title: Selectivity of febuxostat, a novel non-purine inhibitor of xanthine oxidase/xanthine dehydrogenase.
abstract: The purine analogue, allopurinol, has been in clinical use for more than 30 years as an inhibitor of xanthine oxidase (XO) in the treatment of hyperuricemia and gout. As consequences of structural similarities to purine compounds, however, allopurinol, its major active product, oxypurinol, and their respective metabolites inhibit other enzymes involved in purine and pyrimidine metabolism. Febuxostat (TEI-6720, TMX-67) is a potent, non-purine inhibitor of XO, currently under clinical evaluation for the treatment of hyperuricemia and gout. In this study, we investigated the effects of febuxostat on several enzymes in purine and pyrimidine metabolism and characterized the mechanism of febuxostat inhibition of XO activity. Febuxostat displayed potent mixed-type inhibition of the activity of purified bovine milk XO, with Ki and Ki' values of 0.6 and 3.1 nM respectively, indicating inhibition of both the oxidized and reduced forms of XO. In contrast, at concentrations up to 100 muM, febuxostat had no significant effects on the activities of the following enzymes of purine and pyrimidine metabolism: guanine deaminase, hypoxanthine-guanine phosphoribosyltransferase, purine nucleoside phosphorylase, orotate phosphoribosyltransferase and orotidine-5'-monophosphate decarboxylase. These results demonstrate that febuxostat is a potent non-purine, selective inhibitor of XO, and could be useful for the treatment of hyperuricemia and gout.
authors.affiliation: Pharmaceutical Development Research Laboratories, Teijin Institute for Bio-medical Research, Teijin Pharma Limited, 4-3-2, Asahigaoka Hino, Tokyo 191-8512, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takano
authors.forename: Kumiko
authors.initials: K
authors.lastname: Hase-Aoki
authors.forename: Hideki
authors.initials: H
authors.lastname: Horiuchi
authors.forename: Lin
authors.initials: L
authors.lastname: Zhao
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kasahara
authors.forename: Shiro
authors.initials: S
authors.lastname: Kondo
authors.forename: Michael A
authors.initials: MA
authors.lastname: Becker
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D000069465:Febuxostat; D007700:Kinetics; D008892:Milk / Q000201:enzymology; D015394:Molecular Structure; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology*; D014968:Xanthine Dehydrogenase / Q000037:antagonists & inhibitors*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D013844:Thiazoles; D000069465:Febuxostat; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase