Immunotherapy comprises a promising new cancer treatment which is designed to enhance a patient's immune system.1, 2 It includes the administration of monoclonal antibodies (mAbs) to proteins known as immune‐checkpoint inhibitors (ICIs)—cytotoxic T‐lymphocyte‐associated antigen‐4 (CTLA4), programmed cell death protein‐1 (PD1), and programmed death ligand 1 and 2 (PD‐L1 and PD‐L2), resulting in a derepression and/or reactivation of cytotoxic T‐cell function. The gene discussed is CTLA4; the disease is cancer.