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Assay Method Information

Assay Name:  Factor XIa Assay
Description:  The effectiveness of a compound of the present invention as an inhibitor of Coagulation Factor XIa can be determined using a relevant purified serine protease, and an appropriate synthetic substrate. The rate of hydrolysis of the chromogenic or fluorogenic substrate by the relevant serine protease was measured both in the absence and presence of compounds of the present invention. Assays were conducted at room temperature or at 37° C. Hydrolysis of the substrate resulted in release of amino trifluoromethylcoumarin (AFC), which was monitored spectrofluorometrically by measuring the increase in emission at 510 nm with excitation at 405 nm. A decrease in the rate of fluorescence change in the presence of inhibitor is indicative of enzyme inhibition. Such methods are known to one skilled in the art. The results of this assay are expressed as the half-maximal inhibitory concentrations (IC50), or the inhibitory constant, Ki.Compounds were pre-incubated for 30 minutes at 25° C. with human (0.04 nM) Factor XIa in 50 mM HEPES buffer with 150 mM sodium chloride, 5 mM calcium chloride, 0.1% PEG 8000, pH 7.4. Factor XIa enzymatic activity was determined by addition of the substrate glycine-proline-arginine-7-amido-4-trifluoromethylcoumarin (GPR-AFC) and measurement of the fluorescence at 400/505 nm after a 60 minute incubation at 25° C. The % inhibition for each data point was calculated from the data and analyzed using the log (inhibitor) vs. response four parameters equation to determine the half-maximal inhibitory concentrations (IC50). The IC50 were converted to equilibrium inhibitory constants (Ki) using the Cheng-Prusoff equation.
Affinity data for this assay
 

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Last update November 1, 2007
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