Abstract The aim of this study was to test the pharmacological effectiveness of antibody-targeted cyclosporin A. Only free drug is currently available; its administration is accompanied by nephrotoxicity, hepatotoxicity and neurotoxicity which severely limits the treatment. Moreover, due to the high nonspecific binding to a number of tissues, the therapeutic doses are considerably higher than required for the actual treatment. We suggest using antibody-targeted CsA conjugate based on a water-soluble synthetic copolymer of N-(2-hydroxypropyl)methacrylamide to overcome these problems. In this construct the antibody to T lymphocyte subsets (anti-CD3 in human and anti-Thy 1.2 in mouse) is responsible for the specific delivery which limits the drug action to the target tissue. Antibody-targeted CsA effectively inhibits lectin- and alloantigen-induced T cell proliferation and considerably reduces CsA nephrotoxicity.