Immune checkpoint inhibitor therapies (ICIs) targeting immune checkpoints such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death protein (PD-1), and its ligand (PD-L1) have produced long-term tumor responses in multiple advanced cancers [1,2,3,4,5,6,7,8,9,10,11,12]. The gene discussed is CTLA4; the disease is cancer.