Tremelimumab is used in the treatment of certain types of cancer, including advanced liver cancer (hepatocellular carcinoma) and extensive-stage small cell lung cancer. It works by enhancing the body's immune response against cancer cells. As an immune checkpoint inhibitor, it blocks the CTLA-4 protein on T-cells, allowing the immune system to recognize and attack tumors more effectively. It is often used in combination with other immunotherapies like durvalumab, and sometimes with chemotherapy, to improve treatment outcomes. This combination has shown improved survival rates in patients who are not candidates for surgery or local therapies. Tremelimumab is administered intravenously and is part of a growing class of cancer treatments known as immunotherapies, which aim to harness the body’s own defenses to fight disease.