Mechanistic insights on clearance and inhibition discordance between liver microsomes and hepatocytes when clearance in liver microsomes is higher than in hepatocytes - PubMed (original) (raw)

doi: 10.1016/j.ejps.2020.105541. Epub 2020 Sep 12.

George Chang 1, Anthony Carlo 1, Jonathan J Novak 1, Michael Banker 1, Jackie Carey 1, Julie Cianfrogna 2, Heather Eng 1, Caitlin Jagla 1, Nathaniel Johnson 1, Rhys Jones 2, Samantha Jordan 1, Sarah Lazzaro 1, JianHua Liu 1, R Scott Obach 1, Keith Riccardi 1, David Tess 3, John Umland 1, Jillian Racich 1, Manthena Varma 1, Ravi Visswanathan 2, Li Di 4

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Mechanistic insights on clearance and inhibition discordance between liver microsomes and hepatocytes when clearance in liver microsomes is higher than in hepatocytes

Christopher Keefer et al. Eur J Pharm Sci. 2020.

Abstract

Human liver microsomes (HLM) and human hepatocytes (HHEP) are two common in vitro systems used in metabolic stability and inhibition studies. The comparison between the assays using the two systems can provide mechanistic insights on the interplay of metabolism, passive permeability and transporters. This study investigated the critical factors impacting the unbound intrinsic clearance (CLint,u) and IC50 of CYP3A inhibition between HLM and HHEP. The HLM/HHEP CLint,u ratio and HHEP/HLM IC50 ratio are inversely correlated to passive permeability, but have no correlation with P-gp efflux ratio. Cofactor-supplemented permeabilized HHEP (MetMax™) collapses the IC50 differences between HHEP and HLM. P-gp inhibitor, encequidar, shows minimal impact on CLint,u and IC50 in HHEP. This is the first study that is able to separately investigate the effects of passive permeability and efflux transport. These data collectively show that passive permeability plays a critical role in metabolism and enzyme inhibition in HHEP, while P-gp efflux has a minor role. This may be due to low functional P-gp activity in suspension HHEP under the assay conditions. Low passive permeability may limit metabolism and enzyme inhibition in HHEP, leading to lower CLint,u and higher IC50 in HHEP compared to HLM. When liver microsomes give higher CLint,u than hepatocytes, microsomes are more predictive of in vivo clearance than hepatocytes.

Keywords: CYP inhibition; Hepatocytes; IVIVE; Liver microsomes; Metabolism; P-glycoprotein efflux; Passive permeability.

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