Identifying a selective substrate and inhibitor pair for the evaluation of CYP2J2 activity

Drug Metab Dispos. 2012 May;40(5):943-51. doi: 10.1124/dmd.111.043505. Epub 2012 Feb 10.


CYP2J2, an arachidonic acid epoxygenase, is recognized for its role in the first-pass metabolism of astemizole and ebastine. To fully assess the role of CYP2J2 in drug metabolism, a selective substrate and potent specific chemical inhibitor are essential. In this study, we report amiodarone 4-hydoxylation as a specific CYP2J2-catalyzed reaction with no CYP3A4, or other drug-metabolizing enzyme, involvement. Amiodarone 4-hydroxylation enabled the determination of liver relative activity factor and intersystem extrapolation factor for CYP2J2. Amiodarone 4-hydroxylation correlated with astemizole O-demethylation but not with CYP2J2 protein content in a sample of human liver microsomes. To identify a specific CYP2J2 inhibitor, 138 drugs were screened using terfenadine and astemizole as probe substrates with recombinant CYP2J2. Forty-two drugs inhibited CYP2J2 activity by ≥50% at 30 μM, but inhibition was substrate-dependent. Of these, danazol was a potent inhibitor of both hydroxylation of terfenadine (IC(50) = 77 nM) and O-demethylation of astemizole (K(i) = 20 nM), and inhibition was mostly competitive. Danazol inhibited CYP2C9, CYP2C8, and CYP2D6 with IC(50) values of 1.44, 1.95, and 2.74 μM, respectively. Amiodarone or astemizole were included in a seven-probe cocktail for cytochrome P450 (P450) drug-interaction screening potential, and astemizole demonstrated a better profile because it did not appreciably interact with other P450 probes. Thus, danazol, amiodarone, and astemizole will facilitate the ability to determine the metabolic role of CYP2J2 in hepatic and extrahepatic tissues.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amiodarone / chemistry
  • Amiodarone / metabolism*
  • Astemizole / chemistry
  • Astemizole / metabolism*
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 CYP3A / metabolism
  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Danazol* / chemistry
  • Danazol* / metabolism
  • Danazol* / pharmacology
  • Drug Discovery
  • Drug Interactions
  • Enzyme Inhibitors* / chemistry
  • Enzyme Inhibitors* / metabolism
  • Enzyme Inhibitors* / pharmacology
  • Humans
  • Hydroxylation
  • In Vitro Techniques
  • Methylation
  • Microsomes, Liver / enzymology*
  • Microsomes, Liver / metabolism
  • Models, Biological
  • Molecular Structure
  • Substrate Specificity
  • Tandem Mass Spectrometry
  • Terfenadine / chemistry
  • Terfenadine / metabolism*


  • Cytochrome P-450 Enzyme Inhibitors
  • Enzyme Inhibitors
  • Terfenadine
  • Astemizole
  • Cytochrome P-450 Enzyme System
  • Cytochrome P-450 CYP3A
  • arachidonate epoxygenase
  • CYP3A4 protein, human
  • Danazol
  • Amiodarone