Generation and evaluation of a CYP2C9 heteroactivation pharmacophore.
Positive cooperativity (auto- and heteroactivation) of drug oxidation, a potential cause of drug interactions, is well established in vitro for cytochrome P450 (P450) 3A4 but to a much lesser extent for other drug-metabolizing P450 isoforms. Using a high throughput fluorescent-based CYP2C9 effector assay, we identified >30 heteroactivators from a set of 1504 structurally diverse compounds. Several potent heteroactivators of CYP2C9-mediated 7-methoxy-4-trifluoromethyl-coumarin metabolism are marketed drugs or endogenous compounds (amiodarone, niclosamide, liothyronine, meclofenemate, zafirlukast, estropipate, and dichlorphenamide, yielding 150% control reaction velocity at 0.04, 0.09, 0.5, 1, 1.2, 1.5, and 2.5 microM, respectively). Some heteroactivators are also known CYP2C9 substrates or inhibitors, suggesting potential multiple binding sites and substrate-dependent effects. v(150%), the concentration of effector giving 150% of control reaction velocity, was used as pharmacophore modeling parameter based on enzyme kinetic assumptions. The generated pharmacophore (training set: n = 36, v(150%) 0.04-150 microM) contains one hydrogen bond acceptor, one aromatic ring, and two hydrophobes. v(150%) values for 94% of the training set heteroactivators were predicted within 1 log unit for the residual (r [log observed v(150%)] versus [log predicted v(150%)] = 0.71; r2 0.50). The model also correctly identifies close to 70% of potent inhibitors (IC50 < 1 microM) as high-affinity CYP2C9 binders, suggesting that heteroactivators and inhibitors share some common structural CYP2C9 binding features, supporting the previously suggested hypothesis that CYP2C9 heteroactivators can bind within the active site.
Egnell
Ann-Charlotte
AC
AstraZeneca R and D, EST Chemical Computing, S-43183 Mölndal, Sweden. ann-charlotte.egnell@astrazeneca.com
Eriksson
Cecilia
C
Albertson
Nan
N
Houston
Brian
B
Boyer
Scott
S
D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D065729:Cytochrome P-450 CYP2C9; D015195:Drug Design; D004353:Drug Evaluation, Preclinical; D004789:Enzyme Activation / Q000187:drug effects; D020536:Enzyme Activators / Q000494:pharmacology*; D007700:Kinetics; D008958:Models, Molecular; D015203:Reproducibility of Results; D013329:Structure-Activity Relationship
D020536:Enzyme Activators; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases