So far, the FDA has approved cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed cell death protein 1/ligand 1 (PD-1/PD-L1) blockade therapies for treating more than ten different malignancies2; however, only a small fraction of cancer patients respond to these therapies3,4. The gene discussed is PDCD1; the disease is cancer.