The Humanized PXR-CAR-CYP3A4/3A7 Mouse was developed by Taconic in collaboration with CXR Biosciences. The Humanized PXR Mouse model was created through a knock in of a human PXR cDNA/genomic construct onto the ATG of murine Pxr in C57BL/6NTac-derived ES cells. The human PXR sequence that was introduced contains a cDNA fusion of exon 2-4, intron 4, exon 5, intron 5, exon 6, intron 6, exon 7, intron 7, and cDNA fusion exon 8+9. The Humanized CAR Mouse model was created through a knock in of a human CAR construct containing the genomic sequence from the translational start site on exon 2 to exon 9 onto the ATG of murine CAR in C57BL/6NTac-derived ES cells. The expression of the human PXR and CAR receptors is driven by the corresponding mouse promoters. The Humanized CYP3A4/3A7 Mouse model was created by four consecutive rounds of transfection in C57BL/6NTac-derived ES cells. First, mouse exon 1 and 2 of Cyp3a57 was replaced with a hygromycin cassette containing a loxP, lox5171 and frt site through gene targeting. Second, a neomycin cassette with a loxP and f3 site was inserted into intron 4 of the Cyp3a59 gene through gene targeting. Third, transfection of the ES cells with cre recombinase resulted in the deletion of the Cyp3a57, Cyp3a16, Cyp3a41, Cyp3a44, Cyp3a11, Cyp3a25 and Cyp3a59 genes. Fourth, a modified human bacterial artificial chromosome carrying CYP3A4 and CYP3A7 was inserted by cre-mediated recombination into the loxP and lox5171 sites in the mouse Cyp3a locus. In all three cases targeted ES cells were injected into BALB/cJBomTac blastocysts and the resultant chimeras were backcrossed to a Flpe deleter strain on C57BL/6J to eliminate selection markers. The Humanized PXR-CAR-CYP3A4/3A7 Mouse line was obtained by crossing the three single humanized mouse lines. The colony was maintained by mating triple homozygotes.