RT Journal Article SR Electronic T1 Quantitative Prediction of CYP3A4 Induction: Impact of Measured, Free, and Intracellular Perpetrator Concentrations from Human Hepatocyte Induction Studies on Drug-Drug Interaction Predictions JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 692 OP 705 DO 10.1124/dmd.117.075481 VO 45 IS 6 A1 Yongkai Sun A1 Paresh P. Chothe A1 Jennifer E. Sager A1 Hong Tsao A1 Amanda Moore A1 Leena Laitinen A1 Niresh Hariparsad YR 2017 UL http://dmd.aspetjournals.org/content/45/6/692.abstract AB Typically, concentration-response curves are based upon nominal inducer concentrations for in-vitro-to-in-vivo extrapolation of CYP3A4 induction. The limitation of this practice is that it assumes the hepatocyte culture model is a static system. We assessed whether correcting for: 1) changes in perpetrator concentration in the induction medium during the incubation period, 2) perpetrator binding to proteins in the induction medium, and 3) nonspecific binding of perpetrator can improve the accuracy of CYP3A4 induction predictions. Of the seven compounds used in this evaluation, significant parent loss and nonspecific binding were observed for rifampicin (29.3–38.3%), pioglitazone (64.3–78.6%), and rosiglitazone (57.1–75.5%). As a result, the free measured EC50 values (EC50u) of pioglitazone, rosiglitazone, and rifampicin were significantly lower than the nominal EC50 values. In general, the accuracy of the induction predictions, using multiple static models, improved when corrections were made for measured medium concentrations, medium protein binding, and nonspecific binding of the perpetrator, as evidenced by 18–29% reductions in the root mean square error. The relative induction score model performed better than the basic static and mechanistic static models, resulting in lower prediction error and no false-positive or false-negative predictions. However, even when the EC50u value was used, the induction prediction for bosentan, which is a substrate of organic anion transporter proteins, was overpredicted by approximately 2-fold. Accounting for the ratio of unbound intracellular concentrations to unbound medium concentrations (Kpuu,in vitro) (0.5–7.5) and the predicted multiple-dose Kpuu,in vivo (0.6) for bosentan resulted in induction predictions within 35% of the observed interaction.