Induction of human cytochrome P450 3A4 by the irreversible myeloperoxidase inactivator PF-06282999 is mediated by the pregnane X receptor

Xenobiotica. 2018 Jul;48(7):647-655. doi: 10.1080/00498254.2017.1353163. Epub 2017 Jul 24.


1. 2-(6-(5-Chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl) acetamide (PF-06282999) is a member of the thiouracil class of irreversible inactivators of human myeloperoxidase enzyme and a candidate for the treatment of cardiovascular disease. PF-06282999 is an inducer of CYP3A4 mRNA and midazolam-1'-hydroxylase activity in human hepatocytes, which is consistent with PF-06282999-dose dependent decreases in mean maximal plasma concentrations (Cmax) and area under the plasma concentration time curve (AUC) of midazolam in humans following 14-day treatment with PF-06282999. 2. In the present study, the biochemical mechanism(s) of CYP3A4 induction by PF-06282999 was studied. Incubations in reporter cells indicated that PF-06282999 selectively activated human pregnane X receptor (PXR). Treatment of human HepaRG cells with PF-06282999 led to ∼14-fold induction in CYP3A4 mRNA and 5-fold increase in midazolam-1'-hydroxylase activity, which was nullified in PXR-knock out HepaRG cells. TaqMan® gene expression analysis of human hepatocytes treated with PF-06282999 and the prototypical PXR agonist rifampin demonstrated increases in mRNA for CYP3A4 and related CYPs that are regulated by PXR. 3. Docking studies using a published human PXR crystal structure provided insights into the molecular basis for PXR activation by PF-06282999. Implementation of PXR transactivation assays in a follow-on discovery campaign should aid in the identification of back-up compounds devoid of PXR activation and CYP3A4 induction liability.

Keywords: CAR; CYP; PXR; drug–drug interaction; inactivator; induction; myeloperoxidase.

MeSH terms

  • Acetamides / chemistry
  • Acetamides / pharmacology*
  • Cell Line
  • Constitutive Androstane Receptor
  • Cytochrome P-450 CYP3A / biosynthesis*
  • Cytochrome P-450 CYP3A / genetics
  • Enzyme Induction / drug effects
  • Hepatocytes / drug effects
  • Hepatocytes / enzymology
  • Humans
  • Peroxidase / metabolism*
  • Pregnane X Receptor
  • Protein Binding / drug effects
  • Protein Domains
  • Pyrimidinones / chemistry
  • Pyrimidinones / pharmacology*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Receptors, Steroid / chemistry
  • Receptors, Steroid / metabolism*
  • Transcriptional Activation / drug effects


  • Acetamides
  • Constitutive Androstane Receptor
  • Pregnane X Receptor
  • Pyrimidinones
  • RNA, Messenger
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Steroid
  • Peroxidase
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • 2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide