Several recent studies show that inhibition of the hepatic transport proteins organic-anion transporting polypeptide 1B1 (OATP1B1) and 1B3 (OATP1B3) can result in clinically relevant drug-drug interactions (DDI). To avoid late-stage development drug failures due to OATP1B-mediated DDI, predictive in vitro and in silico methods should be implemented at an early stage of the drug candidate evaluation process.
In the present study, we first developed a high-throughput in vitro transporter inhibition assay for the OATP1B subfamily. A total of 2000 compounds were tested as potential modulators of the uptake of the OATP1B substrate sodium fluorescein, in OATP1B1 or 1B3-transfected CHO cells. At an equimolar substrate-inhibitor concentration of 10 µM, 212 and 139 molecules were identified as OATP1B1 and OATP1B3 inhibitors, respectively (min 50 % inhibition). For 69 compounds, previously not identified as OATP1B inhibitors, concentration dependent inhibition was also determined, yielding Ki values ranging from 0.06 to 6.5 µM. Based on these in vitro data, we subsequently developed a proteochemometrics-based in silico model, which predicted OATP1B inhibitors in the test group (20 % of the dataset) with high specificity (86 %) and sensitivity (78 %). Moreover, several physicochemical compound properties and substructures related to OATP1B1/1B3 inhibition or inactivity were identified. Finally, model accuracy was prospectively verified with a set of 54 compounds not included in the original dataset. This validation indicated that 80 % and 74 % of the compounds were correctly classified for OATP1B1 and OATP1B3 inhibition, respectively.