Mechanism-based inhibition of CYP activities in rat liver by fluoxetine and structurally similar alkylamines

Murray, Michael T.; Murray, Keith

doi:10.1080/00498250310001602748

Cited by 25 publications

(12 citation statements)

References 31 publications

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“…MI complex formation has been reported with alkylamines from a variety of drug classes, including macrolide antibiotics, antidepressants (both selective serotonin reuptake inhibitors and tricyclics), antihistamines, and calcium-channel blockers, and with several cytochrome P450 enzymes (McNeil and Murray, 1996;Trieu and Murray, 2000;Murray and Murray, 2003;Fontana et al, 2005;Polasek and Miners, 2008). In the case of alkylamines, the ;455-nm absorbing complex is generally assumed to involve coordinate binding of a nitroso metabolite to the ferrous heme iron (similar to the carbon monoxide complex that absorbs maximally at ;450 nm), although direct evidence for the formation of a nitroso metabolite is often lacking.…”

Section: Introductionmentioning

confidence: 99%

Metabolism-Dependent Inhibition of CYP3A4 by Lapatinib: Evidence for Formation of a Metabolic Intermediate Complex with a Nitroso/Oxime Metabolite Formed via a Nitrone Intermediate

et al. 2013

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Metabolism-dependent inhibition (MDI) of cytochrome P450 (P450) enzymes has the potential to cause clinically relevant drug-drug interactions. In the case of several alkylamine drugs, MDI of P450 involves formation of a metabolite that binds quasi-irreversibly to the ferrous heme iron to form a metabolic intermediate (MI) complex. The specific metabolites coordinately bound to ferrous iron and the pathways leading to MI complex formation are the subject of debate. We describe an approach combining heme iron oxidation with potassium ferricyanide and metabolite profiling to probe the mechanism of MI complex-based CYP3A4 inactivation by the secondary alkylamine drug lapatinib. Ten metabolites formed from lapatinib by CYP3A4-mediated heteroatom dealkylation, Chydroxylation, N-oxygenation with or without further oxidation, or a combination thereof, were detected by accurate mass spectrometry. The abundance of one metabolite, the N-dealkylated nitroso/ oxime lapatinib metabolite (M9), correlated directly with the prevalence or the disruption of the MI complex with CYP3A4. Nitroso/ oxime metabolite formation from secondary alkylamines has been proposed to occur through two possible pathways: (1) sequential N-dealkylation, N-hydroxylation, and dehydrogenation (primary hydroxylamine pathway) or (2) N-hydroxylation with dehydrogenation to yield a nitrone followed by N-dealkylation (secondary hydroxylamine pathway). All intermediates for the secondary hydroxylamine pathway were detected but the primary N-hydroxylamine intermediate of the primary hydroxylamine pathway was not. Our findings support the mechanism of lapatinib CYP3A4 inactivation as MI complex formation with the nitroso metabolite formed through the secondary hydroxylamine and nitrone pathway, rather than by N-dealkylation to the primary amine followed by N-hydroxylation and dehydrogenation as is usually assumed.

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Section: Introductionmentioning

confidence: 99%

Metabolism-Dependent Inhibition of CYP3A4 by Lapatinib: Evidence for Formation of a Metabolic Intermediate Complex with a Nitroso/Oxime Metabolite Formed via a Nitrone Intermediate

et al. 2013

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“…Moreover, because fluoxetine is a racemic mixture, clearly, there could be differences in the CYP3A4 and 2C19 interaction between the R and S form, as reported for CYP2D6 inhibition (Stevens and Wrighton, 1993). Fluoxetine has also been demonstrated to be a mechanism-based inhibitor of rat CYP2C11 (Murray and Murray, 2003).…”

mentioning

confidence: 99%

Evaluation of Time-Dependent Cytochrome P450 Inhibition Using Cultured Human Hepatocytes

McGinnity

Berry²,

Kenny³

et al. 2006

Drug Metab Dispos

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ABSTRACT:Primary human hepatocytes in culture are commonly used to evaluate cytochrome P450 (P450) induction via an enzyme activity endpoint. However, other processes can confound data interpretation. To this end, the impact of time-dependent P450 inhibition in this system was evaluated. Using a substrate-cassette approach, P450 activities were determined after incubation with the prototypic inhibitors tienilic acid (CYP2C9), erythromycin, troleandomycin, and fluoxetine (CYP3A4). Kinetic analysis of enzyme inactivation in hepatocytes was used to describe the effect of these time-dependent inhibitors and derive the inhibition parameters k inact and K I , which generally were in good agreement with the values derived using recombinant P450s and human liver microsomes (HLMs). Tienilic acid selectively inhibited CYP2C9-dependent diclofenac 4-hydroxylation activity, and erythromycin, troleandomycin, and fluoxetine inhibited CYP3A4-dependent midazolam 1-hydroxylation in a time-and concentration-dependent manner. ) effectively abolished CYP2C9 activity over 24 h at low (micromolar) concentrations in primary cultured human hepatocytes. This work demonstrates that caution is warranted in the interpretation of enzyme induction studies with metabolically stable, weak time-dependent inhibitors, which may have dramatic inhibitory effects on P450 activity in this system. Therefore, in addition to enzyme activity, mRNA and/or protein levels should be measured to fully evaluate the P450 induction potential of a drug candidate.Inhibition of cytochrome P450 (P450)-dependent metabolism is a prevalent source of drug-drug interactions (DDIs) and may result in serious clinical consequences (Jankel and Fitterman, 1993; Bertz and Granneman, 1997) via either reversible or irreversible means. An assessment of the potential of a new chemical entity to cause DDIs via inhibition of P450 metabolism is important early in the drug discovery process. Mechanism-based P450 inhibitors can be characterized as displaying NADPH-, concentration-, and time-dependent quasi-irreversible or irreversible inactivation because of chemical modification of the heme and/or protein, and the inactivation rate is diminished in the presence of a competing substrate (Silverman, 1998). Such inhibitors may be of specific concern; first because the in vivo inhibitory effect lasts longer than that for reversible inhibitors and inactivated P450 has to be replaced by newly synthesized protein; and second because of an increased toxicological risk via the generation of reactive species (Zhou et al., 2005).Many drugs are mechanism-based inhibitors of P450, including the macrolide antibiotics erythromycin and troleandomycin (Larrey et al., 1983), tienilic acid (Lopez-Garcia et al., 1994), and fluoxetine (Mayhew et al., 2000). Thus, in vitro screens to determine both the degree and nature of P450 inhibition (typically determining the time dependence of inhibition) are now used across the pharmaceutical industry. More often than not, these assays focus on the five major drugme...

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“…The third type of inhibition is, strictly speaking, still noncovalent and pseudo-irreversible [60]. A CYP inhibition has to meet a number of criteria to be classified as MBI [61], and some of the important ones are briefly described: (i) Time-dependent inactivation occurs at the condition supporting the enzyme reactions, e.g., in the presence of NADPH for CYP-mediated reactions.…”

Section: Irreversible Cyp Inhibition or Mechanism-based Inactivation mentioning

confidence: 99%

“…CYP mechanism-based inactivators (MBI, which is used both for mechanism-based inactivation and the inactivator), though not yet been fully delineated structurally, often confer terminal unsaturated carbon atom, alkylamino, furan or furano-pyridinyl group, or sulphur-containing aromatic systems such as thiophene [60,[62][63][64][65].…”

Section: Irreversible Cyp Inhibition or Mechanism-based Inactivation mentioning

confidence: 99%

Enzyme Kinetics for Clinically Relevant CYP Inhibition

Zy¹,

Yn²

2005

CDM

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In vitro cytochrome P450 (CYP)-associated metabolic studies have been considered cost-effective for predicting the potential clinical drug-drug interactions (DDIs), one of the major attritions in drug development. The breakthroughs during the past decade in understanding the biochemistry of CYP-mediated biotransformation and molecular biology of CYP gene regulation in humans have provided the scientific bases for such endeavors in early drug development. In this review, the enzyme kinetics of CYP inhibitions is described, with the primary focus on the ones proven with clinical relevance, namely the competitive inhibition and mechanism-based inactivation (MBI). Competitive CYP inhibition, the most often detected reversible inhibition, is well understood and has been studied extensively both in vitro and in clinical setting. Recently, MBI has received increasing attention. It has been recognized that MBI could occur more often than anticipated, due in part to the redox cycling-allied enzymatic action of CYPs. As commonly as an irreversible inhibition, MBI would inactivate the target proteins, and thus would be generally considered of high potential for causing clinical DDI. Moreover, the reversible inhibitions other than the competitive, namely noncompetitive, uncompetitive and mixed, were also documented for the important drug-metabolizing CYP members, particularly CYP1A2 and CYP2C9. Finally, the unusual kinetic interactions, which did not follow the Michaelis-Menten (M-M) kinetics, were detected in vitro for the majority of drug-metabolizing CYP members, and manifested for CYP3A4. However, the clinical relevance of the interactions involving the unusual CYP kinetics has not yet been fully understood. Nonetheless, the reversibility and inhibitory potency should be considered as the major determinants of the clinical relevance, particularly in combination with the therapeutic exposure levels. With rapid expansion of knowledge and technology, the evaluation of the clinically relevant CYP-associated DDIs in vitro is not only desirable but also achievable.

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Mechanism-based inhibition of CYP activities in rat liver by fluoxetine and structurally similar alkylamines

Cited by 25 publications

References 31 publications

Metabolism-Dependent Inhibition of CYP3A4 by Lapatinib: Evidence for Formation of a Metabolic Intermediate Complex with a Nitroso/Oxime Metabolite Formed via a Nitrone Intermediate

Metabolism-Dependent Inhibition of CYP3A4 by Lapatinib: Evidence for Formation of a Metabolic Intermediate Complex with a Nitroso/Oxime Metabolite Formed via a Nitrone Intermediate

Evaluation of Time-Dependent Cytochrome P450 Inhibition Using Cultured Human Hepatocytes

Enzyme Kinetics for Clinically Relevant CYP Inhibition

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