One of the breakthroughs in the development of immunotherapy was the approval in 2011 by the US Food and Drug Administration (FDA) of ipilimumab—a monoclonal antibody directed against the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) receptor—which became the first approved immunotherapeutic drug for the treatment of metastatic melanoma [65]. The gene discussed is CTLA4; the disease is metastatic melanoma.