A central drug target for AD is the transmembrane protease BACE1 (β-site APP cleaving enzyme, β-secretase), which cleaves the amyloid precursor protein (APP) and thereby catalyzes the first step in the generation of the amyloid β (Aβ) peptide, which has a key pathogenic role early in AD pathogenesis (1). The gene discussed is APP; the disease is Alzheimer disease.