Abstract
Boceprevir (SCH 503034), a protease inhibitor, is under clinical development for the treatment of human hepatitis C virus infections. In human liver microsomes, formation of oxidative metabolites after incubations with [(14)C]boceprevir was catalyzed by CYP3A4 and CYP3A5. In addition, the highest turnover was observed in recombinant CYP3A4 and CYP3A5. After a single radiolabeled dose to human, boceprevir was subjected to two distinct pathways, namely cytochrome P450-mediated oxidation and ketone reduction. Therefore, attempts were made to identify the enzymes responsible for the formation of carbonyl-reduced metabolites. Human liver S9 and cytosol converted ∼ 28 and ∼ 68% of boceprevir to M28, respectively, in the presence of an NADPH-generating system. Screening of boceprevir with recombinant human aldo-keto reductases (AKRs) revealed that AKR1C2 and AKR1C3 exhibited catalytic activity with respect to the formation of M+2 metabolites (M28 and M31). The formation of M28 was inhibited by 100 μM flufenamic acid (80.3%), 200 μM mefenamic acid (83.7%), and 100 μM phenolphthalein (86.1%), known inhibitors of AKRs, suggesting its formation through carbonyl reduction pathway. Formation of M28 was also inhibited by 100 μM diazepam (75.1%), 1 mM ibuprofen (70%), and 200 μM diflunisal (89.4%). These data demonstrated that CYP3A4 and CYP3A5 are primarily responsible for the formation of oxidative metabolites and the formation of M28 and M31, the keto-reduced metabolites, are most likely mediated by AKR1C2 and AKR1C3. Because the biotransformation and clearance of boceprevir involves two different enzymatic pathways, boceprevir is less likely to be a victim of significant drug-drug interaction with concomitant medication affecting either of these pathways.
MeSH terms
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3-Hydroxysteroid Dehydrogenases / antagonists & inhibitors
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3-Hydroxysteroid Dehydrogenases / genetics
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3-Hydroxysteroid Dehydrogenases / metabolism
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Aldo-Keto Reductase Family 1 Member C3
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Biotransformation / drug effects
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Cytochrome P-450 CYP3A / genetics
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Cytochrome P-450 CYP3A / metabolism
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Cytochrome P-450 CYP3A Inhibitors
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Drugs, Investigational / chemistry
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Drugs, Investigational / metabolism*
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Enzyme Inhibitors / pharmacology
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Hepacivirus / enzymology*
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Humans
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Hydroxyprostaglandin Dehydrogenases / antagonists & inhibitors
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Hydroxyprostaglandin Dehydrogenases / genetics
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Hydroxyprostaglandin Dehydrogenases / metabolism
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Hydroxysteroid Dehydrogenases / antagonists & inhibitors
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Hydroxysteroid Dehydrogenases / genetics
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Hydroxysteroid Dehydrogenases / metabolism
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Kinetics
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Liver / enzymology*
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Molecular Structure
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Oligopeptides / chemistry
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Oligopeptides / metabolism
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Oxidation-Reduction
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Proline / analogs & derivatives*
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Proline / chemistry
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Proline / metabolism
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Recombinant Proteins / metabolism
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Serine Proteinase Inhibitors / chemistry
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Serine Proteinase Inhibitors / metabolism*
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Stereoisomerism
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Subcellular Fractions / drug effects
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Subcellular Fractions / enzymology
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Subcellular Fractions / metabolism
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Urea / analogs & derivatives
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Urea / chemistry
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Urea / metabolism
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Viral Nonstructural Proteins / antagonists & inhibitors*
Substances
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Cytochrome P-450 CYP3A Inhibitors
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Drugs, Investigational
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Enzyme Inhibitors
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NS3 protein, hepatitis C virus
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Oligopeptides
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Recombinant Proteins
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Serine Proteinase Inhibitors
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Viral Nonstructural Proteins
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N-(3-amino-1-(cyclobutylmethyl)-2,3-dioxopropyl)-3-(2-((((1,1-dimethylethyl)amino)carbonyl)amino)-3,3-dimethyl-1-oxobutyl)-6,6-dimethyl-3-azabicyclo(3.1.0)hexan-2-carboxamide
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Urea
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Proline
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3-Hydroxysteroid Dehydrogenases
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Hydroxysteroid Dehydrogenases
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Hydroxyprostaglandin Dehydrogenases
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AKR1C2 protein, human
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AKR1C3 protein, human
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Aldo-Keto Reductase Family 1 Member C3
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CYP3A5 protein, human
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Cytochrome P-450 CYP3A
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CYP3A4 protein, human