Drug-induced cholestasis poses a major hurdle for the pharmaceutical industry as it is one the primary mechanisms of drug-induced liver injury. Hence, detection of drug-induced cholestasis during the early stages of drug development is of utmost importance. The most commonly used in vitro models rely on the extent of inhibition of bile salt export pump-mediated taurocholic acid transport, thereby assuming that drug-induced cholestasis mechanisms are merely restricted to the interaction with this sole hepatic transporter. Sandwich-cultured human hepatocytes represent a more holistic in vitro tool to investigate drug-induced cholestasis as they preserve all relevant disposition pathways and cellular functions involved in bile acid homeostasis. We developed and validated a sandwich-cultured human hepatocytes-based in vitro assay which is able to identify compounds causing cholestasis by altering bile acid disposition. The in vitro cholestatic potential is expressed by calculating a drug-induced cholestasis index value, which reflects the relative residual urea formation of sandwich-cultured human hepatocytes co-incubated with bile acids and test compound as compared to sandwich-cultured human hepatocytes treated with test compound alone. In addition, a safety margin can be calculated to determine the in vivo risk for cholestasis based on the determination of the drug-induced cholestasis index at various concentrations and the peak plasma concentration of the drug candidate. This chapter outlines the various steps involved in performing our sandwich-cultured human hepatocytes-based in vitro assay.
Keywords: Drug-induced cholestasis index; In vitro liver model; Primary hepatocytes; Sandwich-cultured human hepatocytes; Urea assay.