Prediction of Drug Clearance and Drug Drug Interactions in Microscale Cultures of Human Hepatocytes
Accurate prediction of in vivo hepatic drug clearance using in vitro assays is important to properly estimate clinical dosing regimens. Clearance of low turnover compounds is especially difficult to predict using short lived suspensions of unpooled primary human hepatocytes (PHHs) and functionally declining PHH monolayers. Micropatterned cocultures (MPCCs) of PHHs and 3T3 J2 fibroblasts have been shown previously to display major liver functions for several weeks in vitro. In this study, we first characterized long term activities of major cytochrome P450 enzymes in MPCCs created from unpooled cryopreserved PHH donors. MPCCs were then used to predict the clearance of 26 drugs that exhibit a wide range of turnover rates in vivo (0.05 19.5 ml/min per kilogram) MPCCs predicted 73, 92, and 96% of drug clearance values for all tested drugs within 2 fold, 3 fold, and 4 fold of in vivo values, respectively. There was good correlation (R2 0.94, slope 1.05) of predictions between the two PHH donors. On the other hand, suspension hepatocytes and conventional monolayers created from the same donor had significantly reduced predictive capacity (i.e. 30 50% clearance values within 4 fold of in vivo) and were not able to metabolize several drugs. Finally, we modulated drug clearance in MPCCs by inducing or inhibiting P450s. Rifampin mediated CYP3A4 induction increased midazolam clearance by 73% while CYP3A4 inhibition with ritonavir decreased midazolam clearance by 79% Similarly, quinidine mediated CYP2D6 inhibition reduced clearance of dextromethorphan and desipramine by 71 and 22% respectively. In conclusion, MPCCs created using cryopreserved unpooled PHHs can be used for drug clearance predictions and to model drug drug interactions.
Drug Metabolism and Disposition