CTLA4 and metastatic melanoma: Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) and programmed cell death protein 1 (PD1) are 2 main targeted immune-inhibitory checkpoints of T cells in the TME, and anti-CTLA4 therapy was the first approved immunotherapy to demonstrate benefits on the survival of patients with metastatic melanoma (15).