title: Generation and evaluation of a CYP2C9 heteroactivation pharmacophore.
abstract: 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.
authors.affiliation: AstraZeneca R and D, EST Chemical Computing, S-43183 Mölndal, Sweden. ann-charlotte.egnell@astrazeneca.com
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Egnell
authors.forename: Cecilia
authors.initials: C
authors.lastname: Eriksson
authors.forename: Nan
authors.initials: N
authors.lastname: Albertson
authors.forename: Brian
authors.initials: B
authors.lastname: Houston
authors.forename: Scott
authors.initials: S
authors.lastname: Boyer
mesh_terms: 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
chemical_list: D020536:Enzyme Activators; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases