Edit draft

PK-CIA · v2. Save as often as you like — submit for review from the template page.

Assay Identity

How this assay definition is named and why it exists.

Template code*

Assay title*

The name this assay definition is known by.

Assay objective*

The question this assay answers and the decision it supports. One or two sentences.

Assay descriptionoptional

How the assay is run: method, conditions, controls, duration. The objective says why; this says how.

Cocktail Inhibition Assay (CIA): The potential of test compounds to inhibit human cytochrome P450 isoforms (mainly CYP1A2, 2C8, 2C9, 2D6 and 3A4) is investigated with human hepatocytes in suspension. Test compounds (usually 5 µM) are mixed with a cocktail of CYP isoform-specific substrates (mainly phenacetin, repaglinide, diclofenac, dextromethorphan and midazolam) and incubated with hepatocytes in suspension for up to 1.5 h (co-incubation) or up to 3.5 h (pre-incubation) at 37°C to obtain clearance values. Clearance values are obtained by measurement of the substrate depletion via LC/MS analysis. As a control serves the incubation of substrate cocktail in the absence of the test compound. Inhibitory effects are determined by comparison of the clearance values for the isoform-specific substrates in the presence and absence of a potential inhibitor in co- and pre-incubation (the latter for evaluation of time-dependent inhibition). Finally, clearance ratios are calculated. A cocktail of standard inhibitors, specifically inhibiting a single CYP isoform, is always included.