CTLA4 and melanoma: As a result, monoclonal antibodies targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA4), the programmed death-1 receptor (PD-1), and its ligand (PD-L1) have been approved by the European Medicines Agency (EMA) and/or the Food and Drug Administration (FDA) for the treatment of several tumors, especially melanoma and non-small cell lung cancer [27].