The combination drug tegafur/gimeracil/oteracil (trade name Teysuno) is used for the treatment of advanced gastric cancer. It is also being developed for the treatment of hepatocellular carcinoma.
Mechanism of action
Tegafur is the actual chemotherapeutic agent. It is a prodrug of the active substance fluorouracil (5-FU).
Gimeracil inhibits the degradation of fluorouracil by reversibly blocking a dehydrogenase enzyme. This results in higher 5-FU levels and a prolonged half-life of the substance.
Oteracil mainly stays in the gut because of its low permeability, where it reduces the production of 5-FU by blocking the enzyme orotate phosphoribosyltransferase. Lower 5-FU levels in the gut result in a lower gastrointestinal toxicity.