S-ONE TRIO-20 Tablets S-ONE TRIO-20 is an oral fluoropyrimidine combination drug consisting of Tegafur, Gimeracil, and Oteracil potassium in a 1:0.4:1 molar ratio. Tegafur is a prodrug of 5-fluorouracil (5-FU) that generates cytotoxic 5-FU in vivo. Gimeracil inhibits dihydropyrimidine dehydrogenase (DPD), preventing the rapid degradation of 5-FU and maintaining high systemic drug concentrations. Oteracil inhibits orotate phosphoribosyltransferase (OPRT) in the gastrointestinal mucosa, selectively suppressing 5-FU phosphorylation and reducing GI toxicity. It is indicated for the treatment of advanced or metastatic gastric cancer, pancreatic cancer, colorectal cancer, non-small cell lung cancer, and head and neck cancers.