Two PD-1 (programmed cell death 1) inhibitor antibodies, nivolumab (Opdivo) and pembrolizumab (Keytruda), have been approved by the US Food and Drug Administration (FDA) based on efficacy in treating certain types of solid tumors, including advanced melanoma, lung cancer, renal cell cancer, urothelial cancer, Hodgkin-type lymphoma, head and neck cancer, and hepatocellular cancer. The gene discussed is PDCD1; the disease is hepatocellular carcinoma.