TY - JOUR T1 - Predictions of Cytochrome P450-Mediated Drug-Drug Interactions Using Cryopreserved Human Hepatocytes: Comparison of Plasma and Protein-Free Media Incubation Conditions JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 706 LP - 716 DO - 10.1124/dmd.111.043158 VL - 40 IS - 4 AU - Jialin Mao AU - Michael A. Mohutsky AU - John P. Harrelson AU - Steven A. Wrighton AU - Stephen D. Hall Y1 - 2012/04/01 UR - http://dmd.aspetjournals.org/content/40/4/706.abstract N2 - Cryopreserved human hepatocytes suspended in human plasma (HHSHP) have previously provided accurate CYP3A drug-drug interaction (DDI) predictions from a single IC50 that captures both reversible and time-dependent inhibition. The goal of this study was to compare the accuracy of DDI predictions by a protein-free human hepatocyte system combined with the fraction unbound in plasma for inhibitor(s) with those obtained with protein-containing incubations. Seventeen CYP3A, CYP2C9, or CYP2D6 inhibitors were incubated with hepatocytes in human plasma or hepatocyte maintenance medium (HMM) for 20 min over a range of concentrations after which midazolam 1′-hydroxylation, diclofenac 4′-hydroxylation or (R)-bufuralol 1′-hydroxylation were used to quantify the corresponding cytochrome P450 (P450) catalytic activities. Two methods were used to predict the human exposure ratio of the victim drug in the presence and absence of inhibitor. The HMM Ki, app values were combined with the free average systemic plasma concentration (“free [I] with HMM Ki, app”) and the plasma Ki, app values were combined with the total average systemic plasma concentration (“total [I] with plasma Ki, app”). Of 63 clinical DDI studies, the total [I] with plasma Ki, app method predicted 89% of cases within 2-fold of the reported interaction whereas the free [I] with HMM Ki, app method predicted only 59%. There was a general underprediction by the free [I] with HMM Ki, app method, which is consistent with an underestimation of in vitro inhibition potency in this system. In conclusion, the HHSHP system proved to be a simple, accurate predictor of DDIs for three major P450s and superior to the protein-free approach. ER -