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Mechanism‐based Inhibition of CYP3A4 by Podophyllotoxin: Integrating Biophysical Measurements into Predictive Analysis
Author(s) -
Barnaba Carlo,
Nagar Swati,
Korzekwa Ken R,
Jones Jeffrey P
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb546
Subject(s) - podophyllotoxin , cyp3a4 , kinetics , chemistry , enzyme kinetics , in vivo , mechanism (biology) , cytochrome p450 , drug , drug discovery , biophysics , computational biology , pharmacology , enzyme , biochemistry , stereochemistry , biology , microbiology and biotechnology , active site , physics , philosophy , epistemology , quantum mechanics
Avoiding drug‐drug interactions (DDIs) is a critical effort during drug discovery and development. One of the most difficult DDIs to predict with preclinical data is the time‐dependent inhibition (TDI) of the cytochrome P450 enzymes. Since TDIs result in a loss of enzyme over time, the in vivo impact of TDI is more difficult to assess than competitive inhibitors. Current methods to determine TDI parameters have provided limited success in predicting clinical outcomes. A probably more significant complexity in TDI kinetics is the mechanism of metabolic intermediate complex (MIC) formation. Podophyllotoxin is a methylenedioxyphenyl (MDP) compounds known to cause time‐dependent inhibition of CYP3A4, through a carbene intermediate that can form a pseudo‐irreversible complex with the heme of P450. The goal of the present study is to characterize the time‐course of MIC formation using biophysical techniques and relate these rate constants to observed time‐dependent inactivation kinetics. Here we report novel evidence for the existence of a reversible intermediate that plays a key role in the kinetics of MIC formation. This finding is then used with in vitro TDI kinetics, to greatly increase the accuracy of in vivo DDI predictions relative to existing methodologies. Support or Funding Information NIH