Inhibition and modulation of γ-secretase for Alzheimer’s disease

The 4-kDa amyloid β-peptide (Aβ) is strongly implicated the pathogenesis of Alzheimer’s disease (AD), and this peptide is cut out of the amyloid β-protein precursor (APP) by the sequential action of β- and γ-secretases. γ-Secretase is a membrane-embedded protease complex that cleaves the transmembrane region of APP to produce Aβ, and this protease is a top target for developing AD therapeutics. A number of inhibitors of the γ-secretase complex have been identified, including peptidomimetics that block the active site, helical peptides that interact with the initial substrate docking site, and other less peptide-like, more drug-like compounds. To date, one γ-secretase inhibitor has advanced into late-phase clinical trials for the treatment of AD, but serious concerns remain. The γ-secretase complex cleaves a number of other substrates, and γ-secretase inhibitors cause in vivo toxicities by blocking proteolysis of one essential substrate, the Notch receptor. Thus, compounds that modulate γ-secretase, rather than inhibit it, to selectively alter Aβ production without hindering signal transduction from the Notch receptor would be more ideal. Such modulators have been discovered and advanced, with one compound in late-phase clinical trials, renewing interest in γ-secretase as a therapeutic target.