Casein kinase 2 (CK2) is involved in multiple cellular processes such as proliferation, apoptosis, and cell cycle. In particular, its over-expression in human cancers is associated with angiogenesis and tumor progression. As a first orally bioavailable small molecule inhibitor of CK2, CX-4945 exerts anti-proliferative activity in human cancer cells by inhibiting the cell cycle and the PI3K/Akt signaling pathway. Additionally, CX-4945 reduces angiogenesis via blockade of hypoxia-inducible factor-1α transcription and suppresses the inflammatory interleukin-6 production in human breast cancer cells. These effects are supported by results from mouse xenograft model investigations. Here, we discuss the druggability of CX-4945 and its potential to be developed as an anti-cancer drug in clinical trials.