Since its initial success in melanoma patients, it has received Food and Drug Administration (FDA) approvals in combination with nivolumab (anti-programmed cell death receptor (PD-1) antibody) for the treatment of poor-risk advanced renal cell carcinoma (RCC), microsatellite instability-high or mismatch repair deficient metastatic colorectal cancer (CRC), hepatocellular carcinoma (HCC) previously treated with sorafenib and advanced non-small cell lung cancer (NSCLC) or malignant pleural mesothelioma. The gene discussed is PDCD1; the disease is hepatocellular carcinoma.