title: Roles of CYP3A4 and CYP2C19 in methyl hydroxylated and N-oxidized metabolite formation from voriconazole, a new anti-fungal agent, in human liver microsomes.
abstract: Involvement of cytochrome P450 (P450 or CYP) 2C19, 2C9, and 3A4 in N-oxidation of voriconazole, a new triazole antifungal agent, has been demonstrated using human liver microsomes. To confirm the precise roles of P450 isoforms in voriconazole clearance in individuals, we investigated the oxidative metabolism of voriconazole catalyzed by recombinant P450s as well as human liver microsomes genotyped for the CYP2C19 gene. Among recombinant P450 isoforms using Escherichia coli expression systems, CYP2C19 and CYP3A4 had voriconazole N-oxidation activities, but not CYP2C9. Apparent K(m) and V(max) values of CYP2C19 and CYP3A4 for voriconazole N-oxidation were 14+/-6 microM and 0.22+/-0.02 nmol/min/nmol CYP2C19 and 16+/-10 microM and 0.05+/-0.01 nmol/min/nmol CYP3A4, respectively (mean+/-S.E.). CYP3A4 produced a new methyl hydroxylated metabolite from voriconazole, detected by LC/UV and LC/MS/MS and confirmed by 1H and 13C NMR analyses, with K(m) and V(max) values of 11+/-3 microM and 0.10+/-0.01 nmol/min/nmol CYP3A4. The voriconazole 4-hydroxylation to N-oxidation metabolic ratios in liver microsomes from the wild-type CYP2C19*1/*1 individuals (0.07) were lower than those observed in other genotypes (0.20-0.27) at a substrate concentration of 25 microM based on the reported clinical plasma level. These results suggest that the CYP2C19 genotype, but not CYP2C9 genotype, would be evaluated as a key factor in the pharmacokinetics of voriconazole and that 4-hydroxyvoriconazole formation may become an important pathway for voriconazole metabolism in individuals with poor CYP2C19 catalytic function.
authors: Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, 3-3165 Higashi-tamagawa Gakuen, Machida, Tokyo 194-8543, Japan.
authors: Norie
authors: N
authors: Murayama
authors: Naoko
authors: N
authors: Imai
authors: Takahisa
authors: T
authors: Nakane
authors: Makiko
authors: M
authors: Shimizu
authors: Hiroshi
authors: H
authors: Yamazaki
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002853:Chromatography, Liquid; D065731:Cytochrome P-450 CYP2C19; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008956:Models, Chemical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011743:Pyrimidines / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry; D014230:Triazoles / Q000378:metabolism*; D065819:Voriconazole
chemical_list: D000935:Antifungal Agents; D007527:Isoenzymes; D011743:Pyrimidines; D011994:Recombinant Proteins; D014230:Triazoles; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D065819:Voriconazole