Indeed, exciting preclinical and clinical anti-cancer results have been reported with the use of monoclonal antibodies against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1), two important immune checkpoints10, 11, 12, 13, 14, 15, 16. The gene discussed is PDCD1; the disease is cancer.