Substrate-dependent effects of molecular-targeted anticancer agents on activity of organic anion transporting polypeptide 1B1

1. Organic anion-transporting polypeptide 1B1 (OATP1B1) plays an important role in the hepatic uptake of a broad range of substrate drugs. In vitro experiments show that molecular-targeted agents do not always have similar effects on OATP1B1 activity. 2. The purpose of this study was to clarify whether the effects of molecular-targeted agents on OATP1B1 are substrate-dependent. We used OATP1B1-transfected cells to compare the effects of molecular-targeted agents on OATP1B1-mediated uptake of fluorescein (FL), 2',7'-dichlorofluorescein (DCF), atorvastatin, SN-38 and valsartan. 3. Cabozantinib, cediranib, neratinib, pazopanib, regorafenib, sorafenib and tivantinib did not affect or only slightly affected OATP1B1-mediated substrate uptake. Nilotinib and lenvatinib moderately and strongly inhibited OATP1B1-mediated substrate uptake, respectively. In contrast, afatinib stimulated OATP1B1-mediated uptake of FL and SN-38, ceritinib stimulated that of valsartan, and nintedanib stimulated that of FL and valsartan. In addition, the effects of afatinib, ceritinib and nintedanib on OATP1B1 activity differed markedly depending on the type of substrate. Afatinib, ceritinib and nintedanib had a substrate-dependent effect on OATP1B1 activity. 4. We conclude that the evaluation of OATP1B1 activity using only a single probe substrate for some molecular-targeted agents may lead to a faulty understanding of their mechanisms of drug interactions.