Immune checkpoint inhibitors (ICIs), such as anti‐cytotoxic T lymphocyte antigen 4 (CTLA‐4) and anti‐programmed cell death 1 (PD‐1)/programmed cell death‐ligand 1 (PD‐L1) monoclonal antibodies, block the interactions between cancer cells and the immune system to enhance immune response to the tumor by rebalancing immune surveillance and immune evasion. The gene discussed is CTLA4; the disease is neoplasm.