Double-humanized Rats for CYP3A and PXR as an Improved Model for Analyzing Drug-drug Interactions Mediated by CYP3A4

The human cytochrome P450 3A4 (CYP3A4) enzyme, which is expressed in the liver and the intestines, catalyzes the metabolism of numerous drugs. The induction of CYP3A4 by the pregnane X receptor (PXR) represents a significant problem in pharmacotherapy. Since the metabolic properties of CYP3A substrates and the recognition of PXR ligands differ between humans and rats, there are limitations to reproducing human CYP3A4 induction in rat studies. Here, we developed a double-humanized rat model for CYP3A and PXR to mimic drug-drug interactions in humans using a rat model. The model was created using a combination of mammalian artificial chromosome-based chromosome engineering, bacterial artificial chromosome-based transgenic technology, and genome editing. The resulting double-humanized rat model for CYP3A and PXR (huCYP3A-PXR rat) was treated with rifampicin, a human PXR ligand. This treatment increased CYP3A4 mRNA expression in the liver and intestine and enhanced the hydroxylation activities of triazolam, a CYP3A4 substrate. Pretreatment with rifampicin resulted in a reduction of triazolam plasma concentrations and an increase in its metabolites after oral administration. Furthermore, ketoconazole, a CYP3A4 inhibitor, led to an increase in triazolam plasma concentrations and a decrease in its metabolites in huCYP3A-PXR rats regardless of pretreatment with rifampicin. These results suggest that huCYP3A-PXR rats could predict human CYP3A4 induction and inhibition in vivo. This innovative model, in which PXR and CYP3A are humanized, is expected to be a valuable tool for studying drug-drug interactions, including a combination of inducers and inhibitors, and to be integrated into the preclinical drug-development pipeline in future.