In Vivo Evidence of Human Organic Anion Transporting Polypeptide ( OATP ) 1B1 and OATP1B3 Mediated Disposition of Glycyrrhizin and Its Drug–Drug Interactions in Humanized Mice

Organic anion‐transporting polypeptide (OATP) transporters have a significant influence on the disposition of drugs, significantly influencing their efficacy and toxicity. Humans express two transporters (OATP1B1 and OATP1B3), while murine possess only a single ortholog (Oatp1b2). To elucidate the impact of OATP1B1 and 1B3 on the pharmacokinetics of the hepatoprotective agent glycyrrhizin and its potential drug–drug interactions, we conducted a study utilizing wild‐type, murine Oatp1b2 knockout, and newly generated humanized OATP1B1 and OATP1B3 transgenic mice ( Slco1b2 −/− ; 1B1/1B3 tg ). These models were characterized physiologically and biochemically, followed by intravenous administration of glycyrrhizin for pharmacokinetic analysis. Compared to wild‐type controls, Oatp1b2 knockout mice exhibited a 2‐fold decrease in liver AUC 0–7h and up to 26.9‐fold reduction in liver‐to‐plasma ratios, indicating impaired hepatic uptake of glycyrrhizin. Additionally, the absence of Oatp1b2 resulted in a 2.8‐fold increase in plasma AUC 0–7h and enhanced renal distribution of glycyrrhizin. However, the knock‐in of human OATP1B1 and OATP1B3 partially or fully restored the impaired hepatic uptake and reduced plasma levels of glycyrrhizin in Oatp1b2 knockout mice. Furthermore, we evaluated drug–drug interactions between glycyrrhizin and glecaprevir/pibrentasvir, a clinically relevant combination. Glecaprevir/pibrentasvir inhibited OATP1B1/1B3‐mediated hepatic uptake of glycyrrhizin at therapeutic concentrations, increasing systemic exposure and highlighting drug–drug interaction risks. Our study provides the first in vivo evidence of glycyrrhizin hepatic transport by human OATP1B1 and OATP1B3, emphasizing the need for careful dosing in patients with variable OATP1B/1B3 activity due to transporter‐mediated drug–drug interactions. Additionally, this humanized mouse model can serve as a robust in vivo tool for the prediction of human OATP1B1 and 1B3 function.