Since its approval, Ipilimumab has been used in combination with other checkpoint inhibitors, such as Nivolumab (anti-PD-1), to treat various cancers, including metastatic unresectable melanomas with or without BRAF mutation [24,25,26], microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) colorectal cancer (CRC) [27,28], hepatocellular carcinoma (HCC) [29], malignant pleural mesothelioma [30], non-small cell lung cancer (NSCLC) [31] and renal cell carcinoma (RCC) [32]. The gene discussed is PDCD1; the disease is melanoma.