In 2011, the U.S. Food and Drug Administration (FDA) authorized ipilimumab, the first immune checkpoint inhibitor, for use in cancer treatment, after a clinical trial showed that patients with unresectable stage III/IV melanoma had better survival rates after receiving treatment with a fully human IgG1κ anti-CTLA-4 monoclonal antibody [45]. This evidence concerns the gene CTLA4 and cancer.