Gimeracil (5-chloro-2,4-dihydroxypyridine or CDHP) is a potent inhibitor of dihydropyrimidine dehydrogenase (DPD) which is an enzyme that is involved in pyrimidine degradation. Gimeracil itself does not influence cell proliferation, whereas it reversibly inhibits 5-FU [
F0151] degradation and enhanced 5-FU cytotoxicity in tumor cell lines. Gimeracil is often used as combined agents to enhance the antitumor activity of fluoropyrimidines, such as S-1 (tegafur [
F0635] a prodrug of 5-FU, gimeracil and potassium oxonate [
O0164] at a molar ratio of 1:0.4:1). (The product is for research purpose only.)