Finally, immune checkpoint blockade (ICB) with antibodies targeted to cytotoxic T lymphocyte antigen-4 (CTLA-4) (ipilimumab) and programmed cell death protein 1 (PD-1) (nivolumab and pembrolizumab) has resulted in significant improvements in clinical outcomes for a proportion of melanoma patients (39). This evidence concerns the gene CTLA4 and melanoma.