Fast High-Throughput Microsomal Binding Assay

The 20 min assay measures the affinity of drugs to human microsomal membranes and determines microsomal binding in stability incubation experiments.

Off-the-shelf Microsomal Binding Assay Kit

It is important to consider the extent of binding when performing microsomal clearance studies, as only a free unbound drug compound is available to be metabolised by the enzymes present in microsomal incubations. Estimated intrinsic clearance rates can be substantially underestimated without correction for microsomal binding. Furthermore, it has been shown that the prediction of in vivo compound stability significantly improves when correcting the metabolic rates obtained in microsomal incubations.

Sovicell has developed a great ready-made solution – the TRANSIL Microsomal Binding Kit. A 20 minute, high-throughput assay kit which allows the accurate estimation of intrinsic clearance from stability incubations by correcting the experimental clearance with the fraction of drug unbound in the incubation.

Reducing the risks of drug-drug interaction

Microsomal binding not only reduces the concentration of free drug available to be metabolised by CYP enzymes, but it also lowers the concentration which is available to inhibit the enzymes. It has been demonstrated that non-specific microsomal binding can account for underestimation of inhibitor potency (i.e., overestimation of IC₅₀ or K_i values) when dealing with lipophilic basic drugs. Consequently, this can lead to an underestimation of the risk of drug-drug interactions. Specifically, mechanism-based inhibitor studies can be affected to a large extent by microsomal binding, due to the high microsome concentrations that are commonly employed in these experiments. Therefore, the fraction of drug bound to microsomes is also an important correction of experiments assessing the inhibition potential.

Five-step assay kit for measuring the affinity of drugs to human microsomal
membranes

The kit consists of ready-to-go 96 well microtiter plates. One plate can be used for measuring microsomal binding of up to 12 compounds. The fast assay requires only 5 steps:

1. addition of drug candidate
2. mixing and incubation for 12 minutes
3. removal of beads by centrifugation
4. sampling of supernatant
5. quantification of the drug candidate

Capabilities

Detection systems:

• LC/MS/MS
• Scintillation counting
• Others

Parameters estimated:

• Affinity to human liver microsomes
• Human fu(mic)
• Coming soon: fu(mic) for other species

Features & Benefits of the Microsomal Binding Assay Kit

• Fast, requires only 20 minutes total assay time
• Measures the affinity to human microsomal membranes and determines microsomal binding
• Ready-to-go format in 96-well plate format generating highly reproducible results
• Rapid compound quantification due to immobilized brain membranes
• Kit includes a spreadsheet for calculation of final results and traffic light system for data quality rating

For more information please contact Sovicell today.