Quantitative prediction of CYP3A‐mediated drug–drug interactions by correctly estimating fraction metabolized using human liver chimeric mice

Abstract

Background and PurposeFraction metabolized (fm) and fraction transported (ft) are important for understanding drug‐drug interactions (DDIs) in drug discovery and development. However, current in vitro systems cannot accurately estimate in vivo fm due to inability to reflect the ft by efflux transporter (ft,efflux). This study demonstrates how CYP3A‐mediated DDI for CYP3A/P‐gp substrates can be predicted using Hu‐PXB mice as human liver chimeric mice.Experimental ApproachFor estimating human in vitro fm by CYP3A enzyme (fm,CYP3A,in vitro), six drugs including CYP3A/P‐gp substrates (alprazolam, cyclosporine, docetaxel, midazolam, prednisolone, and theophylline) and human hepatocytes were incubated with or without ketoconazole as a CYP3A inhibitor. We calculated fm,CYP3A,in vitro based on hepatic intrinsic clearance. To estimate human in vivo fm,CYP3A (fm,CYP3A,in vivo), we collected information on clinical DDI caused by ketoconazole for these six drugs. We calculated fm,CYP3A,in vivo using the change of total clearance (CLtotal). For evaluating the human DDI predictability, the six drugs were administered intravenously to Hu‐PXB and SCID mice with or without ketoconazole. We calculated the change of CLtotal caused by ketoconazole. We compared the CLtotal change in humans with that in Hu‐PXB and SCID mice.Key ResultsThe fm,CYP3A,in vitro was overestimated compared to the fm,CYP3A,in vivo. Hu‐PXB mice showed much better correlation in the change of CLtotal with humans (R2 = 0.95) compared to SCID mice (R2 = 0.0058).Conclusions and ImplicationsCYP3A‐mediated DDI can be predicted by correctly estimating human fm,CYP3A,in vivo using Hu‐PXB mice. These mice could be a useful tool for predicting hepatic fm and ft,efflux.