Over the last decade, the demonstrated efficacy of cytotoxic lymphocyte antigen-4 (CTLA-4) inhibitors, programmed cell death protein-1 (PD-1) inhibitors, and PD-1 ligand (PD-L1) inhibitors to induce prolonged responses in advanced cancers has been well-documented[1–3]. The gene discussed is PDCD1; the disease is cancer.