Quantitative Prediction of CYP3A4‐ and CYP3A5‐Mediated Drug Interactions

We verified a physiologically‐based pharmacokinetic (PBPK) model to predict cytochrome P450 3A4/5‐mediated drug‐drug interactions (DDIs). A midazolam (MDZ)–ketoconazole (KTZ) interaction study in 24 subjects selected by CYP3A5 genotype, and liquid chromatography and mass spectroscopy quantification of CYP3A4/5 abundance from independently acquired and genotyped human liver (n = 136) and small intestinal (N = 12) samples, were conducted. The observed CYP3A5 genetic effect on MDZ systemic and oral clearance was successfully replicated by a mechanistic framework incorporating the proteomics‐informed CYP3A abundance and optimized small intestinal CYP3A4 abundance based on MDZ intestinal availability (FG) of 0.44. Furthermore, combined with a modified KTZ PBPK model, this framework recapitulated the observed geometric mean ratio of MDZ area under the curve (AUCR) following 200 or 400 mg KTZ, which was, respectively, 2.7–3.4 and 3.9–4.7‐fold in intravenous administration and 11.4–13.4 and 17.0–19.7‐fold in oral administration, with AUCR numerically lower (P > 0.05) in CYP3A5 expressers than nonexpressers. In conclusion, the developed mechanistic framework supports dynamic prediction of CYP3A‐mediated DDIs in study planning by bridging DDIs between CYP3A5 expressers and nonexpressers.