CTLA4 and melanoma: Ipilimumab, a fully human IgG1 anti-CTLA-4 antibody, has been approved as a monotherapy for the treatment of advanced malignant melanoma (7) and together with anti-PD-1 mAb, nivolumab, for the treatment of metastatic melanoma, renal cell carcinoma and metastatic colorectal cancer (8–10).