Carmofur is primarily used as an anticancer agent, particularly in the treatment of colorectal cancer. It functions as a prodrug of 5-fluorouracil (5-FU), which inhibits thymidylate synthase, an enzyme crucial for DNA synthesis, thereby preventing the growth of cancer cells. Additionally, it has shown potential in treating other types of cancers, such as breast and gastric cancers, due to its ability to deliver 5-FU directly to tumor cells. Beyond oncology, carmofur has been investigated for its antiviral properties, particularly against HIV and herpes viruses, by inhibiting viral replication. Its dual role in cancer therapy and antiviral research makes it a compound of significant interest in medical science.