Assay Method Information

Assay Name:  Binding Assay
Description:  The BACE1 and BACE2 binding assays measured beta-site amyloid precursor protein-cleaving enzyme (BACE) binding as a decrease in the counts of radioligand bound in a scintillation proximity assay (SPA). Utilizing a radiolabeled small molecule BACE active site binding inhibitor and crude HEK cell membrane preparations over-expressing full length BACE1 or BACE2, the binding of enzyme by test compound was monitored as a reduction of specific counts bound at pH 6.0. Full length human BACE1 or BACE2 over-expressed in HEK cells was prepared by Pfizer scientists. Frozen stock cell paste was reacted in 50 mM sodium acetate buffer (pH=6.0) containing 3H-(4aR,6R,8aS)-8a-(2,4-difluorophenyl)-6-(1-methyl-1H-pyrazol-4-yl)-4,4a,5,6,8,8a-hexahydropyrano[3,4-d][1,3]thiazin-2-amine ligand, SPA bead and 60 μM to 600 pM of test compound in an assay volume of 27 uL. The compound plate also contained positive (BACE inhibitor) and negative (DMSO) control wells. The binding was carried out at room temperature for 30 minutes and then the plates were read on a TriLux Microbeta reader to determine the number of counts bound. The raw data was converted to percent effect compared to positive and negative control wells and the compound concentrations and % effect values for tested compounds were plotted to determine the 50% effect (IC50) with a four-parameter logistic dose response equation.
Affinity data for this assay
 

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