Perphenazine-macrocycle conjugates rapidly sequester the Aβ42 monomer and inhibit amyloid formation

Alzheimer’s disease is imposing a growing social and economic burden worldwide and effective therapies are required. Strategies aimed at the removal of fibrillar plaques formed by the amyloid-β peptide have not proved therapeutic and the focus has shifted to approaches that target the cytotoxic oligomeric amyloid-β species that are populated before fibrils are deposited. We have designed and synthesized perphenazine-cyclam conjugates that specifically and rapidly bind to the monomeric form of Aβ42, reducing the production of both cytotoxic oligomers and amyloid fibrils. We have applied detailed kinetic analysis and NMR spectroscopy to show that the perphenazine-cyclam conjugates divert the Aβ42 monomer into amorphous aggregates that are not toxic to differentiated SH-SY5Y cells in vitro . Unlike most other amyloid inhibitors studied to date, these conjugates inhibit oligomer and fibril assembly even in the presence of pre-formed fibrillar seeds, demonstrating that they act through a monomer sequestration mechanism. These modular, three-dimensional conjugates therefore effectively prevent monomer-dependent secondary nucleation, the autocatalytic process that generates the majority of toxic oligomers.