LONSURF, known generically as trifluridine/tipiracil, is an oral chemotherapy medication used in the treatment of certain types of cancer, including metastatic colorectal cancer and gastric cancer, after other treatments have not been successful. It works by inhibiting the growth of cancer cells and slowing their spread in the body. LONSURF combines trifluridine, a nucleoside metabolic inhibitor, which interferes with the DNA synthesis of cancer cells, and tipiracil, which increases the bioavailability of trifluridine by inhibiting its degradation. This combination allows for a more effective attack on cancer cells while maintaining manageable levels of the drug in the body. As with many chemotherapy drugs, LONSURF can cause side effects, which may include fatigue, nausea, decreased appetite, and neutropenia, among others. It is important for patients taking LONSURF to be closely monitored by their healthcare provider to manage any adverse effects and to adjust treatment as necessary.