p3 peptide also known as amyloid β- peptide (Aβ)17–40/42 is the peptide resulting from the b- and γ-secretase cleavage from the amyloid precursor protein (APP). It is known to be the major constituent of diffuse plaques observed in Alzheimer's disease (AD) brains and pre-amyloid plaques in people affected of Down syndrome. However, p3 peptide's role in these diseases is not truly known yet.