title: Identification of enzymes responsible for the N-oxidation of darexaban glucuronide, the pharmacologically active metabolite of darexaban, and the glucuronidation of darexaban N-oxides in human liver microsomes.
abstract: Darexaban maleate is a novel oral direct factor Xa inhibitor. Darexaban glucuronide (YM-222714) was the major component in plasma after oral administration of darexaban to humans and is the pharmacologically active metabolite. Additionally, YM-222714 N-oxides were detected as minor metabolites in human plasma and urine. It is possible that YM-222714 N-oxides are formed by the N-oxidation of YM-222714 and/or the glucuronidation of darexaban N-oxides (YM-542845) in vivo. The former reaction is the pharmacological inactivation process. In this study, we identified the human enzymes responsible for YM-222714 N-oxidation and the uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT) isoforms involved in YM-542845 glucuronidation in vitro. YM-222714 N-oxidation activity was detected in human liver microsomes (HLM), but not in human intestinal microsomes. In HLM, YM-222714 N-oxidation activities were significantly correlated with flavin-containing monooxygenase (FMO) marker enzyme activities (p<0.001) and inhibited by methimazole, a typical inhibitor of FMOs. Recombinant human FMO3 and FMO1 were capable of efficiently catalyzing YM-222714 N-oxidation, but not FMO5 or any recombinant human cytochrome P450 (CYP) isoforms. Considering the mRNA expression levels of FMO isoforms in human liver, these results strongly suggest that YM-222714 N-oxidation in HLM is mainly catalyzed by FMO3. In HLM, YM-542845 glucuronidation was strongly inhibited by typical substrates for UGT1A8, UGT1A9, and UGT1A10. Recombinant human UGT1A7, UGT1A8, UGT1A9, and UGT1A10 were capable of catalyzing YM-542845 glucuronidation, and UGT1A9 exhibited the highest intrinsic clearance. Considered together with the expression levels of UGT isoforms in human liver, these results strongly suggest that YM-542845 glucuronidation in HLM is mainly catalyzed by UGT1A9.
authors.affiliation: Drug Metabolism Research Laboratories, Drug Discovery Research, Astellas Pharma Inc, Yodogawa-ku, Osaka, Japan. toshifumi.shiraga@astellas.com
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Shiraga
authors.forename: Kanako
authors.initials: K
authors.lastname: Yajima
authors.forename: Takuya
authors.initials: T
authors.lastname: Teragaki
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Suzuki
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Takafumi
authors.initials: T
authors.lastname: Iwatsubo
authors.forename: Aiji
authors.initials: A
authors.lastname: Miyashita
authors.forename: Takashi
authors.initials: T
authors.lastname: Usui
mesh_terms: D001381:Azepines / Q000378:metabolism*; D001549:Benzamides / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D065427:Factor Xa Inhibitors; D020719:Glucuronides / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D008862:Microsomes, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D001381:Azepines; D001549:Benzamides; D065427:Factor Xa Inhibitors; D020719:Glucuronides; D020033:Protein Isoforms; D011994:Recombinant Proteins; C570990:darexaban glucuronide; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D014453:Glucuronosyltransferase; C569750:darexaban