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Human enteric microsomal CYP4F enzymes O-demethylate the antiparasitic prodrug pafuramidine

Michael Zhuo Wang1, Judy Qiju Wu, Arlene S Bridges

  • 1School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

Drug Metabolism and Disposition: the Biological Fate of Chemicals
|August 22, 2007
PubMed

Insights

Cytochrome P450 (P450) enzymes, specifically CYP4F, are key in the intestinal O-demethylation of antiparasitic drug pafuramidine (DB289). This finding suggests CYP4F enzymes contribute to DB289

Area of Science:

  • Pharmacology
  • Drug Metabolism
  • Biochemistry

Background:

  • The antiparasitic prodrug pafuramidine (DB289) exhibits low oral bioavailability, suggesting significant first-pass metabolism in the intestine and liver.
  • Previous studies identified CYP4F enzymes as major catalysts for DB289 O-demethylation in human liver microsomes.
  • Understanding intestinal biotransformation is crucial for optimizing DB289's therapeutic efficacy.

Purpose of the Study:

  • To characterize the specific intestinal enzymes responsible for the initial O-demethylation of pafuramidine (DB289) to its intermediate metabolite, M1.
  • To investigate the role of cytochrome P450 (P450) enzymes, particularly CYP4F, in the enteric metabolism of DB289.

Main Methods:

  • Utilized human intestinal microsomes (HIM) to study DB289 O-demethylation.
  • Employed P450 inhibitors (ketoconazole, HET0016, 17-octadecynoic acid) and specific antibodies (anti-CYP4F2, anti-CYP3A4/5, anti-CYP2J2) for enzyme identification.
  • Assessed M1 formation rates and correlated them with arachidonic acid omega-hydroxylation rates and CYP4F protein expression via quantitative Western blot.

Main Results:

  • DB289 O-demethylation to M1 in HIM was confirmed to be P450-mediated, requiring NADPH and potently inhibited by ketoconazole.
  • Inhibitors of P450-arachidonic acid metabolism and anti-CYP4F2 antibodies significantly inhibited M1 formation, implicating CYP4F enzymes.
  • M1 formation rates strongly correlated with arachidonic acid omega-hydroxylation rates in HIM lacking CYP4A11, with significant CYP4F expression observed.

Conclusions:

  • Enteric CYP4F enzymes are likely responsible for the initial O-demethylation of DB289 in the human intestine.
  • These findings highlight the potential role of intestinal CYP4F enzymes in the first-pass biotransformation of DB289 and other xenobiotics.
  • Further research into CYP4F-mediated metabolism could inform drug development strategies for compounds with similar metabolic pathways.

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