The monoclonal antibody ipilimumab, which acts by blocking CTLA-4, is considered a landmark agent in this context, being the first immunotherapeutic drug demonstrating a clear benefit in survival of patients with advanced melanoma, which led to its approval by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) in 2011 [5]. The gene discussed is CTLA4; the disease is melanoma.