γ-Secretase is a multi-protein complex that proteolyzes the transmembrane region of the amyloid β-peptide (Aβ) precursor (APP), producing the Aβ peptide implicated in the pathogenesis of Alzheimers disease (AD). This protease has been a top target for AD, and various inhibitors have been identified, including transition-state analogue inhibitors that interact with the active site, helical peptides that interact with the initial substrate docking site, and other less peptidelike, more drug-like compounds. Although one γ-secretase inhibitor has advanced into late-phase clinical trials, concerns about inhibiting this protease remain. The protease complex cleaves a number of other substrates, and in vivo toxicities observed with γ-secretase inhibitors are apparently due to blocking one particularly important substrate, the Notch receptor. Thus, the potential of γ-secretase as therapeutic target likely depends on the ability to selectively inhibit Aβ production without hindering Notch proteolysis (i.e., modulation rather than inhibition). The discovery of γ-secretase modulators has revived γ-secretase as an attractive target and has so far resulted in one compound in late-phase clinical trials. The identification of other modulators in a variety of structural classes raise the hope that more promising agents will soon be in the pipeline.
Center for Neurologic Diseases,Harvard Medical School and Brigham and Women's Hospital, Boston,MA 02115, USA.