TRANSILXL Microsomal Binding Kit FEATURES AND BENEFITS
Fast, requires only 20 minutes total assay time
Measures the affinity to human microsomal membranes and
Ready-to-use format in 96-well plate format generating highly
Rapid compound quantification due to immoblized brain membranes
with a single lipid bilayer reconstituted from synthe-
Kit includes a spreadsheet for calculation of final results and traffic light
natural composition of human liver micromes.
TECHNICAL DESCRIPTION
The TRANSILXL Microsomal Binding kit measures the affinity of drugs to human microsomal membranes and
determines microsomal binding in stability incubation experiments. This allows the accurate estimation of
intrinsic clearance from stability incubations by correcting the experimental clearance with the fraction of drug
The kit consists of ready-to-use 96-well microtiter plates. One plate can be used for measuring microsomal
binding of up to 12 compounds. The assay requires only 5 steps: (i) addition of drug candidate, (ii) mixing and
incubation for 12 minutes, (iii) removal of beads by centrifugation, (iv) sampling of supernatant, and (v) quanti-
CAPABILITIES
Affinity affinity to human liver microsomes
coming soon: fu(mic) for other species
Sovicell Deutscher Platz 5b 04103 Leipzig t. +49 341 520 44 0 f. +49 341 520 44 12 e. info@sovicell.com www.sovicell.com Application and Relevance
Only free unbound compound is available to be metabolised by the enzymes present in microsomal incubations. Therefore,
it is important to consider the extent of binding when performing microsomal clearance studies. Estimated incrinsic
clearance rates can be substantially underestimated without correction for microsomal binding (fig. 2). Moreover, it has been
shown that the prediction of in vivo compound stability improves substantially when correcting the metabolic rates obtained
Microsomal binding not only reduces the concentration of free drug available to be metabolised by CYP enzymes, it also
reduces 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 IC or K values) when dealing with
lipophilic basic drugs. This in turn can lead to an underestimation of risk of drug-drug interactions. In particular, mechanism
based inhibitor studies can be affected to a large extent by microsomal binding, because of the high microsome
concentrations that are typically employed in these experiments. Hence, the fraction of drug bound to microsomes is also an
important correction of experiments assessing the inhibition potential.
Intrinsic Clearance Validation
The intrinsic clearance rate (CL ) is calculated from the
A test set of 24 compounds was chosen for validation.
observed clearance rate in the microsomal incubation
Microsomal binding was measured using the TRANSILXL
Microsomal Binding kit and conventional dialysis with
microsomes (fig. 3). Both methods yield comparable
results which correlate strongly (r2=0.93).
Illustration of the influence of microsomal binding
Comparison of microsomal binding measurements
on clearance rate estimation. Both lines represent
using the TRANSIL Microsomal Binding Kit and
compounds with identical clearance rate. However,
conventional dialysis. The test set comprised alpreno-
the compound represented by the dark blue line
lol, amantadin, buspirone, carbamazepine, cycloben-
does not bind to microsomes, while the compound
zaprine, desipramine, diphenhydramine, Enalaprilat,
represented by the light blue line binds strongly
fexofenadine, fluoxetine, fluvoxamine, faloperidol,
f (mic)=10%. Hence, the intrinisc clearance rate of
ketoconazol, labetalol, levofloxazine, nalidixic acid,
the compound binding to microsomes is highly
nortriptyline, promazine, propranolol, sulfasalazine,
terazosin, venlafaxine, and warfarin. PRODUCT INFORMATION Order Number
TMP-0120-2096 TRANSILXL Microsomal Binding kit
Sovicell Deutscher Platz 5b 04103 Leipzig t. +49 341 520 44 0 f. +49 341 520 44 12 e. info@sovicell.com www.sovicell.com
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TRANSILXL 
Application and Relevance