title: Validation of (-)-N-3-benzyl-phenobarbital as a selective inhibitor of CYP2C19 in human liver microsomes.
abstract: (-)-N-3-Benzyl-phenobarbital (NBPB) was reported to be a potent and selective inhibitor of CYP2C19. To validate the selectivity of NBPB toward CYP2C19 in human liver microsomes, the inhibitory effects on major cytochrome P450 isoform-specific reactions were evaluated in the present study. In human liver microsomes, NBPB showed potent competitive inhibition on CYP2C19-mediated S-mephenytoin 4'-hydroxylation with an IC(50) value of 0.25 microM and K(i) value of 0.12 microM, whereas weak inhibition was observed for CYP1A2-, CYP2A6-, CYP2B6-, CYP2C8-, CYP2C9-, CYP2D6-, and CYP3A4-mediated reactions with IC(50) values >100, >100, 62, 34, 19, >100, and 89 microM, respectively. Importantly, its selectivity toward CYP2C19 among the CYP2C subfamily was demonstrated. Therefore, NBPB can be used as a potent and selective inhibitor to establish the relative contribution of CYP2C19 for in vitro reaction phenotyping studies. This compound can also serve as a positive control inhibitor of CYP2C19 for routine screening of P450 reversible inhibition when human liver microsomes are used as the enzyme source.
authors.affiliation: Department of Drug Metabolism, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
authors.forename: Xiaoxin
authors.initials: X
authors.lastname: Cai
authors.forename: Regina W
authors.initials: RW
authors.lastname: Wang
authors.forename: Richard W
authors.initials: RW
authors.lastname: Edom
authors.forename: David C
authors.initials: DC
authors.lastname: Evans
authors.forename: Magang
authors.initials: M
authors.lastname: Shou
authors.forename: A David
authors.initials: AD
authors.lastname: Rodrigues
authors.forename: Wensheng
authors.initials: W
authors.lastname: Liu
authors.forename: Dennis C
authors.initials: DC
authors.lastname: Dean
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Baillie
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors*; D002851:Chromatography, High Pressure Liquid; D065731:Cytochrome P-450 CYP2C19; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D010634:Phenobarbital / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; C454676:N-3-benzylphenobarbital; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D010634:Phenobarbital