BACE1 and Alzheimer disease: Therefore, BACE-1 is a prime drug target for slowing down Aβ production in early AD [26,27], however, clinical trials have thus far had disappointing results, with a number of phase II and III studies halted early for limited or no effect on symptoms and variable effects on Aβ volume or deposition, with association with a reduction in brain tissue volume in follow-up examinations [28,29,30].