CTLA4 and cancer: Currently, a total of seven monoclonal antibodies against PD-1 (programmed cell death protein 1) or its ligand PD-L1 (programmed cell death 1 ligand 1), and two antibodies against CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) have been approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for anti-cancer therapy in more than 85 indications [8].