The Checkmate 067 trial investigated the impact of treatment of metastatic melanoma with the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitor ipilimumab alone, the programmed death-ligand 1 (PD-L1) inhibitor nivolumab alone, and combination therapy [7]. Here, CTLA4 is linked to metastatic melanoma.