BACE1 and Alzheimer disease: Beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) is an aspartyl protease widely expressed in the brain, essential for the synthesis of monomeric amyloid-β (Aβ), which spontaneously self-aggregates to form the insoluble fibers known as senile plaques, initiating toxicity in AD [97].