Identification of cytochrome P450 3A4 modification site with reactive metabolite using linear ion trap-Fourier transform mass spectrometry.

Covalent binding of reactive metabolites to cytochrome P450s (P450s) often causes their mechanism-based inactivation (MBI), resulting in drug-drug interactions or toxicity. The detection and identification of the P450 sites to which reactive metabolites bind would elucidate MBI mechanisms. We describe a proteomic approach using nano-LC/linear ion trap-Fourier transform ion cyclotron resonance (FTICR) mass spectrometry to characterize the binding of a reactive metabolite of raloxifene, which is a known P450 3A4 inhibitor, to the P450 3A4 isozyme.

Risk assessment for drug-drug interaction caused by metabolism-based inhibition of CYP3A using automated in vitro assay systems and its application in the early drug discovery process.

The CYP3A family is a major drug metabolism enzyme in humans. Metabolism-based inhibition of CYP3A might cause clinically significant drug-drug interactions (DDIs). To assess the risk of DDIs caused by metabolism-based inhibition (MBI) of CYP3A, we established an automated single time- and concentration-dependent inhibition assay.

In vitro metabolism of the calmodulin antagonist DY-9760e (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate) by human liver microsomes: involvement of cytochromes p450 in atypical kinetics and potential drug interactions.

Human cytochrome P450 (P450) isozyme(s) responsible for metabolism of the calmodulin antagonist 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate (DY-9760e) and kinetic profiles for formation of its six primary metabolites [M3, M5, M6, M7, M8, and DY-9836 (3-[2-[4-(3-chloro-2-methylphenyl)piperazinyl]ethyl]-5,6-dimethoxyindazole)] were identified using human liver microsomes and recombinant P450 enzymes. In vitro experiments, including an immunoinhibition study, correlation analysis, and reactions with recombinant P450 enzymes, revealed that CYP3A4 is the primary P450 isozyme responsible for the formation of the DY-9760e metabolites, except for M5, which is metabolized by CYP2C9.

Pharmacokinetics and disposition of DY-9760e, a novel calmodulin antagonist, in rats and monkeys.

DY-9760e (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate, CAS 162496-41-5) is a novel calmodulin antagonist that is being evaluated for the treatment of ischemia. The objective of this study was to characterize the pharmacokinetics and disposition of DY-9760e in rats and monkeys.