PDCD1 and cancer: Numerous immunotherapy agents, including monoclonal antibodies targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and PD-1 ligand 1 (PD-L1), as well as CAR T cell therapy, have received approval from the U.S. Food and Drug Administration (FDA) for cancer treatment.