LAUSR

It is of great challenge to predict human brain penetration for substrates of multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP), 2 major efflux transporters at blood-brain barrier. Thus, a physiologically based pharmacokinetic (PBPK) model with the incorporation of in vitro MDR1 and BCRP transporter function data and transporter protein expression levels has been developed. As such, it is crucial to generate MDR1 and BCRP substrate data with a high fidelity. In this study, 2 widely used human MDR1 cell lines from Borst and National Institutes of Health laboratories were evaluated using rodent brain penetration data, and the study suggested that the MDR1 expressed in Madin-Darby canine kidney (MDCK) cell line from National Institutes of Health laboratory predicted brain penetration better, particularly for compounds with a high passive permeability. In addition, human BCRP-MDCK cell line with 1 μM PSC833, a specific MDR1 inhibitor, demonstrated the ability to identify BCRP substrates without the confounding of endogenous canine Mdr1. Comparison of human BCRP and mouse Bcrp transporter functions revealed that the functional differences of BCRP between the 2 species is minimal. The incorporation of both the validated MDR1 and BCRP assays into our brain PBPK model has significantly improved the prediction for the brain penetration of MDR1 and BCRP substrates across species.