Category: Preclinical Development
Purpose: CYP450 drug-drug interaction potential assessment is critical to inform small molecule compound selection and clinical/commercial strategy. Both reversible (DDI) and time dependent inhibition (TDI) information is necessary for full characterization of a compound’s liability in the P450 metabolic space, but this requirement must be balanced with the stage of research and resourcing constraints. The goal of this work was to assess the potential for a single assay to provide estimates of both DDI and TDI across multiple isoforms in a single experiment for discovery stage assessment of potential DDI/TDI risk.
Methods: A structurally diverse set of proprietary and literature derived compounds that have tested positive for DDI and/or TDI were used in the evaluation. This approach attempts to combine the IC50 shift assay developed to assess TDI with an assessment of reversible DDI using established probe substrates. The method uses preincubation arms plus and minus NADPH to determine a reversible IC50 through the pre-incubation arm without NADPH, and the kinact/KI ratio from the pre-incubation with NADPH. Independent DDI experiments with no preincubation and full kinetic characterization were used to verify the validity of the outcome from the combined experiment.
Results: Without NADPH, preincubated samples for 3A4 show a strong correlation with compounds measured with a standard reversible protocol. Nearly 80% of compounds show similar ranking across methods, with only 1% of compounds being off by more than one risk bin. The samples preincubated with NADPH compared to the kinact/KI determination show a clear reversible linear correlation, as well, with an R2 >0.95 for 3A4.
Conclusion: The results suggest that this combined approach may be suitable to flag potential DDI and/or TDI risk and to inform design of subsequent experiments to refine the assessment if the compound is to be further developed. Compounds can be rank ordered across both types of inhibition within a series or across series to better hone chemistry efforts prior to candidate selection.