Currently, ICIs that target cytotoxic T lymphocyte-associated antigen 4 (CTLA4) or programmed cell death protein 1 and its ligand (PD-1 and PD-L1) have been approved by the US Food and Drug Administration (FDA) for clinical application owing to their notable successes against melanoma and other solid malignancies (155–159). The gene discussed is CTLA4; the disease is melanoma.