A human monoclonal antibody directed against the negative immunoregulatory human cell surface receptor programmed cell death 1 (PD-1, PCD-1) protein, with potential immune checkpoint inhibitory and antineoplastic activity. Upon administration, cemiplimab binds to PD-1, inhibits its binding to the PD-1 ligand programmed cell death-1 ligand 1 (PD-L1), and prevents the activation of its downstream signaling pathways. This may restore immune function through the activation of cytotoxic T-cells. PD-1, a transmembrane protein in the immunoglobulin superfamily expressed on activated T-cells, negatively regulates T-cell activation and effector function when activated by its ligand; it plays an important role in tumor evasion from host immunity.