High responses to monoclonal antibodies targeting the immune checkpoints cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) (e.g., ipilimumab) and programmed death 1 (PD-1) (e.g., pembrolizumab and nivolumab) led to the approval of these checkpoint inhibitors for the treatment of various cancers[141]. Here, CTLA4 is linked to cancer.