Background: Several tyrosine kinase inhibitors (TKIs) evaluated in combination regimens with docetaxel, including axitinib, pazopanib, and sorafenib, can increase the systemic exposure to taxane in cancer patients by an unknown mechanism. We previously reported that differential expression of organic anion transporting polypeptides of the OATP1B-family in the human liver regulate the initial, rate-limiting step in the elimination of docetaxel, in advance of metabolism. In the current study, we tested the hypothesis that these interactions are mediated by the hepatic uptake transporter OATP1B1 using in vitro and in vivo models.

Materials and Methods: The influence of 16 approved TKIs on transport was studied in vitro using HEK293 cells expressing OATP1B1 or its mouse equivalent OATP1B2, determined by assessing the effect of TKIs on the intracellular accumulation of estradiol-17β-D-glucuronide, or docetaxel. Contribution of this process to an interaction with docetaxel in vivo was determined by pharmacokinetic studies using mice that are knock-out for OATP1B2 or knock-in for OATP1B1.

Results: Axitinib, nilotinib, pazopanib, and sorafenib were identified as potent inhibitors of OATP1B1 (>90% inhibition) when using estradiol-17β-D-glucuronide as a prototypical model substrate. As a representative of this class of TKIs, sorafenib was further evaluated and found to also potently inhibit OATP1B1-mediated transport of docetaxel with a half-inhibitory maximum concentration (IC50) of 6.96 nM, and almost completely inhibited the function of OATP1B1 and OATP1B2 at a concentration readily achievable in humans and mice. While OATP1B2-deficiency was associated with significantly increased exposure to docetaxel, as measured by peak plasma concentration (Cmax, P<0.05) and area under the curve (AUC, P<0.001), co-administration of a single or multiple oral dose of sorafenib did not result in statistically significantly altered exposure to docetaxel in either wildtype or OATP1B2 (-/-) mice.

Conclusion: These findings support a direct contribution of OATP1B1 in previously recorded pharmacokinetic interactions between TKIs and docetaxel, which can be predicted from a simple in vitro experiment. Our failure to reproduce this interaction in mice suggests that caution is warranted when attempting to extrapolate in vivo findings to a clinical scenario.

Citation Format: Shuiying Hu, Peter De Bruijn, Ron H.j. Mathijssen, Sharyn D. Baker, Alex Sparreboom. Inhibition of OATP1B1 by tyrosine kinase inhibitors: in vitro-in vivo correlations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3696. doi:10.1158/1538-7445.AM2014-3696