fluoropyrimidines

Fluoropyrimidines are a class of antineoplastic (cancer-fighting) drugs derived from the pyrimidine nucleotide, which are essential components of DNA and RNA. These compounds are widely used in chemotherapy due to their ability to inhibit DNA synthesis and cell proliferation, thereby targeting rapidly dividing cells such as cancerous ones. The most well-known fluoropyrimidines include 5-fluorouracil (5-FU) and its prodrugs, capecitabine and tegafur.

5-fluorouracil was first synthesized in 1957 and remains one of the most commonly prescribed chemotherapy agents. It functions primarily by being incorporated into DNA and RNA, where it disrupts normal cellular processes. The drug is metabolized into active forms that inhibit thymidylate synthase, an enzyme critical for DNA synthesis, leading to cell cycle arrest and apoptosis (programmed cell death). Due to its broad-spectrum activity, 5-FU is used to treat various cancers, including colorectal, breast, gastric, pancreatic, and head and neck cancers.

Capecitabine, an oral fluoropyrimidine, is a prodrug that undergoes enzymatic conversion in the body to release 5-FU selectively in tumor tissues. This targeted approach reduces systemic toxicity while maintaining efficacy, making it a preferred option for certain patients. Tegafur, another prodrug, is often combined with other agents like uracil or gimeracil to enhance its anticancer effects.

While fluoropyrimidines are effective, they are associated with significant side effects, including bone marrow suppression (leading to anemia, neutropenia, and thrombocytopenia), gastrointestinal toxicity (nausea, diarrhea, and mucositis), and hand-foot syndrome. Toxicity management often involves dose adjustments, supportive care, and, in some cases, the use of protective agents like leucovorin (folinic acid), which modulates the drug’s activity.

Resistance to fluoropyrimidines can develop through various mechanisms, including reduced drug uptake, enhanced thymidylate synthase activity, or increased repair of DNA damage. Research continues to explore combination therapies and novel formulations to improve outcomes and reduce resistance.