Evaluation of Calibration Curve–Based Approaches to Predict Clinical Inducers and Noninducers of CYP3A4 with Plated

Cytochrome P450 (P450) induction is often considered a liability in drug development. Using calibration curve–based approaches, we assessed the induction parameters R3 (a term indicating the amount of P450 induction in the liver, expressed as a ratio between 0 and 1), relative induction score, Cmax/EC50, and area under the curve (AUC)/F2 (the concentration causing 2-fold increase from baseline of the dose-response curve), derived from concentration-response curves of CYP3A4 mRNA and enzyme activity data in vitro, as predictors of CYP3A4 induction potential in vivo. Plated cryopreserved human hepatocytes from three donors were treated with 20 test compounds, including several clinical inducers and noninducers of CYP3A4. After the 2-day treatment, CYP3A4 mRNA levels and testosterone 6b-hydroxylase activity were determined by real-time reverse tran-scription polymerase chain reaction and liquid chromatography