Cosibelimab (CK-301) is a human immunoglobulin G1 (IgG1) monoclonal antibody that binds programmed death ligand-1 (PD-L1) and blocks the interaction between PD-L1 and its T cell receptors, programmed death receptor-1 (PD-1) and B7.1. This interaction releases the inhibitory effects of PD-L1 on the anti-tumor immune response. Cosibelimab has also been shown to induce antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro.