title: Interactions of two major metabolites of prasugrel, a thienopyridine antiplatelet agent, with the cytochromes P450.
abstract: The biotransformation of prasugrel to R-138727 (2-[1-2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl]-4-mercapto-3-piperidinylidene]acetic acid) involves rapid deesterification to R-95913 (2-[2-oxo-6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl]-1-cyclopropyl-2-(2-fluorophenyl)ethanone) followed by cytochrome P450 (P450)-mediated formation of R-138727, the metabolite responsible for platelet aggregation. For identification of the P450s responsible for the formation of the active metabolite, the current studies were conducted with R-95913 as the substrate. Incubations required supplementation with reduced glutathione. Hyperbolic kinetics (K(m) 21-30 microM), consistent with a single enzyme predominating, were observed after incubations with human liver microsomes. Correlation analyses revealed a strong relationship between R-138727 formation and CYP3A-mediated midazolam 1'-hydroxylation (r(2) = 0.98; p < 0.001) in a bank of characterized human liver microsomal samples. The human lymphoblast-expressed enzymes capable of forming R-138727, in rank order of rates, were CYP3A4>CYP2B6>CYP2C19 approximately CYP2C9>CYP2D6. A monoclonal antibody to CYP2B6 and the CYP3A inhibitor ketoconazole substantially inhibited R-138727 formation, whereas inhibitors of CYP2C9 (sulfaphenazole) and CYP2C19 (omeprazole) did not. Scaling of in vitro intrinsic clearance values from expressed enzymes to the whole liver using a relative abundance approach indicated that either CYP3A4 alone or CYP3A4 and CYP2B6 are the major contributors to R-138727 formation. R-95913 and R-138727 were also examined for their ability to inhibit metabolism mediated by five P450s. R-138727 did not inhibit the P450s tested. In vitro, R-95913 inhibited CYP2C9, CYP2C19, CYP2D6, and CYP3A, with K(i) values ranging from 7.2 microM to 82 microM, but did not inhibit CYP1A2. These K(i) values exceed circulating concentrations in humans by 3.8- to 43-fold. Therefore, neither R-95913 nor R-138727 is expected to substantially inhibit the P450-mediated metabolism of coadministered drugs.
authors.affiliation: Department of Drug Disposition, Eli Lilly and Company, Lilly Corporate Center DC0714, Indianapolis, IN 46285, USA. jfayer@lilly.com
authors.forename: Jessica L Fayer
authors.initials: JL
authors.lastname: Rehmel
authors.forename: James A
authors.initials: JA
authors.lastname: Eckstein
authors.forename: Nagy A
authors.initials: NA
authors.lastname: Farid
authors.forename: John B
authors.initials: JB
authors.lastname: Heim
authors.forename: Steve C
authors.initials: SC
authors.lastname: Kasper
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kurihara
authors.forename: Steven A
authors.initials: SA
authors.lastname: Wrighton
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Ring
mesh_terms: D000911:Antibodies, Monoclonal; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007654:Ketoconazole / Q000494:pharmacology; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010879:Piperazines / Q000378:metabolism*; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism*; D000068799:Prasugrel Hydrochloride; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013876:Thiophenes / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D010879:Piperazines; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; D013876:Thiophenes; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating; D000068799:Prasugrel Hydrochloride; D007654:Ketoconazole