title: CYP3A4 substrate selection and substitution in the prediction of potential drug-drug interactions.
abstract: The complexity of in vitro kinetic phenomena observed for CYP3A4 substrates (homo- or heterotropic cooperativity) confounds the prediction of drug-drug interactions, and an evaluation of alternative and/or pragmatic approaches and substrates is needed. The current study focused on the utility of the three most commonly used CYP3A4 in vitro probes for the prediction of 26 reported in vivo interactions with azole inhibitors (increase in area under the curve ranged from 1.2 to 24, 50% in the range of potent inhibition). In addition to midazolam, testosterone, and nifedipine, quinidine was explored as a more "pragmatic" substrate due to its kinetic properties and specificity toward CYP3A4 in comparison with CYP3A5. Ki estimates obtained in human liver microsomes under standardized in vitro conditions for each of the four probes were used to determine the validity of substrate substitution in CYP3A4 drug-drug interaction prediction. Detailed inhibitor-related (microsomal binding, depletion over incubation time) and substrate-related factors (cooperativity, contribution of other metabolic pathways, or renal excretion) were incorporated in the assessment of the interaction potential. All four CYP3A4 probes predicted 69 to 81% of the interactions with azoles within 2-fold of the mean in vivo value. Comparison of simple and multisite mechanistic models and interaction prediction accuracy for each of the in vitro probes indicated that midazolam and quinidine in vitro data provided the best assessment of a potential interaction, with the lowest bias and the highest precision of the prediction. Further investigations with a wider range of inhibitors are required to substantiate these findings.
authors.affiliation: School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Oxford Rd., Manchester M13 9PL, UK. aleksandra.galetin@manchester.ac.uk
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Galetin
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Ito
authors.forename: David
authors.initials: D
authors.lastname: Hallifax
authors.forename: J Brian
authors.initials: JB
authors.lastname: Houston
mesh_terms: D000465:Algorithms; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D019540:Area Under Curve; D001393:Azoles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004347:Drug Interactions; D005544:Forecasting; D006801:Humans; D006993:Hypnotics and Sedatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D008874:Midazolam / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009543:Nifedipine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011802:Quinidine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D013739:Testosterone / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D001393:Azoles; D002121:Calcium Channel Blockers; D006993:Hypnotics and Sedatives; D013739:Testosterone; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D009543:Nifedipine; D011802:Quinidine; D008874:Midazolam