Biochem/physiol Actions

CINPA1 is a ligand-binding domain (LBD)-targeting constitutive androstane receptor (CAR) inhibitor that prevents CAR recruitment to promoter regions of regulated genes (by >85%; 1 µM CINPA1 against 0.1 µM CITCO-induced CAR recruitment to CYP2B6 or CYP3A4 promoters; human hepatocytes) by altering CAR-coregulator interactions. CINPA1 inhibits CAR-mediated transcription in a potent (IC50 = 70 nM; HepG2-hCAR1 CYP2B6-luc reporter cells) and selective manner with only weak PXR antagonist potency (68% inhibition by 18 µM CINPA1 against 5 µM rifampicin; HepG2-PXR reporter cells) and no cytotoxicity or agonist/antagonist activity toward FXR, GR, LXRα/β, PPARγ, RXRα/β, VDR.