Amyloid-beta peptide aggregates and fibrils (EFRH epitope) (Aβ aggregates (EFRH))

Amyloid-beta (Aβ) aggregates and fibrils are the primary constituents of senile plaques, a pathological hallmark of Alzheimer's disease (Hardy & Higgins, 1992, Science). The EFRH sequence, corresponding to residues 3-6 of the Aβ peptide, represents a critical N-terminal epitope that is highly immunogenic and accessible in both soluble oligomers and insoluble fibrils (Frenkel et al., 2000, PNAS). Therapeutic strategies targeting this specific epitope utilize monoclonal antibodies, such as bapineuzumab and aducanumab, to promote the clearance of existing amyloid deposits and neutralize toxic species (Salloway et al., 2014, NEJM; Sevigny et al., 2016, Nature). By binding to the EFRH region, these drugs trigger Fc-receptor-mediated phagocytosis by microglia and may inhibit the further recruitment of monomers into growing fibrils (Bard et al., 2000, Nature Medicine). While effective at reducing plaque burden, targeting this epitope is frequently associated with amyloid-related imaging abnormalities (ARIA), reflecting changes in vascular permeability and microhemorrhages (Sperling et al., 2011, Alzheimer's & Dementia). This target is also relevant in Cerebral Amyloid Angiopathy, where Aβ deposits in the walls of cerebral blood vessels (Viswanathan & Greenberg, 2011, Lancet Neurology). Understanding the structural presentation of the EFRH epitope is essential for developing next-generation immunotherapies with improved safety and efficacy profiles.

Other names

Aβ aggregatesAmyloid-beta fibrilsEFRH N-terminal epitopeAβ(3-6) epitopeSoluble and insoluble Amyloid-betaN-terminal Aβ epitope

The mechanism of action involves passive immunotherapy where monoclonal antibodies bind to the N-terminal EFRH epitope (residues 3-6) of Amyloid-beta aggregates. This binding facilitates the clearance of amyloid plaques through Fc-receptor-mediated phagocytosis by microglia (Bard et al., 2000, Nature Medicine). Additionally, antibody binding can lead to the dissolution of existing fibrils and the neutralization of soluble toxic oligomers, preventing them from disrupting synaptic function (Sevigny et al., 2016, Nature). Some antibodies also act by preventing the recruitment of new Aβ monomers into established aggregates or by promoting the efflux of Aβ from the brain to the periphery (DeMattos et al., 2001, PNAS).