Cosibelimab (Anti-B7-H1 / PD-L1 / CD274) is an immunoglobulin G1 (IgG1), human monoclonal antibody directed against the immunosuppressive ligand programmed cell death-1 ligand 1 (PD-L1; cluster of differentiation 274; CD274), with potential immune checkpoint inhibitory and antineoplastic activities. MW : 144.64 KD.