title: Drug-drug interactions and metabolism in cytochrome P450 2C knockout mice: application to troleandomycin and midazolam.
abstract: Drug-drug interactions (DDIs) may cause serious drug toxicity and delay development of candidate drugs. Screening using human liver microsomes and hepatocytes can help predict DDIs but do not always provide the degree of certainty required for confident progression of a candidate drug. Thus a suitable in vivo test system could be of great value. Here a Cyp2c knockout (KO) mouse was investigated for studying DDIs using midazolam (MDZ) a standard human CYP3A4 substrate and troleandomycin (TAO) a potent human CYP3A4 inhibitor. Pharmacokinetics (PK) and biotransformation of MDZ were investigated following dosing to Cyp2c KO and wild type mice before and after TAO treatment. The noteworthy differences in the metabolism of MDZ in Cyp2c KO compared to wild type mice confirms the important role that Cyp2c enzymes play in the murine metabolism of MDZ in vivo. The impact of Cyp3a inhibition produced a further increase in circulating MDZ concentrations in all individuals from both strains of mice though the impact of the elimination of the Cyp2c pathway in the KO mice on the AUC was less than perhaps expected. We have shown that TAO produces an increase in the MDZ concentration and a reduction in the 1'hydroxymidazolam/midazolam formation ratio but the expected difference in the magnitude of this effect between the wild type and the Cyp2c KO mice was not seen. The magnitude of the TAO effect was also smaller than is reported in humans. Hence further work is required before this animal model could be used to predict clinical interactions.
authors.affiliation: Global DMPK, AstraZeneca UK Ltd., Alderley Park, Macclesfield SK10 4TG, United Kingdom.
authors.forename: Aidan
authors.initials: A
authors.lastname: Grimsley
authors.forename: Richard
authors.initials: R
authors.lastname: Gallagher
authors.forename: Michael
authors.initials: M
authors.lastname: Hutchison
authors.forename: Kathryn
authors.initials: K
authors.lastname: Pickup
authors.forename: Ian D
authors.initials: ID
authors.lastname: Wilson
authors.forename: Kristin
authors.initials: K
authors.lastname: Samuelsson
mesh_terms: D000818:Animals; D001646:Bile / Q000378:metabolism; D001711:Biotransformation; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D065692:Cytochrome P-450 CYP3A Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004347:Drug Interactions; D051379:Mice; D018345:Mice, Knockout; D008874:Midazolam / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics*; D014217:Troleandomycin / Q000494:pharmacology*
chemical_list: D065692:Cytochrome P-450 CYP3A Inhibitors; C400322:cytochrome P-450 CYP2C subfamily; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; C040081:1-hydroxymethylmidazolam; D051544:Cytochrome P-450 CYP3A; D008874:Midazolam
keywords: AUC; C(max); CV; CYPs; Cyp2c KO mouse; DDI; DMPK; HESI; HPLC–MS/MS; KO; LOQ; MDZ; MRM; Metabolism; Midazolam; QC; Rt; SCID; TAO; Troleandomycin; UPLC–MS/MS; area under the concentration–time curve; coefficient of variation; cytochrome P450 enzymes; drug metabolism and pharmacokinetics; drug–drug interaction; heated electrospray ionisation; high performance liquid chromatography with mass spectrometry; knock out; limits of quantification; midazolam; multiple reaction monitoring; peak blood concentrations; quality control; retention time; severely combined immunodeficient; troleandomycin; ultraperformance liquid chromatography with mass spectrometry