Used primarily in the treatment of colorectal cancer, this drug functions as a thymidylate synthase inhibitor, disrupting DNA synthesis in cancer cells. It is administered intravenously and offers an alternative to 5-fluorouracil-based regimens, particularly in patients who cannot tolerate those therapies. Its targeted mechanism allows for a more specific action against rapidly dividing tumor cells, helping to slow disease progression. Due to its toxicity profile, careful patient selection and monitoring are required during treatment.