Pregnane X Receptor Antagonists Small Molecules and Peptides

Pregnane X receptors (PXRs) are nuclear receptors that regulate the expression of CYP3A genes, thus generating key enzymes involved in xenobiotic metabolism. PXRs also help regulate the induction of P-gp. PXRs are highly expressed in the liver, small intestine and colon.

Numerous ligands activate PXRs, including a range of xenobiotics such as dexamethasone and nifedipine, and naturally occurring steroids. PXR forms a non-permissive heterodimer with RXR receptors in order to bind the promoter and enhancer of the CYP3A4 gene.