Aβ has been identified as the key subunit of the extracellular plaques found in the brains of patients with Alzheimer’s disease (AD) and Down’s syndrome (DS). Aβ has therefore been extensively studied as a potential target for treatment of AD.

Aβ is formed from the cleavage of the large, transmembrane protein; APP (amyloid precursor protein). Cleavage of APP by β- and then γ-secretases results in the formation of Aβ. Aβ can aggregate to produce amyloid-β oligomers, which are thought to be highly neurotoxic. Over time Aβ can further aggregate to produce the characteristic senile plaques present in AD and DS. Aβ can be degraded by enzymes such as neprilysin, insulin degrading enzyme or endothelin converting enzyme. At physiological levels Aβ may be involved in controlling synaptic activity and neuronal survival.