) at least three substitutions selected from the group consisting of:(1) F243L, R292P and Y300L;(2) F243L, R292P and V305I;(3) F243L, R292P and P396L; and(4) R292P, V305I and P396L;(D) at least four substitutions selected from the group consisting of:(1) F243L, R292P, Y300L and P396L; and(2) F243L, R292P, V305I and P396L; or(E) at least the five substitutions selected from the group consisting of:(1) F243L, R292P, Y300L, V305I and P396L; and(2) L235V, F243L, R292P, Y300L and P396L.In another specific embodiment, the variant Fc Region comprises substitutions of:(A) F243L, R292P, and Y300L;(B) L235V, F243L, R292P, Y300L, and P396L; or(C) F243L, R292P, Y300L, V305I, and P396L.In one embodiment, a PD-1-binding molecule of the invention, as defined by and for use in accordance with claims 1-6, comprises a variant Fc Region that exhibits decreased(or substantially no) binding to FcyRIA (CD64), FcyRIIA (CD32A), FcyRIIB (CD32B), FcyRIIIA (CD16a) or FcyRIIIB (CD16b) (relative to the binding exhibited by the wild-type IgG1 Fc Region(SEQ ID NO:1)).In one embodiment, a PD-1-binding molecule of the invention, as defined by and for use in accordance with claims 1-6, will comprise a variant Fc Region that exhibits reduced (or substantially no) binding to an FcyR (e.g., FcyRIIIA) and reduced (or substantially no) ADCC effector function. In certain embodiments, the variant Fc Region comprises at least one substitution selected from the group consisting of L234A, L235A, D265A,N297Q, and N297G. In a specific embodiment, the variant Fc Region comprises the substitution of L234A; L235A; L234A and L235A; D265A; N297Q, or N297G.A preferred IgG1 sequence for the CH2 and CH3 Domains of the PD-1-binding molecules of the invention will have the L234A/L235A substitutions(SEQ ID NO:5):wherein, x is a lysine (K) or is absent.In a different embodiment, a PD-1-binding molecule of the invention, as defined by and for use in accordance with claims 1-6, comprises an Fc Region which inherently exhibits decreased (or substantially no) binding to FcyRIIIA (CD16a) and/or reduced effector function (relative to the binding exhibited by the wild-type IgG1 Fc Region(SEQ ID NO:1)).In a specific embodiment, a PD-1-binding molecule of the present invention, as defined by and for use in accordance with claims 1-6, comprises an IgG2 Fc Region(SEQ ID NO:2)or an IgG4Fc Region(SEQ ID:NO:4).When an IgG4 Fc Region in utilized, the instant invention also encompasses the introduction of a stabilizing mutation, such the IgG4 hinge region S228P substitution (see,e.g.,SEQ ID NO:13:ESKYGPPCPPCP, (Lu et al., (2008) "The Effect Of A Point Mutation On The Stability Of Igg4 As Monitored By Analytical Ultracentrifugation," J. Pharmaceutical Sciences 97:960-969) to reduce the incidence of strand exchange. Other stabilizing mutations known in the art may be introduced into an IgG4 Fc Region (Peters, P et al., (2012) "Engineering an Improved IgG4 Molecule with Reduced Disulfide Bond Heterogeneity and Increased Fab Domain Thermal Stability," J. Biol. Chem., 287:24525-24533;PCT Patent Publication No: WO 2008/145142).In other embodiments, the invention encompasses the use of any variant Fc Region known in the art, such as those disclosed inJefferis, B.J. et al. (2002) "Interaction Sites On Human IgG-Fc For FcgammaR: Current Models," Immunol. Lett. 82:57-65;Presta, L.G. et al. (2002) "Engineering Therapeutic Antibodies For Improved Function," Biochem. Soc. Trans. 30:487-90;Idusogie, E.E. et al. (2001) "Engineered Antibodies With Increased Activity To Recruit Complement," J. Immunol. 166:2571-75;Shields, R.L. et al. (2001) "High Resolution Mapping Of The Binding Site On Human IgG1 For Fc Gamma RI, Fc Gamma RII, Fc Gamma RIII, And FcRn And Design Of IgG1 Variants With Improved Binding To The Fc gamma R," J. Biol. Chem. 276:6591-6604;Idusogie, E.E. et al. (2000) "Mapping Of The C1q Binding Site On Rituxan, A Chimeric Antibody With A Human IgG Fc," J. Immunol. 164:4178-84;Reddy, M.P. et al. (2000) "Elimination Of Fc Receptor-Dependent Effector Functions Of A Modified IgG4 Monoclonal Antibody To Human CD4," J. Immunol. 164:1925-1933;Xu, D. et al. (2000) "In Vitro Characterization of Five Humanized OKT3 Effector Function Variant Antibodies," Cell. Immunol. 200:16-26;Armour, K.L. et al. (1999) "Recombinant human IgG Molecules Lacking Fcgamma Receptor I Binding And Monocyte Triggering Activities," Eur. J. Immunol. 29:2613-24;Jefferis, R. et al. (1996) "Modulation Of Fc(Gamma)R And Human Complement Activation By IgG3-Core Oligosaccharide Interactions," Immunol. Lett. 54:101-04;Lund, J. et al. (1996) "Multiple Interactions Of IgG With Its Core Oligosaccharide Can Modulate Recognition By Complement And Human Fc Gamma Receptor I And Influence The Synthesis Of Its Oligosaccharide Chains," J. Immunol. 157:4963-4969;Hutchins et al. (1995) "Improved Biodistribution, Tumor Targeting, And Reduced Immunogenicity In Mice With A Gamma 4 Variant Of Campath-1H," Proc. Natl. Acad. Sci. (U.S.A.) 92:11980-84;Jefferis, R. et al. (1995) "Recognition Sites On Human IgG For Fc Gamma Receptors: The Role Of Glycosylation," Immunol. Lett. 44:111-17;Lund, J. et al. (1995) "Oligosaccharide-Protein Interactions In IgG Can Modulate Recognition By FcGamma Receptors," FASEB J. 9:115-19;Alegre, M.L. et al. (1994) "A Non-Activating "Humanized" Anti-CD3 Monoclonal Antibody Retains Immunosuppressive Properties In Vivo," Transplantation 57:1537-1543;Lund et al. (1992) "Multiple Binding Sites On The CH2 Domain Of IgG For Mouse Fc Gamma R11," Mol. Immunol. 29:53-59;Lund et al. (1991) "Human Fc Gamma RI And Fc Gamma RII Interact With Distinct But Overlapping Sites On Human IgG," J. Immunol. 147:2657-2662;Duncan, A.R. et al. (1988) "Localization Of The Binding Site For The Human High-Affinity Fc Receptor On IgG," Nature 332:563-564;US PatentNos. 5,624,821;5,885,573;6,194,551;7,276,586; and7,317,091; andPCT Publications WO 00/42072andPCT WO 99/58572.In some embodiments, the molecules of the invention, as defined by and for use in accordance with claims 1-6, may further comprise one or more glycosylation sites, so that one or more carbohydrate moieties are covalently attached to the molecule. Preferably, the molecules of the invention with one or more glycosylation sites and/or one or more modifications in the Fc Region confer or have an enhanced antibody mediated effector function,e.g., enhanced ADCC activity, compared to the unmodified antibody. In some embodiments, the invention further comprises molecules comprising one or more modifications of amino acids that are directly or indirectly known to interact with a carbohydrate moiety of the Fc Region, including but not limited to amino acids at positions 241, 243, 244, 245, 245, 249, 256, 258, 260, 262, 264, 265, 296, 299, and 301. Amino acids that directly or indirectly interact with a carbohydrate moiety of an Fc Region are known inthe art,see, e.g.,Jefferis et al., 1995 Immunology Letters, 44: 111-7.In another embodiment, the invention encompasses molecules that have been modified by introducing one or more glycosylation sites into one or more sites of the molecules, preferably without altering the functionality of the molecules,e.g., binding activity to target antigen or FcyR. Glycosylation sites may be introduced into the variable and/or constant region of the molecules of the invention. As used herein, "glycosylation sites" include any specific amino acid sequence in an antibody to which an oligosaccharide (i.e., carbohydrates containing two or more simple sugars linked together) will specifically and covalently attach. Oligosaccharide side chains are typically linked to the backbone of an antibody via either N-or O-linkages. N-linked glycosylation refers to the attachment of an oligosaccharide moiety to the side chain of an asparagine residue. O-linked glycosylation refers to the attachment of an oligosaccharide moiety to a hydroxyamino acid,e.g.,serine, threonine. The molecules of theinvention, as defined by and for use in accordance with claims 1-6, may comprise one or more glycosylation sites, including N-linked and O-linked glycosylation sites. Any glycosylation site for N-linked or O-linked glycosylation known in the art may be used in accordance with the instant invention. An exemplary N-linked glycosylation site that is useful in accordance with such methods is the amino acid sequence: Asn-X-Thr/Ser, wherein X may be any amino acid and Thr/Ser indicates a threonine or a serine. Such a site or sites may be introduced into a molecule of the invention using methods well known in the art (see for example,IN VITRO MUTAGENESIS, RECOMBINANT DNA: A SHORT COURSE, J. D. Watson, et al. W.H. Freeman and Company, New York, 1983, chapter 8, pp. 106-116.) An exemplary method for introducing a glycosylation site into a molecule of the invention may comprise: modifying or mutating an amino acid sequence of the molecule so that the desired Asn-X-Thr/Ser sequence is obtained.Methods for modifying the carbohydrate content of antibodies (and molecules comprising antibody domains,e.g.,Fc Region) are well known in the art,see, e.g.,U.S. Patent No. 6,218,149;EP 0 359 096 B1; U.S. Publication No.US 2002/0028486;WO 03/035835;U.S. Publication No. 2003/0115614;U.S. Patent No. 6,218,149;U.S. Patent No. 6,472,511. Methods of modifying the carbohydrate content of a molecule of the invention, as defined by and for use in accordance with claims 1-6, include deleting one or more endogenous carbohydrate moieties of the molecule or shifting the glycosylation site of the Fc Region of an antibody, by modifying positions adjacent to 297. Position 296 may be modified so that position 296 and not position 297 is glycosylated.Effector function can also be modified by techniques such as by introducing one or more cysteine residues into the Fc Region, thereby allowing interchain disulfide bond formation in this region to occur, resulting in the generation of a homodimeric antibody that may have improved internalization capability and/or increased complement-mediated cell killing and ADCC (Caron, P.C. et al. (1992) "Engineered Humanized Dimeric Forms Of IgG Are More Effective Antibodies," J. Exp. Med. 176:1191-1195;Shopes, B. (1992) "A Genetically Engineered Human IgG Mutant With Enhanced Cytolytic Activity," J. Immunol. 148(9):2918-2922. Homodimeric antibodies with enhanced antitumor activity may also be prepared using heterobifunctional cross-linkers as described inWolff, E.A. et al. (1993) "Monoclonal Antibody Homodimers: Enhanced Antitumor Activity In Nude Mice," Cancer Research 53:2560-2565. Alternatively, an antibody can be engineered which has dual Fc Regions and may thereby have enhanced complement lysis and ADCC capabilities (Stevenson,G.T. et al. (1989) "A Chimeric Antibody With Dual Fc Regions (bisFabFc) Prepared By Manipulations At The IgG Hinge," Anti-Cancer Drug Design 3:219-230).The serum half-life of the molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprising Fc Regions may be increased by increasing the binding affinity of the Fc Region for FcRn. The term "half-life" as used herein means a pharmacokinetic property of a molecule that is a measure of the mean survival time of the molecules following their administration. Half-life can be expressed as the time required to eliminate fifty percent (50%) of a known quantity of the molecule from a subject's body(e.g.,human patient or other mammal) or a specific compartment thereof, for example, as measured in serum, i.e., circulating half-life, or in other tissues. In general, an increase in half-life results in an increase in mean residence time (MRT) in circulation for the molecule administered.In some embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, wherein said variant Fc Region comprises at least one amino acid modification relative to a wild-type Fc Region, such that said molecule has an increased half-life (relative to a wild-type Fc Region).In some embodiments, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise a variant Fc Region, wherein said variant Fc Region comprises a half-live extending amino acid substitution at one or more positions selected from the group consisting of 238, 250, 252, 254, 256, 257, 256, 265, 272, 286, 288, 303, 305, 307, 308, 309, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 413, 424, 428, 433, 434, 435, and 436 . Numerous specific mutations capable of increasing the half-life of an Fc Region-containing molecule are known in the art and include, for example M252Y, S254T, T256E, and combinations thereof. For example, see the mutations described inU.S. PatentNos. 6,277,375,7,083,784;7,217,797,8,088,376;U.S. PublicationNos. 2002/0147311;2007/0148164; and International Publication Nos.WO 98/23289;WO 2009/058492; andWO 2010/033279. Fc Region-containing molecules with enhanced half-life also include those with substitutions at two or more of Fc Region residues 250, 252, 254, 256, 257, 288, 307, 308, 309, 311, 378, 428, 433, 434, 435 and 436. In particular, two or more substitutions selected from: T250Q, M252Y, S254T, T256E, K288D, T307Q, V308P, A378V, M428L, N434A, H435K, and Y436I.In a specific embodiment, the variant Fc Region comprises substitutions of:(A) M252Y, S254T and T256E;(B) M252Y and S254T;(C) M252Y and T256E;(D) T250Q and M428L;(E) T307Q and N434A;(F) A378V and N434A;(G) N434A and Y436I;(H) V308P and N434A; or(I) K288D and H435K.Variant Fc Regions may comprise:(A) one or more mutations which alter effector function and/or FcyR; and(B) one or more mutations which extend serum half-life.VI. Bispecific Anti-Human PD-1-Binding MoleculesDisclosed but not claimed are bispecific binding molecules that are capable of binding to a"first epitope"and a"second epitope,"wherein the first epitope is an epitope of human PD-1 and the second epitope is the same or a different epitope of PD-1, or is an epitope of another molecule that is present on the surface of an immune cell (such as a T lymphocyte) and is involved in regulating an immune checkpoint. In one instance, the second epitope is an epitope of B7-H3, B7-H4, BTLA, CD3, CD8, CD16, CD27, CD32, CD40, CD40L, CD47, CD64, CD70, CD80, CD86, CD94, CD137, CD137L, CD226, CTLA-4, Galectin-9, GITR, GITRL, HHLA2, ICOS, ICOSL, KIR, LAG-3, LIGHT, MHC class I or II, NKG2a, NKG2d, OX40, OX40L, PD1H, PD-1, PD-L1, PD-L2, PVR, SIRPa, TCR, TIGIT, TIM-3 or VISTA. In one instance, the second epitope not an epitope of PD-1. In a specific instance, the second epitope is CD137, CTLA-4, LAG-3, OX40, TIGIT, or TIM-3. In certain instances, a bispecific molecule comprises more than two epitope binding sites. Such bispecific molecules may bind two or more different epitopes of LAG-3 and at least one epitope of a molecule that is not LAG-3.Bispecific antibodies may be capable of simultaneously binding to PD-1 and the second epitope(e.g.B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In some instances, the bispecific antibody capable of simultaneously binding to PD-1 and the second epitope isproduced using any of the methods described inPCT Publication Nos. WO 1998/002463,WO 2005/070966,WO 2006/107786WO 2007/024715,WO 2007/075270,WO 2006/107617,WO 2007/046893,WO 2007/146968,WO 2008/003103,WO 2008/003116,WO 2008/027236,WO 2008/024188,WO 2009/132876,WO 2009/018386,WO 2010/028797,WO2010028796,WO 2010/028795,WO 2010/108127,WO 2010/136172,WO 2011/086091,WO 2011/133886,WO 2012/009544,WO 2013/003652,WO 2013/070565,WO 2012/162583,WO 2012/156430,WO 2013/174873, andWO 2014/022540.A. Bispecific Diabodies Lacking Fc RegionsDisclosed but not claimed are bispecific diabodies that comprise, and most preferably are composed of, a first polypeptide chain and a second polypeptide chain, whose sequences permit the polypeptide chains to covalently bind to each other to form a covalently associated diabody that is capable of simultaneously binding to a first epitope and a second epitope, such epitopes not being identical to one another. Such bispecific diabodies thus comprise"VL1"/"VH1"domains that are capable of binding to the first epitope and"VL2"/"VH2"domains that are capable of binding to the second epitope. The notation"VL1"and"VH1"denote respectively, the Variable Light Chain Domain and Variable Heavy Chain Domain that bind the "first" epitope of such bispecific diabody. Similarly, the notation"VL2"and"VH2"denote respectively, the Variable Light Chain Domain and Variable Heavy Chain Domain that bind the "second" epitope of such bispecific diabody. It is irrelevant whether a particular epitope is designated as the first vs. the second epitope; such notation having relevance only with respect to the presence and orientation of domains of the polypeptide chains of the binding moleucles. One of such epitopes is an epitope of PD-1 and the other of such epitopes is not an epitope of PD-1 (for example, an epitope of B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).The VL Domain of the first polypeptide chain interacts with the VH Domain of the second polypeptide chain to form a first functional antigen-binding site that is specific for a first antigen(i.e.,either PD-1 or an antigen that contains the second epitope). Likewise, the VL Domain of the second polypeptide chain interacts with the VH Domain of the first polypeptide chain in order to form a second functional antigen-binding site that is specific for a second antigen(i.e.,either an antigen that contains the second epitope or PD-1). Thus, the selection of the VL and VH Domains of the first and second polypeptide chains is coordinated,such that the two polypeptide chains of the diabody collectively comprise VL and VH Domains capable of binding to both an epitope of PD-1 and to the second epitope(i.e.,they comprise VLPD-1/VHPD-1and VL2/VH2, wherein PD-1 is the "first" epitope, or VL1/VH1 and VLPD-1/VHPD-1, wherein PD-1 is the "second" epitope).The first polypeptide chain of an instance of such bispecific diabodies comprises, in the N-terminal to C-terminal direction, an N-terminus, the VL1 Domain of a monoclonal antibody capable of binding to either the first or second epitope (i.e., either VLPD-1or VLEpitope 2), a first intervening spacer peptide (Linker 1), a VH2 Domain of a monoclonal antibody capable of binding to either the second epitope (if such first polypeptide chain contains VLPD-1) or the first epitope (if such first polypeptide chain contains VLEpitope 2), a second intervening spacer peptide (Linker 2) optionally containing a cysteine residue, a Heterodimer-Promoting Domain and a C-terminus(Figure 1).The second polypeptide chain of this instance of bispecific diabodies comprises, in the N-terminal to C-terminal direction, an N-terminus, a VL2 Domain of a monoclonal antibody capable of binding to either PD-1 or the second epitope (i.e., either VLPD-1or VLEpitope 2, and being the VL Domain not selected for inclusion in the first polypeptide chain of the diabody), an intervening linker peptide (Linker 1), a VH1 Domain of a monoclonal antibody capable of binding to either the second epitope (if such second polypeptide chain contains VLPD-1) or to PD-1 (if such second polypeptide chain contains VLEpitope 2), a second intervening spacer peptide (Linker 2) optionally containing a cysteine residue, a Heterodimer-Promoting Domain, and a C-terminus(Figure 1).Most preferably, the length of the intervening linker peptide (e.g., Linker 1) that separates such VL and VH Domains is selected to substantially or completely prevent the VL and VH Domains of the polypeptide chain from binding to one another. Thus the VL and VH Domains of the first polypeptide chain are substantially or completely incapable of binding to one another. Likewise, the VL and VH Domains of the second polypeptide chain are substantially or completely incapable of binding to one another. A preferred intervening spacer peptide (Linker 1) has the sequence(SEQ ID NO:14):GGGSGGGG.The length and composition of the second intervening linker peptide (Linker 2) is selected based on the choice of heterodimer-promoting domains. Typically, the second intervening linker peptide (Linker 2) will comprise 3-20 amino acid residues. In particular,where the heterodimer-promoting domains do not comprise a cysteine residue a cysteine-containing second intervening linker peptide (Linker 2) is utilized. A cysteine-containing second intervening spacer peptide (Linker 2) will contain 1, 2, 3 or more cysteines. A preferred cysteine-containing spacer peptide (Linker 2) has the sequence isSEQ ID NO:15:GGCGGG. Alternatively, Linker 2 does not comprise a cysteine (e.g., GGG, GGGS(SEQ ID NO:29),LGGGSG(SEQ ID NO:261),GGGSGGGSGGG(SEQ ID NO:262),ASTKG(SEQ ID NO:30),LEPKSS(SEQ ID NO:33),APSSS(SEQ ID NO:34),etc.)and a Cysteine-Containing Heterodimer-Promoting Domain, as described below is used. Optionally, both a cysteine-containing Linker 2 and a cysteine-containing Heterodimer-Promoting Domain are used.The Heterodimer-Promoting Domains may be GVEPKSC(SEQ ID NO:16)or VEPKSC(SEQ ID NO:17)or AEPKSC(SEQ ID NO:18)on one polypeptide chain and GFNRGEC(SEQ ID NO:19)or FNRGEC(SEQ ID NO:20)on the other polypeptide chain (US2007/0004909).More preferably, however, the Heterodimer-Promoting Domains of such diabodies are formed from one, two, three or four tandemly repeated coil domains of opposing charge that comprise a sequence of at least six, at least seven or at least eight amino acid residues such that the Heterodimer-Promoting Domain possesses a net charge (Apostolovic, B. et al. (2008) "pH-Sensitivity of the E3/K3 Heterodimeric Coiled Coil," Biomacromolecules 9:3173-3180;Arndt, K.M. et al. (2001) "Helix-stabilized Fv (hsFv) Antibody Fragments: Substituting the Constant Domains of a Fab Fragment for a Heterodimeric Coiled-coil Domain," J. Molec. Biol. 312:221-228;Arndt, K.M. et al. (2002) "Comparison of In Vivo Selection and Rational Design of Heterodimeric Coiled Coils," Structure 10:1235-1248;Boucher, C. et al. (2010) "Protein Detection By Western Blot Via Coiled-Coil Interactions," Analytical Biochemistry 399:138-140;Cachia, P.J. et al. (2004) "Synthetic Peptide Vaccine Development: Measurement Of Polyclonal Antibody Affinity And Cross-Reactivity Using A New Peptide Capture And Release System For Surface Plasmon Resonance Spectroscopy," J. Mol. Recognit. 17:540-557;De Crescenzo, G.D. et al. (2003) "Real-Time Monitoring of the Interactions of Two-Stranded de novo Designed Coiled-Coils: Effect of Chain Length on the Kinetic and Thermodynamic Constants of Binding," Biochemistry 42:1754-1763;Fernandez-Rodriquez, J. et al. (2012) "Induced Heterodimerization And Purification Of Two Target Proteins By A Synthetic Coiled-Coil Tag," Protein Science 21:511-519;Ghosh, T.S. et al. (2009) "End To End And End- To-Middle Interhelical Interactions: New Classes OfInteracting Helix Pairs In Protein Structures," Acta Crystallographica D65:1032-1041;Grigoryan, G. et al. (2008) "Structural Specificity In Coiled-Coil Interactions," Curr. Opin. Struc. Biol. 18:477-483;Litowski, J.R. et al. (2002) "Designing Heterodimeric Two-Stranded α-Helical Coiled-Coils: The Effects Of Hydrophobicity And α-Helical Propensity On Protein Folding, Stability, And Specificity," J. Biol. Chem. 277:37272-37279;Steinkruger, J.D. et al. (2012) "The d'--d--d' Vertical Triad is Less Discriminating Than the a'--a--a' Vertical Triad in the Antiparallel Coiled-coil Dimer Motif," J. Amer. Chem. Soc. 134(5):2626-2633;Straussman, R. et al. (2007) "Kinking the Coiled Coil - Negatively Charged Residues at the Coiled-coil Interface," J. Molec. Biol. 366:1232-1242;Tripet, B. et al. (2002) "Kinetic Analysis of the Interactions between Troponin C and the C-terminal Troponin I Regulatory Region and Validation of a New Peptide Delivery/Capture System used for Surface Plasmon Resonance," J. Molec. Biol. 323:345-362;Woolfson, D.N. (2005) "The Design Of Coiled-Coil Structures And Assemblies," Adv. Prot. Chem. 70:79-112;Zeng, Y. et al. (2008) "A Ligand-Pseudoreceptor System Based On de novo Designed Peptides For The Generation Of Adenoviral Vectors With Altered Tropism," J. Gene Med. 10:355-367).Such repeated coil domains may be exact repeats or may have substitutions. For example, the coil domain of the Heterodimer-Promoting Domain of the first polypeptide chain may comprise a sequence of eight amino acid residues selected to confer a negative charge to such Heterodimer-Promoting Domain, and the coil domain of the Heterodimer-Promoting Domain of the second polypeptide chain may comprise a sequence of eight amino acid residues selected to confer a positive charge to such Heterodimer-Promoting Domain. It is immaterial which coil is provided to the first or second polypeptide chains, provided that a coil of opposite charge is used for the other polypeptide chain. The positively charged amino acid may be lysine, arginine, histidine,etc.and/or the negatively charged amino acid may be glutamic acid, aspartic acid,etc.The positively charged amino acid is preferably lysine and/or the negatively charged amino acid is preferably glutamic acid. It is possible for only a single Heterodimer-Promoting Domain to be employed (since such domain will inhibit homodimerization and thereby promote heterodimerization), however, it is preferred for both the first and second polypeptide chains of the diabodies to contain Heterodimer-Promoting Domains.In a preferred instance, one of the Heterodimer-Promoting Domains will comprise four tandem "E-coil" helical domains (SEQ ID NO:21:EVAALEK-EVAALEK-EVAALEK-EVAALEK), whose glutamate residues will form a negative charge at pH 7, while the other ofthe Heterodimer-Promoting Domains will comprise four tandem "K-coil" domains(SEQ ID NO:22:KVAALKE-KVAALKE-KVAALKE-KVAALKE), whose lysine residues will form a positive charge at pH 7. The presence of such charged domains promotes association between the first and second polypeptides, and thus fosters heterodimer formation. Especially preferred is a Heterodimer-Promoting Domain in which one of the four tandem "E-coil" helical domains ofSEQ ID NO:21has been modified to contain a cysteine residue:EVAACEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:23).Likewise, especially preferred is a Heterodimer-Promoting Domain in which one of the four tandem "K-coil" helical domains ofSEQ ID NO:22has been modified to contain a cysteine residue:KVAACKE-KVAALKE-KVAALKE-KVAALKE(SEQ ID NO:24).As disclosed inWO 2012/018687, in order to improve thein vivopharmacokinetic properties of diabodies, a diabody may be modified to contain a polypeptide portion of a serum-binding protein at one or more of the termini of the diabody. Most preferably, such polypeptide portion of a serum-binding protein will be installed at the C-terminus of the diabody. Albumin is the most abundant protein in plasma and has a half-life of 19 days in humans. Albumin possesses several small molecule binding sites that permit it to non-covalently bind to other proteins and thereby extend their serum half-lives. The Albumin-Binding Domain 3 (ABD3) of protein G of Streptococcus strain G148 consists of 46 amino acid residues forming a stable three-helix bundle and has broad albumin-binding specificity (Johansson, M.U. et al. (2002) "Structure, Specificity, And Mode Of Interaction For Bacterial Albumin-Binding Modules," J. Biol. Chem. 277(10):8114-8120. Thus, a particularly preferred polypeptide portion of a serum-binding protein for improving thein vivopharmacokinetic properties of a diabody is the Albumin-Binding Domain (ABD) from streptococcal protein G, and more preferably, the Albumin-Binding Domain 3 (ABD3) of protein G ofStreptococcus dysgalactiaestrain G148(SEQ ID NO:25):LAEAKVLANR ELDKYGVSDY YKNLIDNAKS AEGVKALIDE ILAALP.As disclosed inWO 2012/162068,"deimmunized"variants ofSEQ ID NO:25have the ability to attenuate or eliminate MHC class II binding. Based on combinational mutation results, the following combinations of substitutions are considered to be preferred substitutions for forming such a deimmunized ABD: 66D/70S +71A; 66S/70S +71A; 66S/70S +79A; 64A/65A/71A; 64A/65A/71A+66S; 64A/65A/71A+66D; 64A/65A/71A+66E; 64A/65A/79A+66S; 64A/65A/79A+66D; 64A/65A/79A+66E. Variant ABDs having themodifications L64A, I65A and D79A or the modifications N66S, T70S and D79A. Variant deimmunized ABD having the amino acid sequence:LAEAKVLANR ELDKYGVSDY YKNLID66NAKS70A71EGVKALIDE ILAALP(SEQ ID NO:26),or the amino acid sequence:LAEAKVLANR ELDKYGVSDY YKNA64A65NNAKT VEGVKALIA79E ILAALP(SEQ ID NO:27),or the amino acid sequence:LAEAKVLANR ELDKYGVSDY YKNLIS66NAKS70VEGVKALIA79E ILAALP(SEQ ID NO:28),are particularly preferred as such deimmunized ABD exhibit substantially wild-type binding while providing attenuated MHC class II binding. Thus, the first polypeptide chain of such a diabody having an ABD contains a peptide linker preferably positioned C-terminally to the E-coil (or K-coil) Domain of such polypeptide chain so as to intervene between the E-coil (or K-coil) Domain and the ABD (which is preferably a deimmunized ABD). A preferred sequence for such a peptide linker isSEQ ID NO:29:GGGS.B. Bispecific Diabodies Containing Fc RegionsDisclosed but not claimed are bispecific diabodies comprising an Fc Region capable of simultaneously binding to PD-1 and a second epitope(e.g.B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-1, PD-L1, TCR, TIM-3,etc.).The addition of an IgG CH2-CH3 Domain to one or both of the diabody polypeptide chains, such that the complexing of the diabody chains results in the formation of an Fc Region, increases the biological half-life and/or alters the valency of the diabody. Incorporating an IgG CH2-CH3 Domains onto both of the diabody polypeptides will permit a two-chain bispecific Fc-Region-containing diabody to form(Figure 2).Alternatively, incorporating an IgG CH2-CH3 Domains onto only one of the diabody polypeptides will permit a more complex four-chain bispecific Fc Region-containing diabody to form(Figures 3A-3C).Figure 3Cshows a representative four-chain diabody possessing the Constant Light (CL) Domain and the Constant Heavy CH1 Domain, however fragments of such domains as well as other polypeptides may alternatively be employed (see,e.g.,Figures 3Aand3B,United States Patent Publications No. 2013-0295121;2010-0174053and2009-0060910; European Patent Publication No.EP 2714079;EP 2601216;EP 2376109;EP 2158221andPCT Publications No. WO 2012/162068;WO 2012/018687;WO 2010/080538). Thus, for example, in lieu of the CH1 Domain, one may employ a peptide having the amino acid sequence GVEPKSC(SEQ ID NO:16)VEPKSC(SEQ ID NO:17),or AEPKSC (SEQ ID NO:18), derived from the hinge domain of a human IgG, and in lieu of the CL Domain, one may employ the C-terminal 6 amino acids of the human kappa light chain, GFNRGEC(SEQ ID NO:19)or FNRGEC(SEQ ID NO:20).A representative peptide containing four-chain diabody is shown inFigure 3A.Alternatively, or in addition, one may employ a peptide comprising tandem coil domains of opposing charge such as the "E-coil" helical domains (SEQ ID NO:21:EVAALEK-EVAALEK-EVAALEK-EVAALEK orSEQ ID NO:23:EVAACEK-EVAALEK-EVAALEK-EVAALEK); and the "K-coil" domains(SEQ ID NO:22:KVAALKE-KVAALKE-KVAALKE-KVAALKE orSEQ ID NO:24:KVAACKE-KVAALKE-KVAALKE-KVAALKE). A representative coil domain containing four-chain diabody is shown inFigure 3B.The Fc Region-containing diabody molecules generally include additional intervening linker peptides (Linkers). Typically, the additional Linkers will comprise 3-20 amino acid residues. Additional or alternative linkers that may be employed in the Fc Region-containing diabody molecules include: GGGS(SEQ ID NO:29),LGGGSG(SEQ ID NO:261),GGGSGGGSGGG(SEQ ID NO:262),ASTKG(SEQ ID NO:30),DKTHTCPPCP(SEQ ID NO:31),EPKSCDKTHTCPPCP(SEQ ID NO:32),LEPKSS(SEQ ID NO:33),APSSS(SEQ ID NO:34),and APSSSPME(SEQ ID NO:35),LEPKSADKTHTCPPCSEQ ID NO:36),GGC, and GGG.SEQ ID NO:33may be used in lieu of GGG or GGC for ease of cloning. Additionally, the amino acids GGG, orSEQ ID NO:33may be immediately followed bySEQ ID NO:31to form the alternate linkers: GGGDKTHTCPPCP(SEQ ID NO:263);and LEPKSSDKTHTCPPCP(SEQ ID NO:37).Fc Region-containing diabody molecule may incorporate an IgG hinge region in addition to or in place of a linker. Exemplary hinge regions include: EPKSCDKTHTCPPCP(SEQ ID NO:32)from IgG1, ERKCCVECPPCP(SEQ ID NO:11)from IgG2, ESKYGPPCPSCP(SEQ ID NO:12)from IgG4, and ESKYGPPCPPCP(SEQ ID NO:13)an IgG4 hinge variant comprising a stabilizing substitute to reduce strand exchange.As highlighted inFigure 3A-3C,diabodies may comprise four different chains. The first and third polypeptide chains of such a diabody contain three domains: (i) a VL1-containing Domain, (ii) a VH2-containing Domain, (iii) Heterodimer-Promoting Domain and (iv) aDomain containing a CH2-CH3 sequence. The second and fourth polypeptide chains contain: (i) a VL2-containing Domain, (ii) a VH1-containing Domain and (iii) a Heterodimer-Promoting Domain, where the Heterodimer-Promoting Domains promote the dimerization of the first/third polypeptide chains with the second/fourth polypeptide chains. The VL and/or VH Domains of the third and fourth polypeptide chains, and VL and/or VH Domains of the first and second polypeptide chains may be the same or different so as to permit tetravalent binding that is either monospecific, bispecific or tetraspecific. The notation"VL3"and"VH3"denote respectively, the Variable Light Chain Domain and Variable Heavy Chain Domain that bind the "third" epitope of such diabody. Similarly, the notation"VL4"and"VH4"denote respectively, the Variable Light Chain Domain and Variable Heavy Chain Domain that bind the "fourth" epitope of such diabody. The general structure of the polypeptide chains of a representative four-chain Fc Region-containing diabodies is provided inTable 2:Table 2Bispecific2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH2ndChainNH2-VL2-VH1-HPD-COOHTetraspecific2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH3rdChainNH2-VL3-VH4-HPD-CH2-CH3-COOH4thChainNH2-VL4-VH3-HPD-COOHHPD = Heterodimer-Promoting DomainIn a specific instance, diabodies are bispecific, tetravalent (i.e., possess four epitope-binding sites), Fc-containing diabodies(Figures 3A-3C)that are composed of four total polypeptide chains. The bispecific, tetravalent, Fc-containing diabodies comprise two epitope-binding sites immunospecific for PD-1 (which may be capable of binding to the same epitope of PD-1 or to different epitopes of PD-1), and two epitope-binding sites specific for a second epitope(e.g.,B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In a further instance, the bispecific Fc Region-containing diabodies may comprise three polypeptide chains. The first polypeptide of such a diabody contains three domains: (i) a VL1-containing Domain, (ii) a VH2-containing Domain and (iii) a Domain containing a CH2-CH3 sequence. The second polypeptide of such diabodies contains: (i) a VL2-containingDomain, (ii) a VH1-containing Domain and (iii) a Domain that promotes heterodimerization and covalent bonding with the diabody's first polypeptide chain. The third polypeptide of such diabodies comprises a CH2-CH3 sequence. Thus, the first and second polypeptide chains of such diabodies associate together to form a VL1/VH1 binding site that iscapable of binding to the first epitope, as well as a VL2/VH2 binding site that is capable of binding to the second epitope. The first and second polypeptides are bonded to one another through a disulfide bond involving cysteine residues in their respective Third Domains. Notably, the first and third polypeptide chains complex with one another to form an Fc Region that is stabilized via a disulfide bond. Such diabodies have enhanced potency.Figures 4Aand4Billustrate the structures of such diabodies. Such Fc-Region-containing bispecific diabodies may have either of two orientations(Table 3):Table 3First Orientation3rdChainNH2-CH2-CH3-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH2ndChainNH2-VL2-VH1-HPD-COOHSecond Orientation3rdChainNH2-CH2-CH3-COOH1stChainNH2-CH2-CH3-VL1-VH2-HPD-COOH2ndChainNH2-VL2-VH1-HPD-COOHHPD = Heterodimer-Promoting DomainIn a specific instance, diabodies are bispecific, bivalent (i.e., possess two epitope-binding sites), Fc-containing diabodies(Figures 4A-4B)that are composed of three total polypeptide chains. The bispecific, bivalent Fc-containing diabodies of the disclosure comprise one epitope-binding site immunospecific for PD-1, and one epitope-binding site specific for a second epitope(e.g.,B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In a further instance, the bispecific Fc Region-containing diabodies may comprise a total of five polypeptide chains. In a particular instance, two of said five polypeptide chains have the same amino acid sequence. The first polypeptide chain of such diabodies contains: (i) a VH1-containing domain, (ii) a CH1-containing domain, and (iii) a Domain containing a CH2-CH3 sequence. The first polypeptide chain may be the heavy chain of an antibody that contains a VH1 and a heavy chain constant region. The second and fifth polypeptide chains of such diabodies contain: (i) a VL1-containing domain, and (ii) a CL-containing domain. Thesecond and/or fifth polypeptide chains of such diabodies may be light chains of an antibody that contains a VL1 complementary to the VH1 of the first/third polypeptide chain. The first, second and/or fifth polypeptide chains may be isolated from naturally occurring antibodies. Alternatively, they may be constructed recombinantly. The third polypeptide chain of such diabodies contains: (i) a VH1-containing domain, (ii) a CH1-containing domain, (iii) a Domaincontaining a CH2-CH3 sequence, (iv) a VL2-containing Domain, (v) a VH3-containing Domain and (vi) a Heterodimer-Promoting Domain, where the Heterodimer-Promoting Domains promote the dimerization of the third chain with the fourth chain. The fourth polypeptide of such diabodies contains: (i) a VL3-containing Domain, (ii) a VH2-containing Domain and (iii) a Domain that promotes heterodimerization and covalent bonding with the diabody's third polypeptide chain.Thus, the first and second, and the third and fifth, polypeptide chains of such diabodies associate together to form two VL1/VH1 binding sites capable of binding a first epitope. The third and fourth polypeptide chains of such diabodies associate together to form a VL2/VH2 binding site that is capable of binding to a second epitope, as well as a VL3/VH3 binding site that is capable of binding to a third epitope. The first and third polypeptides are bonded to one another through a disulfide bond involving cysteine residues in their respective constant regions. Notably, the first and third polypeptide chains complex with one another to form an Fc Region. Such diabodies have enhanced potency.Figure 5illustrates the structure of such diabodies. It will be understood that the VL1/VH1, VL2/VH2, and VL3/VH3 Domains may be the same or different so as to permit binding that is monospecific, bispecific or trispecific. However, as provided herein, these domains are preferably selected so as to bind PD-1 and a second epitope(e.g.,B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).The VL and VH Domains of the polypeptide chains are selected so as to form VL/VH binding sites specific for a desired epitope. The VL/VH binding sites formed by the association of the polypeptide chains may be the same or different so as to permit tetravalent binding that is monospecific, bispecific, trispecific or tetraspecific. In particular, the VL and VH Domains maybe selected such that a bispecific diabody may comprise two binding sites for a first epitope and two binding sites for a second epitope, or three binding sites for a first epitope and one binding site for a second epitope, or two binding sites for a first epitope, one binding site for a second epitope and one binding site for a third epitope (as depicted inFigure5).The general structure of the polypeptide chains of representative five-chain Fc Region-containing diabodies is provided inTable 4:Table 4Bispecific (2x2)2ndChainNH2-VL1-CL-COOH1stChainNH2-VH1-CH1-CH2-CH3-COOH3rdChainNH2-VH1-CH1-CH2-CH3-VL2-VH2-HPD-COOH5ndChainNH2-VL1-CL-COOH4thChainNH2-VL2-VH2-HPD-COOHBispecific (3x1)2ndChainNH2-VL1-CL-COOH1stChainNH2-VH1-CH1-CH2-CH3-COOH3rdChainNH2-VH1-CH1-CH2-CH3-VL1-VH2-HPD-COOH5ndChainNH2-VL1-CL-COOH4thChainNH2-VL2-VH1-HPD-COOHTrispecific (2x1x1)2ndChainNH2-VL1-CL-COOH1stChainNH2-VH1-CH1-CH2-CH3-COOH3rdChainNH2-VH1-CH1-CH2-CH3-VL2-VH3-HPD-COOH5ndChainNH2-VL1-CL-COOH4thChainNH2-VL3-VH2-HPD-COOHHPD = Heterodimer-Promoting DomainIn a specific instance, diabodies are bispecific, tetravalent (i.e., possess four epitope-binding sites), Fc-containing diabodies that are composed of five total polypeptide chains having two binding sites for a first epitope and two binding sites for a second epitope. In one instance, the bispecific, tetravalent, Fc-containing diabodies comprise two epitope-binding sites immunospecific for PD-1 (which may be capable of binding to the same epitope of PD-1 or to different epitopes of PD-1), and two epitope-binding sites specific for a second epitope(e.g.,B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In another instance, the bispecific, tetravalent, Fc-containing diabodies comprise three epitope-binding sites immunospecific for PD-1 which may be capable of binding to the same epitope of PD-1 or to different epitopes of PD-1), and one epitope-binding sites specific for a second epitope (e.g., B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In another instance, the bispecific, tetravalent, Fc-containing diabodies comprise one epitope-binding sites immunospecific for PD-1, and three epitope-binding sites specific fora second epitope(e.g.,B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).C. Bispecific Trivalent Binding Molecules Containing Fc RegionsDisclosed but not claimed are bispecific, trivalent binding molecules, comprising an Fc Region, and being capable of simultaneously binding to a first epitope, a second epitope and a third epitope, wherein at least one of such epitopes is not identical to another. Such bispecific diabodies thus comprise"VL1"/"VH1"domains that are capable of binding to the first epitope,"VL2"/"VH2"domains that are capable of binding to the second epitope and"VL3"/"VH3"domains that are capable of binding to the third epitope. In one instance, oneor two of such epitopes is an epitope of PD-1 and another (or the other) of such epitopes is not an epitope of PD-1 (for example, an epitope of B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-1, PD-L1, TCR, TIM-3,etc.).Such bispecific trivalent binding molecules comprise three epitope-binding sites, two of which are diabody-type binding domains, which provide binding Site A and binding Site B, and one of which is a non-diabody-type binding domain, which provides binding Site C (see,e.g.,Figures 6A-6F,and PCT Application No:PCT/US15/33081; andPCT/US15/33076).Typically, the trivalent binding molecules will comprise four different polypeptide chains (seeFigures 6A-6B),however, the molecules may comprise fewer or greater numbers of polypeptide chains, for example by fusing such polypeptide chains to one another (e.g., via a peptide bond) or by dividing such polypeptide chains to form additional polypeptide chains, or by associating fewer or additional polypeptide chains via disulfide bonds.Figures 6B-6Fillustrate this aspect by schematically depicting such molecules having three polypeptide chains. As provided inFigures 6A-6F,the trivalent binding molecules may have alternative orientations in which the diabody-type binding domains are N-terminal(Figures 6A,6Cand6D)or C-terminal(Figures 6B,6Eand6F)to an Fc Region.In certain instances, the first polypeptide chain of such trivalent binding molecules contains: (i) aVL1-containing Domain, (ii) aVH2-containing Domain, (iii) a Heterodimer-Promoting Domain, and (iv) a Domain containing a CH2-CH3 sequence. The VL1 and VL2 Domains are located N-terminal or C-terminal to the CH2-CH3-containing domain as presented inTable 5 (Figures 6Aand6B).The second polypeptide chain of such instances contains: (i) a VL2-containing Domain, (ii) a VH1-containing Domain, and (iii) a Heterodimer-Promoting Domain. The third polypeptide chain of such instances contains: (i) a VH3-containingDomain, (ii) a CH1-containing Domain and (iii) a Domain containing a CH2-CH3 sequence. The third polypeptide chain may be the heavy chain of an antibody that contains a VH3 and a heavy chain constant region. The fourth polypeptide of such instances contains: (i) a VL3-containing Domain and (ii) a CL-containing Domain. The fourth polypeptide chains may be a light chain of an antibody that contains a VL3 complementary to the VH3 of the third polypeptide chain. The third or fourth polypeptide chains may be isolated from naturally occurring antibodies. Alternatively, they may be constructed recombinantly, synthetically or by other means.The Variable Light Chain Domain of the first and second polypeptide chains are separated from the Variable Heavy Chain Domains of such polypeptide chains by an intervening spacer linker having a length that is too short to permit their VL1/VH2 (or their VL2/VH1) domains to associate together to form epitope-binding site capable of binding to either the first or second epitope. A preferred intervening spacer peptide (Linker 1) for this purpose has the sequence(SEQ ID NO:14):GGGSGGGG. Other Domains of the trivalent binding molecules may be separated by one or more intervening spacer peptides, optionally comprising a cysteine residue. Exemplary linkers useful for the generation of trivalent binding molecules are provided herein and are also provided in PCT Application Nos:PCT/US15/33081; andPCT/US15/33076. Thus, the first and second polypeptide chains of such trivalent binding molecules associate together to form a VL1/VH1 binding site capable of binding a first epitope, as well as a VL2/VH2 binding site that is capable of binding to a second epitope. The third and fourth polypeptide chains of such trivalent binding molecules associate together to form a VL3/VH3 binding site that is capable of binding to a third epitope. It will be understood that the VL1/VH1, VL2/VH2, and VL3/VH3 Domains may be the same or different so as to permit binding that is monospecific, bispecific or trispecific.As described above, the trivalent binding molecules may comprise three polypeptides. Trivalent binding molecules comprising three polypeptide chains may be obtained by linking the domains of the fourth polypeptide N-terminal to the VH3-containing Domain of the third polypeptide. Alternatively, a third polypeptide chain of a trivalent binding molecule containing the following three domains is utilized: (i) a VL3-containing Domain, (ii) a VH3-containing Domain, and (iii) a Domain containing a CH2-CH3 sequence, wherein the VL3 and VH3 are spaced apart from one another by an intervening spacer peptide that is sufficiently long (at least 9 or more amino acid residues) so as to allow the association of these domains to form an epitope-binding site.It will be understood that the VL1/VH1, VL2/VH2, and VL3/VH3 Domains may be the same or different so as to permit binding that is monospecific, bispecific or trispecific. However, as provided herein, these domains are preferably selected so as to bind PD-1 and a second epitope (or a second and third epitope) (preferably, such epitopes are epitopes of B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3 MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).In particular, the VL and VH Domains may be selected such that a trivalent binding molecule comprises two binding sites for a first epitope and one binding sites for a second epitope, or one binding site for a first epitope and two binding sites for a second epitope, or one binding site for a first epitope, one binding site for a second epitope and one binding site for a third epitope. The general structure of the polypeptide chains of representative trivalent binding molecules is provided inFigures 6A-6Fand inTable 5:Table 5Four Chain 1stOrientation2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH3rdChainNH2-VH3-CH1-CH2-CH3-COOH4thChainNH2-VL3-CL-COOHFour Chain 2ndOrientation2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-CH2-CH3--VL1-VH2-HPD COOH3rdChainNH2-VH3-CH1-CH2-CH3-COOH4thChainNH2-VL3-CL-COOHThree Chain 1stOrientation2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-VL1-VH2-HPD-CH2-CH3-COOH3rdChainNH2-VL3-VH3-HPD-CH2-CH3-COOHThree Chain 2ndOrientation2ndChainNH2-VL2-VH1-HPD-COOH1stChainNH2-CH2-CH3-VL1-VH2-HPD COOH3rdChainNH2-VL3-VH3-HPD-CH2-CH3-COOHHPD = Heterodimer-Promoting DomainOne instance relates to bispecific trivalent binding molecules that comprise two epitope-binding sites for PD-1 and one epitope-binding site for the second epitope present on a molecule other than PD-1 (e.g.B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).The two epitope-binding sites for PD-1 may bind the same epitope or different epitopes. Another instancerelates to bispecific trivalent binding molecules that comprise, one epitope-binding site for PD-1 and two epitope-binding sites that bind a second antigen present on a molecule other than PD-1 (e.g.B7-H3, B7-H4, BTLA, CD40, CD80, CD86, CD137, CTLA-4, ICOS, KIR, LAG-3, MHC class I or II, OX40, PD-L1, TCR, TIM-3,etc.).The two epitope-binding sites for the second antigen may bind the same epitope or different epitopes of the antigen(e.g.,the same or different epitopes of LAG-3). As provided above, such bispecific trivalent binding molecules may comprise three or four polypeptide chains.VII. Constant Domains and Fc RegionsProvided herein are antibody Constant Domains useful in the generation of the PD-1-binding molecules(e.g.,antibodies, diabodies, trivalent binding molecules,etc.).A preferred CL Domain is a human IgG CL Kappa Domain. The amino acid sequence of an exemplary human CL Kappa Domain is(SEQ ID NO:8):Alternatively, an exemplary CL Domain is a human IgG CL Lambda Domain. The amino acid sequence of an exemplary human CL Kappa Domain is(SEQ ID NO:9):As provided herein, the PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, may comprise an Fc Region. The Fc Region of such molecules of the invention may be of any isotype (e.g., IgG1, IgG2, IgG3, or IgG4). The PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, may further comprise a CH1 Domain and/or a hinge region. When present, the CH1 Domain and/or hinge region may be of any isotype (e.g., IgG1, IgG2, IgG3, or IgG4), and is preferably of the same isotype as the desired Fc Region.An exemplary CH1 Domain is a human IgG1 CH1 Domain. The amino acid sequence of an exemplary human IgG1 CH1 Domain is(SEQ ID NO:10):An exemplary CH1 Domain is a human IgG2 CH1 Domain. The amino acid sequence of an exemplary human IgG2 CH1 Domain is(SEQ ID NO:257):An exemplary CH1 Domain is a human IgG4 CH1 Domain. The amino acid sequence of an exemplary human IgG4 CH1 Domain is(SEQ ID NO:254):One exemplary hinge region is a human IgG1 hinge region. The amino acid sequence of an exemplary human IgG1 hinge region is(SEQ ID NO:32):EPKSCDKTHTCPPCP .Another exemplary hinge region is a human IgG2 hinge region. The amino acid sequence of an exemplary human IgG2 hinge region is(SEQ ID NO:11):ERKCCVECPPCP .Another exemplary hinge region is a human IgG4 hinge region. The amino acid sequence of an exemplary human IgG4 hinge region is(SEQ ID NO:12):ESKYGPPCPSCP . As described herein, an IgG4 hinge region may comprise a stabilizing mutation such as the S228P substitution. The amino acid sequence of an exemplary stabilized IgG4 hinge region is(SEQ ID NO:13):ESKYGPPCPPCP .The Fc Region of the Fc Region-containing molecules may be either a complete Fc Region (e.g., a complete IgG Fc Region) or only a fragment of an Fc Region. Optionally, the Fc Region of the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, lacks the C-terminal lysine amino acid residue. In particular, the Fc Region of the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, may be an engineered variant Fc Region Fc Regions of the bispecific Fc Region-containing molecules may possess the ability to bind to one or more Fc receptors (e.g., FcyR(s)), more preferably such variant Fc Region have altered binding to FcyRIA (CD64), FcyRIIA (CD32A), FcyRIIB (CD32B), FcyRIIIA (CD16a) or FcyRIIIB (CD16b) (relative to the binding exhibited by a wild-type Fc Region) or will have substantially reduced or no ability to bind to inhibitory receptor(s). The Fc Region of the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, may include some or all of the CH2 Domain and/or some or all of the CH3 Domain of a complete Fc Region, or may comprise a variant CH2 and/or a variant CH3sequence (that may include, for example, one or more insertions and/or one or more deletions with respect to the CH2 or CH3 domains of a complete Fc Region). Such Fc Regions may comprise non-Fc polypeptide portions, or may comprise portions of non-naturally complete Fc Regions, or may comprise non-naturally occurring orientations of CH2 and/or CH3 Domains (such as, for example, two CH2 domains or two CH3 domains, or in the N-terminal to C-terminal direction, a CH3 Domain linked to a CH2 Domain,etc.).Fc Region modifications identified as altering effector function are known in the art, including modifications that increase binding to activating receptors (e.g., FcyRIIA (CD16A) and reduce binding to inhibitory receptors (e.g., FcyRIIB (CD32B) (see,e.g.,Stavenhagen, J.B. et al. (2007) "Fc Optimization Of Therapeutic Antibodies Enhances Their Ability To Kill Tumor Cells In Vitro And Controls Tumor Expansion In Vivo Via Low-Affinity Activating Fcgamma Receptors," Cancer Res. 57(18):8882-8890). Exemplary variants of human IgG1 Fc Regions with reduced binding to CD32B and/or increased binding to CD16A contain F243L, R292P, Y300L, V305I or P296L substitutions. These amino acid substitutions may be present in a human IgG1 Fc Region in any combination or sub-combination. In one embodiment, the human IgG1 Fc Region variant contains a F243L, R292P and Y300L substitution. In another embodiment, the human IgG1 Fc Region variant contains F243L, R292P, Y300L, V305I and P296L substitutions.In particular, it is preferred for the Fc Regions of the polypeptide chains of the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, to exhibit decreased (or substantially no) binding to FcyRIA (CD64), FcyRIIA (CD32A), FcyRIIB (CD32B), FcyRIIIA (CD16a) or FcyRIIIB (CD16b) (relative to the binding exhibited by the wild-type IgG1 Fc Region(SEQ ID NO:1).Variant Fc Regions and mutant forms capable of mediating such altered binding are described above. In a specific embodiment, the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise an IgG Fc Region that exhibits reduced ADCC effector function. In a preferred embodiment the CH2-CH3 Domain of the first and/or third polypeptide chains of such Fc Region-containing molecules include any 1, 2, or 3, of the substitutions: L234A, L235A, N297Q, and N297G. In another embodiment, the human IgG Fc Region variant contains an N297Q substitution, an N297G substitution, L234A and L235A substitutions or a D265A substitution, as these mutations abolish FcR binding. Alternatively, a CH2-CH3 Domain of an Fc region which inherently exhibits decreased (or substantially no)binding to FcyRIIIA (CD16a) and/or reduced effector function (relative to the binding exhibited by the wild-type IgG1 Fc Region(SEQ ID NO:1))is utilized. In a specific embodiment, the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, comprise an IgG2 Fc Region(SEQ ID NO:2)or an IgG4 Fc Region (SEQ ID:NO:4). When an IgG4 Fc Region in utilized, the instant invention also encompasses the introduction of a stabilizing mutation, such as the hinge region S228P substitution described above (see,e.g.,SEQ ID NO:13).Since the N297G, N297Q, L234A, L235A and D265A substitutions abolish effector function, in circumstances in which effector function is desired, these substitutions would preferably not be employed.In particular, it is preferred for the Fc Regions of the polypeptide chains of the Fc Region-containing molecules of the present invention, as defined by and for use in accordance with claims 1-6, to exhibit increased serum half-life (relative to the half-life exhibited by the corresponding wild-type Fc). Variant Fc Regions and mutant forms exhibiting extended serum half-life are described above. In a preferred embodiment the CH2-CH3 Domain of the first and/or third polypeptide chains of such Fc Region-containing molecules include any 1, 2, or 3, of the substitutions: M252Y, S254T and T256E. The invention further encompasses Fc Region-containing molecules of the present invention comprising variant Fc Regions comprising:(A) one or more mutations which alter effector function and/or FcyR; and(B) one or more mutations which extend serum half-life.A preferred IgG1 sequence for the CH2 and CH3 Domains of the Fc Region-containing molecules of the present invention will comprise the substitutions L234A/L235A/M252Y/S254T/T256E(SEQ ID NO:258):wherein, X is a lysine (K) or is absent.A preferred IgG4 sequence for the CH2 and CH3 Domains of the Fc Region-containing molecules of the present invention will comprise the M252Y/S254T/T256E substitutions(SEQ ID NO:259):wherein, X is a lysine (K) or is absent.For diabodies and trivalent binding molecules whose first and third polypeptide chains are not identical), it is desirable to reduce or prevent homodimerization from occurring between the CH2-CH3 Domains of two first polypeptide chains or between the CH2-CH3 Domains of two third polypeptide chains. The CH2 and/or CH3 Domains of such polypeptide chains need not be identical in sequence, and advantageously are modified to foster complexing between the two polypeptide chains. For example, an amino acid substitution (preferably a substitution with an amino acid comprising a bulky side group forming a "knob",e.g.,tryptophan) can be introduced into the CH2 or CH3 Domain such that steric interference will prevent interaction with a similarly mutated domain and will obligate the mutated domain to pair with a domain into which a complementary, or accommodating mutation has been engineered,i.e.,"the hole"(e.g.,a substitution with glycine). Such sets of mutations can be engineered into any pair of polypeptides comprising CH2-CH3 Domains that forms an Fc Region. Methods of protein engineering to favor heterodimerization over homodimerization are well known in the art, in particular with respect to the engineering of immunoglobulin-like molecules, and are encompassed herein (seee.g.,Ridgway et al. (1996) " 'Knobs-Into-Holes' Engineering Of Antibody CH3 Domains For Heavy Chain Heterodimerization, " Protein Engr. 9:617-621,Atwell et al. (1997) "Stable Heterodimers From Remodeling The Domain Interface Of A Homodimer Using A Phage Display Library, " J. Mol. Biol. 270: 26-35, andXie et al. (2005) "A New Format Of Bispecific Antibody: Highly Efficient Heterodimerization, Expression And Tumor Cell Lysis, " J. Immunol. Methods 296:95-101). Preferably the "knob" is engineered into the CH2-CH3 Domains of the first polypeptide chain and the "hole" is engineered into the CH2-CH3 Domains of the third polypeptide chain of diabodies comprising three polypeptide chains. Thus, the "knob" will help in preventing the first polypeptide chain from homodimerizing via its CH2 and/or CH3 Domains. As the third polypeptide chain preferably contains the "hole" substitution it will heterodimerize with the first polypeptide chain as well as homodimerize with itself. This strategy may be utilized for diabodies and trivalent binding molecules comprising three, four or five chains as detailed above, where the "knob" is engineered into the CH2-CH3 Domains of the first polypeptide chain and the "hole" is engineered into the CH2-CH3 Domains the third polypeptide chain.A preferred knob is created by modifying an IgG Fc Region to contain the modification T366W. A preferred hole is created by modifying an IgG Fc Region to contain the modification T366S, L368A and Y407V. To aid in purifying the hole-bearing third polypeptide chain homodimer from the final bispecific heterodimeric Fc Region-containing molecule, the protein A binding site of the hole-bearing CH2 and CH3 Domains of the third polypeptide chain is preferably mutated by amino acid substitution at position 435 (H435R). Thus, the hole-bearing third polypeptide chain homodimer will not bind to protein A, whereas the bispecific heterodimer will retain its ability to bind protein A via the protein A binding site on the first polypeptide chain. In an alternative embodiment, the hole-bearing third polypeptide chain may incorporate amino acid substitutions at positions 434 and 435 (N434A/N435K).A preferred IgG1 amino acid sequence for the CH2 and CH3 Domains of the first polypeptide chain of an Fc Region-containing molecule may have the"knob-bearing"sequence(SEQ ID NO:6):wherein, x is a lysine (K) or is absent.A preferred IgG1 amino acid sequence for the CH2 and CH3 Domains of the second polypeptide chain of an Fc Region-containing molecule having two polypeptide chains (or the third polypeptide chain of an Fc Region-containing molecule having three, four, or five polypeptide chains) will have the"hole-bearing"sequence(SEQ ID NO:7):wherein, x is a lysine (K) or is absent.As will be noted, the CH2-CH3 Domains ofSEQ ID NO:6,andSEQ ID NO:7include a substitution at position 234 with alanine and 235 with alanine, and thus form an Fc Region exhibit decreased (or substantially no) binding to FcyRIA (CD64), FcyRIIA (CD32A), FcyRIIB (CD32B), FcyRIIIA (CD16a) or FcyRIIIB (CD16b) (relative to the binding exhibited by the wild-type Fc Region(SEQ ID NO:1).CH2-CH3 Domains, may comprise alternative and/or additional substitutions which modify effector function and/or FyR binding activity ofthe Fc region. CH2-CH3 Domains, may further comprise one or more half-live extending amino acid substitutions. The hole-bearing and knob-bearing CH2-CH3 Domains may further comprise the M252Y/S254T/T256E.It is preferred that the first polypeptide chain will have a "knob-bearing" CH2-CH3 sequence, such as that ofSEQ ID NO:6.However, as will be recognized, a "hole-bearing" CH2-CH3 Domain (e.g.,SEQ ID NO:7)could be employed in the first polypeptide chain, in which case, a "knob-bearing" CH2-CH3 Domain (e.g.,SEQ ID NO:6)would be employed in the second polypeptide chain of an Fc Region-containing molecule of the present invention having two polypeptide chains (or in the third polypeptide chain of an Fc Region-containing molecule having three, four, or five polypeptide chains).Fc Region-containing molecules (e.g., antibodies and Fc Region-containing diabodies) having wild type CH2 and CH3 Domains, or having CH2 and CH3 Domains may comprisecombinations of the substitutions described above. An exemplary amino acid sequence of an IgG1 CH2-CH3 Domain encompassing such variations is(SEQ ID NO:260):wherein:(a) X1and X2are both L (wild type), or are both A (decreased FcyR binding);(b) X3, X4, and X5respectively are M, S and T (wild type), or are Y, T and E (extended half-life),(c) X6, X7, and X8respectively are: T, L and Y (wild type), or are W, L and Y (knob), or S, A and V (hole);(d) X9and X10respectively are N and H (wild type), or are N and R (no protein A binding), or A and K (no protein A binding); and(e) X11is K or is absent.PD-1-binding molecules may comprise CH2 and/or CH3 Domains that have been engineered to favor heterodimerization over homodimerization using mutations known in the art, such as those disclosed inPCT Publication No. WO 2007/110205;WO 2011/143545;WO 2012/058768;WO 2013/06867.VIII. PD-1 x LAG-3 Bispecific Binding MoleculesDisclosed but not claimed are PD-1 x LAG-3 bispecific binding molecules (e.g., bispecific antibodies, bispecific diabodies,etc.) comprising an epitope-binding fragment of an anti-PD-1 antibody, and preferably one of the novel anti-human PD-1 antibodies provided herein, and an epitope-binding fragment of an anti-human LAG-3 antibody, preferably one of the novel anti-human LAG-3 antibodies provded herein. The preferred PD-1 x LAG-3 bispecific binding molecules possess epitope-binding fragments of antibodies that enable them to be able to coordinately bind to two different epitopes: an epitope of PD-1 and an epitope of LAG-3, so as to attenuate the inhibitory activities of such molecules. As used herein, such attenuation refers to a decrease of at least 20%, a decrease of at least 50%, a decrease of at least 80%, or a decrease of at least 90% in detectable PD-1 and/or LAG-3 inhibitory activity, or the complete elimination of detectable PD-1 and/or LAG-3 inhibitory activity. Selection of the epitope-binding fragments (e.g., VL and VH Domains) of the anti-human PD-1 antibody and anti-LAG-3 antibody is coordinated such that the polypeptides chains that make up such PD-1 x LAG-3 bispecific binding molecules assemble to form at least one functional antigen binding site that is specific for the first antigen (i.e., either PD-1 or LAG-3) and at least one functional antigen binding site that is specific for the second antigen (i.e., either PD-1 or LAG-3, depending upon the identity of the first antigen).In a particular instance, a PD-1 x LAG-3 bispecific binding molecule is a bispecific diabody, which preferably comprises two, three, four, or five polypeptide chains as described herein. In another particular instance, a PD-1 x LAG-3 bispecific binding molecule is a bispecific antibody, which preferably comprises two, three, or four polypeptide chains as described herein (also see,e.g.,WO 2007/024715;WO2007/110205;WO 2009/080251;WO 2009/080254;WO 2009/089004;WO 2011/069104;WO 2011/117329;WO 2011/131746;WO 2011/133886;WO 2011/143545;WO 2012/023053;WO 2013/060867).A. Anti-Human LAG-3 AntibodiesDisclosed but not claimed are antibodies that are immunospecific for human LAG-3 are provided below. Additional desired antibodies may be made by isolating antibody-secreting hybridomas elicited using LAG-3 or a peptide fragment thereof, or by screening recombinant antibody libraries for binding to LAG-3 or a peptide fragment thereof. Human LAG-3 (including a 28 amino acid residue signal sequence (shown underlined) and the 497 amino acid residue mature protein) has the amino acid sequence(SEQ ID NO:38):1. LAG-3 mAb AThe anti-human LAG-3 antibody BMS-986016 (25F7; Medarex/BMS), designated herein as"LAG-3 mAb A,"and variants thereof have been described (see,e.g.,WO 2014/008218). The amino acid sequence of the Heavy Chain Variable Domain ofLAG-3 mAb Ahas the amino acid sequence(SEQ ID NO:39)(CDRs are shown underlined):The amino acid sequence of the Light Chain Variable Domain ofLAG-3 mAb Ahas the amino acid sequence(SEQ ID NO:40)(CDRs are shown underlined):Additional murine anti-human LAG-3 antibodies possessing unique binding characteristics have recently been identified (see,United States Patent Application No. 62/172,277). Preferred PD-1 x LAG-3 bispecific binding molecules comprise the epitope-binding fragments of the anti-human LAG-3 antibodyLAG-3 mAb 1orLAG-3 mAb 6,antibodies, which bind a novel epitope and do not compete with BMS-986016 for LAG-3 binding. Particularly preferred, are PD-1 x LAG-3 bispecific binding molecules which possess a humanized VH and/or VL Domains of LAG-3 mAb 1 or LAG-3 mAb 6.2. LAG-1 mAb 1The amino acid sequence of the VH Domain of LAG-3 mAb 1(SEQ ID NO:41)is shown below (CDRHresidues are shown underlined).CDRH1 of LAG-3 mAb 1(SEQ ID NO:42):RNYGMNCDRH2 of LAG-3 mAb 1(SEQ ID NO43):WINTYTGESTYADDFEGCDRH3 of LAG-3 mAb 1(SEQ ID NO:44):ESLYDYYSMDYThe amino acid sequence of the VL Domain of LAG-3 mAb 1(SEQ ID NO:45)is shown below (CDRLresidues are shown underlined):CDRL1 of LAG-3 mAb 1(SEQ ID NO:46):KSSQSLLHSDGKTYLNCDRL2 of LAG-3 mAb 1(SEQ ID NO:47):LVSELDSCDRL3 of LAG-3 mAb 1(SEQ ID NO:48):WQGTHFPYTTwo exemplary humanized VH Domains of LAG-3 mAb 1 designated herein as"hLAG-3 mAb 1 VH1,"and"hLAG-3 mAb 1 VH2,"and four exemplary humanized VL Domains of LAG-3 mAb 1"hLAG-3 mAb 1 VL1," "hLAG-3 mAb 1 VL2," "hLAG-3 mAb 1 VL3,"and"hLAG-3 mAb 1 VL4,"are provided below. Any of the humanized VL Domains may be paired with any of the humanized VH Domains to generate a LAG-3 binding domain. Accordingly, any antibody comprising one of the humanized VL Domains paired with the humanized VH Domain is referred to generically as"hLAG-3 mAb 1,"and particular combinations of humanized VH/VL Domains are referred to by reference to the specific VH/VL Domains, for example a humanized antibody comprising hLAG-3 mAb 1 VH1 and hLAG-3 mAb 1 VL2 is specifically referred to as"hLAG-3 mAb 1(1.2)."The amino acid sequence of the VH Domain ofhLAG-3 mAb 1 VH1 (SEQ ID NO:49)is shown below (CDRHresidues are shown underlined):The amino acid sequence of the VH Domain ofhLAG-3 mAb 1 VH2 (SEQ ID NO:50)is shown below (CDRHresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 1 VL1 (SEQIDNO:51)is shown below (CDRLresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 1 VL2 (SEQIDNO:52)is shown below (CDRLresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 1 VL3 (SEQIDNO:53)is shown below (CDRLresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 1 VL4 (SEQIDNO:54)is shown below (CDRLresidues are shown underlined):The CDRL1 of the VL Domain of hLAG-3 mAb 1 VL4 comprises an glycine to alanine amino acid substitution and has the amino acid sequence: KSSQSLLHSDAKTYLN(SEQ ID NO:55),the substituted alanine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the LAG-3 mAb 1 CDRL1 Domains described above.3. LAG-3 mAb 6The amino acid sequence of the VH Domain of LAG-3 mAb 6(SEQ ID NO:56)is shown below (CDRHresidues are shown underlined):CDRH1 of LAG-3 mAb 6(SEQ ID NO:57):DYNMDCDRH2 of LAG-3 mAb 6(SEQ ID NO:58):DINPDNGVTIYNQKFEGCDRH3 of LAG-3 mAb 6(SEQ ID NO:59):EADYFYFDYThe amino acid sequence of the VL Domain of LAG-3 mAb 6(SEQ ID NO:60)is shown below (CDR residues are shown underlined):CDRL1 of LAG-3 mAb 6(SEQ ID NO:61):KASQDVSSWACDRL2 of LAG-3 mAb 6(SEQ ID NO:62):SASYRYTCDRL3 of LAG-3 mAb 6(SEQ ID NO:63):HYSTPWTTwo exemplary humanized VH Domains of LAG-3 mAb 6 designated herein as"hLAG-3 mAb 6 VH1,"and"hLAG-3 mAb 6 VH2,"and two exemplary humanized VL Domains of LAG-3 mAb 6"hLAG-3 mAb 1 VL1,"and"hLAG-3 mAb 1 VL2,"are provided below. Any of the humanized VL Domains may be paired with any of the humanized VH Domains to generate a LAG-3 binding domain. Accordingly, any antibody comprising one of the humanized VL Domains paired with the humanized VH Domain is referred to generically as"hLAG-3 mAb 6,"and particular combinations of humanized VH/VL Domains are referred to by reference to the specific VH/VL Domains, for example a humanized antibody comprising hLAG-3 mAb 6 VH1 and hLAG-3 mAb 6 VL2 is specifically referred to as"hLAG-3 mAb6(1.2)."The amino acid sequence of the VH Domain ofhLAG-3 mAb 6 VH1 (SEQ ID NO:294) is shown below CDRHresidues are shown underlined):An amino acid sequence of the VH Domain ofhLAG-3 mAb 6 VH2 (SEQ IDNO:295) is shown below (CDRHresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 6 VL1 (SEQ ID NO:296)is shown below (CDRLresidues are shown underlined):The amino acid sequence of the VL Domain ofhLAG-3 mAb 6 VL2 (SEQ ID NO:297)is shown below (CDRLresidues are shown underlined):The CDRL1 of the VL Domain of hLAG-3 mAb 6 VL1 and VL2 comprises a lysine to arginine amino acid substitution and has the amino acid sequence: RASQDVSSWA(SEQ ID NO:298),the substituted arginine is shown underlined). It is contemplated that a similar substitution may be incorporated into any of the LAG-3 mAb 6 CDRL1 Domains described above.B. Exemplary Four Chain Fc Region-Containing Diabodies Having E/K-CoilsDisclosed but not claimed are four exemplary PD-1 X LAG-3 bispecific, four chain Fc Region-containing diabodies comprising E/K-coil Heterodimer-Promoting Domains (designated"DART A," "DART B," "DART C,"and"DART I")were generated. The structure of these Fc Region-containing diabodies is detailed below.1. DART ADART A is a bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, a variant IgG4 Fc Region engineered for extended half-life, and cysteine-containing E/K-coil Heterodimer-Promoting Domains. The first and third polypeptide chains of DART A comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (E-coil) Domain (EVAACEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:23));a stabilized IgG4 hinge region(SEQ ID NO:13);a variant IgG4 CH2-CH3Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:259);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART A is a variant ofSEQ ID NO:267:wherein X1, X2, X3and X4are independently selected, and wherein X1is A or G; X2is Y or M; X3is T or S; and X4is E or T.The amino acid sequences of the first and third polypeptide chains of DART A isSEQ ID NO:267,wherein X1is A; X2is Y; X3is T; and X4is E.The second and fourth polypeptide chains of DART A comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (K-coil) Domain (KVAACKE- KVAALKE- KVAALKE- KVAALKE(SEQ ID NO:24);and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART A is(SEQ ID NO:268):2. DART BDART B is identical to DART A, except that the first and third polypeptide chains of DART B comprise the VL Domain of hLAG-3 mAb 1 VL3(SEQ ID NO:53),which comprises an amino acid substitution in CDRL1. Thus, the first and third polypeptide chains of DART B comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL3)(SEQ ID NO:53);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (E-coil) Domain (EVAACEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:23));a stabilized IgG4 hinge region(SEQ ID NO:13);a variant of IgG4 CH2-CH3 Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:259);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART B isSEQ ID NO:267,wherein X1is G; X2is Y; X3is T; and X4is E.The amino acid sequence of the second and fourth polypeptide chains of DART B isSEQ ID NO:268.3. DART CDART C is identical to DART B, except that the first and third polypeptide chains of DART B comprise a wild type IgG4 CH2-CH3 Domain lacking the C-terminal residue(SEQ ID NO:4).Thus, the first and third polypeptide chains of DART C comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL3)(SEQ ID NO:53);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (E-coil) Domain (EVAACEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:23));a stabilized IgG4 hinge region(SEQ ID NO:13);an IgG4 CH2-CH3 Domain lacking the C-terminal residue(SEQ ID NO:4);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART C isSEQ ID NO:267,wherein X1is G; X2is M; X3is S; and X4is T.The amino acid sequence of the second and fourth polypeptide chains of DART C isSEQ ID NO:268.4. DART IDART I is a bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, a variant IgG4 Fc Region engineered for extended half-life, and cysteine-containing E/K-coil Heterodimer-Promoting Domains. The first and third polypeptide chains of DART I comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 6 VL1)(SEQ ID NO:296);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (E-coil) Domain (EVAACEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:23));a stabilized IgG4 hinge region(SEQ ID NO:13);a variant IgG4 CH2-CH3 Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:259);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART I is(SEQ ID NO:290):The second and fourth polypeptide chains of DART I comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding LAG-3 (VHLAG-3hLAG-3 mAb 6 VH1)(SEQ ID NO:294);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a cysteine-containing Heterodimer-Promoting (K-coil) Domain (KVAACKE- KVAALKE- KVAALKE- KVAALKE(SEQ ID NO:24);and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART I is(SEQ ID NO:291):C. Exemplary Four Chain Fc Region-Containing Diabodies Having CL/CH1 DomainsDisclosed but not claimed are four exemplary PD-1 X LAG-3 bispecific, four chain Fc Region-containing diabodies comprising CL/CH1 Domains designated"DART D," "DART E," "DART J"and "DART 1"were generated. The structure of these Fc Region-containing diabodies is detailed below.1. DART DDART D is a bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, CL/CH1 Domains, and a variant IgG4 Fc Region engineered for extended half-life. The first and third polypeptide chains of DART D comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));an IgG4 CH1 Domain(SEQ ID NO:254);a stabilized IgG4 hinge region(SEQ ID NO: 13);a variant of an IgG4 CH2-CH3 Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:259);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART D is(SEQ ID NO:269):The second and fourth polypeptide chains of DART D comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));a Kappa CL Domain(SEQ ID NO:8);and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART D is(SEQ ID NO:270):2. DART EDART E is another bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, CL/CH1 Domains, and a variant IgG4 Fc Region engineered for extended half-life. The position of the PD-1 and LAG-3 binding sites of DART E is reversed as compared to DART D.The first and third polypeptide chains of DART E comprise, in the N-terminal to C-terminal direction: an N-terminus, a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));an IgG4 CH1 Domain(SEQ ID NO:254);a stabilized IgG4 hinge region(SEQ ID NO: 13);a variant of an IgG4 CH2-CH3 Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ IDNO:259); and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART E is(SEQ ID NO:271):The second and fourth polypeptide chains of DART E comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));a Kappa CL Domain(SEQ ID NO:8),and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART E is(SEQ ID NO:272):3. DART JDART J is a bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, CL/CH1 Domains, and a variant IgG4 Fc Region engineered for extended half-life. The first and third polypeptide chains of DART J comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 6 VL1)(SEQ ID NO:296);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));an IgG4 CH1 Domain(SEQ ID NO:254);a stabilized IgG4 hinge region(SEQ ID NO: 13);a variant of an IgG4 CH2-CH3 Domain comprising substitutions M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:259);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART J is(SEQ ID NO:292):The second and fourth polypeptide chains of DART J comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capableof binding to LAG-3 (VHLAG-3hLAG-3 mAb 6 VH1)(SEQ ID NO:294);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));a Kappa CL Domain(SEQ ID NO:8);and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART J is(SEQ ID NO:293):4. DART 1DART 1 is a bispecific, four chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, CL/CH1 Domains, and a variant IgG1 Fc Region engineered for reduced FcγR binding. The first and third polypeptide chains of DART 1 comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1PD-1 mAb A VL)(SEQ ID NO:65);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3LAG-3 mAb A VH1)(SEQ ID NO:39);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));an IgG1 CH1 Domain(SEQ ID NO:10);an IgG1 hinge region(SEQ ID NO: 32);a variant of an IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A and lacking the C-terminal residue(SEQ ID NO:5);and a C-terminus.The amino acid sequence of the first and third polypeptide chains of DART 1 is(SEQ ID NO:284):The second and fourth polypeptide chains of DART 1 comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3LAG-3 mAb A VL)(SEQ ID NO:40);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1PD-1 mAb A VH)(SEQ ID NO:64);an intervening linker peptide(Linker 2:LGGGSG(SEQ ID NO:261));a Kappa CL Domain(SEQ ID NO:8);and a C-terminus.The amino acid sequence of the second and fourth polypeptide chains of DART 1 is(SEQ ID NO:285):D. Exemplary Five Chain Fc Region-Containing DiabodiesDisclosed but not claimed are two exemplary PD-1 X LAG-3 bispecific, five chain Fc Region-containing diabodies comprising CL/CH1 Domains and E/K-coil Heterodimer-Promoting Domains designated"DART F,"and"DART G"were generated. The structure of these Fc Region-containing diabodies is detailed below.1. DART FDART F is a bispecific, five chain, Fc Region-containing diabody having three binding sites specific for PD-1, one binding site specific for LAG-3, CL/CH1 Domains, a variant knob/hole-bearing IgG1 Fc Region engineered for reduced FcyR binding and extended half-life, and E/K-coil Heterodimer-Promoting Domains. The first polypeptide chain of DART F comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an IgG1 CH1 Domain(SEQ ID NO:10);an IgG1 hinge region(SEQ ID NO:32);a hole-bearing IgG1 CH2-CH3 Domain comprising substitutionsL234A/L235A/M252Y/S254T/T256E/N434A/H435K and lacking the C-terminal residue(SEQ ID NO:260,wherein X1is A, X2is A; X3is Y, X4is T, X5is E, X6is S, X7is A, X8is V, X9is A, X10is K, and X11is absent); and a C-terminus.The amino acid sequence of the first polypeptide chain of DART F is(SEQ ID NO:273):The second and fifth polypeptide chains of DART F comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153),a Kappa CL Domain(SEQ ID NO:8),and a C-terminus.The amino acid sequence of the second and fifth polypeptide chain of DART F is(SEQ ID NO:274):The third polypeptide chain of DART F comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an IgG1 CH1 Domain(SEQ ID NO:10);an IgG1 hinge region(SEQ ID NO:32);a knob-bearing IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A/M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:260,wherein X1is A, X2is A; X3is Y, X4is T, X5is E, X6is W, X7is L, X8is Y, X9is N, X10is H, and X11is absent); an intervening linker peptide (GGGSGGGSGGG(SEQ ID NO:262));a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14)); aVH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (E-coil) Domain (EVAALEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:21));and a C-terminus.The amino acid sequence of the third polypeptide chain of DART F is(SEQ ID NO:275):The fourth polypeptide chain of DART F comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (K-coil) Domain (KVAALKE-KVAALKE-KVAALKE-KVAALKE(SEQ ID NO:22));and a C-terminus.The amino acid sequence of the fourth polypeptide chains of DART F is(SEQ ID NO:276):2. DART GDART G is a bispecific, five chain, Fc Region-containing diabody having two binding sites specific for PD-1, two binding sites specific for LAG-3, CL/CH1 Domains, a variant knob/hole-bearing IgG1 Fc Region engineered for reduced FcyR binding and extended half-life, and E/K-coil Heterodimer-Promoting Domains. The first polypeptide chain of DART G comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);an IgG1 CH1 Domain(SEQ ID NO:10);an IgG1 hinge region(SEQ ID NO:32);a hole-bearing IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A/M252Y/S254T/T256E/N434A/H435K and lacking the C-terminal residue(SEQ ID NO:260,wherein X1is A, X2is A; X3is Y, X4is T, X5is E, X6is S, X7is A, X8is V, X9is A, X10is K, and X11is absent); and a C-terminus.The amino acid sequence of the first polypeptide chain of DART G is(SEQ ID NO:277):The second and fifth polypeptide chains of DART G comprise, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54),a Kappa CL Domain(SEQ ID NO:8),and a C-terminus.The amino acid sequence of the second and fifth polypeptide chain of DART G is(SEQ ID NO:278):The third polypeptide chain of DART G comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);an IgG1 CH1 Domain(SEQ ID NO:10);an IgG1 hinge region(SEQ ID NO:32);a knob-bearing IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A/M252Y/S254T/T256E and lacking the C-terminal residue(SEQ ID NO:260,wherein X1is A, X2is A; X3is Y, X4is T, X5is E, X6is W, X7is L, X8is Y, X9is N, X10is H, and X11is absent); an intervening linker peptide (GGGSGGGSGGG(SEQ ID NO:262));a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (E-coil) Domain (EVAALEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:21));and a C-terminus.The amino acid sequence of the third polypeptide chain of DART G is(SEQ ID NO:279):The fourth polypeptide chain of DART G comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linkerpeptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (K-coil) Domain (KVAALKE-KVAALKE-KVAALKE-KVAALKE(SEQ ID NO:22);and a C-terminus.The amino acid sequence of the fourth polypeptide chains of DART G is(SEQ ID NO:280):E. Exemplary Three Chain Fc Region-Containing Diabody Having E/K-CoilsDisclosed but not claimed are PD-1 X LAG-3 bispecific, three chain Fc Region-containing diabodiesy comprising E/K-coil Heterodimer-Promoting Domains. An exemplary PD-1 X LAG-3 bispecific, three chain Fc Region-containing diabody comprising E/K-coil Heterodimer-Promoting Domains designated"DART H"was generated. The structure of this Fc Region-containing diabodies is detailed below.DART H is a bispecific, three chain, Fc Region-containing diabody having one binding site specific for PD-1, one binding site specific for LAG-3, a variant knob/hole-bearing IgG1 Fc Region engineered for reduced FcyR binding, and E/K-coil Heterodimer-Promoting Domains.The first polypeptide chain of DART H comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1 (VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (E-coil) Domain (EVAALEK-EVAALEK-EVAALEK-EVAALEK(SEQ ID NO:21));an intervening linker(Spacer-Linker 3:GGGDKTHTCPPCP(SEQ ID NO:263));a knob-bearing IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A and having the C-terminal lysine residue(SEQ ID NO:6);and a C-terminus.The amino acid sequence of the first polypeptide chain of DART H is(SEQ ID NO:281):The second polypeptide chain of DART H comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);an intervening linker peptide(Linker 1:GGGSGGGG(SEQ ID NO:14));a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);a cysteine-containing intervening linker peptide(Linker 2:GGCGGG(SEQ ID NO:15));a Heterodimer-Promoting (K-coil) Domain (KVAALKE-KVAALKE-KVAALKE-KVAALKE(SEQ ID NO:22));and a C-terminus.The amino acid sequence of the second polypeptide chain of DART H is(SEQ ID NO:282):The third polypeptide chain of DART H comprises, in the N-terminal to C-terminal direction: an N-terminus; a hinge region (DKTHTCPPCP(SEQ ID NO:31);a hole-bearing IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A and having the C-terminal lysine residue(SEQ ID NO:7);and a C-terminus.The amino acid sequence of the third polypeptide chain of DART H is(SEQ ID NO:283):F. Exemplary Bispecific AntibodyDisclosed but not claimed is an exemplary PD-1 X LAG-3 four chain bispecific antibody designated"BSAB A"was generated. The structure of this bispecific antibody is detailed below.BSAB A is a bispecific antibody having one binding site specific for PD-1, one binding site specific for LAG-3, a variant IgG1 Fc Region engineered to reduce FcyR binding and to foster complexing between the two different heavy chain polypeptides (see,e.g.,WO 2011/143545).The first polypeptide chain of BSAB A comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding to PD-1 (VHPD-1hPD-1 mAb 7 VH1)(SEQ ID NO:147);an IgG1 CH1 Domain(SEQ ID NO:10);a variant IgG1 hinge region comprising substitutions D221E/P228E (numbered by the EU index as in Kabat and underlined inSEQ ID NO:286,below); a variant IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A/L368E (underlined inSEQ ID NO:286,below) and lacking the C-terminal residue; and a C-terminus.The amino acid sequence of the first polypeptide chain of BSAB A is(SEQ ID NO:286):The second polypeptide chain of BSAB comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to PD-1(VLPD-1hPD-1 mAb 7 VL2)(SEQ ID NO:153);a Kappa CL Domain(SEQ ID NO:8),and a C-terminus.The amino acid sequence of the second polypeptide chain of BSAB is(SEQ ID NO:287):The third polypeptide chain of BSAB A comprises, in the N-terminal to C-terminal direction: an N-terminus; a VH Domain of a monoclonal antibody capable of binding to LAG-3 (VHLAG-3hLAG-3 mAb 1 VH1)(SEQ ID NO:49);an IgG1 CH1 Domain(SEQ ID NO:10);a variant IgG1 hinge region comprising substitutions D221R/P228R (underlined inSEQ ID NO:288,below); a variant IgG1 CH2-CH3 Domain comprising substitutions L234A/L235A/L409R (underlined inSEQ ID NO:288,below) and lacking the C-terminal residue; and a C-terminus.The amino acid sequence of the third polypeptide chain of BSAB A is(SEQ ID NO:288):The fourth polypeptide chain of BSAB A comprises, in the N-terminal to C-terminal direction: an N-terminus; a VL Domain of a monoclonal antibody capable of binding to LAG-3 (VLLAG-3hLAG-3 mAb 1 VL4)(SEQ ID NO:54);a Kappa CL Domain(SEQ ID NO:8),and a C-terminus.The amino acid sequence of the fourth polypeptide chain of BSAB A is(SEQ ID NO:289):IX. Reference AntibodiesA. Reference Anti-Human PD-1 AntibodiesIn order to assess and characterize the novel anti-human PD-1-binding molecules disclosed herein, the following reference antibodies were employed: nivolumab (also known as 5C4, BMS-936558, ONO-4538, MDX-1106, and marketed as OPDIVO®by Bristol-Myers Squibb), a human IgG4 antibody designated herein as"PD-1 mAb A;"and pembrolizumab (formerly known as lambrolizumab, also known as MK-3475, SCH-900475, and marketed as KEYTRUDA®by Merck) a humanized IgG4 antibody designated herein as"PD-1 mAb B."1. Nivolumab ("PD-1 mAb A")The amino acid sequence of the Heavy Chain Variable Domainof PD-1 mAb Ahas the amino acid sequence(SEQ ID NO:64)(CDRHresidues are shown underlined):The amino acid sequence of the Light Chain Variable Domain ofPD-1 mAb Ahas the amino acid sequence(SEQIDNO:65)(CDRLresidues are shown underlined):2. Pembrolizumab ("PD-1 mAb B")The amino acid sequence of the Heavy Chain Variable Domain ofPD-1 mAb Bhas the amino acid sequence(SEQIDNO:66)(CDRHresidues are shown underlined):The amino acid sequence of the Light Chain Variable Domainof PD-1 mAb Bhas the amino acid sequence(SEQ ID NO:67)(CDRLresidues are shown underlined):X. Methods of ProductionAn anti-human PD-1 polypeptide, and other PD-1 agonists, antagonists and modulators can be created from the polynucleotides and/or sequences of the anti-PD-1 antibodies PD-1 mAb 1-15 by methods known in the art, for example, synthetically or recombinantly. One method of producing such peptide agonists, antagonists and modulators involves chemical synthesis of the polypeptide, followed by treatment under oxidizing conditions appropriate to obtain the native conformation, that is, the correct disulfide bond linkages. This can be accomplished using methodologies well known to those skilled in the art (see,e.g.,Kelley, R. F. et al. (1990) In: GENETIC ENGINEERING PRINCIPLES AND METHODS, Setlow, J.K. Ed., Plenum Press, N.Y., vol. 12, pp 1-19;Stewart, J.M et al. (1984) SOLID PHASE PEPTIDE SYNTHESIS, Pierce Chemical Co., Rockford, IL; see alsoUnited States Patents Nos. 4,105,603;3,972,859;3,842,067; and3,862,925).Polypeptides may be conveniently prepared using solid phase peptide synthesis (Merrifield, B. (1986) "Solid Phase Synthesis," Science 232(4748):341-347;Houghten, R.A. (1985) "General Method For The Rapid Solid-Phase Synthesis Of Large Numbers Of Peptides: Specificity Of Antigen-Antibody Interaction At The Level Of Individual Amino Acids," Proc. Natl. Acad. Sci. (U.S.A.) 82(15):5131-5135;Ganesan, A. (2006) "Solid Phase Synthesis In The Twenty-First Century," Mini Rev. Med. Chem. 6(1):3-10).In yet another alternative, fully human antibodies having one or more of the CDRs of PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15, or which compete with PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15, for binding to human PD-1 or a soluble form thereof may be obtained through the use of commercially available mice that have been engineered to express specific human immunoglobulin proteins. Transgenic animals that are designed to produce a more desirable(e.g.,fully human antibodies) or more robust immune response may also be used for generation of humanized or human antibodies. Examples of such technology are XENOMOUSE™(Abgenix, Inc., Fremont, CA) and HUMAB-MOUSE®and TC MOUSE™(both from Medarex, Inc., Princeton, NJ).In an alternative, antibodies may be made recombinantly and expressed using any method known in the art. Antibodies may be made recombinantly by first isolating the antibodies made from host animals, obtaining the gene sequence, and using the gene sequence to express the antibody recombinantly in host cells (e.g., CHO cells). Another method that may be employed is to express the antibody sequence in plants {e.g., tobacco) or transgenic milk. Suitable methods for expressing antibodies recombinantly in plants or milk have been disclosed (see, for example,Peeters et al. (2001) "Production Of Antibodies And Antibody Fragments In Plants," Vaccine 19:2756;Lonberg, N. et al. (1995) "Human Antibodies From Transgenic Mice," Int. Rev. Immunol 13:65-93; andPollock et al. (1999) "Transgenic Milk As A Method For The Production Of Recombinant Antibodies," J. Immunol Methods 231:147-157). Suitable methods for making derivatives of antibodies,e.g., humanized, single-chain,etc.are known in the art. In another alternative, antibodies may be made recombinantly by phage display technology (see, for example,U.S. Patent Nos. 5,565,332;5,580,717;5,733,743;6,265,150; andWinter, G. et al. (1994) "Making Antibodies By Phage Display Technology," Annu. Rev. Immunol. 12.433-455).The antibodies or protein of interest may be subjected to sequencing by Edman degradation, which is well known to those of skill in the art. The peptide information generated from mass spectrometry or Edman degradation can be used to design probes or primers that are used to clone the protein of interest.An alternative method of cloning the protein of interest is by "panning" using purified PD-1 or portions thereof for cells expressing an antibody or protein of interest that possesses one or more of the CDRs of PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15, or of an antibody that competes with PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15, for binding to human PD-1. The "panning" procedure may be conducted by obtaining a cDNA library from tissues or cells that express PD-1, overexpressing the cDNAs in a second cell type, and screening the transfected cells of the second cell type for a specific binding to PD-1 in the presence or absence of PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14,or PD-1 mAb 15. Detailed descriptions of the methods used in cloning mammalian genes coding for cell surface proteins by "panning" can be found in the art (see, for example,Aruffo, A. et al. (1987) "Molecular Cloning Of A CD28 cDNA By A High-Efficiency COS Cell Expression System," Proc. Natl. Acad. Sci. (U.S.A.) 84:8573-8577andStephan, J. etal. (1999) "Selective Cloning Of Cell Surface Proteins Involved In Organ Development: Epithelial Glycoprotein Is Involved In Normal Epithelial Differentiation," Endocrinol. 140:5841-5854).Vectors containing polynucleotides of interest can be introduced into the host cell by any of a number of appropriate means, including electroporation, transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE- dextran, or other substances; microprojectile bombardment; lipofection; and infection (e.g., where the vector is an infectious agent such as vaccinia virus). The choice of introducing vectors or polynucleotides will often depend on features of the host cell.Any host cell capable of overexpressing heterologous DNAs can be used for the purpose of isolating the genes encoding the antibody, polypeptide or protein of interest. Nonlimiting examples of suitable mammalian host cells include but are not limited to COS, HeLa, and CHO cells. Preferably, the host cells express the cDNAs at a level of about 5-fold higher, more preferably 10-fold higher, even more preferably 20-fold higher than that of the corresponding endogenous antibody or protein of interest, if present, in the host cells. Screening the host cells for a specific binding to PD-1 is effected by an immunoassay or FACS. A cell overexpressing the antibody or protein of interest can be identified.. The polypeptides of this invention, as defined by and for use in accordance with claims 1-6, can be made by procedures known in the art. The polypeptides can be produced by proteolytic or other degradation of the antibodies, by recombinant methods (i.e., single or fusion polypeptides) as described above or by chemical synthesis. Polypeptides of the antibodies, especially shorter polypeptides up to about 50 amino acids, are conveniently made by chemical synthesis. Methods of chemical synthesis are known in the art and are commercially available. For example, an anti-human PD-1 polypeptide could be produced by an automated polypeptide synthesizer employing the solid phase method.Disclosed but not claimed are variants of PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15 antibodiesand their polypeptide fragments that bind to PD-1, including functionally equivalent antibodies and fusion polypeptides that do not significantly affect the properties of such molecules as well as variants that have enhanced or decreased activity. Modification of polypeptides is routine practice in the art and need not be described in detail herein. Examples of modified polypeptides include polypeptides with conservative substitutions of amino acid residues, one or more deletions or additions of amino acids which do not significantly deleteriously change the functional activity, or use of chemical analogs. Amino acid residues that can be conservatively substituted for one another include but are not limited to: glycine/alanine; serine/threonine; valine/isoleucine/leucine; asparagine/glutamine; aspartic acid/glutamic acid; lysine/arginine; and phenylalanine/tyrosine. These polypeptides also include glycosylated and non-glycosylated polypeptides, as well as polypeptides with other post-translational modifications, such as, for example, glycosylation with different sugars, acetylation, and phosphorylation. Preferably, the amino acid substitutions would be conservative, i.e., the substituted amino acid would possess similar chemical properties as that of the original amino acid. Such conservative substitutions are known in the art, and examples have been provided above. Amino acid modifications can range from changing or modifying one or more amino acids to complete redesign of a region, such as the Variable Domain. Changes in the Variable Domain can alter binding affinity and/or specificity. Other methods of modification include using coupling techniques known in the art, including, but not limited to, enzymatic means, oxidative substitution and chelation. Modifications can be used, for example, for attachment of labels for immunoassay, such as the attachment of radioactive moieties for radioimmunoassay. Modified polypeptides are made using established procedures in the art and can be screened using standard assays known in the art.Disclosed but not claimed are fusion proteins comprising one or more of the polypeptides or PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, or PD-1 mAb 15 antibodies. In one instance, a fusion polypeptide is provided that comprises a light chain, a heavy chain or both a light and heavy chain. In another instance, the fusion polypeptide contains a heterologous immunoglobulin constant region. In another instance, the fusion polypeptide contains a Light Chain Variable Domain and a Heavy Chain Variable Domain of an antibody produced from a publicly-deposited hybridoma. For purposes of this disclosure, an antibody fusion protein contains one or more polypeptide domains that specifically bind to PD-1 and another amino acid sequenceto which it is not attached in the native molecule, for example, a heterologous sequence or a homologous sequence from another region.XI. Uses of the PD-1-Binding Molecules of the Present InventionA. Therapeutic UsesAs discussed above, PD-1 plays an important role in negatively regulating T-cell proliferation, function and homeostasis. The PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, have the ability to inhibit PD-1 function, and thus reverse the PD-1-mediated immune system inhibition. PD-1 mAb 1, PD-1 mAb 3, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15, their humanized derivatives, and molecules comprising their PD-1-binding fragments (e.g., bispecific antibodies, bispecific diabodies (including, but not limited to, DART-A, DART-B, DART-C, DART-D, DART-E, DART-F, DART-G, DART-H, DART-I, and DART-J),etc.),or that compete for binding with such antibodies, may be used to block PD-1-mediated immune system inhibition, and thereby promote the activation of the immune system.Bispecific PD-1-binding molecules disclosed but not claimed herein that bind to PD-1 and another molecule involved in regulating an immune check point present on the cell surface (e.g., LAG-3) augment the immune system by blocking immune system inhibition mediated by PD-1 and such immune check point molecules. Thus, such PD-1-binding molecules are useful for augmenting an immune response (e.g., the T-cell mediated immune response) of a subject. In particular, such PD-1-binding molecules may be used to treat any disease or condition associated with an undesirably suppressed immune system, including cancer and diseases that are associated with the presence of a pathogen (e.g., a bacterial, fungal, viral or protozoan infection).The cancers that may be treated by such PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, include cancers characterized by the presence of a cancer cell selected from the group consisting of a cell of: an adrenal gland tumor, an AIDS-associated cancer, an alveolar soft part sarcoma, an astrocytic tumor, bladder cancer, bone cancer, a brain and spinal cord cancer, a metastatic brain tumor, a breast cancer, a carotid body tumors, a cervical cancer, a chondrosarcoma, a chordoma, a chromophobe renal cell carcinoma, a clear cell carcinoma, a colon cancer, a colorectal cancer,a cutaneous benign fibrous histiocytoma, a desmoplastic small round cell tumor, an ependymoma, a Ewing's tumor, an extraskeletal myxoid chondrosarcoma, a fibrogenesis imperfecta ossium, a fibrous dysplasia of the bone, a gallbladder or bile duct cancer, gastric cancer, a gestational trophoblastic disease, a germ cell tumor, a head and neck cancer, hepatocellular carcinoma, an islet cell tumor, a Kaposi's Sarcoma, a kidney cancer, a leukemia, a lipoma/benign lipomatous tumor, a liposarcoma/malignant lipomatous tumor, a liver cancer, a lymphoma, a lung cancer, a medulloblastoma, a melanoma, a meningioma, a multiple endocrine neoplasia, a multiple myeloma, a myelodysplastic syndrome, a neuroblastoma, a neuroendocrine tumors, an ovarian cancer, a pancreatic cancer, a papillary thyroid carcinoma, a parathyroid tumor, a pediatric cancer, a peripheral nerve sheath tumor, a phaeochromocytoma, a pituitary tumor, a prostate cancer, a posterious uveal melanoma, a rare hematologic disorder, a renal metastatic cancer, a rhabdoid tumor, a rhabdomysarcoma, a sarcoma, a skin cancer, a soft-tissue sarcoma, a squamous cell cancer, a stomach cancer, a synovial sarcoma, a testicular cancer, a thymic carcinoma, a thymoma, a thyroid metastatic cancer, and a uterine cancer.In particular, such PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, may be used in the treatment of colorectal cancer, hepatocellular carcinoma, glioma, kidney cancer, breast cancer, multiple myeloma, bladder cancer, neuroblastoma; sarcoma, non-Hodgkin's lymphoma, non-small cell lung cancer, ovarian cancer, pancreatic cancer and rectal cancer.Pathogen-associated diseases that may be treated by such PD-1-binding molecules include chronic viral, bacterial, fungal and parasitic infections. Chronic infections that may be treated by the PD-1-binding molecules include Epstein Barr virus, Hepatitis A Virus (HAV); Hepatitis B Virus (HBV); Hepatitis C Virus (HCV); herpes viruses (e.g. HSV-1, HSV-2, HHV-6, CMV), Human Immunodeficiency Virus (HIV), Vesicular Stomatitis Virus (VSV),Bacilli, Citrobacter, Cholera, Diphtheria, Enterobacter, Gonococci, Helicobacter pylori, Klebsiella, Legionella, Meningococci,mycobacteria,Pseudomonas, Pneumonococci,rickettsia bacteria,Salmonella, Serratia, Staphylococci, Streptococci, Tetanus, Aspergillus(fumigatus, niger,etc.), Blastomyces dermatitidis, Candida(albicans, krusei, glabrata, tropicalis,etc.), Cryptococcus neoformans, GenusMucorales(mucor, absidia, rhizopus),Sporothrix schenkii, Paracoccidioides brasiliensis, Coccidioides immitis, Histoplasma capsulatum, Leptospirosis, Borrelia burgdorferi, helminth parasite(hookworm, tapeworms, flukes, flatworms (e.g. Schistosomia),Giardia lambia,trichinella,Dientamoeba Fragilis, Trypanosoma brucei, Trypanosoma cruzi,andLeishmania donovani.PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, can be combined with other anti-cancer agents, in particular, molecules that specifically bind a cancer antigen (e.g., antibodies, diabodies). Anti-cancer therapies that may be combined with the PD-1-binding molecules of the invention include molecules which specifically bind one more cancer antigens including:19.9as found in colon cancer, gastric cancer mucins;4.2; A33(a colorectal carcinoma antigen;Almqvist, Y. 2006, Nucl Med Biol. Nov;33(8):991-998);ADAM-9(United States Patent Publication No. 2006/0172350;PCT Publication No. WO 06/084075);AH6as found in gastric cancer;ALCAM(PCT Publication No. WO 03/093443);APO-1 (malignant human lymphocyte antigen)(Trauth et al. (1989) "Monoclonal Antibody Mediated Tumor Regression By Induction Of Apoptosis, " Science 245:301-304);B1(Egloff, A.M. et al. 2006, Cancer Res. 66(1):6-9);B7-H3(Collins, M. et al. (2005) "The B7 Family Of Immune-Regulatory Ligands," Genome Biol. 6:223.1-223.7).Chapoval, A. et al. (2001) "B7-H3: A Costimulatory Molecule For T Cell Activation and IFN-γ Production," Nature Immunol. 2:269-274;Sun, M. et al. (2002) "Characterization of Mouse and Human B7-H3 Genes," J. Immunol. 168:6294-6297);BAGE(Bodey, B. 2002 Expert Opin Biol Ther. 2(6):577-84);beta-catenin(Prange W. et al. 2003 J Pathol. 201(2):250-9);blood group ALeb/Leyas found in colonic adenocarcinoma;Burkitt's lymphoma antigen-38.13, C14as found in colonic adenocarcinoma;CA125 (ovarian carcinoma antigen)(Bast, R.C. Jr. et al. 2005 Int J Gynecol Cancer 15 Suppl 3:274-81;Yu et al. (1991) "Coexpression Of Different Antigenic Markers On Moieties That Bear CA 125 Determinants, " Cancer Res. 51(2):468-475);Carboxypeptidase M(United States Patent Publication No. 2006/0166291);CDS(Calin, G.A. et al. 2006 Semin Oncol. 33(2):167-73;CD19(Ghetie et al. (1994) "Anti-CD19 Inhibits The Growth Of Human B-Cell Tumor Lines In Vitro And Of Daudi Cells In SCID Mice By Inducing Cell Cycle Arrest, " Blood 83:1329-1336;Troussard, X. et al. 1998 Hematol Cell Ther. 40(4):139-48);CD20(Reff et al. (1994) "Depletion Of B Cells In Vivo By A Chimeric Mouse Human Monoclonal Antibody To CD20, " Blood 83:435-445;Thomas, D.A. et al. 2006 Hematol Oncol Clin North Am. 20(5):1125-36);CD22(Kreitman, R.J. 2006 AAPS J. 18;8(3):E532-51);CD23(Rosati, S. et al. 2005 Curr Top Microbiol Immunol. 5;294:91-107);CD25(Troussard, X. et al. 1998 Hematol Cell Ther. 40(4):139-48);CD27(Bataille, R. 2006 Haematologica 91(9):1234-40);CD28(Bataille, R. 2006 Haematologica 91(9):1234-40);CD33(Sgouros et al. (1993) "Modeling And Dosimetry Of Monoclonal Antibody M195 (Anti-CD33)In Acute Myelogenous Leukemia, " J. Nucl. Med. 34:422-430);CD36(Ge, Y. 2005 Lab Hematol. 11(1):31-7); CD40/CD154 (Messmer, D. et al. 2005 Ann N Y Acad Sci. 1062:51-60);CD45(Jurcic, J.G. 2005 Curr Oncol Rep. 7(5):339-46); CD56 (Bataille, R. 2006 Haematologica 91(9):1234-40);CD46(United States Patent No. 7,148,038;PCT Publication No. WO 03/032814);CD52(Eketorp, S.S. et al. (2014) "Alemtuzumab (Anti-CD52 Monoclonal Antibody) As Single-Agent Therapy In Patients With Relapsed/Refractory Chronic Lymphocytic Leukaemia (CLL)-A Single Region Experience On Consecutive Patients," Ann Hematol. 93(10):1725-1733;Suresh, T. et al. (2014) "New Antibody Approaches To Lymphoma Therapy," J. Hematol. Oncol. 7:58;Hoelzer, D. (2013) "Targeted Therapy With Monoclonal Antibodies In Acute Lymphoblastic Leukemia," Curr. Opin. Oncol. 25(6):701-706);CD56(Bataille, R. 2006 Haematologica 91(9):1234-40);CD79a/CD79b(Troussard, X. et al. 1998 Hematol Cell Ther. 40(4):139-48;Chu, P.G. et al. 2001 Appl Immunohistochem Mol Morphol. 9(2):97-106);CD103(Troussard, X. et al. 1998 Hematol Cell Ther. 40(4):139-48);CD317(Kawai, S. et al. (2008) "Interferon-A Enhances CD317 Expression And The Antitumor Activity Of Anti-CD317 Monoclonal Antibody In Renal Cell Carcinoma Xenograft Models," Cancer Science 99(12):2461-2466;Wang, W. et al. (2009) HM1.24 (CD317) Is A Novel Target Against Lung Cancer For Immunotherapy Using Anti-HM]. 24 Antibody," Cancer Immunology, Immunotherapy 58(6):967-976;Wang, W. et al. (2009) "Chimeric And Humanized Anti-HM1.24 Antibodies Mediate Antibody-Dependent Cellular Cytotoxicity Against Lung Cancer Cells. Lung Cancer," 63(1):23-31;Sayeed, A. et al. (2013) "Aberrant Regulation Of The BST2 (Tetherin) Promoter Enhances Cell Proliferation And Apoptosis Evasion In High Grade Breast Cancer Cells," PLoS ONE 8(6)e67191, pp. 1-10);CDK4(Lee, Y.M. et al. 2006 Cell Cycle 5(18):2110-4);CEA(carcinoembryonic antigen;Foon etal. (1995) "Immune Response To The Carcinoembryonic Antigen In Patients Treated With An Anti-Idiotype Antibody Vaccine, " J. Clin. Invest. 96(1):334-42);Mathelin, C. 2006 Gynecol Obstet Fertil. 34(7-8):638-46;Tellez-Avila, F.I. et al. 2005 Rev Invest Clin. 57(6):814-9);CEACAM9/CEACAM6(Zheng, C. et al. (2011) "A Novel Anti-CEACAMS Monoclonal Antibody, CC4, Suppresses Colorectal Tumor Growth and Enhances NK Cells Mediated Tumor Immunity," PLoS One 6(6):e21146, pp. 1-11);CO17-1A(Ragnhammar et al. (1993) "Effect Of Monoclonal Antibody 17-1A And GM-CSF In Patients With Advanced Colorectal Carcinoma - Long-Lasting, Complete Remissions Can Be Induced, " Int. J. Cancer 53:751-758);CO-43(blood group Leb);CO-514(blood group Lea) as found in adenocarcinoma;CTA-1; CTLA-4(Peggs, K.S. et al. 2006 Curr Opin Immunol. 18(2):206-13);Cytokeratin8 (PCT Publication No. WO 03/024191);D1.1; D156-22; DR5(Abdulghani, J. et al. (2010) "TRAILReceptor Signaling And Therapeutics," Expert Opin. Ther. Targets 14(10):1091-1108;Andera, L. (2009) "Signaling Activated By The Death Receptors Of The TNFR Family," Biomed. Pap. Med. Fac. Univ. Palacky Olomouc Czech. Repub. 153(3):173-180;Carlo-Stella, C. et al. (2007) "Targeting TRAIL Agonistic Receptors for Cancer Therapy," Clin, Cancer 13(8):2313-2317;Chaudhari, B.R. et al. (2006) "Following the TRAIL to Apoptosis," Immunologic Res. 35(3):249-262);Eiseries (blood group B) as found in pancreatic cancer;EGFR(Epidermal Growth Factor Receptor;Adenis, A. et al. 2003 Bull Cancer. 90 Spec No:S228-32);Ephrin receptors(and in particularEphA2(United States Patent No. 7,569,672;PCT Publication No. WO 06/084226);Erb(ErbB1; ErbB3; ErbB4;Zhou, H. et al. 2002 Oncogene 21(57):8732-8740;Rimon, E. et al. 2004 Int J Oncol. 24(5):1325-1338);GAGE(GAGE-1; GAGE-2;Akcakanat, A. et al. 2006 Int J Cancer. 118(1):123-128);GD2/GD3/GM2(Livingston, P.O. et al. 2005 Cancer Immunol Immunother. 54(10):1018-1025);ganglioside GD2(GD2;Saleh et al. (1993) "Generation Of A Human Anti-Idiotypic Antibody That Mimics The GD2 Antigen, " J.Immunol., 151, 3390-3398);ganglioside GD3(GD3;Shitara et al. (1993) "A Mouse/Human Chimeric Anti-(Ganglioside GD3) Antibody With Enhanced Antitumor Activities, " Cancer Immunol. Immunother. 36:373-380);ganglioside GM2(GM2;Livingston et al. (1994) "Improved Survival In Stage III Melanoma Patients With GM2 Antibodies: A Randomized Trial Of Adjuvant Vaccination With GM2 Ganglioside, " J. Clin. Oncol. 12:1036-1044);ganglioside GM3(GM3;Hoon et al. (1993) "Molecular Cloning Of A Human Monoclonal Antibody Reactive To Ganglioside GM3 Antigen On Human Cancers, " Cancer Res. 53:5244-5250);GICA 19-9(Herlyn et al. (1982) "Monoclonal Antibody Detection Of A Circulating Tumor-Associated Antigen. I. Presence Of Antigen In Sera Of Patients With Colorectal, Gastric, And Pancreatic Carcinoma, " J. Clin. Immunol. 2:135-140);gp100(Lotem, M. et al. 2006 J Immunother. 29(6):616-27);Gp37(human leukemia T cell antigen;Bhattacharya-Chatterjee et al. (1988) "Idiotype Vaccines Against Human T Cell Leukemia. II. Generation And Characterization Of A Monoclonal Idiotype Cascade (Abl, Ab2, and Ab3), " J. Immunol. 141:1398-1403);gp75(melanoma antigen;Vijayasardahl et al. (1990) "The Melanoma Antigen Gp75 Is The Human Homologue Of The Mouse B (Brown) Locus Gene Product, " J. Exp. Med. 171(4):1375-1380);gpA33(Heath, J.K. et al. (1997) "The Human A33 Antigen Is A Transmembrane Glycoprotein And A Novel Member Of The Immunoglobulin Superfamily," Proc. Natl. Acad. Sci. (U.S.A.) 94(2):469-474;Ritter, G. et al. (1997) "Characterization Of Posttranslational Modifications Of Human A33 Antigen, A Novel Palmitoylated Surface Glycoprotein Of Human Gastrointestinal Epithelium," Biochem. Biophys. Res. Commun. 236(3):682-686;Wong, N.A. et al. (2006) "EpCAM and gpA33 Are Markers Of Barrett'sMetaplasia," J. Clin. Pathol. 59(3):260-263);HER2 antigen(HER2/neu, p185HER2;Kumar, Pal S et al. 2006 Semin Oncol. 33(4):386-91);HMFG(human milk fat globule antigen;WO1995015171);human papillomavirus-E6/human papillomavirus-E7(DiMaio, D. et al. 2006 Adv Virus Res. 66:125-59;HMW-MAA(high molecular weight melanoma antigen;Natali et al. (1987) "Immunohistochemical Detection Of Antigen In Human Primary And Metastatic Melanomas By The Monoclonal Antibody 140.240 And Its Possible Prognostic Significance, " Cancer 59:55-63;Mittelman et al. (1990) "Active Specific Immunotherapy In Patients With Melanoma. A Clinical Trial With Mouse Antiidiotypic Monoclonal Antibodies Elicited With Syngeneic Anti-High Molecular-Weight Melanoma Associated Antigen Monoclonal Antibodies," J. Clin. Invest. 86:2136-2144);I antigen(differentiation antigen;Feizi (1985) "Demonstration By Monoclonal Antibodies That Carbohydrate Structures Of Glycoproteins And Glycolipids Are Onco-Developmental Antigens," Nature 314:53-57);IL13Rα2(PCT Publication No. WO 2008/146911;Brown, C.E. et al. (2013) "Glioma IL13Rα2 Is Associated With Mesenchymal Signature Gene Expression And Poor Patient Prognosis," PLoS One. 18;8(10):e77769;Barderas, R. et al. (2012) "High Expression Of IL-13 Receptor A2 In Colorectal Cancer Is Associated With Invasion, Liver Metastasis, And Poor Prognosis," Cancer Res. 72(11):2780-2790;Kasaian, M.T. et al. (2011) "IL-13 Antibodies Influence IL-13 Clearance In Humans By Modulating Scavenger Activity Of IL-13Rα2," J. Immunol. 187(1):561-569;Bozinov, O. et al. (2010) "Decreasing Expression Of The Interleukin-13 Receptor IL-13Ralpha2 In Treated Recurrent Malignant Gliomas," Neurol. Med. Chir. (Tokyo) 50(8):617-621;Fujisawa, T. et al. (2009) "A novel role of interleukin-13 receptor alpha2 in pancreatic cancer invasion and metastasis," Cancer Res. 69(22):8678-8685);Integrin β6(PCT Publication No. WO 03/087340);JAM-3(PCT Publication No. WO 06/084078);KIDS(PCT Publication No. WO 05/028498);HID31(PCT Publication No. WO 06/076584);KS 1/4 pan-carcinoma antigen(Perez et al. (1989) "Isolation And Characterization Of A cDNA Encoding The Ks1/4 Epithelial Carcinoma Marker, " J. Immunol. 142:3662-3667;Möller et al. (1991) "Bi-specific Monoclonal Antibody-Directed Lysis Of Ovarian Carcinoma Cells By Activated Human T Lymphocytes, " Cancer Immunol. Immunother. 33(4):210-216;Ragupathi, G. 2005 Cancer TreatRes. 123:157-80);L6andL20(human lung carcinoma antigens;Hellström et al. (1986) "Monoclonal Mouse Antibodies Raised Against Human Lung Carcinoma, " Cancer Res. 46:3917-3923);LEA; LUCA-2(United States Patent Publication No. 2006/0172349;PCT Publication No. WO 06/083852);M1:22:25:8; M18; M39; MAGE(MAGE-1; MAGE-3; (Bodey, B. 2002 Expert Opin Biol Ther. 2(6):577-84);MART(Kounalakis, N. et al. 2005 Curr Oncol Rep. 7(5):377-82;mesothelin(Chang K, and Pastan I. 1996 "Molecular cloning of mesothelin, a differentiation antigen present onmesothelium, mesotheliomas, and ovarian cancers," Proc Natl Acad Sci USA 93:136-40),MUC-1(Mathelin, C. 2006 Gynecol Obstet Fertil. 34(7-8):638-46);MUM-1(Castelli, C. et al. 2000 J Cell Physiol. 182(3):323-31);Myl; N-acetylglucosaminyltransferase(Dennis, J.W. 1999 Biochim Biophys Acta. 6;1473(1):21-34);neoglycoprotein; NS-10as found in adenocarcinomas;OFA-1; OFA-2; Oncostatin M(Oncostatin Receptor Beta;United States Patent No. 7,572,896;PCT Publication No. WO 06/084092);p15(Gil, J. et al. 2006 Nat Rev Mol Cell Biol. 7(9):667-77);p97(melanoma-associated antigen;Estin et al. (1989) "Transfected Mouse Melanoma Lines That Express Various Levels Of Human Melanoma-Associated Antigen p97," J. Natl. Cancer Instit. 81(6):445-454);PEM(polymorphic epithelial mucin;Hilkens et al. (1992) "Cell Membrane-Associated Mucins And Their Adhesion-Modulating Property, " Trends in Biochem. Sci. 17:359-363);PEMA (polymorphic epithelial mucin antigen); PIPA(United States Patent No. 7,405,061;PCT Publication No. WO 04/043239);PSA(prostate-specific antigen;Henttu et al. (1989) "cDNA Coding For The Entire Human Prostate Specific Antigen Shows High Homologies To The Human Tissue Kallikrein Genes, " Biochem. Biophys. Res. Comm. 10(2):903-910;Israeli et al. (1993) "Molecular Cloning Of A Complementary DNA Encoding A Prostate-Specific Membrane Antigen, " Cancer Res. 53:227-230;Cracco, C.M. et al. 2005 Minerva Urol Nefrol. 57(4):301-11);PSMA(prostate-specific membrane antigen;Ragupathi, G. 2005 Cancer Treat Res. 123:157-180);prostatic acid phosphate(Tailor et al. (1990) "Nucleotide Sequence Of Human Prostatic Acid Phosphatase Determined From A Full-Length cDNA Clone, " Nucl. Acids Res. 18(16):4928);R24as found in melanoma;ROR1(United States Patent No. 5,843,749);sphingolipids; SSEA-1; SSEA-3; SSEA-4; sTn(Holmberg, L.A. 2001 Expert Opin Biol Ther. 1(5):881-91);T cell receptor derived peptidefrom a cutaneous T cell lymphoma (seeEdelson (1998) "Cutaneous T-Cell Lymphoma: A Model For Selective Immunotherapy, " Cancer J Sci Am. 4:62-71);T5A7found in myeloid cells;TAG-72(Yokota et al. (1992) "Rapid Tumor Penetration Of A Single-Chain Fv And Comparison With Other Immunoglobulin Forms, " Cancer Res. 52:3402-3408);TL5(blood group A);TNF-receptor(TNF-α receptor, TNF-β receptor;TNF-y receptor(van Horssen, R. et al. 2006 Oncologist. 11(4):397-408;Gardnerova, M. et al. 2000 Curr Drug Targets. 1(4):327-64);TRA-1-85(blood group H);Transferrin Receptor(United States Patent No. 7,572,895;PCT Publication No. WO 05/121179);5T4(TPBG, trophoblast glycoprotein;Boghaert, E.R. et al. (2008) "The Oncofetal Protein, 5T4, Is A Suitable Target For Antibody-Guided Anti-Cancer Chemotherapy With Calicheamicin," Int. J. Oncol. 32(1):221-234;Eisen, T. et al. (2014)"Naptumomab Estafenatox: Targeted Immunotherapy with a Novel Immunotoxin," Curr. Oncol. Rep. 16:370, pp. 1-6);TSTA (tumor-specific transplantation antigen)such as virally-induced tumor antigens including T-antigen DNA tumor viruses and envelope antigens of RNA tumor viruses, oncofetal antigen-alpha-fetoprotein such as CEA of colon, bladder tumor oncofetal antigen (Hellström et al. (1985) "Monoclonal Antibodies To Cell Surface Antigens Shared By Chemically Induced Mouse Bladder Carcinomas, " Cancer. Res. 45:2210-2188);VEGF(Pietrantonio, F. et al. (2015) "Bevacizumab-Based Neoadjuvant Chemotherapy For Colorectal Cancer Liver Metastases: Pitfalls And Helpful Tricks In A Review For Clinicians," Crit. Rev. Oncol. Hematol. 95(3):272-281;Grabowski, J.P. (2015) "Current Management Of Ovarian Cancer," Minerva Med. 106(3):151-156;Field, K.M. (2015) "Bevacizumab And Glioblastoma: Scientific Review, Newly Reported Updates, And Ongoing Controversies," Cancer 121(7):997-1007;Suh, D.H. et al. (2015) "Major Clinical Research Advances In Gynecologic Cancer In 2014," J. Gynecol. Oncol. 26(2):156-167;Liu, K.J. et al. (2015) "Bevacizumab In Combination With Anticancer Drugs For Previously Treated Advanced Non-Small Cell Lung Cancer," Tumour Biol. 36(3):1323-1327;Di Bartolomeo, M. et al. (2015) "Bevacizumab treatment in the elderly patient with metastatic colorectal cancer," Clin. Interv. Aging 10:127-133);VEGF Receptor(O'Dwyer. P.J. 2006 Oncologist. 11(9):992-998);VEP8; VEP9; VIM-D5;andY hapten, Leyas found in embryonal carcinoma cells.In certain embodiments, such anti-PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, are used in combination with one or more molecules that specifically bind 5T4, B7H3, CD19, CD20, CD51, CD123, DR5, EGFR, EpCam, GD2, gpA33, HER2, ROR-1, TAG-72, VEGF-A antibody, and/or VEGFR2.Such PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 4-6, can be combined with an immunogenic agent such as a tumor vaccine. Such vaccines may comprise purified tumor antigens (including recombinant proteins, peptides, and carbohydrate molecules), autologous or allogeneic tumor cells. A number of tumor vaccine strategies have been described (see for example,Palena, C., et al., (2006) "Cancer vaccines: preclinical studies and novel strategies," Adv. Cancer Res. 95, 115-145;Mellman, I., et al. (2011) "Cancer immunotherapy comes of age," Nature 480, 480-489;Zhang, X. M. et al. (2008) "The anti-tumor immune response induced by a combination of MAGE-3/MAGE-n-derived peptides," Oncol. Rep. 20, 245-252;Disis, M. L. et al. (2002) "Generation of T-cell immunity to theHER-2/neu protein after active immunization with HER-2/neupeptide-based vaccines," J. Clin. Oncol. 20, 2624-2632;Vermeij, R. et al. (2012) "Potentiation of a p53-SLP vaccine by cyclophosphamide in ovarian cancer: a single-arm phase II study." Int. J. Cancer 131, E670-E680). Such PD-1-binding molecules of the invention can be combined with chemotherapeutic regimes. In these instances, it may be possible to reduce the dose of chemotherapeutic reagent administered (Mokyr et al. (1998) Cancer Research 58: 5301-5304).PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, can be combined with other immunostimulatory molecules such as antibodies which activate host immune responsiveness to provide for increased levels of T-cell activation. In particular, anti-PD-1 antibodies, anti-PD-L1 antibodies and/or an anti-CTLA-4 antibodies have been demonstrated to active the immune system (see,e.g.,del Rio, M-L. et al. (2005) "Antibody-Mediated Signaling Through PD-1 Costimulates T Cells And Enhances CD28-Dependent Proliferation," Eur. J. Immunol 35:3545-3560;Barber, D. L. et al. (2006) "Restoring function in exhausted CD8 T cells during chronic viral infection," Nature 439, 682-687;Iwai, Y. et al. (2002) "Involvement Of PD-L1 On Tumor Cells In The Escape From Host Immune System And Tumor Immunotherapy By PD-L1 Blockade," Proc. Natl Acad. Sci. USA 99, 12293-12297;Leach, D. R., et al., (1996) "Enhancement Of Antitumor Immunity By CTLA-4 Blockade," Science 271, 1734-1736). Additional immunostimulatory molecules that may be combined with the PD-1-binding molecules of the invention include antibodies to molecules on the surface of dendritic cells that activate dendritic cell (DC) function and antigen presentation, anti-CD40 antibodies able to substitute for T-cell helper activity, and activating antibodies to T-cell costimulatory molecules such as PD-L1, CTLA-4, OX-40 4-1BB, and ICOS (see, for example,Ito et al. (2000) "Effective Priming Of Cytotoxic T Lymphocyte Precursors By Subcutaneous Administration Of Peptide Antigens In Liposomes Accompanied By Anti-CD40 And Anti-CTLA-4 Antibodies,"Immunobiology 201:527-40;U.S. Pat. No. 5,811,097;Weinberg et al. (2000) "Engagement of the OX-40 Receptor In Vivo Enhances Antitumor Immunity," Immunol 164:2160-2169;Melero et al. (1997) "Monoclonal Antibodies Against The 4-IBB T-Cell Activation Molecule Eradicate Established Tumors," Nature Medicine 3: 682-685;Hutloff et al. (1999) "ICOS Is An Inducible T-Cell Co-Stimulator Structurally And Functionally Related To CD28," Nature 397: 263-266; andMoran, A.E. et al. (2013) "The TNFRs OX40, 4-IBB, and CD40 As Targets For Cancer Immunotherapy," Curr Opin Immunol. 2013 Apr; 25(2): 10.1016/j.coi.2013.01.004), and/or stimulatory Chimeric Antigen Receptors(CARs)comprising an antigen binding domain directed against a diseaseantigen fused to one or more intracellular signaling domains from various costimulatory protein receptors (e.g.,CD28, 4-1BB, ICOS, OX40,etc.) which serve to stimulate T-cells upon antigen binding (see, for example,Tettamanti, S. et al. (2013) "Targeting Of Acute Myeloid Leukaemia By Cytokine-Induced Killer Cells Redirected With A Novel CD123-Specific Chimeric Antigen Receptor," Br. J. Haematol. 161:389-401;Gill, S. et al. (2014) "Efficacy Against Human Acute Myeloid Leukemia And Myeloablation Of Normal Hematopoiesis In A Mouse Model Using Chimeric Antigen ReceptorModified T Cells," Blood 123(15): 2343-2354;Mardiros, A. et al. (2013) "T Cells Expressing CD123-Specific Chimeric Antigen Receptors Exhibit Specific Cytolytic Effector Functions And Antitumor Effects Against Human Acute Myeloid Leukemia," Blood 122:3138-3148;Pizzitola, I. et al. (2014) "Chimeric Antigen Receptors Against CD33/CD123 Antigens Efficiently Target Primary Acute Myeloid Leukemia Cells in vivo," Leukemia doi:10.1038/leu.2014.62).PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, can be combined with inhibitory Chimeric Antigen Receptors(iCARs)to divert off target immunotherapy responses. iCARs an antigen binding domain directed against a disease antigen fused to one or more intracellular signaling domains from various inhibitory protein receptors (e.g.,CTLA-4, PD-1,etc.) which serve to constrain T-cell responses upon antigen binding (see, for example,Fedorov V.D. (2013) "PD-1-and CTLA-4-Based Inhibitory Chimeric Antigen Receptors (iCARs) Divert Off-Target Immunotherapy Responses," Sci. Tranl. Med. 5:215ra172 doi:10.1126/ scitranslmed.3006597.In particular, such anti-PD-1-binding molecules of the invention, as defined by and for use in accordance with claims 1-6, are used in combination with an anti-CD137 antibody, an anti-CTLA-4 antibody, an anti-OX40 antibody, an anti-LAG-3 antibody, an anti-PD-L1 antibody, an anti-TIGIT antibody, and/or an anti TIM-3 antibody.B. Diagnostic and Theranostic UtilityCertain of the PD-1-binding molecules disclosed herein exhibit little of no ability to block binding between PD-1 and the PD-1L ligand. As such, antibodies PD-1 mAb 2 and PD-1 mAb 4, their humanized derivatives, and molecules comprising their PD-1-binding fragments (e.g.,bispecific diabodies,etc.) or that compete for binding with such antibodies may be detectably labeled (e.g., with radioactive, enzymatic, fluorescent, chemiluminescent, paramagnetic, diamagnetic, or other labelling moieties) and used in the detection of PD-1 in samples or in the imaging of PD-1 on cells. Since such molecules do not affect the biologicalactivity of PD-1, they are particularly useful in methods of determining the extent, location and change in PD-1 expression in subjects (e.g., subjects being treated for cancer associated with the expression or targeting of PD-1).XII. Pharmaceutical CompositionsCompositions include bulk drug compositions useful in the manufacture of pharmaceutical compositions (e.g., impure or non-sterile compositions) and pharmaceutical compositions (i.e., compositions that are suitable for administration to a subject or patient) that can be used in the preparation of unit dosage forms. Such compositions may comprise a prophylactically or therapeutically effective amount of the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, or a combination of such agents and a pharmaceutically acceptable carrier. Preferably, compositions may comprise a prophylactically or therapeutically effective amount of the PD-1-binding molecules of the present invention and a pharmaceutically acceptable carrier.Such pharmaceutical compositions may additionally include a second therapeutic antibody (e.g., tumor-specific monoclonal antibody) that is specific for a particular cancer antigen, and a pharmaceutically acceptable carrier.The term "pharmaceutically acceptable" means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant (e.g., Freund's adjuvant (complete and incomplete), excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like. Water is a preferred carrier when the pharmaceutical composition is administered intravenously. Saline solutions and aqueous dextrose and glycerol solutions can also be employed as liquid carriers, particularly for injectable solutions. Suitable pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, ethanol and the like. The composition, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. These compositions can take the form of solutions, suspensions, emulsion, tablets, pills, capsules, powders, sustained-release formulations and the like.Generally, the ingredients of compositions are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline. Where the composition is administered by inj ection, an ampoule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration.Compositions can be formulated as neutral or salt forms. Pharmaceutically acceptable salts include, but are not limited to those formed with anions such as those derived from hydrochloric, phosphoric, acetic, oxalic, tartaric acids,etc.,and those formed with cations such as those derived from sodium, potassium, ammonium, calcium, ferric hydroxides, isopropylamine, triethylamine, 2-ethylamino ethanol, histidine, procaine,etc.A kit can comprise any of the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6. The kit can further comprise one or more other prophylactic and/or therapeutic agents useful for the treatment of cancer, in one or more containers; and/or the kit can further comprise one or more cytotoxic antibodies that bind one or more cancer antigens associated with cancer. In certain embodiments, the other prophylactic or therapeutic agent is a chemotherapeutic. In other embodiments, the prophylactic or therapeutic agent is a biological or hormonal therapeutic.XIII. Methods of AdministrationVarious delivery systems are known and can be used to administer the compositions disclosed herein,e.g., encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the antibody or fusion protein, receptor-mediated endocytosis (See,e.g.,Wu et al. (1987) "Receptor Mediated In Vitro Gene Transformation By A Soluble DNA Carrier System, " J. Biol. Chem. 262:4429-4432), construction of a nucleic acid as part of a retroviral or other vector,etc.Methods of administering a molecule of the invention, as defined by and for use in accordance with claims 1-6, include, but are not limited to, parenteral administration (e.g., intradermal, intramuscular, intraperitoneal, intravenous and subcutaneous), epidural, and mucosal (e.g., intranasal and oral routes). In a specific embodiment, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6,are administered intramuscularly, intravenously, or subcutaneously. The compositions may be administered by any convenient route, for example, by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa,etc.) and may be administered together with other biologically active agents. Administration can be systemic or local. In addition, pulmonary administration can also be employed,e.g., by use of an inhaler or nebulizer, and formulation with an aerosolizing agent. See,e.g.,U.S. Patent Nos. 6,019,968;5,985, 320;5,985,309;5,934,272;5,874,064;5,855,913;5,290,540; and4,880,078; andPCT Publication Nos. WO 92/19244;WO 97/32572;WO 97/44013;WO 98/31346; andWO 99/66903.The PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, may be packaged in a hermetically sealed container such as an ampoule or sachette indicating the quantity of the molecule. Such molecules may be supplied as a dry sterilized lyophilized powder or water free concentrate in a hermetically sealed container and can be reconstituted,e.g., with water or saline to the appropriate concentration for administration to a subject. Preferably, the PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, are supplied as a dry sterile lyophilized powder in a hermetically sealed container.The lyophilized PD-1-binding molecules of the present invention, as defined by and for use in accordance with claims 1-6, should be stored at between 2°C and 8°C in their original container and the molecules should be administered within 12 hours, preferably within 6 hours, within 5 hours, within 3 hours, or within 1 hour after being reconstituted. In an alternative embodiment, such molecules are supplied in liquid form in a hermetically sealed container indicating the quantity and concentration of the molecule, fusion protein, or conjugated molecule. Preferably, such PD-1-binding molecules when provided in liquid form are supplied in a hermetically sealed container.The amount of the composition which will be effective in the treatment, prevention or amelioration of one or more symptoms associated with a disorder can be determined by standard clinical techniques. The precise dose to be employed in the formulation will also depend on the route of administration, and the seriousness of the condition, and should be decided according to the judgment of the practitioner and each patient's circumstances. Effective doses may be extrapolated from dose-response curves derived from in vitro or animal model test systems.As used herein, an "effective amount"of a pharmaceutical composition, is an amount sufficient to effect beneficial or desired results including, without limitation, clinical results such as decreasing symptoms resulting from the disease, attenuating a symptom of infection (e.g., viral load, fever, pain, sepsis,etc.) or a symptom of cancer (e.g.,the proliferation, of cancer cells, tumor presence, tumor metastases,etc.),thereby increasing the quality of life of those suffering from the disease, decreasing the dose of other medications required to treat the disease, enhancing the effect of another medication such as via targeting and/or internalization, delaying the progression of the disease, and/ or prolonging survival of individuals.An effective amount can be administered in one or more administrations.An effective amount of drug, compound, or pharmaceutical composition is an amount sufficient to reduce the proliferation of (or the effect of) viral presence and to reduce and /or delay the development of the viral disease, either directly or indirectly. In some instances, an effective amount of a drug, compound, or pharmaceutical composition may or may not be achieved in conjunction with another drug, compound, or pharmaceutical composition. Thus, an "effective amount" may be considered in the context of administering one or more chemotherapeutic agents, and a single agent may be considered to be given in an effective amount if, in conjunction with one or more other agents, a desirable result may be or is achieved. While individual needs vary, determination of optimal ranges of effective amounts of each component is within the skill of the art.For the PD-1-binding molecules encompassed by the invention, as defined by and for use in accordance with claims 1-6, the dosage administered to a patient is preferably determined based upon the body weight (kg) of the recipient subject. For the PD-1-binding molecules encompassed by the invention, the dosage administered to a patient is typically at least about 0.01 µg/kg, at least about 0.05 µg/kg, at least about 0.1 µg/kg, at least about 0.2 µg/kg, at least about 0.5 µg/kg, at least about 1 µg/kg, at least about 2 µg/kg, at least about 5 µg/kg, at least about 10 µg/kg, at least about 20 µg/kg, at least about 50 µg/kg, at least about 0.1 mg/kg, at least about 1 mg/kg, at least about 3 mg/kg, at least about 5 mg/kg, at least about 10 mg/kg, at least about 30 mg/kg, at least about 50 mg/kg, at least about 75 mg/kg, at least about 100 mg/kg, at least about 125 mg/kg, at least about 150 mg/kg or more of the subject's body weight.The dosage and frequency of administration of a PD-1-binding molecule of the present invention, as defined by and for use in accordance with claims 1-6, may be reduced or altered by enhancing uptake and tissue penetration of the molecule by modifications such as, for example, lipidation.The dosage of a PD-1-binding molecule of the invention, as defined by and for use in accordance with claims 1-6, administered to a patient may be calculated for use as a single agent therapy. Alternatively, the molecule may be used in combination with other therapeutic compositions and the dosage administered to a patient are lower than when said molecules are used as a single agent therapy.The pharmaceutical compositions disclosed herein may be administered locally to the area in need of treatment; this may be achieved by, for example, and not by way of limitation, local infusion, by injection, or by means of an implant, said implant being of a porous, non-porous, or gelatinous material, including membranes, such as sialastic membranes, or fibers. Preferably, when administering a molecule of the invention, as defined by and for use in accordance with claims 1-6, care must be taken to use materials to which the molecule does not absorb.The compositions disclosed herein can be delivered in a vesicle, in particular a liposome (SeeLanger (1990) "New Methods Of Drug Delivery," Science 249:1527-1533);Treat et al., in LIPOSOMES IN THE THERAPY OF INFECTIOUS DISEASE AND CANCER, Lopez-Berestein and Fidler (eds.), Liss, New York, pp. 353- 365 (1989); Lopez-Berestein, ibid., pp. 3 17-327).The compositions disclosed herein can be delivered in a controlled-release or sustained-release system. Any technique known to one of skill in the art can be used to produce sustained-release formulations comprising one or more of the PD-1-binding molecule(s) of the invention, as defined by and for use in accordance with claims 1-6.See, e.g.,U.S. Patent No. 4,526,938;PCT publication WO 91/05548;PCT publication WO 96/20698;Ning et al. (1996) "Intratumoral Radioimmunotheraphy Of A Human Colon Cancer Xenograft Using A Sustained-Release Gel, " Radiotherapy& Oncology 39:179-189,Song et al. (1995) "Antibody Mediated Lung Targeting Of Long-Circulating Emulsions, " PDA Journal of Pharmaceutical Science& Technology 50:372-397;Cleek et al. (1997) "Biodegradable Polymeric Carriers For A bFGF Antibody For Cardiovascular Application, " Pro. Int'l. Symp. Control. Rel.Bioact. Mater. 24:853-854; andLam et al. (1997) "Microencapsulation Of Recombinant Humanized Monoclonal Antibody For Local Delivery, " Proc. Int'l. Symp. Control Rel. Bioact. Mater. 24:759-760. A pump may be used in a controlled-release system(SeeLanger,supra;Sefton, (1987) "Implantable Pumps, " CRC Crit. Rev. Biomed. Eng. 14:201-240;Buchwald et al. (1980) "Long-Term, Continuous Intravenous Heparin Administration By An Implantable Infusion Pump In Ambulatory Patients With Recurrent Venous Thrombosis, " Surgery 88:507-516; andSaudek et al. (1989) "A Preliminary Trial Of The Programmable Implantable Medication System For Insulin Delivery, "N. Engl. J. Med. 321:574-579). Polymeric materials can be used to achieve controlled-release of the molecules (see e.g.,MEDICAL APPLICATIONS OF CONTROLLED RELEASE, Langer and Wise (eds.), CRC Pres., Boca Raton, Florida (1974);CONTROLLED DRUG BIOAVAILABILITY, DRUG PRODUCT DESIGN AND PERFORMANCE, Smolen and Ball (eds.), Wiley, New York (1984);Levy et al. (1985) "Inhibition Of Calcification Of Bioprosthetic Heart Valves By Local Controlled-Release Diphosphonate, " Science 228:190-192;During et al. (1989) "Controlled Release Of Dopamine From A Polymeric Brain Implant: In Vivo Characterization, " Ann. Neurol. 25:351-356;Howard et al. (1989) "Intracerebral Drug Delivery In Rats With Lesion-Induced Memory Deficits, " J. Neurosurg. 7(1):105-112);U.S. Patent No. 5,679,377;U.S. Patent No. 5,916,597;U.S. Patent No. 5,912,015;U.S. Patent No. 5,989,463;U.S. Patent No. 5,128,326;PCT Publication No. WO 99/15154; andPCT Publication No. WO 99/20253). Examples of polymers used in sustained-release formulations include, but are not limited to, poly(2-hydroxy ethyl methacrylate), poly(methyl methacrylate), poly(acrylic acid), poly(ethylene-co-vinyl acetate), poly(methacrylic acid), polyglycolides (PLG), polyanhydrides, poly(N-vinyl pyrrolidone), poly(vinyl alcohol), polyacrylamide, poly(ethylene glycol), polylactides (PLA), poly(lactide-co-glycolides) (PLGA), and polyorthoesters. A controlled-release system can be placed in proximity of the therapeutic target (e.g.,the lungs), thus requiring only a fraction of the systemic dose (see,e.g.,Goodson, in MEDICAL APPLICATIONS OF CONTROLLED RELEASE, supra, vol. 2, pp. 115-138 (1984)). Polymeric compositions useful as controlled-release implants can be used according to Dunnet al.(SeeU.S. 5,945,155). This particular method is based upon the therapeutic effect of the in situ controlled-release of the bioactive material from the polymer system. The implantation can generally occur anywhere within the body of the patient in need of therapeutic treatment. A non-polymeric sustained delivery system can be used, whereby a non-polymeric implant in the body of the subject is used as a drug delivery system. Upon implantation in the body, the organic solvent of the implant will dissipate, disperse, or leach from the composition intosurrounding tissue fluid, and the non-polymeric material will gradually coagulate or precipitate to form a solid, microporous matrix (SeeU.S. 5,888,533).Controlled-release systems are discussed in the review byLanger (1990, "New Methods Of Drug Delivery, " Science 249:1527-1533). Any technique known to one of skill in the art can be used to produce sustained-release formulations comprising one or more therapeutic agents of the invention referred to herein. See,e.g.,U.S. Patent No. 4,526,938; International Publication Nos.WO 91/05548andWO 96/20698;Ning et al. (1996) "Intratumoral Radioimmunotheraphy Of A Human Colon Cancer Xenograft Using A Sustained-Release Gel, " Radiotherapy& Oncology 39:179-189,Song et al. (1995) "Antibody Mediated Lung Targeting Of Long-Circulating Emulsions, " PDA Journal of Pharmaceutical Science& Technology 50:372-397;Cleek et al. (1997) "Biodegradable Polymeric Carriers For A bFGF Antibody For Cardiovascular Application, " Pro. Int'l. Symp. Control. Rel. Bioact. Mater. 24:853-854; andLam et al. (1997) "Microencapsulation Of Recombinant Humanized Monoclonal Antibody For Local Delivery, " Proc. Int'l. Symp. Control Rel. Bioact. Mater. 24:759-760.Treatment of a subject with a therapeutically or prophylactically effective amount of a PD-1-binding molecule of the present invention, as defined by and for use in accordance with claims 1-6, can include a single treatment or, preferably, can include a series of treatments. The pharmaceutical compositions disclosed herein can be administered once a day, twice a day, or three times a day. Alternatively, the pharmaceutical compositions can be administered once a week, twice a week, once every two weeks, once a month, once every six weeks, once every two months, twice a year or once per year. It will also be appreciated that the effective dosage of the molecules used for treatment may increase or decrease over the course of a particular treatment.ExamplesThe following examples illustrate various methods for compositions in the diagnostic or treatment methods.Example 1Characterization of Anti-Human PD-1 Monoclonal AntibodiesFifteen murine monoclonal antibodies were isolated as being capable specifically binding to both human and cynomolgus monkey PD-1, and accorded the designations"PD-1mAb 1," "PD-1 mAb 2," "PD-1 mAb 3," "PD-1 mAb 4," "PD-1 mAb 5,""PD-1 mAb 6,""PD-1 mAb 7," "PD-1 mAb 8," "PD-1 mAb 9," "PD-1 mAb 10 > " "PD-1 mAb 11,""PD-1 mAb 12," "PD-1 mAb 13," "PD-1 mAb 14," and "PD-1 mAb 15."The CDRs of these antibodies were found to differ and are provided above. Binding to the extracellular domain of human and cynomologus monkey PD-1 was evaluated as follows, flat bottom maxisorb 96-well plates were coated with soluble human or cynomolgus monkey PD-1 (the extracellular domain of human PD-1 fused to a His tag (shPD-1 His) or to a human Fc Region (shPD-1 hFc), or the extracellular domain of cynomolgus monkey PD-1 fused to a human Fc Region (scyno-PD1 Fc)) each at 0.5 or 1 µg/mL, the plates were washed and incubated with one of the isolated anti-PD-1 antibodies PD-1 mAb 1-15. For these studies the anti-PD-1 antibodies were utilized at 3, 1.0, 0.3333, 0.1111, 0.0370, 0.0123, or 0.0041 µg/mL (three fold serial dilutions). The amount of antibody binding to the immobilized PD-1 (human or cynomolgus monkey) was assessed using a goat anti-mouse IgG-HRP secondary antibody. All samples were analyzed on a plate reader (Victor 2 Wallac, Perkin Elmers). Representative binding curves for soluble human and soluble cynomolgus PD-1 are shown inFigures 7A-7DandFigures 8A-8C,respectively.The results of these binding assays(Figures 7A-7DandFigures 8A-8C)show that all the anti-PD-1 antibodies PD-1 mAb 1-15 bind to both soluble human and soluble cynomolgus monkey PD-1.In order to further characterize the murine anti-PD-1 antibodies their ability to block binding of soluble human PD-L1 to soluble human PD-1 was assessed in two different assays. In one assay the ability of the antibodies to block the binding of human PD-1 to PD-L1 immobilized on a surface was examined. For this assay each of the anti-PD-1 antibodies PD-1 mAb 1-15, or a reference anti-PD-1 antibody (PD-1 mAb A) was mixed with shPD-1 His fusion protein, (at 2.5 µg/mL) and was separately incubated with biotin labeled soluble human PD-L1 (the extracellular domain of PD-L1 fused to human Fc (sPD-L1)) at 1 µg/mL immobilized on a streptavidin coated plate. For these studies the anti-PD-1 antibodies were utilized at 10, 5.0, 2.5, 1.25, 0.625, 0.3125, or 0.1563 µg/mL (two fold serial dilutions). The amount of shPD-1 His binding to the immobilized sPD-L1 was assessed via the His-Tag using an anti-His-Tag-HRP secondary antibody. All samples were analyzed on a plate reader (Victor 2 Wallac, Perkin Elmers). The results of this experiment are shown inFigures 9A-9D.The results of these inhibition assays(Figures 9A-9D)show that the anti-PD-antibodies PD-1 mAb 1, PD-1 mAb 3, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 8, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15, were able to block the binding of soluble human PD-L1 to soluble human PD-1 to varying degrees while PD-1 mAb 2 and PD-1 mAb 4 exhibited little to no blocking activity in this assay format.In the second assay the ability of the murine anti-PD-1 antibodies PD-1 mAb 1-15 to block binding of PD-1 ligand (i.e., human PD-L1 or human PD-L2) to PD-1 expressed on the surface of NSO cells was examined. For this assay each of the anti-PD-1 antibodies PD-1 mAb 1-15, or a reference anti-PD-1 antibody (PD-1 mAb A or PD-1 mAb B) was separately mixed with a biotinylated-soluble human PD-L1 (shPD-L1 fusion protein) or biotinylated-soluble human PD-L2-muIgFc fusion protein (shPD-L2; Ancell Cat# 573-030), each at 0.1 µg/test, and incubated with NSO cells expressing human PD-1 (~250,000 cells/well) in blocking buffer (FACS + 10% human serum albumin). For these studies the anti-PD-1 antibodies were utilized at 4.0, 1.0, 2.5 ×10-1, 6.25 × 10-2, 1.56 × 10-2, 3.90 × 10-3, 9.76 × 10-4, 2.4 × 10-4, 0.6 × 10-4µg/test (four fold serial dilutions). The amount of shPD-L1 (or shPD-L2) binding to the surface of the NSO cells was determined using a PE-conjugated Streptavidin secondary antibody by FACS analysis. The IC50 values for inhibition of PD-1/PD-L1 binding were determined and the sample mean (x) of at least two experiments are provided (except where indicated) inTable 6.Table 6Anti-PD-1 AntibodyIC50 (µg/test)Anti-PD-1 AntibodyIC50 (µg/test)PD-1 mAb A0.0044PD-1 mAb 80.6611 ‡PD-1 mAb B0.0064PD-1 mAb 90.0154PD-1 mAb 10.0048PD-1 mAb 100.0057PD-1 mAb 20.0110PD-1 mAb 110.0259 ‡PD-1 mAb 30.0361 ‡PD-1 mAb 120.0238 ‡PD-1 mAb 40.0156 ‡PD-1 mAb 130.0117PD-1 mAb 50.0039PD-1 mAb 140.0149 ‡PD-1 mAb 60.0051PD-1 mAb 150.0060PD-1 mAb 70.0024‡ Results from a single experimentThe results of the shPD-L1 inhibition assays(Table 6)show that the anti-PD-1 antibodies PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 11, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, and PD-1 mAb 15, were able to block the binding of human PD-L1 to human PD-1expressed on the surface of NSO cells. In particular, PD-1 mAb 1, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 10, and PD-1 mAb 15 blocked shPD-L1 binding as well as or better than the reference PD-1 antibodies (PD-1 mAb A, PD-1 mAb B), while PD-1 mAb 8 was essentially non-blocking in this assay format. Both PD-1 mAb 2 and PD-1 mAb 4 were able to block PD-1/PD-L1 binding in this assay format.Similarly, the anti-PD-1 antibodies PD-1 mAb 1, PD-1 mAb 2, and PD-1 mAb 3, PD-1 mAb 4, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, PD-1 mAb 9, PD-1 mAb 10, PD-1 mAb 12, PD-1 mAb 13, PD-1 mAb 14, were able to block the binding of human PD-L2 to human PD-1 expressed on the surface of NSO cells, while PD-1 mAb 8 was essentially non-blocking in this assay format. In particular, PD-1 mAb 1, PD-1 mAb 5, PD-1 mAb 6, PD-1 mAb 7, and PD-1 mAb 10 blocked shPD-L2 binding as well as, or better than the reference PD-1 antibodies (PD-1 mAb A, PD-1 mAb B). The PD-1 antibodies PD-1 mAb 11 and PD-1 mAb 15 were not tested in this assay. The results for several humanized anti-PD-1 antibodies including hPD-1 mAb 15 are provided below.Example 2Humanization and Further CharacterizationThe Variable Domains of the anti-PD-1 antibodies PD-1 mAb 1, PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 were humanized, where antigenic epitopes were identified the antibodies were further deimmunized to generate the final humanized Variable Domains. Humanization of PD-1 mAb 1, PD-1 mAb 2, and PD-1 mAb 15 yielded one humanized VH Domain and one humanized VL Domain for each antibody designated herein as"hPD-1 mAb 1 VH1,"and"hPD-1 mAb 1 VL1;" "hPD-1 mAb 2 VH1,"and"hPD-1 mAb 2 VL1;"and"hPD-1 mAb 15 VH1,"and"hPD-1 mAb 15 VL1."Humanization of PD-1 mAb 7 yielded two humanized VH Domains, designated herein as"hPD-1 mAb 7 VH1,"and"hPD-1 mAb 7 VH2,"and three humanized VL Domains designated herein as"hPD-1 mAb 1 VL1," "hPD-1 mAb 7 VL2,"and"hPD-1 mAb 7 VL3."Humanization of PD-1 mAb 9 yielded two humanized VH Domains, designated herein as"hPD-1 mAb 9 VH1,"and"hPD-1 mAb 9 VH2,"and two humanized VL Domains designated herein as"hPD-1 mAb 9 VL1,"and"hPD-1 mAb 1 VL2."Where multiple humanized Variable Domains were generated the humanized heavy and light chain Variable Domains of a particular anti-PD-1 antibody (e.g., PD-1 mAb 7) may be used in any combination and particular combinations of humanized chains are referred to by reference to the specific VH/VL Domains, for example a humanized antibody comprising hPD-1 mAb 7 VH1 and hPD-1 mAb 7 VL2 is specifically referred to as"hPD-1 mAb 7(1.2)."Full length humanized antibodies were generated with either a human IgG1 constant region comprising the L234A/L235A substitutions (IgG1 (AA)) or a human IgG4 constant region comprising the S228P substitution (IgG4 (P)).Full length IgG1 humanized antibody heavy chains were constructed as follows: the C-terminus of the humanized VH Domain was fused to the N-terminus of a human IgG1 Constant Region having a variant CH2-CH3 Domain (comprising the L234A/L235A (AA) substitutions) and lacking the C-terminal lysine residue(SEQ ID NO:255):InSEQ ID NO:255,amino acid residues 1-98 correspond to the IgG1 CH1 Domain(SEQ ID NO: 10),amino acid residues 99-113 correspond to the IgG1 hinge region(SEQ ID NO: 32)and amino acid residues 114-329 correspond to the IgG1 CH2-CH3 Domain comprising the L234A/L235A substitutions (underlined)(SEQ ID NO:5)but lacking the C-terminal lysine residue.The amino acid sequence of a heavy chain of an exemplary humanized antibody ((hPD-1 mAb 7(1.2)) having an IgG1 heavy chain constant region comprising the L234A/L235A mutation and lacking the C-terminal lysine residue is(SEQ ID NO:265):InSEQ ID NO: 265,amino acid residues 1-119 correspond to the VH Domain of hPD-1 mAb 7 VH1(SEQ ID NO: 147),amino acid residues 120-217 correspond to the IgG1 CH1 Domain(SEQ ID NO: 10),residues 218-232 correspond to the IgG1 hinge region(SEQ ID NO: 32)and residues 233-448 correspond to the IgG1 CH2-CH3 Domain comprising theL234A/L235A substitutions (underlined)(SEQ ID NO:5)but lacking the C-terminal lysine residue.Full length IgG4 humanized antibody heavy chains were constructed as follows: the C-terminus of the humanized VH Domain was fused to the N-terminus of a human IgG4 Constant Region having a stabilized hinge region (comprising the S228P substitution) and lacking the C-terminal lysine residue(SEQ ID NO:256):InSEQ ID NO:256,amino acid residues 1-98 correspond to the IgG4 CH1 Domain(SEQ ID NO:254),amino acid residues 99-110 correspond to the stabilized IgG4 hinge region comprising the S228P substitutions (underlined)(SEQ ID NO: 13)and amino acid residues 111-326 correspond to the IgG4 CH2-CH3 Domain(SEQ ID NO:4)but lacking the C-terminal lysine residue.The amino acid sequence of a heavy chain of an exemplary humanized antibody ((hPD-1 mAb 7(1.2)) having an IgG4 heavy chain constant region comprising a stabilized hinge region having the S228P mutation and lacking the C-terminal lysine residue is(SEQ ID NO:266):InSEQ ID NO:266,amino acid residues 1-119 correspond to the VH Domain of hPD-1 mAb 7 VH1(SEQ ID NO:147),amino acid residues 120-217 correspond to the IgG4 CH1 Domain(SEQ ID NO:254),amino acid residues 218-229 correspond to the stabilized IgG4 hinge region comprising the S228P substitutions (underlined)(SEQ ID NO:13)andamino acid residues 230-445 correspond to the IgG4 CH2-CH3 Domain(SEQ ID NO:4)but lacking the C-terminal lysine residue.Full length humanized antibody light chains were constructed as follows: the C-terminus of the humanized VL Domain was fused to the N-terminus of a human light chain kappa region(SEQ ID NO:8).The same light chain is paired with the IgG1 (AA) and the IgG4 (P) heavy chains.The amino acid sequence of a light chain of an exemplary humanized PD-1 antibody (hPD-1 mAb 7(1.2)) having a kappa constant region is(SEQ ID NO:264):InSEQ ID NO:264,amino acid residues 1-111 correspond to the VL Domain of hPD-1 mAb 7 VL2(SEQ ID NO:153),and amino acid residues 112-218 correspond to the light chain kappa constant region(SEQ ID NO: 8).Anti-PD-1 antibodies having alternative Constant Regions, for example Engineered Fc Regions, are readily generated by incorporating different Constant Regions and/or by introducing one or more amino acid substitutions, additions or deletions. For example, where a bispecific antibody is desired knob-bearing and hole-bearing CH2-CH3 domains are used to facilitate heterodimerization. Chimeric anti-PD-1 antibodies comprising the murine Variable Domains and human Constant Regions are generated as described above.The humanized antibodies (IgG1 (AA) and/or IgG4 (P)) were tested for binding and blocking activity as described in above. The binding to human PD-1 (shPD-1 His, and shPD-1 hFc) and cynomolgus monkey PD-1 (shPD-L1 hFc) of the humanized antibodies was comparable to that of the corresponding murine antibody. In addition, the humanized antibodies retained the ability to block the binding of human PD-L1 to human PD-1 in an ELISA assay.The binding kinetics of the murine antibodies PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, PD-1 mAb 15, the humanized antibodies hPD-1 mAb 2, hPD-1 mAb 7(1.2), hPD-1 mAb 9(1.1), hPD-1 mAb 15, and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb Bwas investigated using Biacore analysis. The anti-PD-1 antibodies were captured on immobilized Protein A and were incubated with His-tagged soluble human PD-1 (shPD-1-His) or soluble human cynomolgus monkey PD-1 Fc fusion (scyno PD-1 hFc) cleaved to remove Fc portion, and the kinetics of binding was determined via Biacore analysis. In additional studies the anti-PD-1 antibodies hPD-1 mAb 7(1.2) IgG1 (AA), hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 9(1.1) IgG1 (AA), hPD-1 mAb 9(1.1) IgG4 (P), PD-1 mAb A IgG1 (AA), PD-1 mAb A IgG4 (P), PD-1 mAb B IgG1 (AA), and PD-1 mAb B IgG4 (P), were captured on immobilized F(ab)2goat anti-human Fc and the binding kinetics were determined by Biacore analysis as described above. The calculated ka, kd and KD from these studies are presented inTable 7.Table 7Protein A CaptureAnti-PD-1 AntibodyHumanaCynomolgus Monkeybka(x104)kd(x10-4)KD(nM)ka(x104)kd(x10-4)KD(nM)PD-1 mAb A60183149.66.9PD-1 mAb B140352.537123.2PD-1 mAb 7212.81.31763.5hPD-1 mAb 7(1.2)1104.30.39376.41.7PD-1 mAb 94.34.29.82.21672.7hPD-1 mAb 9(1.1)1.86.536.11.51173.3PD-1 mAb 154.51.32.92.71140.7hPD-1 mAb 152.43.213.32.31878.3PD-1 mAb 25.55.610.24.26.014.3hPD-1 mAb 23.21.65.02.33.917F(ab)2goat anti-human Fc CapturePD-1 mAb A IgG1 (AA)138.46.58.14.55.6PD-1 mAb A IgG4 (P)137.96.18.45.06.0PD-1 mAb B IgG1 (AA)252811.2206.43.2PD-1 mAb B IgG4 (P)26259.6207.94.0hPD-1 mAb 7(1.2) IgG1 (AA)253.81.5167.84.9hPD-1 mAb 7(1.2) IgG4 (P)274.11.5177.84.6hPD-1 mAb 9(1.1) IgG1 (AA)5.66.110.95.65.29.3hPD-1 mAb 9(1.1) IgG4 (P)6.15.89.54.97.415.1aHis tagged soluble human PD-1 (shPD-1 His)bsoluble cynomolgus monkey PD-1 (scyno PD-1 hFc) cleavedThe results demonstrate that PD-1 mAb 7 and the humanized hPD-1 mAb 7(1.2) exhibit better binding kinetics relative to the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B. PD-1 mAb 2, and hPD-1 mAb 2 exhibit binding kinetics within about two fold of the reference anti-PD-1 antibodies while PD-1 mAb 9, hPD-1 mAb 9(1.1), PD-1 mAb 15, and hPD-1 mAb 15 exhibit binding kinetics within about 2-6 fold of the reference anti-PD-1 antibodies.The tissue specificity of the anti-human PD-1 antibody PD-1 mAb 7 was investigated. Normal tissue was contacted with PD-1 mAb 7 or with an isotype control (0.313 µg/mL) and the extent of staining was visualized. Bloxall used for endogenous enzyme block to reduce non-specific mucin staining in the colon tissue. As shown inFigure 10A, Panels i-xii,PD-1 mAb 7 and the isotype control both failed to label cells of normal colon, liver, lung, pancreas, kidney and heart tissue. In addition, PD-1 mAb 7 and the isotype control failed to stain normal skin(Figure 10B, Panels i-ii).In contrast, PD-1 mAb 7 was found to strongly label lymphocytes present in normal tonsil tissue and PDCD1 transfected NSO cells expressing PD-1(Figure 10B, Panels iii and v),while the isotype control failed to label either(Figure 10B, Panels iv and vi).The results presented inFigures 10A-10Bthus indicate that PD-1 mAb 7 was capable of specifically binding to lymphocytes and cells expressing PD-1.The binding saturation profiles of hPD-1 mAb 2 IgG1 (AA), hPD-1 mAb 7(1.1) IgG1 (AA), hPD-1 mAb 7(1.2) IgG1, (AA), hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 9(1.1) IgG1 (AA), hPD-1 mAb 9(1.1) IgG4 (P), hPD-1 mAb 15 IgG1 (AA), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B was examined. Briefly, each of the anti-PD-1 antibodies, PD-1 mAb 1-15, or the reference anti-PD-1 antibodies (PD-1 mAb A and PD-1 mAb B) was mixed with NSO cells expressing human PD-1 (~250,000 cells/well) in blocking buffer (FACS + 10% human serum albumin). For these studies the anti-PD-1 antibodies were utilized at 50, 12.5, 3.13, 2.0 ×10-1, 4.9 × 10-2, 1.2 × 10-2, 3.0 × 10-3, 1.9 × 10-4, 7.6 × 10-4, 4.75 × 10-5, or 1.19 × 10-5µg/test (four fold serial dilutions). The amount of antibody binding to the surface of the NSO cells was determined using goat anti-human-APC secondary antibody byFACS analysis. Representative saturation curves are shown inFigure 11.The EC50 and EC90 values were determined and the sample mean (SM) and standard deviation (SD σ) from four separate experiments are provided inTable 8.Table 8Saturation BindingEC50 (µg/test)EC90 (µg/test)Anti-PD-1 AntibodySMSD σSMSD σPD-1 mAb A IgG1 (AA)0.19910.13091.45280.8040PD-1 mAb A IgG4 (P)0.15810.11611.54641.7690PD-1 mAb B IgG1 (AA)0.13470.06811.39170.9573PD-1 mAb B IgG4 (P)0.13980.09511.16191.2681hPD-1 mAb 2 IgG1 (AA)0.44310.19972.43741.2637hPD-1 mAb 7(1.1) IgG1 (AA)0.10690.05000.91020.5476hPD-1 mAb 7(1.2) IgG1 (AA)0.18720.15530.68100.3226hPD-1 mAb 7(1.2) IgG4 (P)0.13760.09260.66090.3437hPD-1 mAb 9(1.1) IgG1 (AA)0.31230.22911.64860.9117hPD-1 mAb 9(1.1) IgG4 (P)0.51280.22283.05630.9437hPD-1 mAb 15 IgG1 (AA)0.29270.13332.06400.6096The binding saturation studies demonstrate that the humanized versions of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 have favorable profile for binding to cell surface PD-1. In particular, humanized PD-1 mAb 7 (hPD-1 mAb 7(1.1), and hPD-1 mAb 7(1.2) having either an IgG1 (AA) or an IgG4 (P) Fc Region) have the lowest EC90 values of all the antibodies examined.In order to further characterize the humanized anti-PD-1 antibodies hPD-1 mAb 2 IgG1 (AA), hPD-1 mAb 7(1.1) IgG1 (AA), hPD-1 mAb 7(1.2) IgG1, (AA), hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 9(1.1) IgG1 (AA), hPD-1 mAb 9(1.1) IgG4 (P), and hPD-1 mAb 15 IgG1 (AA), their ability to block binding of human PD-L1 (shPD-L1) and human PD-L2 (shPD-L2) to PD-1 expressed on the surface of NSO cells was examined. These assays were performed essentially as described above. Representative curves for inhibition of sPD-L1 and sPD-L2 binding to PD-1 expressed on NSO cells are shown inFigures 12Aand12B,respectively. The IC50 and IC90 values were determined and the sample mean (SM) and standard deviation (SD σ) from three separate experiments are provided inTable 9.Table 9sPD-L1sPD-L2IC50 (µg/test)IC90 (µg/test)IC50 (µg/test)IC90 (µg/test)Anti-PD-1 AntibodySMSD σSMSD σSMSD σSMSD σPD-1 mAb A IgG1 (AA)0.02030.00890.29850.32790.04140.01240.16010.066PD-1 mAb A IgG4 (P)0.01560.00960.07760.02080.02800.00700.15940.1153PD-1 mAb B IgG1 (AA)0.01480.00080.10340.01000.02800.00590.11900.060PD-1 mAb B IgG4 (P)0.01430.00130.07980.02390.02800.00550.09240.0065hPD-1 mAb 2 IgG1 (AA)0.05780.01240.24800.0500.12940.01430.38130.0656hPD-1 mAb 7(1.1) IgG1 (AA)0.01660.00320.06740.00410.02830.01470.08860.0166hPD-1 mAb 7(1.2) IgG1 (AA)0.01180.00270.06780.00310.02120.00310.06720.0043hPD-1 mAb 7(1.2) IgG4 (P)0.01030.00230.05200.00330.02130.00190.06160.0063hPD-1 mAb 9(1.1) IgG1 (AA)0.05930.00360.32380.05080.40020.50000.45730.1805hPD-1 mAb 9(1.1) IgG4 (P)0.04600.01180.24610.05130.11050.01460.29140.0526hPD-1 mAb 15 IgG1 (AA)0.04400.00920.20680.0350.09450.00220.30930.0588The ligand binding inhibition studies demonstrate that the humanized versions of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 are able to inhibit the binding of sPD-L1 and sPD-L2 to PD-1 on the cell surface. In particular, humanized PD-1 mAb 7 (hPD-1 mAb 7(1.1), and hPD-1 mAb 7(1.2)) have the lowest IC90 values of all the antibodies examined.Example 3Blockade of the PD-1/PD-L1 Checkpoint by Humanized Anti-Human PD-1 AntibodiesThe ability of hPD-1 mAb 2 IgG1 (AA), hPD-1 mAb 7(1.1) IgG1 (AA), hPD-1 mAb 7(1.2) IgG1, (AA), hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 9(1.1) IgG1 (AA), hPD-1 mAb 9(1.1) IgG4 (P), hPD-1 mAb 15 IgG1 (AA), and the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B to antagonize the PD-1/PD-L1 axis (i.e., block the PD-1/PD-L1 interaction and prevent down-regulation of T-cell responses) was examined in a Jurkat-luc-NFAT / CHO-PD-L1 luciferase reporter assay. Briefly, CHO cells expressing PD-L1 (CHO/PD-L1) were plated at 40,000/well in 100 µL of culture medium (RPMI + 10% FBS + 100 µg/mLHygromycine B + 100 µg/mL G418) and incubated overnight. The next day the media was removed and MNFAT-luc2/PD-1 Jurkat cells (Promega) at 50,000 cells/well in 40 µL in assay buffer (RPMI + 2% FBS), and the anti-PD-1 antibodies PD-1 mAb 1-15, or a reference anti-PD-1 antibodies (PD-1 mAb A and PD-1 mAb B) (0-25 µg/mL; eight 2.5 fold serial dilutions in assay buffer) were added to each well and incubated for 6 hours at 37°C followed by a 5-10 minutes incubated at ambient temperature. 80 µL of BioGlo Substrate (Promega) was then added to each well and the plate was incubated for an additional 5-10 minutes at ambient temperature, the luminescence was measured in a Victor Plate Reader. Representative saturation curves are shown inFigure 13. The EC50 and EC90 values were determined and the sample mean (SM) and standard deviation (SDσ) from four separate experiments are provided inTable 10.Table 10Anti-PD-1 AntibodyReporter SignalingEC50 (µg/test)EC90 (µg/test)SMSD σSMSD σPD-1 mAb A IgG1 (AA)0.25490.04802.44741.2228PD-1 mAb A IgG4 (P)0.20490.07192.55351.2139PD-1 mAb B IgG1 (AA)0.21190.17812.20362.0118PD-1 mAb B IgG4 (P)0.11420.03230.94180.2863hPD-1 mAb 2 IgG1 (AA)0.35390.09833.89752.0054hPD-1 mAb 7(1.1) IgG1 (AA)0.10800.03861.19920.5103hPD-1 mAb 7(1.2) IgG1 (AA)0.09440.01530.64520.2615hPD-1 mAb 7(1.2) IgG4 (P)0.09650.01690.6885.01858hPD-1 mAb 9 IgG1 (AA)0.28350.05302.99680.8866hPD-1 mAb 9 IgG4 (P)0.31540.08725.09404.0496hPD-1 mAb 15 IgG1 (AA)0.25850.05923.31381.0532The reporter signaling studies demonstrate that the humanized versions of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 can block the PD-1/PD-L1 axis and will prevent down-regulation of T-cell responses. In particular, humanized PD-1 mAb 7 (hPD-1 mAb 7(1.1), and hPD-1 mAb 7(1.2) having either an IgG1 (AA) or an IgG4 (P) Fc Region) have the lowest EC50/EC90 values.Example 4Functional Activity of Anti-Human PD-1 AntibodiesStaphylococcus aureusenterotoxin type B (SEB) is a microbial superantigen capable of activating a large proportion of T-cells (5-30%) in SEB-responsive donors. SEB binds to MHC II outside the peptide binding grove and thus is MHC II dependent, but unrestricted and TCR mediated. SEB-stimulation of T-cells results in oligoclonal T-cell proliferation and cytokine production (although donor variability may be observed and some donors will not respond). Within 48 hours of SEB-stimulation PMBCs upregulatePD-1 and LAG-3 with a further enhancement see at day 5, post-secondary culture in 96-well plate with SEB-stimulation. Upregulation of the immune check point proteins PD-1 and LAG-3 following SEB-stimulation of PBMCs limits cytokine release upon restimulation. The ability of anti-PD-1 antibodies alone and in combination with anti-LAG-3 antibodies to enhance cytokine release through checkpoint inhibition was examined.Briefly, PBMCs were purified using the Ficoll-Paque Plus (GE Healthcare) density gradient centrifugation method according to manufacturer's instructions from whole blood obtained under informed consent from healthy donors (Biological Specialty Corporation) and T cells were then purified using the Dynabeads®Untouched Human T Cells Kit (Life Technologies) according to manufacturer's instructions. Purified PBMCs were cultured in RPMI-media + 10% heat inactivated FBS + 1% Penicillin/Streptomycin in T-25 bulk flasks for 2-3 days alone or with SEB (Sigma-Aldrich) at 0.1 ng/mL (primary stimulation). At the end of the first round of SEB-stimulation, PBMCs were washed twice with PBS and immediately plated in 96-well tissue culture plates at a concentration of 1-5 × 105cells/well in media alone, media with a control or an anti-PD-1 antibody, media with SEB at 0.1 ng/mL (secondary stimulation) and no antibody, or media with SEB and a control IgG or an anti-PD-1 antibody +/- an anti-LAG-3 mAb, and cultured for an additional 2-3 days. At the end of the second stimulation, supernatants were harvested to measure cytokine secretion using human DuoSet ELISA Kits for IFNy, TNFα, IL-10, and IL-4 (R&D Systems) according to the manufacturer's instructions.The ability of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 alone, or in combination with the unique anti-LAG-3 antibody LAG-3 mAb 1 to enhance cytokine release through checkpoint inhibition was examined. These studies also included one or more of the following reference anti-PD-1 antibodies: PD-1 mAb A; PD-1 mAb B; and LAG-3 mAbA, alone or in combination.Figure 14shows the IFNy secretion profiles from SEB-stimulated (0.1 ng/mL) PBMCs from a representative responding donor (D:38941), treated with: no antibody; isotype control antibody; PD-1 mAb 7 and/or LAG-3 mAb 7; PD-1 mAb 9 and/or LAG-3 mAb 1; PD-1 mAb 15 and/or LAG-3 mAb 1; PD-1 mAb 2 and/or LAG-3 mAb 1; or the reference anti-PD-1 antibodies PD-1 mAb B and/or LAG-3 mAb A (antibodies were used at 10 µg/mL).In additional studies the ability of the humanized versions of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 (comprising a human IgG1 (AA) or a human IgG4 (P) Fc Region) as well as the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B to enhance cytokine release through checkpoint inhibition was examined. For these studies the antibodies were utilized at 0.625, 2.5, and 10 µg/mL.Figures 15A-15Bshows the IFNy (Figure 15A) and TNFα (Figure 15B), secretion profiles from SEB-stimulated (0.2 ng/mL) PBMCs from a representative responding donor (D:57709), treated with no antibody or one of the following antibodies: isotype control; hPD-1 mAb 2 IgG1 (AA); hPD-1 mAb 7(1.2) IgG1 (AA); hPD-1 mAb 7(1.2) IgG4 (P); hPD-1 mAb 9(1.1) IgG1 (AA); hPD-1 mAb 9(1.1) IgG4 (P); hPD-1 mAb 15 IgG1 (AA); or the reference anti-PD-1 antibodies PD-1 mAb A IgG1 (AA), PD-1 mAb A IgG4 (P), PD-1 mAb B IgG1 (AA), PD-1 mAb B IgG4 (P). The total pg/mg of IFNy in samples treated with SEB+Ab were determined for the samples treated with the anti-PD-1 antibodies at 0.625, 2.5 and 10 µg/mL and the sample mean (SM) and standard deviation (SDσ) from 3 different responding donors (except where noted) are provided inTable 11. The ratio of IFNy secreted in sample treated with the humanized versions of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 (comprising a human IgG1 (AA) or a human IgG4 (P) Fc Region) over the reference anti-PD-1 antibodies PD-1 mAb A and PD-1 mAb B (i.e., humanized anti-PD-1/PD-1 mAb A, and humanized anti-PD-1/PD-1 mAb B) is presented inTable 12andTable 13, respectively.Table 11IFNγ Secretion (pg/mL)µg/mL anti-PD1 antibody0.625 µg/mL2.5 µg/mL10 µg/mLanti-PD-1 AntibodySMSD σSMSD σSMSD σPD-1 mAb A IgG1 (AA)221.18110.89341.13247.93347.46144.72PD-1 mAb A IgG4 (P)281.36132.65495.15190.57399.41117.56PD-1 mAb B IgG1 (AA)366.69196.64387.682215.51387.32282.81PD-1 mAb B IgG4 (P)348.40185.96433.382163.23551.68125.08hPD-1 mAb 7(1.2) IgG1 (AA)302.05185.71610.70209.77414.63272.65hPD-1 mAb 7(1.2) IgG4 (P)384.57‡323.79‡411.40398.59370.06108.12hPD-1 mAb 9(1.1) IgG1 (AA)340.81207.76442.598303.70655.29567.91hPD-1 mAb 9(1.1) IgG4 (P)309.82130.30468.62350.15424.35288.95hPD-1 mAb 15 IgG1 (AA)360.00274.28373.32160.25541.83444.22hPD-1 mAb 2 IgG1 (AA)275.88135.23372.7353.53496.70235.37Control IgG137.1476.61100.6548.67138.10120.81No Antibody120.0573.90120.0573.90109.4685.18‡ Results from two responding donorsTable 12Ratio IFNγ Secretion (New Anti-PD-1/PD-1 mAb A)µg/mL anti-PD1 antibody0.625 µg/mL2.5 µg/mL10 µg/mLanti-PD-1 AntibodySMSD σSMSD σSMSD σPD-1 mAb A IgG1 (AA)1.000.001.000.001.000.00PD-1 mAb A IgG4 (P)1.000.001.000.001.000.00PD-1 mAb B IgG1 (AA)1.770.921.280.361.070.42PD-1 mAb B IgG4 (P)1.230.160.920.271.400.12hPD-1 mAb 7(1.2) IgG1 (AA)1.360.372.461.851.170.41hPD-1 mAb 7(1.2) IgG4 (P)1.20‡0.35‡0.790.540.950.22hPD-1 mAb 9(1.1) IgG1 (AA)1.480.191.460.711.700.84hPD-1 mAb 9(1.1) IgG4 (P)1.130.130.910.421.020.46hPD-1 mAb 15 IgG1 (AA)1.500.391.511.231.480.71hPD-1 mAb 2 IgG1 (AA)1.320.531.480.861.420.12Control IgG0.630.20.330.080.390.24No Antibody0.540.120.390.140.310.17‡ Results from two responding donorsTable 13Ratio IFNγ Secretion (New Anti-PD-1/PD-1 mAb B)µg/mL anti-PD1 antibody0.625 µg/mL2.5 µg/mL10 µg/mLanti-PD-1 AntibodySMSD σSMSD σSMSD σPD-1 mAb A IgG1 (AA)0.370.370.820.201.060.48PD-1 mAb A IgG4 (P)0.820.121.160.380.720.07PD-1 mAb B IgG1 (AA)1.00.001.00.001.00.00PD-1 mAb B IgG4 (P)1.00.001.00.001.00.00hPD-1 mAb 7(1.2) IgG1 (AA)0.840.221.770.811.110.07hPD-1 mAb 7(1.2) IgG4 (P)0.91‡0.26‡0.830.500.680.17hPD-1 mAb 9(1.1) IgG1 (AA)1.040.591.120.291.600.42hPD-1 mAb 9(1.1) IgG4 (P)0.920.090.990.360.750.39hPD-1 mAb 15 IgG1 (AA)1.010.481.070.571.340.15hPD-1 mAb 2 IgG1 (AA)0.780.121.100.381.460.53Control IgG0.390.080.270.080.340.13No Antibody0.340.110.310.030.280.08‡ Results from two responding donorsThe results of these studies demonstrate that the PD-1 antibodies PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, and PD-1 mAb 15 dramatically enhanced IFNγ (Figures 14and15A, andTables 11-13), and TNFα (Figure 15B) production from SEB-stimulated PBMCs upon restimulation. In addition, the combination of anti-PD-1 antibodies with anti-LAG-3 antibodies resulted in a further enhancement of cytokine release (Figure 14) from SEB-stimulated PBMCs upon restimulation. In particular, the combination of PD-1 mAb 2, PD-1 mAb 7, PD-1 mAb 9, or PD-1 mAb 15 with the unique anti-LAG-3 antibody LAG-3 mAb 1 provided the largest enhancement.Example 5PD-1 × LAG-3 Bispecific Molecules Binding StudiesA number of PD-1 × LAG-3 bispecific molecules were generated, including Fc Region-containing diabodies comprising three, four, and five chains and a bispecific antibody. Four diabodies having four chains and comprising E/K-coil Heterodimer-Promoting Domains were generated and accorded the designations "DART A," "DART B," "DART C, and "DART I." Four diabodies having four chains and comprising CH1/CL Domains were generated and accorded the designations "DART D," "DART E," "DART J," and "DART 1." Two diabodies having five chains and comprising E/K-coil Heterodimer-Promoting Domains and CH1/CL Domains were generated and accorded the designations "DART F," and "DART G." One diabody having three chains and comprising E/K-coil Heterodimer-Promoting Domains was generated and accorded the designation "DART H." One bispecific antibody having four chains was generated and accorded the designation "BSAB A." Thestructure and amino acid sequences of these PD-1 × LAG-3 bispecific molecules are provided above and are summarized inTable 14below.Table 14NameParental mAbsFc‡ChainsSEQ ID NOs:Other ComponentsDART AhPD-1 mAb 7(1.2)IgG4 (YTE)4267 (X1=A; X2=Y; X3=T; X4=E) and 268E/K-Coils; seeFigure 3BhLAG-3 mAb 1(1.4)DART BhPD-1 mAb 7(1.2)IgG4 (YTE)4267 (X1=G; X2=Y; X3=T; X4=E) and 268E/K-Coils; seeFigure 3BhLAG-3 mAb 1(1.3)DART ChPD-1 mAb 7(1.2)IgG44267 (X1=G; X2=M; X3=S; X4=T) and 268E/K-Coils; seeFigure 3BhLAG-3 mAb 1(1.3)DART DhPD-1 mAb 7(1.2)IgG4 (YTE)4269 and 270CL/CH1; seeFigure 3ChLAG-3 mAb 1(1.4)DART EhPD-1 mAb 7(1.2)IgG4 (YTE)4271 and 272CL/CH1; seeFigure 3ChLAG-3 mAb 1(1.4)DART FhPD-1 mAb 7(1.2)IgG1 (AA/ YTE)5273, 274, 275, and 276CL/CH1 and E/K-Coils; seeFigure 5hLAG-3 mAb 1(1.4)DART GhPD-1 mAb 7(1.2)IgG1 (AA/ YTE)5277, 278, 279, and 280CL/CH1 and E/K-Coils; seeFigure 5hLAG-3 mAb 1(1.4)DART HhPD-1 mAb 7(1.2)IgG1 (AA)3281, 282, and 283E/K Coils; SeeFigure 4AhLAG-3 mAb 1(1.4)DART IhPD-1 mAb 7(1.2)IgG4 (YTE)4290 and 291E/K-Coils; seeFigure 3BhLAG-3 mAb 6(1.1)DART JhPD-1 mAb 7(1.2)IgG4 (YTE)4292 and 293CL/CH1; seeFigure 3ChLAG-3 mAb 6(1.1)DART 1PD-1 mAb AIgG1 (AA)4284 and 285CL/CH1; seeFigure 3CLAG-3 mAb ABSAB AhPD-1 mAb 7(1.2)IgG1 (AA)4286, 287, 288, and 289mAb with charge engineered Fc RegionhLAG-3 mAb 1(1.4)‡ Molecules incorporating IgG4 Fc regions also incorporate a stabilized IgG4 hinge region.Additional PD-1 × LAG-3 bispecific molecules comprising alternative PD-1 and/or LAG-3 epitope-binding sites may be readily generated by incorporating different VH and VL Domains. Similarly, molecules binding an antigen other than LAG-3 may be generated by incorporating the VH and VL having the desired specificity.The binding saturation profiles of the PD-1 × LAG-3 bispecific diabody constructs: DART A, DART B, DART D, DART E, DART F, DART G, DART H, DART I, and DART1; the anti-PD-1 antibodies: hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 7(1.2) IgG1 (AA), PD-1 mAb A IgG1 (AA) and PD-1 mAb A IgG4 (P); and the anti-LAG-3 antibodies: hLAG-3 mAb 1(1.4) IgG4 (P), LAG-3 mAb A IgG4 (P), hLAG-3 mAb 1(1.4) IgG1 (AA), and LAG-3 mAb A IgG1 (AA) were examined essentially as described above. The PD-1 × LAG-3 bispecific diabody constructs were tested for both PD-1 and LAG-3 binding, while the anti-PD-1 and anti-LAG-3 antibodies were only tested for binding to their respective antigens. For these studies NSO cells expressing PD-1 or LAG-3 were utilized. The diabodies and antibodies were utilized (170.0-0.013 µM or 85.0-0.0021 µM (four fold serial dilutions). The EC50 and EC90 values were determined and are presented inTables 15-16. The sample mean (SM) and standard deviation (SDσ) are provided where 2 or more separate experiments were performed.Table 15MoleculeSaturation Binding PD-1EC50 (µM)EC90 (µM)SMSD σSMSD σDART A1.92970.43249.60270.4801DART B1.7640§12.2700§DART D2.22670.414010.93132.6351DART E3.21800.574223.8403.2385DART F1.4320§14.5800§DART G1.14880.62273.42202.4600DART H4.5310§22.6600§DART I1.32320.48907.81354.0821DART 12.13291.485013.81139.0256hPD-1 mAb 7(1.2) IgG4 (P)1.20830.81123.93401.8746PD-1 mAb A IgG4 (P)2.34701.236222.777015.0690hPD-1 mAb 7(1.2) IgG1 (AA)1.08790.39587.41533.0794PD-1 mAb A IgG1 (AA)1.67330.54649.95436.6569§ results from a single experimentTable 16MoleculeSaturation Binding LAG-3EC50 (µM)EC90 (µM)SMSD σSMSD σDART A0.84020.22314.44482.4770DART B1.0750§9.8580§DART D0.89850.53265.79674.7329DART E0.92500.80755.64505.6809DART F5.00900.577019.33504.7447DART G0.93960.30458.55074.7448DART H2.3840§9.78104.2412DART I0.53210.05474.1983.2188DART 120.02332.1454115.9715.2425hLAG-3 mAb 1(1.4) IgG4 (P)1.00570.19695.13604.7904LAG-3 mAb A IgG4 (P)0.59680.13762.08330.3244hLAG-3 mAb 1(1.4) IgG1 (AA)0.60690.34303.63732.4762LAG-3 mAb A IgG1 (AA)0.45230.16602.01870.7035§ results from a single experimentThe binding saturation studies demonstrate that the PD-1 × LAG-3 bispecific diabody constructs retain binding to PD-1 and have binding profiles that are similar to the binding profiles of the parental anti-PD-1 antibodies. Similarly, the PD-1 × LAG-3 bispecific diabody constructs retain binding to LAG-3 and, with the exception of DART 1, have binding profiles that are similar to the binding profiles of the parental anti-LAG-3 antibodies.Example 6PD-1 × LAG-3 Bispecific Molecules Inhibition StudiesThe ability of the PD-1 × LAG-3 bispecific molecules: DART A, DART B, DART D, DART E, DART F, DART G, DART H, DART I, DART 1 and BSAB A; and the anti-PD-1 antibodies: hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 7(1.2) IgG1 (AA), PD-1 mAb A IgG1 (AA) and PD-1 mAb A IgG4 (P), to block binding of human PD-L1 (shPD-L1) and human PD-L2 (shPD-L2) to PD-1 expressed on the surface of NSO cells was examined essentially as described above. The diabodies and antibodies were utilized at 33.75-0.002 µM or 107.5-0.0001 µM (four fold serial dilutions).The IC50 and IC90 values were determined and are presented inTable 17. The sample mean (SM) and standard deviation (SDσ) are provided where 2 or more separate experiments were performed.Table 17Moleculeblock sPD-L1/PD-1 bindingblock sPD-L2/PD-1 bindingIC50 (µM)IC90 (µM)IC50 (µM)IC90 (µM)SMSD σSMSD σSMSD σSMSD σDART A0.96450.14855.63121.52471.62730.42856.93353.9849DART B1.15150.00074.86150.21992.11500.31547.95500.0933DART D1.55480.16927.89502.51353.12550.58699.29735.5426DART E1.65330.33077.84701.16422.94600.77366.61350.0177DART F0.56970.17292.03600.11740.83890.08461.79950.2171DART G1.60130.35818.19531.57082.55400.78917.48100.2333DART H3.39500.101818.6409.57426.20653.684729.3953.8679DART I0.83630.13025.31150.31251.2860.31256.24851.3951DART 11.74670.30975.45331.02142.83551.82507.27353.9831BSAB A2.15900.309711.0750.81324.87750.543815.5801.3294hPD-1 mAb 7(1.2) IgG4 (P)0.51860.16683.80501.22271.04250.25633.48800.5459PD-1 mAb A IgG4 (P)0.92090.32564.30230.70691.38590.38825.16750.2943hPD-1 mAb 7(1.2) IgG 1 (AA)0.73200.23373.20481.14790.97690.28932.84371.4801PD-1 mAb A IgG1 (AA)1.07650.23935.27750.99331.95100.88145.08801.3831The ligand binding inhibition studies demonstrate that the PD-1 × LAG-3 bispecific diabody constructs retain the ability to inhibit the binding of sPD-L1 and sPD-L2 to PD-1 on the cell surface.In addition, the ability of the PD-1 × LAG-3 bispecific molecules: DART A, DART B, DART D, DART E, DART F, DART G, DART H, DART I, DART 1 and BSAB A; and the anti-LAG-3 antibodies: hLAG-3 mAb 1(1.4) IgG4 (P), LAG-3 mAb A IgG4 (P), hLAG-3 mAb 1(1.4) IgG1 (AA), and LAG-3 mAb A IgG1 (AA), to block binding of human LAG-3 to native MHC class II on the surface of Daudi cells was examined. Briefly, each PD-1 × LAG-3 bispecific molecule and control anti-LAG-3 antibody was mixed with a biotinylated-soluble human LAG-3-Fc fusion protein (shLAG-3), (at 0.5 µg/ml) and were separately incubated with MHC II-positiveDaudi cells (2.5 × 106cells). The amount of LAG-3 binding to the surface of the Daudi cells was determined using a PE-conjugated Streptavidin secondary antibody by FACS analysis. The diabodies and antibodies were utilized at 27.5-0.026 µM (two fold serial dilutions) or 107.5-0.0001 µM (four fold serial dilutions), or 35-0.002 µM (four fold serial dilutions).The IC50 and IC90 values were determined and are presented inTable 18. The sample mean (SM) and standard deviation (SDσ) are provided where 2 or more separate experiments were performed.Table 18MoleculeBlock shLAG-3/MHC Class II BindingEC50 (µM)EC90 (µM)SMSD σSMSD σDART A1.38351.64658.3961028.3962DART B0.40810.11043.06450.3924DART D1.18431.13988.00417.3317DART E3.27062.917728.968324.1694DART F1.53471.267410.392011.2555DART G2.06183.355211.442212.4964DART H2.89674.981717.253321.1420DART I0.48640.15492.3391.1780DART 115.961014.088387.1486109.533BSAB A0.71010.05717.24701.0706hLAG-3 mAb 1(1.4) IgG4 (P)0.48150.21763.48371.7564LAG-3 mAb A IgG4 (P)0.70110.19002.42320.3481hLAG-3 mAb 1(1.4) IgG1 (AA)0.36370.14099.44227.9319LAG-3 mAb A IgG1 (AA)0.59230.34072.14511.1139The ligand binding inhibition studies demonstrate that the PD-1 × LAG-3 bispecific diabody constructs retain the ability to inhibit the binding of a shLAG-3-Fc fusion protein to MHC class II on the cell surface. With the exception of DART 1 the PD-1 × LAG-3 bispecific molecules have similar inhibition profiles as the parental anti-LAG-3 antibodies.Example 7Blockade of the PD-1/PD-L1 Checkpoint by PD-1 × LAG-3 Bispecific MoleculesThe ability of the PD-1 × LAG-3 bispecific molecules: DART A, DART B, DART D, DART E, DART F, DART G, DART H, DART I, DART 1 and BSAB A; and the anti-PD-1 antibodies: hPD-1 mAb 7(1.2) IgG4 (P), hPD-1 mAb 7(1.2) IgG1 (AA), PD-1 mAb A IgG1 (AA) and PD-1 mAb A IgG4 (P), to antagonize the PD-1/PD-L1 axis (i.e., block the PD-1/PD-L1 interaction and prevent down-regulation of T-cell responses) was examined in a Jurkat-luc2-NFAT/CHO-PD-L1 luciferase reporter assay (using CHO/PD-L1 cells and MNFAT-luc2/PD-1 Jurkat cells) essentially as described above. The diabodies and antibodies were utilized at 100-0.0065 µM (four fold serial dilutions) or 100-0.0013 µM (five fold serial dilutions).The IC50 and IC90 values were determined and are presented inTable 19. The sample mean (SM) and standard deviation (SDσ) are provided where 2 or more separate experiments were performed.Table 19MoleculeReporter SignalingIC50 (µM)IC90 (µM)SMSD σSMSD σDART A0.88040.19497.91151.3232DART B1.0790.15357.54133.1483DART D1.40440.258412.07863.6616DART E1.40600.122213.78671.4981DART F0.34040.01031.87100.481DART G0.69140.02064.20900.7331DART H36.616720.8078968.300811.8471DART I1.33350.364112.1466.8787DART 111.88073.49051048.20001508.9992BSAB A9.78251.0288113.335022.2951hPD-1 mAb 7(1.2) IgG4 (P)0.64600.30356.07362.5513PD-1 mAb A IgG4 (P)1.3280.743916.51389.7149hPD-1 mAb 7(1.2) IgG1(AA)0.52140.15414.75922.1044PD-1 mAb A IgG1 (AA)1.45141.004935.738240.9858The reporter signaling studies demonstrate that the majority of the PD-1 × LAG-3 bispecific diabody constructs retain the ability to inhibit the binding of sPD-L1 to PD-1 on the cell surface. The tetravalent PD-1 × LAG-3 bispecific diabody constructs, DART A, DART B, DART D, DART-E, DART F, DART G and DART I were the strongest inhibitors in this assay. Similar results were obtained for several of these bispecific constructs examined in a PD-L2 reporter assay.Example 8Functional Activity of PD-1 × LAG-3 Bispecific MoleculesThe ability of PD-1 × LAG-3 bispecific molecules to enhance cytokine release through checkpoint inhibition was examined in SEB-stimulated PBMCs upon restimulation essentially as described above except where noted.In initial studies the ability of the PD-1 × LAG-3 bispecific molecules: DART A, DART D, DART E, DART F, DART G, DART H; and the anti-PD-1 and anti-LAG antibodies:PD-1 mAb A IgG4 (P) and LAG-3 mAb A IgG4 (P), alone or in combination to enhance cytokine release through checkpoint inhibition was examined. In these assays the PD-1 × LAG-3 bispecific molecules and antibodies were used at a total concentration of 3.125, 12.5, or 50 nM, and the PBMCs were stimulated with 0.2 ng/mL of SEB (previous studies used 0.1 ng/mL). For these studies, where a combination of antibodies is used each antibody is provided at one half of the total concentration, (i.e., 1.563, 6.25, or 25 nM).Figures 16Aand16Bshows the IFNy secretion profiles from SEB-stimulated PBMCs from two representative responding donors, D: 35644 and D: 59697, respectively.As noted, not all donors respond to SEB at 0.1 or 0.2 ng/mL. To enhance SEB stimulation of PBMCs from a wider number of donors SEB was used at a high concentration of 85 ng/mL, or a middle concentration of 0.5 ng/mL in additional studies. At these concentrations SEB stimulation is more robust across more donors, although donor to donor variability may still be seen.In one such study the ability of the PD-1 × LAG-3 bispecific molecules: DART A, DART B; the anti-PD-1 antibody: hPD-1 mAb 7(1.2) IgG4(P); the anti-LAG-3 antibody: LAG-3 mAb 1(1.4) IgG4(P); and the combination of: PD-1 mAb A IgG4 (P) and LAG-3 mAb A IgG4 (P), to enhance cytokine release through checkpoint inhibition was examined. In these assays the PD-1 × LAG-3 bispecific molecules and antibodies were used at a concentration of 0.019, 0.078, 0.3125, 1.25, 5, or 20 nM and the PBMCs were stimulated with 85 ng/mL of SEB. For this assay where a combination of antibodies is used each antibody was provided at the indicated concentration and thus the total antibody concentration is twice the concentration used for each antibody (i.e., 0.038, 0.156, 0.625, 2.5, 10, or 40 nM).Figures 17A and 17Bshow the IFNy secretion profiles from SEB-stimulated PBMCs from two representative donors, D: 55515 and D: 54024, respectively.In another study the PD-1 × LAG-3 bispecific molecules: DART A, DART B, DART C; the anti-PD-1 antibody: hPD-1 mAb 7(1.2) IgG4(P); the anti-LAG-3 antibody: LAG-3 mAb 1(1.4) IgG4(P); and the combination of: PD-1 mAb A IgG4 (P) and LAG-3 mAb A IgG4 (P), to enhance cytokine release through checkpoint inhibition was examined. In these assays the PD-1 × LAG-3 bispecific molecules and antibodies were used at a total concentration of 0.048, 0.195, 0.78, 3.125, 12.5, or 50 nM and the PBMCs were stimulated with 0.5 ng/mL of SEB. For these studies, where a combination of antibodies is used each antibody is provided at one half of the total concentration (i.e., 0.024, 0.098, 0.39, 1.563, 6.25, or 25 nM).Figures 18Aand18Bshow the IFNy secretion profiles from SEB-stimulated PBMCs from two representative donors, D: 20990 and D: 54947, respectively).In a further study, the release of the cytokine IL-2 was examined. Specifically, the PD-1 × LAG-3 bispecific molecules: DART D, DART H; the anti-PD-1 antibodies: PD-1 mAb A IgG4 (P), hPD-1 mAb 7(1.2) IgG4(P); the anti-LAG-3 antibodies: LAG-3 mAb A IgG4 (P) and LAG-3 mAb 1(1.4) IgG4(P); and the combination of: PD-1 mAb A IgG4 (P) and LAG-3 mAb A IgG4 (P), and hPD-1 mAb 7(1.2) IgG4(P) and LAG-3 mAb 1(1.4) IgG4(P), to enhance IL-2 release through checkpoint inhibition was examined. In these assays the PD-1 × LAG-3 bispecific molecules and antibodies were used at a total concentration of 3.125, 12.5, or 50 nM and the PBMCs were stimulated with the high 85 ng/mL concentration of SEB. For these studies, where a combination of antibodies is used each antibody is provided at one half of the total concentration (i.e., 1.563, 6.25, or 25 nM).Figure 19shows the IL-2 secretion profile from SEB-stimulated PBMCs from a representative donor (D: 54024).In additional studies the PD-1 × LAG-3 bispecific molecules: DART B, and DART I; the anti-PD-1 antibodies: PD-1 mAb A IgG4 (P), and hPD-1 mAb 7(1.2) IgG4(P); the anti-LAG-3 antibodies: LAG-3 mAb A IgG4 (P), hLAG-3 mAb 1(1.4) IgG4(P), and hLAG-3 mAb 6(1.1) IgG4 (P); and the combinations of: PD-1 mAb A IgG4 (P) and LAG-3 mAb A IgG4 (P), hPD-1 mAb 7(1.2) IgG4(P) and hLAG-3 mAb 1(1.4) IgG4(P), and hPD-1 mAb 7(1.2) IgG4(P) and hLAG-3 mAb 6(1.1) IgG4 (P) to enhance cytokine release through checkpoint inhibition was examined. In these assays the PD-1 × LAG-3 bispecific molecules and antibodies were used at a concentration of 0.0061, 0.024, 0.09, 0.39, 1.56, 6.25 or 25 nM and the PBMCs were stimulated with 0.5 ng/mL of SEB. For these studies, where a combination of antibodies is used each antibody is provided at the indicated concentration and thus the total antibody concentration is twice the concentration used for each antibody (i.e., 0.0122, 0.048, 0.18, 0.78, 3.12, 12.5 or 50 nM).Figure 20shows the IFNy secretion profiles from SEB-stimulated PBMCs from a representative donor D: 56041).The ability of the PD-1 × LAG-3 bispecific molecule DART I; the combination of the anti-PD-1antibody PD-1 mAb A IgG4 and the anti-LAG-3 antibody LAG-3 mAb A IgG4 (P); and a negative control antibody to enhance antigen-specific T cell responses was examined using a Tetanus-Toxoid Recall Assay. In particular, the response of antigen-specific enhanced secretion of cytokines was measured using tetanus toxoid as a recall antigen in coculture assay system. Briefly, CD4 memory T cells (0.5 - 1.0 X105cells/well) were isolated using negativeselection isolation kits (Miltenyi Biotec, San Diego, CA and Invitrogen, Carlsbad, CA) from human peripheral blood and cultured for 5-7 days with irradiated monocytes (0.01 - 0.05X105cells/well, 3500 rads) from the same donor in the presence or absence of 5 µg/mL the recall antigen tetanus toxoid (TTd) and dilution (starting at 25nM) of DART I, PD-1 mAb A IgG4 + LAG-3 mAb A IgG4(P), or an isotype control. In parallel plates, proliferation was measured through the incorporation of tritiated thymidine and IL-2 and IFNy was measured using ELISA (R&D systems, Minneapolis, MN) at days 5-7.Figures 21A-Dshow the IFNγ (Figure 21A,21C) and IL-2 (Figure 21B,21D) secretion profiles at day 7, from two representative donors (D50702 and D54267).The results of these studies demonstrate that the PD-1 × LAG-3 bispecific molecules dramatically enhanced IFNγ (Figures 16A-16B,17A-17B,18A-18B,20), and IL-2 (Figure 19) production from SEB-stimulated PBMCs upon restimulation. In addition, the PD-1 × LAG-3 bispecific molecules dramatically enhanced IFNγ production (Figures 21Aand21C) from CD4 memory T cells stimulated with tetanus toxoid. In particular, the tetravalent PD-1 × LAG-3 bispecific molecules provided a greater enhancement than the combination of anti-PD-1 antibodies with anti-LAG-3 antibodies.Example 9Pharmacokinetics of PD-1 × LAG-3 Bispecific MoleculesThe pharmacokinetics of a representative PD-1 × LAG-3 bispecific molecule, DART I and a representative anti-PD-1 antibody, PD-1 mAb A were examined in Cynomolgus monkeys. Briefly, two cynomolgus monkeys (one male and one female) were infused with a single dose of DART I (5 mg/kg) or PD-1 mAb A (10 mg/kg) and the serum concentration of the molecules was monitored over time using a sandwich ELISA assay. Briefly, maxisorb 96-well assay plates were coated with soluble human PD-1 (shPD-1), blocked with bovine serum albumin, washed and incubated with calibration standards, quality control standards and diluted serum samples. The amount of captured DART I and PD-1 mAb A was assessed by the sequential addition of a goat anti-human IgG Fc-biotin secondary and streptavidin-horseradish peroxidase (SA-HRP). HRP activity was detected using TMB substrate. All samples were analyzed a microplate reader (SpectraMax M2e, Molecular Device, Sunnyvale, CA) and the OD signals produced by the standard calibrators were used in the four-parameter logistic model using SoftMax Pro software (Version 5.4, Molecular Devices). The concentrations of PD-1 mAb A, or DART I were determined from the interpolation of thesamples' OD signal data with the equation describing the standard curve. The lower limit of quantitation (LLOQ) for this assay was estimated at 9.775 ng/mL.Figure 22shows the serum concentration over time, the lines represents the mean ofboth male (filled symbols) and female (open symbols) monkeys infused with DART I (solid line, triangles) or PD-1 mAb A (dashed line, circles). These data demonstrate that the pharmacokinetics of a PD-1 × LAG-3 bispecific molecule are comparable to those of an anti-PD-1 antibody in cynomolgus monkeys.Example 10Toxicology Study of PD-1 Antibodies and PD-1 × LAG-3 Bispecific MoleculesThe safety profile of a representative a representative anti-PD1 antibody, hPD-1 mAb 7 (1.2) IgG4 (P), and a representative PD1 × LAG3 bispecific molecule, DART I, was assessed in a non-GLP (Good Laboratory Practice) dosing study in cynomolgus monkeys.In this study the potential toxicity and toxicokinetics of the anti-PD-1 antibody (hPD-1 mAb 7 (1.2) IgG4 (P)), when administered by multiple intravenous infusions was evalulated. In addition, the potential toxicity and pharmacokinetics of the PD-1 × LAG-3 DART molecule (DART I), when administered by single intravenous infusion was also evaluated. The study design is presented inTable 20.Table 20Group No.Test MaterialDose Level (mg/kg)Dosing DaysDose VolumeDose (mg/mL)No. of AnimalsMalesFemales1Control01, 8, 15501a1a2AhPD-1 mAb 7 (1.2) IgG4 (P)11, 8, 1550.21a1a2BhPD-1 mAb 7 (1.2) IgG4 (P)11, 8, 1550.21b1b3AhPD-1 mAb 7 (1.2) IgG4 (P)1001, 8, 155201a1a3BhPD-1 mAb 7 (1.2) IgG4 (P)1001, 8, 155201b1b4DART I51511c1caGroups 1, 2A, and 3A were dosed beginning on Day 1 and necropsied 72 hours following their last (third) dose on Day 18.bGroups 2B and 3B were dosed beginning on Day 1 and necropsied 7 days following their last (third) dose on Day 22.cGroup 4 was dosed beginning on Day 1 and followed for 28 days post single dose administration (to Day 29); animals were then returned to colony.The following parameters and endpoints were evaluated in this study: clinical signs, body weights, food consumption, body temperature, clinical pathology parameters (hematology, coagulation, and clinical chemistry), bioanalysis and toxicokinetic parameters, anti-drug antibody analysis, flow cytometry, cytokine, gross necropsy findings, organ weights, and histopathologic examinations.All animals survived until scheduled euthanasia on Day 18 or 22 or release from study on Day 29. For hPD-1 mAb 7 (1.2) IgG4 (P) there were no test article-related changes in clinical signs, food consumption, body weights, body temperature, hematology, coagulation, or clinical chemistry parameters, or gross necropsy findings. At Days 18 and 22, increases in spleen weight and a dose-dependent mild to moderate lymphohistiocytic infiltrate of the red pulp were evident in animals receiving hPD-1 mAb 7 (1.2) IgG4 (P) at 1 or 100 mg/kg. As compared to surrounding lymphocytes, the lymphohistiocytic cells had pale cytoplasm and irregular nuclei. Rare mitotic figures were evident. The infiltrate was a microscopic correlate for the increased spleen weight.The serum concentration-time profiles for animals given hPD-1 mAb 7 (1.2) IgG4 (P) show the profile expected for an antibody in this species, with a few exceptions. The slopes of the curves after the third dose dropped more sharply than after the first dose for two animals in the 1 mg/kg dose group and two animals in the 100 mg/kg dose group, indicating the possible emergence of anti-drug antibodies (ADA) at the later cycles. Analysis showed that 2/4 animals developed ADA in the 1 mg/kg group and 1/4 animals developed ADA in the 100 mg/kg group.In conclusion, administration of hPD-1 mAb 7 (1.2) IgG4 (P) by intravenous infusion once weekly for 3 weeks (Days 1, 8, and 15) was well-tolerated in cynomolgus monkeys at levels of 1 and 100 mg/kg. A dose-dependent mild to moderate lymphohistiocytic cellular infiltrate of the splenic red pulp was present at 1 and 100 mg/kg hPD-1 mAb 7 (1.2) IgG4 (P).For DART I, there were no test article-related changes in clinical signs, food consumption, body weights, body temperature, hematology, or coagulation parameters. DART I-related changes in clinical chemistry parameters included non-adverse, transient elevations in aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) on Day 2. The average AST change was 3.2x vehicle-treated control animals and 7.8x prestudy levels, with levels above the control reference range2. The average LDH change was 2.5x vehicle-treated controlanimals and 6.9x prestudy levels. Both parameters returned to near baseline levels on Day 8. In conclusion, single administration of DART-I by intravenous infusion was well tolerated in cynomolgus monkeys at a level of 5 mg/kg.Example 11Single Dose PK Study with anti-PD-1 AntibodiesA single-dose PK study with selected toxicological endpoints was conducted in cynomolgus monkeys. In this study, hPD-1 mAb 7 (1.2) IgG4 (P) was compared to two other anti-PD1 IgG4 (P), κ mAbs: PD-1 mAb A IgG4 (P) and PD-1 mAb B IgG4 (P). Each antibody was administered at 10 mg/kg by 1-hour intravenous infusion to 2 monkeys (1M, 1F) and animals were monitored for 65 days.There were no test article-related clinical signs, changes in body weight, food consumption, cytokine, or immunophenotyping associated with administration of hPD-1 mAb 7 (1.2) IgG4 (P) or PD-1 mAb A IgG4 (P). Data were similar for PD-1 mAb B IgG4 (P)with the exception that elevations in IL-5 were observed following PD-1 mAb B IgG4 (P) administration.Anti-PD-1 antibody binding to PD-1 on the surface of T cells was determined by flow cytometry using a competition method in which the mean fluorescence intensity (MFI) of fluorescently labeled hPD-1 mAb 7 (1.2) IgG4 (P) binding to T cells in the absence (PBS control) or presence of excess competitor (unlabeled hPD-1 mAb 7 (1.2) IgG4 (P)) for the full time course of blood samples collected from the cynomolgus monkeys treated with hPD-1 mAb 7 (1.2) IgG4 (P), PD-1 mAb A IgG4 (P) or PD-1 mAb B IgG4 (P). As shown inFigures 23A-23C, hPD-1 mAb 7 (1.2) IgG4 (P) and PD-1 mAb B IgG4 (P) demonstrated prolonged binding to PD-1 on the surface of CD4+ and CD8+ T cells (PD-1 binding maintained at ≥ 80% for 28 days or more) (Figures 23Aand23C, respectively) compared to PD-1 mAb A IgG4 (P) (PD-1 binding maintained at ≥ 80% for 21 days or less) (Figure 23B). For each of the anti-PD-1 antibodies, the T-cell PD-1 binding data correlated with their serum concentrations.Example 12Repeat Dose Toxicology StudiesTo assess the safety, toxicokinetic, and pharmacodynamic profile of the therapeutic molecules disclosed herein, an exemplary molecule (hPD-1 mAb 7 (1.2) IgG4 (P)) was administered to cynomolgus monkeys and a GLP (Good Laboratory Practice) dosing study was performed. In this study, four groups of animals (10 per group, 5 males, and 5 females) were treatedwith hPD-1 mAb 7 (1.2) IgG4 (P) or a control article, once weekly by infusion at 3 dose levels. The animals were evaluated for any potential toxicity during a 4-week drug dosing period followed by monitoring during an additional 10-week drug-free period. The experimental design of this study is presented inTable 21.Animals were dosed once weekly via a one-hour intravenous infusion using a calibrated infusion pump on Study Days 1, 8, 15, and 22. One male and one female from each group were sacrificed on Day 25, the remaining animals were sacrificed on Study Day 95. The effects of hPD-1 mAb 7 (1.2) IgG4 (P) administration on the leukocyte subpopulations in circulation, including the occupancy of PD-1 receptors on T-lymphocytes were assessed. In addition, the anti-drug antibody (ADA) profiles were determined.Table 21Group No.Test MaterialaDose Level (mg/kg)Dose Volume (mL/kg)Dose (mg/mL)No. of AnimalsbMain StudyRecovery StudyMFMF1Control05.88033222hPD-1 mAb 7 (1.2) IgG4 (P)105.881.733223hPD-1 mAb 7 (1.2) IgG4 (P)405.886.833224hPD-1 mAb 7 (1.2) IgG4 (P)1505.8825.53322aControl and hPD-1 mAb 7 (1.2) IgG4 (P) were administered weekly via intravenous infusionbSix monkeys (3M/3F) per group were necropsied on Day 25, while the remaining recovery group monkeys (2M/2F) were necropsied on Day 95Once weekly intravenous (IV) infusions of hPD-1 mAb 7 (1.2) IgG4 (P) at 0, 10, 40, and 150 mg/kg in cynomolgus monkeys were well tolerated and all animals survived to their scheduled euthanasia on Days 25 or 95. There were no hPD-1 mAb 7 (1.2) IgG4 (P)-related changes in clinical signs, food consumption, body weights, physical, ophthalmic, and neurological examinations, electrocardiology, body temperatures, respiratory rates, blood pressure and heart rates, coagulation, clinical chemistry, and urinalysis parameters, organ weights, or gross necropsy findings.hPD-1 mAb 7 (1.2) IgG4 (P)-related changes in hematology parameters included transient decreases in lymphocyte titers. Lymphocyte titers were moderately decreased compared to pre-study (Day 1 predose) on Day 2 (23 hours post infusion) in males and females at ≥ 10 mg/kg, statistically significant for males at 10 and 40 mg/kg and females at 40 and 150mg/kg compared to controls. Lymphocyte titers returned to near prestudy levels on Day 8 predose but were mildly decreased for some individual males and females at all dose levels (0.47x to 0.68x prestudy) on Day 9 (23 hours post infusion). Lymphocyte titers increased prior to dosing on Days 15 and 22, but decreased for some individual males and females (0.36x to 0.54x prestudy) on Days 16 and 23 (23 hours post infusion).A dose-independent, transient decline in circulating immune cell populations, including total leukocytes, T cells, B cells, and NK cells, was observed 23 hours following the end of infusion in hPD-1 mAb 7 (1.2) IgG4 (P)-treated animals compared with the control group. The largest magnitude in change was observed following the first dose administration on Day 1; smaller magnitude changes were transiently observed following subsequent doses on Days 8, 15, or 22. Immune cell populations generally recovered to at or near baseline values by 72 hours post-EOI and throughout the recovery phase. No changes in circulating monocytes were observed in hPD-1 mAb 7 (1.2) IgG4 (P)-treated animals compared with the control group.Maximal hPD-1 mAb 7 (1.2) IgG4 (P) binding to PD-1+/CD4+ and PD-1+/CD8+ cells was observed during the hPD-1 mAb 7 (1.2) IgG4 (P) treatment phase of the study at all doses tested (10, 40 or 150 mg/kg). In recovery, animals that did not develop anti-drug antibody (ADA) responses, serum hPD-1 mAb 7 (1.2) IgG4 (P) concentrations remained above 29 µg/mL and maximal hPD-1 mAb 7 (1.2) IgG4 (P) binding to PD-1+/CD4+ and PD-1+/CD8+ T cells was maintained during the entire 10-week recovery period. In these animals, there was no evidence of PD-1 modulation on the T cells. In recovery animals that developed ADA responses, the frequency of MGD012-bound PD-1+ T cells declined to baseline levels. The declines from maximal hPD-1 mAb 7 (1.2) IgG4 (P) binding on PD-1+/CD4+ and PD-1+/CD8+ cells of ADA-positive animals generally occurred when the apparent serum hPD-1 mAb 7 (1.2) IgG4 (P) concentrations dropped below approximately 25 µg/mL. However, it is not known if this apparent threshold relationship applies to ADA-negative animals, since the presence of ADA in ADA-positive animals may contribute to blocking the binding of PD-1 antibodies to PD-1.There were minimal sex-associated differences in the pharmacokinetic responses of hPD-1 mAb 7 (1.2) IgG4 (P), which were linear across the dose range evaluated (10 to 150 mg/kg). For hPD-1 mAb 7 (1.2) IgG4 (P) at 10, 40, and 150 mg/kg, the gender combined mean Cmaxwas 240 µg/mL (0.240 mg/mL), 1078 µg/mL (1.08 mg/mL), and 3938 µg/mL(3.94 mg/mL) and the AUC was 47310 h•µg/mL (47.3 h•mg/mL), 205723 h•µg/mL (206 h•mg/mL), and 745681 h•µg/mL (746 h•mg/mL), respectively. Mean clearance by non-compartmental analysis (NCA) of the first cycle of hPD-1 mAb 7 (1.2) IgG4 (P) before the emergence of ADA, was 0.21 mL/h/kg, substantially lower than the glomerular filtration rate of cynomolgus monkeys, as would be expected for a large molecular weight protein. Mean steady-state volume of distribution by NCA of the first cycle of hPD-1 mAb 7 (1.2) IgG4 (P) was 68 mL/kg, approximately 1.5 times the serum volume, but less than the extracellular water space. This suggests that hPD-1 mAb 7 (1.2) IgG4 (P) extravasates from the vascular compartment into the tissue extracellular space, but that not all of the extracellular space was accessible to this molecule. The average value of the mean residence time (MRT) by NCA of the first cycle of hPD-1 mAb 7 (1.2) IgG4 (P) was 335 hours or approximately 14 days. Emergence of ADA decreased the concentrations of hPD-1 mAb 7 (1.2) IgG4 (P) in Cycles 2 to 4. Evidence of decreased hPD-1 mAb 7 (1.2) IgG4 (P) serum concentrations following repeated doses of hPD-1 mAb 7 (1.2) IgG4 (P) were observed in 7/10, 4/10, and 3/10 animals in the 10, 40, and 150 mg/kg dose groups, respectively. The presence of ADA against hPD-1 mAb 7 (1.2) IgG4 (P) was confirmed in 4, 2, and 1 of these animals in the 10, 40, and 150 mg/kg dose groups, respectively; all the animals in which ADA was not confirmed were in the terminal necropsy group during which hPD-1 mAb 7 (1.2) IgG4 (P) serum concentrations likely interfered with the ability to detect ADA. Accordingly, in subsequent TK analysis, when a trough concentration was lower than the preceding trough concentration, data from this time forward were censored. From two-compartment modeling of data across all cycles for the 3 dose groups, excluding points that were affected by ADA, mean values for the primary TK parameters for a 2-compartment model were 0.22 mL/h/kg for clearance, 38.5 mL/kg for initial volume of distribution (V1), and 33.8 mL/kg for V2, which yielded a mean steady-state volume of distribution (Vss) of 72.3 mL/kg, and an MRT of 329 hours. These values were consistent with parameters obtained from NCA of the first dose. In the absence of ADA, simulations predict that with weekly dosing, steady state would be achieved in cynomolgus monkeys after the 5th dose and the accumulation index would be 2.4.On Day 25, hPD-1 mAb 7 (1.2) IgG4 (P)-related minimal multifocal perivascular mononuclear cell infiltrates were present in the superficial dermis of the IV injection site in males at ≥ 40 mg/kg and in females at ≥ 10 mg/kg and were an expected reaction to repeated injection of a foreign protein (monoclonal antibody). On Day 95, there were no hPD-1 mAb 7(1.2) IgG4 (P)-related microscopic changes noted, indicating recovery of the test article-related change present on Day 25.In summary, the results of this study indicate that administration of hPD-1 mAb 7 (1.2) IgG4 (P) via intravenous infusion once weekly (Days 1, 8, 15, and 22) was clinically well tolerated in cynomolgus monkeys at levels of 10, 40, or 150 mg/kg. Effects observed were limited to transient decreases in circulating lymphocytes and minimal injection-site changes related to injection of a foreign protein. Based on these results, the no-observed-adverse-effect level (NOAEL) was considered to be 150 mg/kg (gender combined mean Cmaxof 3.94 mg/mL and AUC of 746 h•mg/mL). See more