Definition

A humanized monoclonal antibody directed against the negative immunoregulatory human cell receptor programmed cell death protein 1 (PD-1; PDCD1; CD279), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-PD-1 monoclonal antibody QL1604 targets, binds to and inhibits PD-1 and its downstream signaling pathways. This may restore immune function through the activation of T cells and T-cell-mediated immune responses against tumor cells. PD-1, a transmembrane protein in the immunoglobulin superfamily (IgSF) expressed on T cells, functions as an immune checkpoint that negatively regulates T-cell activation and effector function when activated by its ligands programmed cell death-1 ligand 1 (PD-L1; cluster of differentiation 274; CD274) or 2 (PD-L2); it plays an important role in tumor evasion from host immunity.