Clinical data shows that 20% of melanoma patients respond to ipilimumab (anti-CTLA-4)2, 33% respond to pembrolizumab (anti-PD-1)3, and 58% respond to a dual immune checkpoint blockade (anti-PD-1+anti-CTLA-4), but with significant toxicity4,5. This evidence concerns the gene CTLA4 and melanoma.