Immune checkpoints are molecules on the surface of immune cells involved in the regulation of the immune response, while ICIs are monoclonal antibodies directed against certain immune checkpoints, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) (ipilimumab) and programmed death 1 (PD-1) (nivolumab, pembrolizumab) and its ligand (PD-L1) (atezolizumab, avelumab), resulting in T-cell activation and anti-tumor activity. The gene discussed is CTLA4; the disease is neoplasm.