Individual Differences in Metabolic Clearance of S-Warfarin Efficiently Mediated by Polymorphic Marmoset Cytochrome P450 2C19 in Livers

Marmoset cytochrome P450 2C19, highly homologous to human P450 2C9 and 2C19, has been identified in common marmosets (Callithrix jacchus), a nonhuman primate species used in drug metabolism studies. Although genetic variants in human and macaque P450 2C genes account for the interindividual variability in drug metabolism, genetic variants have not been investigated in the marmoset P450 2C19. In this study, sequencing of P450 2C19 in 24 marmosets identified three variants p.[(Phe7Leu; Ser254Leu; Thr469Ile)], which showed substantially reduced metabolic capacity of S-warfarin compared with the wild-type group in vivo and in vitro. Although mean plasma concentrations of R-warfarin in marmosets determined after chiral separation were similar between the homozygous mutant and wild-type groups up to 24 hours after the intravenous and oral administrations of racemic warfarin, S-warfarin depletion from plasma was significantly faster in the three wild-type marmosets compared with the three homozygous mutant marmosets. These variants, cosegregating in the marmosets analyzed, influenced metabolic activities in 18 marmoset liver microsomes because the homozygotes and heterozygotes showed significantly reduced catalytic activities in liver microsomes toward S-warfarin 7-hydroxylation compared with the wild-type group. Kinetic analysis for S-warfarin 7-hydroxylation indicated that the recombinant P450 2C19 Ser254Leu variant would change the metabolic capacity. These results indicated that the interindividual variability of P450 2C–dependent drug metabolism such as S-warfarin clearance is at least partly accounted for by P450 2C19 variants in marmosets, suggesting that polymorphic P450 2C–dependent catalytic functions are relatively similar between marmosets and humans.