The advent of immune checkpoint blockade (ICB) therapies, particularly those targeting cytotoxic T lymphocyte–associated protein 4 (CTLA-4) and the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathways, has marked a transformative era in the clinical management of various advanced cancers. The gene discussed is PDCD1; the disease is cancer.