Impact of OATP2B1 on Pharmacokinetics of Atorvastatin Investigated in rSlco2b1-Knockout and SLCO2B1-Knockin Rats

The organic anion transporting polypeptide (OATP) 2B1 is considered an emerging drug transporter that is found expressed in pharmacokinetically relevant organs such as the liver, small intestine, and kidney. Despite its interaction with various substrate drugs, the understanding of its in vivo relevance is still limited. In this study, we first validated the interaction of atorvastatin with rat OATP2B1 using transiently transfected HeLa cells. Moreover, we characterized our rSlco2b1-knockout and SLCO2B1-knockin rats for mRNA, protein expression, and localization of OATP2B1 in the liver, small intestine, and kidney. The transporter showed the highest expression in the liver followed by the small intestine. In humanized rats, human OATP2B1 is localized on the sinusoidal membrane of hepatocytes. In enterocytes of wildtype and humanized rats, the transporter was detected in the luminal membrane with the vast majority being localized subapical. Subsequently, we assessed atorvastatin pharmacokinetics in male wildtype, rSlco2b1-knockout, and SLCO2B1-knockin rats after a single-dose administration (orally and intravenously). Investigating the contribution of rat OATP2B1 or human OATP2B1 to oral atorvastatin pharmacokinetics revealed no differences in neither concentration-time profiles nor pharmacokinetic parameters. However, when comparing the pharmacokinetics of atorvastatin after intravenous administration in SLCO2B1-humanized rats and knockout animals, notable differences were observed. In particular, the systemic exposure (AUC) decreased by approximately 40% in humanized animals, while the clearance (CL) was 57% higher in animals expressing human OATP2B1. These findings indicate that human OATP2B1 influences pharmacokinetics of atorvastatin after intravenous administration, most likely by contributing to the hepatic uptake. Significance StatementWildtype, rSlco2b1-knockout and SLCO2B1-humanized Wistar rats were characterized for the expression of rat and human SLCO2B1/OATP2B1. Pharmacokinetic studies of atorvastatin over 24 hours were conducted in male wildtype, rSlco2b1-knockout, and SLCO2B1-humanized rats. After a single-dose i.v. administration, a lower systemic exposure and an increase in clearance were observed in SLCO2B1-humanized rats compared to knockout animals indicating a contribution of OATP2B1 to the hepatic clearance.