Aβ is cleaved from the amyloid precursor protein (APP) to produce several peptides of different amino acid‐length peptides including 1‐39, 1‐40, 1‐42, 1‐43 and 1‐46 as well as the N‐truncated Aβ4‐42 3 While Aβ1‐40 is the predominant species in unaffected individuals, the ratio of Aβ1‐42:1‐40 increases in AD 4. Here, APP is linked to Alzheimer disease.