Since the approval of the first immune checkpoint inhibitor (ICI), the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) antibody ipilimumab, in 2011, ICIs targeting PD-1, PD-L1, and CTLA-4 have revolutionized cancer therapy and significantly improved survival outcomes across multiple tumor types (3). The gene discussed is PDCD1; the disease is neoplasm.