Generation and Evaluation of a CYP2C9 Heteroactivation Pharmacophore

Egnell, Ann-Charlotte E.; Eriksson, Cecilia S.; Albertson, Nan H.; Houston, B.; Boyer, Scott

doi:10.1124/jpet.103.054999

Cited by 50 publications

(58 citation statements)

References 33 publications

(44 reference statements)

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“…Amiodarone had no effect on the kinetic profile of naproxen demethylation, irrespective of the studied amiodarone concentration. This activation of naproxen demethylation is similar to that observed by McGinnity et al (2005) using concentrations from 2.5 -1000 M and analogous to the activation of 7-methoxyfluorocoumarin by amiodarone previously reported (Egnell et al, 2003). Though we also observed activation with amiodarone, in the current study a weak inhibition was noted at amiodarone concentrations above 250 M in both CYP2C9.1 and CYP2C9.3.…”

Section: Discussionsupporting

confidence: 56%

“…In contrast, in CYP2C9.1, in vitro activation of 7-methoxy-4-trifluoromethyl-coumarin and naproxen demethylation by amiodarone have been reported (Egnell et al, 2003;McGinnity et al, 2005), suggesting that the type of effect observed (inhibition versus activation) may be analog-and substrate-dependent. Similarly, benzbromarone (BZBR) and its analogs are some of the most potent inhibitors of CYP2C9 described to date.…”

Section: Introductionmentioning

confidence: 85%

“…Amiodarone is a clinically important antiarrhythmic agent and has been observed to inhibit CYP2C9-mediated warfarin metabolism both in vivo and in vitro (O'Reilly et al, 1987;Nolan et al, 1989;Heimark et al, 1992;Hirmerova et al, 2003), but activation of 7-methoxyfluorocoumarin metabolism also has been observed, thus suggesting that substrate-dependent actions of amiodarone may occur (Egnell et al, 2003). Desethylamiodarone (the deethylation metabolite) is an even more potent inhibitor of CYP2C9-mediated metabolism of warfarin than the parent compound (Ohyama et al, 2000;Naganuma et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

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Amiodarone Analog-Dependent Effects on CYP2C9-Mediated Metabolism and Kinetic Profiles

et al. 2006

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ABSTRACT:CYP2C9 substrates can exhibit both hyperbolic and atypical kinetic profiles, and their metabolism can be activated or inhibited depending on the effector studied. CYP2C9 genetic variants can also affect both substrate turnover and kinetic profile. The present study assessed whether analogs of the effector amiodarone differentially altered the atypical kinetic profile of the substrate naproxen and whether this effect was genotype-dependent. Amiodarone, desethylamiodarone, benzbromarone, and its dimethyl analog (benz(meth)arone) were incubated with naproxen and either CYP2C9.1 or CYP2C9.3. Amiodarone activated naproxen demethylation at lower concentrations, regardless of the CYP2C9 allele, and inhibited metabolism at higher concentrations without altering the kinetic profile. Desethylamiodarone was a potent inhibitor of naproxen demethylation, irrespective of the CYP2C9 allele. Benzbromarone altered naproxen demethylation kinetics from a biphasic profile to that of a hyperbolic form in CYP2C9.1 and CYP2C9.3, resulting in inhibition and activation, respectively. In contrast, benz(meth)arone activated naproxen demethylation in both CYP2C9.1 and CYP2C9.3. In addition, the kinetic profile of naproxen demethylation became more hyperbolic at lower concentrations of benz(meth)arone and then reverted back to biphasic as the benz(meth)arone was increased further. Equilibrium binding and multiple-ligand docking studies were used to propose how such similar compounds exerted very different effects on naproxen metabolism. In summary, effectors of CYP2C9 metabolism can alter not only the degree of substrate turnover (activation or inhibition) but also the kinetic profile of metabolism of CYP2C9 substrates through effects on substrate binding and orientation. In addition, these kinetics effects are concentration-and genotypedependent.The cytochrome P450 family of enzymes is involved in the oxidative metabolism of drugs and xenobiotics. Cytochrome P450 2C9 (CYP2C9) is a member of this enzyme family and has been estimated to be responsible for the metabolism of about 20% of marketed drugs (Rendic and Di Carlo, 1997). CYP2C9 exhibits genetic polymorphisms, and 24 variant alleles of CYP2C9 have been discovered to date (http://www.imm.ki.SE/CYPalleles/). One of these variants, CYP2C9.3, is observed frequently in the white (not Hispanic) population (ϳ10 -15% allele frequency) (Lee et al., 2002) and has been the subject of many studies. The CYP2C9.3 variant substantially affects turnover for some substrates as evidenced by reductions in V m of 50 to 90% compared with the wild-type enzyme. Furthermore, the K m of the substrate can be increased severalfold in the CYP2C9.3 variant compared with wild-type enzyme, but again, the magnitude of these effects is substrate-dependent. These alterations in V m and K m , therefore, also affect the intrinsic clearance (V m /K m ) for this enzyme. For example, Takanashi et al. (2000) studied the effect of CYP2C9 variants on the V m /K m ratio for seven CYP2C9 substrates (diclofenac, warfari...

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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

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Amiodarone Analog-Dependent Effects on CYP2C9-Mediated Metabolism and Kinetic Profiles

et al. 2006

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“…This may result in a sigmoidal kinetic profile (for testosterone), substrate inhibition (for nifedipine), and limited substrate substitution and inhibitory reciprocity (Korzekwa, 2002;. These "atypical" phenomena attributed to the existence of multiple binding sites have been associated with CYP3A4; however recent studies indicate similar behavior for other P450s (Egnell et al, 2003;Hutzler et al, 2003) and UDP glucuronosyltransferase enzymes (Uchaipichat et al, 2004 ABBREVIATIONS: DDI, drug-drug interaction(s); AUC, area under the curve; AUCi, area under the curve in the presence of the inhibitor; P450, cytochrome P450; LC, liquid chromatography; MS, mass spectometry; MS/MS, tandem mass spectrometry; S, substrate; I, inhibitor; SEI, ISE, SES, SESI, inhibitor and substrate or two-substrate bound complexes with an enzyme. …”

mentioning

confidence: 88%

“…This may result in a sigmoidal kinetic profile (for testosterone), substrate inhibition (for nifedipine), and limited substrate substitution and inhibitory reciprocity (Korzekwa, 2002;. These "atypical" phenomena attributed to the existence of multiple binding sites have been associated with CYP3A4; however recent studies indicate similar behavior for other P450s (Egnell et al, 2003;Hutzler et al, 2003) and UDP glucuronosyltransferase enzymes (Uchaipichat et al, 2004). The incor-poration of homo/heterotropic cooperativity in the in vitro-in vivo prediction of either clearance or DDI is not widely adopted.…”

mentioning

confidence: 88%

CYP3A4 Substrate Selection and Substitution in the Prediction of Potential Drug-Drug Interactions

Galetin¹,

K²,

Hallifax³

et al. 2005

J Pharmacol Exp Ther

142

125

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The complexity of in vitro kinetic phenomena observed for CYP3A4 substrates (homo-or heterotropic cooperativity) confounds the prediction of drug-drug interactions, and an evaluation of alternative and/or pragmatic approaches and substrates is needed. The current study focused on the utility of the three most commonly used CYP3A4 in vitro probes for the prediction of 26 reported in vivo interactions with azole inhibitors (increase in area under the curve ranged from 1.2 to 24, 50% in the range of potent inhibition). In addition to midazolam, testosterone, and nifedipine, quinidine was explored as a more "pragmatic" substrate due to its kinetic properties and specificity toward CYP3A4 in comparison with CYP3A5. K i estimates obtained in human liver microsomes under standardized in vitro conditions for each of the four probes were used to determine the validity of substrate substitution in CYP3A4 drug-drug interaction prediction. Detailed inhibitor-related (microsomal binding, depletion over incubation time) and substrate-related factors (cooperativity, contribution of other metabolic pathways, or renal excretion) were incorporated in the assessment of the interaction potential. All four CYP3A4 probes predicted 69 to 81% of the interactions with azoles within 2-fold of the mean in vivo value. Comparison of simple and multisite mechanistic models and interaction prediction accuracy for each of the in vitro probes indicated that midazolam and quinidine in vitro data provided the best assessment of a potential interaction, with the lowest bias and the highest precision of the prediction. Further investigations with a wider range of inhibitors are required to substantiate these findings.CYP3A4 is the most abundant human P450 enzyme, metabolizing a wide range of structurally diverse therapeutic agents; hence, it is the target for many drug-drug interactions (DDI). A recent Food and Drug Administration report (Yuan et al., 2002) has shown testosterone to be the most commonly used in vitro CYP3A4 probe (50% of reported studies) in contrast to midazolam (15-20% of in vitro estimates of CYP3A4 activity) whereas nifedipine, felodipine, and erythromycin were used in less than 10% of studies. The existence of different substrate subgroups for CYP3A4 was based on correlation and cluster analysis of CYP3A4 inhibition data for a range of modifiers (Kenworthy et al., 1999). This was substantiated by others (Stresser et al., 2000) and further investigated in a number of detailed mechanistic kinetic studies that indicated the existence of distinct and preferential binding domains for each substrate subgroup, namely, midazolam, testosterone, and nifedipine. Due to the substrate-differential response observed for CYP3A4, the recommended approach to CYP3A4 DDI analysis is the use of multiprobes (Tucker et al., 2001;Bjornsson et al., 2003) where the lowest inhibition constant (K i ) obtained indicates the "worst case scenario" for a potential interaction. However, an inappropriate selection of a probe substrate may lead to fal...

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Utilization ofIn VitroCytochromeP450 Inhibition Data for Projecting Clinical Drug–Drug Interactions

Kenny

McGinnity

Grime

et al. 2010

Pharmaceutical Sciences Encyclopedia

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The CYP family of enzymes are the primary facilitators of oxidative biotransformation in the liver and are responsible for the metabolism of the majority of human drugs. The CYP family metabolize a very broad range of substrates and play a central role in the mediation of clinically relevant drug–drug interactions (DDIs). This article summarizes the current knowledge base and the complexities of CYP inhibition and provides a guide for embarking on prediction of clinical DDIs with particular emphasis on the drug discovery setting.

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Generation and Evaluation of a CYP2C9 Heteroactivation Pharmacophore

Cited by 50 publications

References 33 publications

Amiodarone Analog-Dependent Effects on CYP2C9-Mediated Metabolism and Kinetic Profiles

Amiodarone Analog-Dependent Effects on CYP2C9-Mediated Metabolism and Kinetic Profiles

CYP3A4 Substrate Selection and Substitution in the Prediction of Potential Drug-Drug Interactions

Utilization ofIn VitroCytochromeP450 Inhibition Data for Projecting Clinical Drug–Drug Interactions

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