Screening of OATP1B1/3 and OCT1 inhibitors in cryopreserved hepatocytes in suspension

Abstract

Drug–drug interactions involving hepatic drug transporters may have clinical consequences and jeopardize development of promising drug candidates. Organic anion transporting polypeptides (OATP/Oatp) and the organic cation transporters (OCT/Oct) are among the most important transporters involved in xenobiotic uptake in the liver. In the present study, 179 molecules have been tested as inhibitors of the uptake of estradiol-17βD-glucuronide (E 217βG), substrate of OATP1B1/3 (rOatp), or 1-methyl-4-phenylpyridinium (MPP+), substrate of OCT1 (rOct1), into suspended cryopreserved hepatocytes from humans and rats. Uptake was assessed in 96-well plates by measuring intracellular accumulation of radioactive substrate in hepatocytes in presence or absence of inhibitor. In rat hepatocytes 140 compounds were identified as inhibitors (inhibition at 20 μM ≥ 30%) of E 217βG uptake and 77 compounds inhibitors of MPP+ uptake. The most potent inhibitors of rOatp and rOct1 were dantrolene sodium ( K i = 2 ± 9 μM) and bepridil ( K i = 14 ± 2 μM), respectively. In human hepatocytes, the most potent inhibitors of E 217βG and MPP+ uptake were capsazepine ( K i = 14 ± 5 μM) and cyproheptadine ( K i = 19 ± 3 μM), respectively. Structure–activity relationship (SAR) analysis of all tested compounds suggested that lipophilicity, polarity, p K a and the number of hydrogen bond donors and acceptors play a role in their interaction with the transporters investigated. The method used here is a simple tool to screen large number of compounds as inhibitors of the uptake of substrates into suspended hepatocytes.