Characterization of human liver enzymes involved in the biotransformation of boceprevir, a hepatitis C virus protease inhibitor.
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.
Drug Metabolism and Pharmacokinetics, Merck Research Laboratories, 2015 Galloping Hill Road, K-15-1945, Kenilworth, NJ 07033, USA. anima.ghosal@merck.com
Anima
A
Ghosal
Yuan
Y
Yuan
Wei
W
Tong
Ai-Duen
AD
Su
Chunyan
C
Gu
Swapan K
SK
Chowdhury
Narendra S
NS
Kishnani
Kevin B
KB
Alton
D015096:3-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000074425:Aldo-Keto Reductase Family 1 Member C3; D001711:Biotransformation / Q000187:drug effects; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D065692:Cytochrome P-450 CYP3A Inhibitors; D015507:Drugs, Investigational / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016174:Hepacivirus / Q000201:enzymology*; D006801:Humans; D006911:Hydroxyprostaglandin Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006913:Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D014508:Urea / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
D015096:3-Hydroxysteroid Dehydrogenases; D000074425:Aldo-Keto Reductase Family 1 Member C3; D051544:Cytochrome P-450 CYP3A; D065692:Cytochrome P-450 CYP3A Inhibitors; D015507:Drugs, Investigational; D004791:Enzyme Inhibitors; D006911:Hydroxyprostaglandin Dehydrogenases; D006913:Hydroxysteroid Dehydrogenases; D009842:Oligopeptides; D011392:Proline; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D014508:Urea; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C512204: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; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); C487341:AKR1C3 protein, human; C510164:CYP3A5 protein, human; C510163:CYP3A4 protein, human