Probing Ligand Structure-Activity Relationships in PregnaneX Receptor (PXR): Efavirenz and 8-Hydroxyefavirenz Exhibit Divergence in Activation

Bhargavi Narayanan, Julie M. Lade, Carley J.S. Heck, Kevin D. Dietz, Herschel Wade, Namandje N Bumpus

Research output: Contribution to journalArticle

Abstract

Efavirenz (EFV), an antiretroviral that interacts clinically with co-administered drugs via activation of the pregnaneX receptor (PXR), is extensively metabolized by the cytochromes P450. We tested whether its primary metabolite, 8-hydroxyEFV (8-OHEFV) can activate PXR and potentially contribute to PXR-mediated drug-drug interactions attributed to EFV. Luciferase reporter assays revealed that despite only differing from EFV by an oxygen atom, 8-OHEFV does not activate PXR. Corroborating this, treatment with EFV for 72h elevated the mRNA abundance of the PXR target gene, Cyp3a11, by approximately 28-fold in primary hepatocytes isolated from PXR-humanized mice, whereas treatment with 8-OHEFV did not result in a change in Cyp3A11 mRNA levels. FRET-based competitive binding assays and isothermal calorimetry demonstrated that even with the lack of ability to activate PXR, 8-OHEFV displays an affinity for PXR (IC50 12.1μm; KD 7.9μm) nearly identical to that of EFV (IC50 18.7μm; KD 12.5μm). The use of 16 EFV analogues suggest that other discreet changes to the EFV structure beyond the 8-position are well tolerated. Molecular docking simulations implicate an 8-OHEFV binding mode that may underlie its divergence in PXR activation from EFV.

Original languageEnglish (US)
JournalChemMedChem
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

efavirenz
Structure-Activity Relationship
Chemical activation
Ligands
Inhibitory Concentration 50
Assays
Molecular Docking Simulation
Drug interactions
Drug Receptors
Messenger RNA
Calorimetry
Competitive Binding
8-hydroxyefavirenz
Metabolites
Luciferases
Drug Interactions
Pharmaceutical Preparations
Cytochrome P-450 Enzyme System

Keywords

  • Cytochrome P450
  • Drug metabolism
  • Ligand binding
  • Molecular docking
  • Nuclear receptors

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology, Toxicology and Pharmaceutics(all)
  • Organic Chemistry

Cite this

Probing Ligand Structure-Activity Relationships in PregnaneX Receptor (PXR) : Efavirenz and 8-Hydroxyefavirenz Exhibit Divergence in Activation. / Narayanan, Bhargavi; Lade, Julie M.; Heck, Carley J.S.; Dietz, Kevin D.; Wade, Herschel; Bumpus, Namandje N.

In: ChemMedChem, 01.01.2018.

Research output: Contribution to journalArticle

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abstract = "Efavirenz (EFV), an antiretroviral that interacts clinically with co-administered drugs via activation of the pregnaneX receptor (PXR), is extensively metabolized by the cytochromes P450. We tested whether its primary metabolite, 8-hydroxyEFV (8-OHEFV) can activate PXR and potentially contribute to PXR-mediated drug-drug interactions attributed to EFV. Luciferase reporter assays revealed that despite only differing from EFV by an oxygen atom, 8-OHEFV does not activate PXR. Corroborating this, treatment with EFV for 72h elevated the mRNA abundance of the PXR target gene, Cyp3a11, by approximately 28-fold in primary hepatocytes isolated from PXR-humanized mice, whereas treatment with 8-OHEFV did not result in a change in Cyp3A11 mRNA levels. FRET-based competitive binding assays and isothermal calorimetry demonstrated that even with the lack of ability to activate PXR, 8-OHEFV displays an affinity for PXR (IC50 12.1μm; KD 7.9μm) nearly identical to that of EFV (IC50 18.7μm; KD 12.5μm). The use of 16 EFV analogues suggest that other discreet changes to the EFV structure beyond the 8-position are well tolerated. Molecular docking simulations implicate an 8-OHEFV binding mode that may underlie its divergence in PXR activation from EFV.",
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