title: Stochastic prediction of CYP3A-mediated inhibition of midazolam clearance by ketoconazole.
abstract: Conventional methods to forecast CYP3A-mediated drug-drug interactions have not employed stochastic approaches that integrate pharmacokinetic (PK) variability and relevant covariates to predict inhibition in terms of probability and uncertainty. Empirical approaches to predict the extent of inhibition may not account for nonlinear or non-steady-state conditions, such as first-pass effects or accumulation of inhibitor concentration with multiple dosing. A physiologically based PK model was developed to predict the inhibition of CYP3A by ketoconazole (KTZ), using midazolam (MDZ) as the substrate. The model integrated PK models of MDZ and KTZ, in vitro inhibition kinetics of KTZ, and the variability and uncertainty associated with these parameters. This model predicted the time- and dose-dependent inhibitory effect of KTZ on MDZ oral clearance. The predictive performance of the model was validated using the results of five published KTZ-MDZ studies. The model improves the accuracy of predicting the inhibitory effect of increasing KTZ dosing on MDZ PK by incorporating a saturable KTZ efflux from the site of enzyme inhibition in the liver. The results of simulations using the model supported the KTZ dose of 400 mg once daily as the optimal regimen to achieve maximum inhibition by KTZ. Sensitivity analyses revealed that the most influential variable on the prediction of inhibition was the fractional clearance of MDZ mediated by CYP3A. The model may be used prospectively to improve the quantitative prediction of CYP3A inhibition and aid the optimization of study designs for CYP3A-mediated drug-drug interaction studies in drug development.
authors.affiliation: Department of Drug Disposition, Lilly Research Laboratories, Indianapolis, IN 46285, USA. jchien@lilly.com
authors.forename: Jenny Y
authors.initials: JY
authors.lastname: Chien
authors.forename: Aroonrut
authors.initials: A
authors.lastname: Lucksiri
authors.forename: Charles S
authors.initials: CS
authors.lastname: Ernest
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Gorski
authors.forename: Steven A
authors.initials: SA
authors.lastname: Wrighton
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Hall
mesh_terms: D000367:Age Factors; D001835:Body Weight; D003198:Computer Simulation; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D065692:Cytochrome P-450 CYP3A Inhibitors; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005544:Forecasting; D006801:Humans; D007654:Ketoconazole / Q000493:pharmacokinetics / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008874:Midazolam / Q000493:pharmacokinetics; D008954:Models, Biological; D010599:Pharmacokinetics; D015203:Reproducibility of Results; D012737:Sex Factors; D012984:Software; D013269:Stochastic Processes
chemical_list: D065692:Cytochrome P-450 CYP3A Inhibitors; D004791:Enzyme Inhibitors; D051544:Cytochrome P-450 CYP3A; D008874:Midazolam; D007654:Ketoconazole