Adeno-associated virus-mediated knockdown demonstrates the major role of hepatic Bcrp in the overall disposition of the active metabolite of the tyrosine kinase inhibitor regorafenib in mice

Breast cancer resistance protein (BCRP) is expressed on hepatic bile canalicular membranes; however, its impact on substrate drug disposition is limited. This study proposes an in vivo knockdown approach using adeno-associated virus encoding short hairpin RNA (shRNA) targeting the bcrp gene (AAV-shBcrp) to clarify the substrate, the overall disposition of which is largely governed by hepatic Bcrp. The disposition of the tyrosine kinase inhibitor, regorafenib, was first examined in bcrp gene knockout (Bcrp-/ -) and wild-type (WT) mice, as it was sequentially converted to active metabolites M -2 and M -5, which are BCRP substrates. After oral administration of regorafenib, plasma and liver concentrations of M -5, but not regorafenib, were higher in Bcrp-/- than WT mice. To directly examine the role of hepatic Bcrp in M -5 disposition, M -5 was intravenously injected into mice three weeks after the intravenous injection of AAV-shBcrp, when mRNA of Bcrp in the liver (but not the small intestine) was down-regulated. AAV-shBcrp-treated mice showed higher M -5 concentration in plasma and liver, but lower biliary excretion than the control mice, indicating the fundamental role of hepatic Bcrp in M -5 disposition. This is the first application of AAV-knockdown strategy to clarify the pharmacokinetic role of xenobiotic efflux transporters in the liver.(c) 2022 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study used an in vivo knockdown approach to investigate the role of BCRP in the disposition of regorafenib. The results showed that BCRP plays a key role in the disposition of the active metabolite M-5. Knockdown of hepatic Bcrp led to increased concentrations of M-5 in plasma and liver, and decreased biliary excretion.