Development of an OATP1-humanized transchromosomic mouse model for prediction of hepatic drug uptake in humans

Transchromosomic technology using mouse artificial chromosomes (MACs) offers a promising approach for transferring gene clusters into host organisms. This study focused on the multispecific organic anion-transporting polypeptides (OATPs) in the liver, which exhibit significant species differences between mice (Oatp1a1/Slco1a1, Oatp1a4/Slco1a4, Oatp1b2/Slco1b2) and humans (OATP1B1/SLCO1B1 and OATP1B3/SLCO1B3). We generated an OATP1-humanized transchromosomic mouse model using a MAC vector (hOATP1-MAC mice) by transferring the human OATP1 gene cluster (SLCO1C1-SLCO1B3-SLCO1B7-SLCO1B1-SLCO1A2, 700 kbp) via an MAC into Slco1a/1b cluster knockout (KO) mice (Oatp1-KO). The human OATP1 genes were expressed in a tissue-specific manner. Plasma concentrations of the OATP1B biomarkers, coproporphyrin I and III, which were 7.2- and 23.3-fold higher in Oatp1-KO mice than in wild-type mice, were decreased by 68% and 96% in hOATP1-MAC mice, respectively. A pharmacokinetics study using pitavastatin revealed greater total body clearance (168 mL/min/kg) in hOATP1-MAC mice than in Oatp1-KO mice (100 mL/min/kg) but lower clearance than in wild-type mice (484 mL/min/kg), with bioavailability ranging from 0.66 to 0.77. In addition, drug-drug interactions were investigated using rifampicin, an OATP1B inhibitor. Rifampicin (60 mg/kg orally) increased the area under the plasma concentration-time curves of orally administered pitavastatin and grazoprevir in hOATP1-MAC mice, but not of asunaprevir. These findings demonstrated the functional expression of OATP1B1 and OATP1B3 in the mouse liver and their significant role in the systemic elimination of substrates. This is the first study to introduce multiple solute carrier drug transporter genes using artificial chromosome technology, highlighting its potential to overcome species differences in drug transport. SIGNIFICANCE STATEMENT: Transchromosomic technology holds promise for addressing species differences by introducing multiple solute carrier drug transporter genes such as OATP1. Mice OATP1-humanized using a mouse artificial chromosome vector demonstrated enhanced clearance of endogenous OATP1B biomarkers and probe drugs.