Tegafur, gimeracil, oteracil (S-1)

Note: this drug is approved in Japan and has been extensively studied there. Full references will not be provided until if/when the drug is FDA approved.

Mechanism of action

From the NCI Drug Dictionary: An orally bioavailable fluoropyrimidine antagonist composed of tegafur combined with two modulators of 5-flurouracil (5-FU) activity, 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate, in a molar ratio of 1:0.4:1. Tegafur is a prodrug of 5-fluorouracil, an antimetabolite that inhibits thymidylate synthase, DNA synthesis and cell division, and competes with uridine triphosphate, thus inhibiting RNA and protein synthesis. CDHP is a reversible inhibitor of dihydropyrimidine dehydrogenase (DPD), the liver enzyme responsible for rapid catabolism of 5-FU into inactive metabolites. Potassium oxonate preferentially localizes in the gut and inhibits the enzyme orotate phosphoribosyl-transferase (OPRT), thereby decreasing activation of 5-FU in the gut and activated 5-FU-related gastrointestinal toxicity.

Preliminary data

Pancreatic cancer

1. Uesaka K, Boku N, Fukutomi A, Okamura Y, Konishi M, Matsumoto I, Kaneoka Y, Shimizu Y, Nakamori S, Sakamoto H, Morinaga S, Kainuma O, Imai K, Sata N, Hishinuma S, Ojima H, Yamaguchi R, Hirano S, Sudo T, Ohashi Y; JASPAC 01 Study Group. Adjuvant chemotherapy of S-1 versus gemcitabine for resected pancreatic cancer: a phase 3, open-label, randomised, non-inferiority trial (JASPAC 01). Lancet. 2016 Jul 16;388(10041):248-57. Epub 2016 Jun 2. link to original article PubMed