Background: The metabolism of tyrosine kinase inhibitors (TKIs) is mainly mediated via hepatic route, but the mechanism responsible for their hepatocellular accumulation is still unknown. This study was designed to understand the contribution of organic anion transporting polypeptides (OATPs) in the hepatic uptake of selected TKIs - pazopanib, canertinib, erlotinib, vandetanib and nilotinib.
Methods: Michaelis-Menten (MM) kinetic parameters for TKIs were determined by concentration-dependent cellular accumulation of selected TKIs using Chinese hamster ovary cells - wild type as well as transfected with humanized OATP-1B1 and OATP-1B3 transporter proteins.
Results: The MM constant (Km) values of OATP-1B1 for nilotinib and vandetanib are 10.14±1.91 and 2.72±0.25 μM, respectively, and Vmax values of OATP-1B1 for nilotinib and vandetanib were 6.95±0.47 and 75.95±1.99 nmol/mg protein per minute, respectively. Likewise, Km values of OATP-1B3 for canertinib, nilotinib and vandetanib were 12.18±3.32, 7.84±1.43 and 4.37±0.79 μM, respectively, and Vmax values of OATP-1B3 for canertinib, nilotinib and vandetanib were 15.34±1.59, 6.75±0.42 and 194.64±10.58 nmol/mg protein per minute, respectively. Canertinib did not exhibit any substrate specificity toward OATP-1B1. Also, erlotinib and pazopanib did not exhibit any substrate specificity toward OATP-1B1 and -1B3.
Conclusions: Because selected TKIs are the substrates of OATP-1B1 and -1B3 expressed in hepatic tissue, these compounds can be regarded as molecular targets for transporter-mediated drug-drug interactions (DDIs). Any alteration in the function of these hepatic OATPs might account for the pharmacokinetic variability of TKIs.