BACE1 and Alzheimer disease: β‐Site amyloid precursor protein (APP)‐cleaving enzyme 1 (BACE1 or β‐secretase) is a prime drug target for Alzheimer's disease (AD),1, 2 since this enzyme is responsible for initiating the generation of amyloid‐β (Aβ) that triggers a pathogenic cascade ultimately leading to neuron death and memory deficits.3