Immune checkpoint blockade methods targeting cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) or programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) are currently being pursued by oncologists, because of their ability to treat cancer by restoring T-cell cytotoxicity against tumor cells. The gene discussed is PDCD1; the disease is neoplasm.