Identification of polymorphisms in the 3′-untranslated region of the human pregnane X receptor (PXR) gene associated with variability in cytochrome P450 3A (CYP3A) metabolism

Single nucleotide polymorphisms in the 3′-untranslated region (3′UTR) of the human pregnane X receptor (PXR) gene might contribute to interindividual variability in cytochrome P450 3A (CYP3A) activity.Genotype–phenotype associations involving PXR-3′UTR single nucleotide polymorphisms were investigated through in vitro (53 human livers from primarily White donors) and in vivo (26 mainly White or African-American volunteers) studies using midazolam 1′-hydroxylation and midazolam apparent oral clearance (CL/F), respectively, as CYP3A-specific probes.PXR-3′UTR resequencing identified twelve single nucleotide polymorphisms, including two that were novel. Although none of the single nucleotide polymorphisms evaluated were associated with altered midazolam 1′-hydroxylation in the liver bank, both rs3732359 homozygotes and rs3732360 carriers showed 80% higher (p < 0.05) CL/F compared with homozygous reference individuals. These differences in CL/F were even larger (100% and 120% higher, respectively; p < 0.01) wh...