The pregnane X receptor (PXR, NR1I2) is a nuclear receptor superfamily member. Nuclear receptors are mostly activated by exogenous and endogenous compounds. Interestingly, the classified nuclear receptors conserve the DNA binding domain (DBD), but not its ligand-binding domain (LBD). PXR belongs to the NR1I subfamily together with the vitamin D receptor (VDR, NR1I1) and the constitutive androstane receptor (CAR, NR1I3).