Anti-PD-1 monoclonal antibodies such as nivolumab and pembrolizumab, and anti-CTLA-4 monoclonal antibodies, such as ipilimumab, together referred to as immune-checkpoint inhibitors (ICI) are an important class of cancer therapies that have demonstrated significant activity, including some durable responses, in a number of cancers, including melanoma, non-small cell lung cancer, bladder cancer, and kidney cancer. The gene discussed is CTLA4; the disease is cancer.