Technical Pitfalls and Improvements for High-speed Screening and QSAR Analysis to Predict Inhibitors of the Human Bile Salt Export Pump (ABCB11/BSEP)

Drug-induced hepatotoxicity is one of the major problems encountered in drug discovery and development. Selection of a candidate compound for pre-clinical studies in the drug discovery process is a critical step that can determine the speed and expenditure of clinical development. Because inhibition of human adenosine triphosphate-binding cassette transporter ABCB11 (SPGP/bile salt export pump) has severe consequences, which include intrahepatic cholestasis and hepatotoxicity, resulting from exposure to toxic xenobiotics or drug interactions, in vitro screening methods are necessary for quantifying and characterizing the inhibition of ABCB11. In line with such initiatives, we developed methods for in vitro high-speed screening and quantitative structure-activity relationship (QSAR) analysis to investigate the interaction of ABCB11 with a variety of compounds. We identified one set of chemical fragmentation codes closely linked with inhibition of ABCB11. Furthermore, the high-speed screening method enables us to analyze the kinetics of ABCB11-inhibition by test compounds and to distinguish competitive and non-competitive inhibitors. Troglitazone and novobiocin were found to be competitive inhibitors to taurocholate, whereas porphyrins were non-competitive inhibitors. Kinetics-based classification of inhibitors is considered important to improve the accuracy of our QSAR analysis. The present mini-review addresses technical pitfalls and improvements for high-speed screening and QSAR analysis in the ABCB11 inhibition study.