PDCD1 and cancer: Immune checkpoint‐inhibitors are a distinct and novel form of immune‐therapy, targeting the proteins programmed death cell protein 1 (PD‐1), programmed death ligand‐1 (PDL‐1) and cytotoxic T‐lymphocyte‐4 (CTLA‐4), leading to activation of cytotoxic T‐lymphocytes against cancer cells.1, 2, 3