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bioRxiv · 10.1101/2023.08.04.552030

Discovery of an APP-Selective BACE1 Inhibitor for Alzheimer's Disease

Abstract

Inhibition of amyloid precursor protein (APP) beta-site cleaving enzyme 1 (BACE1; BACE) has been a target for Alzheimers disease (AD) therapeutic development, but has been impaired by off-target effects of clinically evaluated inhibitors, including inhibition of cleavage of non-APP substrates. Here, we report our identification of a BACE inhibitors series that are not only selective for the APP substrate, but also for BACE1 as the targeted enzyme. These APP-selective fluoro aminohydantoin (FAH) inhibitor compounds were identified by screening a compound library for inhibition of BACE cleavage of a maltose binding protein (MBP)-conjugated-APPC125 substrate followed by IC50 determination using the P5-P5 substrate assay. In multiple substrate and enzyme cell-free assays, the lead compound FAH65 displayed substrate selectivity for inhibition of APP cleavage, with little activity against BACE substrates neuregulin 1 (NRG1) or p-selectin glycoprotein ligand -1 (PSGL1). We also demonstrate FAH65 shows little inhibitory activity against the enzyme cathepsin D (Cat D) or BACE2. FAH65 inhibits production of BACE cleavage products soluble APP{beta} (sAPP{beta}) and the {beta} C-terminal fragment ({beta}CTF), as well as amyloid-{beta} (A{beta})1-40 and 1-42, in vitro in cells and in vivo in an animal model of AD. In a murine model of AD, FAH65 improved the discrimination score in the Novel Object Recognition (NOR) memory testing paradigm. The active enantiomer of FAH65, FAH65E(-), was obtained and tested in in vivo pharmacokinetic and pharmacodynamic (PK/PD) analysis, wherein it displayed good brain-penetrance and target engagement. Given its demonstrated selectivity for both enzyme and substrate, along with evidence it can improve cognitive performance in an animal model, FAH65 and its E(-) enantiomer merit continued pre-clinical development towards clinical testing as an APP-selective BACE1 inhibitor. Such a candidate would reduce A{beta} levels and overcome the deleterious effects of the non-selective BACE1 inhibitors that have failed in the clinic and potentially could be used as a maintenance therapy along with or following clearance of A{beta} from the brain with the approved antibody therapy for AD.

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BibTeXRIS

Campagna, J., Jagodzinska, B., Wi, D., Zhu, C., Lee, J. T., Cohn, W., Jun, M., Elias, C. J., Descamps, O., Zhang, Q., Gorostiza, O., Poksay, K., Spilman, P., Bredesen, D. E., John, V.. 2023-08-07. Discovery of an APP-Selective BACE1 Inhibitor for Alzheimer's Disease. https://doi.org/10.1101/2023.08.04.552030

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