| Assay Method Information | |
| | CYP Inhibition and Pre-Incubation CYP Inhibition Assays |
| Description: | Use of in vitro assays to evaluate the inhibition potential of new drug candidates towards CYP-mediated metabolism has been shown to be effective as part of a strategy to minimise the chances of drug interactions with co-administered drugs. The inhibitory potency of the test compound towards 5 human cytochrome P450 isoforms (CYP1A2, 2C8, 2C9, 2D6, and 3A4) was determined. More preferred examples of the present invention have CYP inhibition IC50≥10 μM.For CYP3A4 time dependent inhibitory potential was also tested by applying a 30 min pre-incubation time of the test compound in metabolically active incubation system. If a time-dependent inhibition of CYP3A4 is observed, this is a hint of an irreversible mechanism-based inhibition of the CYP3A4 activity by the test compound. More preferred examples of the present invention have pre-incubation CYP inhibition IC50≥20 μM.Method Description CYP Inhibition AssayHuman liver microsomes (pooled, >30 male and female donors) were incubated with individual CYP isoform-selective standard probes (phenacetin for CYP1A2, amodiquine for CYP2C8, diclofenac for CYP2C9, dextromethorphan for CYP2D6 and midazolam for CYP3A4) in the absence and presence of increasing concentrations of the test compound in order to compare the extent of formation of the respective metabolite. In addition, a set of incubation in the absence of test compound was used as a negative control. Furthermore, the inhibitory potency of standard inhibitors was included as positive controls (fluvoxamine for CYP1A2, montelukast for CYP2C8, sulfaphenazole for CYP2C9, fluoxetine for CYP2D6, ketoconazole for CYP3A4 and mibefradil for CYP3A4-preincubation). Incubation conditions (protein and probe substrate concentration, incubation time) were optimised with regard to linearity and metabolite turnover. Incubation medium consisted of 50 mM potassium phosphate buffer (pH 7.4) containing 1 mM EDTA, NADPH regenerating system (1 mM NADP, 5 mM glucose 6-phosphate, glucose 6-phosphate dehydrogenase (1.5 U/mL). Sequential dilutions and incubations were performed on a Genesis Workstation (Tecan, Crailsheim, FRG) in 96-well plates at 37° C. A final incubation volume of 200 μL was used. Reactions were stopped by addition of 100 μL acetonitrile containing the respective internal standard. Precipitated proteins were removed by centrifugation of the well plate, supernatants were combined and analyses were performed by LC-MS/MS. The LC-MS/MS quantification of the metabolites paracetamol (CYP1A2), desethylamodiaquine (CYP2C8), 4-hydroxydiclofenac (CYP2C9), dextrorphan (CYP2D6), and 1-hydroxyidazolam (CYP3A4) was performed with a PE SCIEX API 3000 LC/MS/MS system (Applied Biosystems, MDS Sciex, Concord, Ontario, Canada). |
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