DAPT (GSI-IX) is a potent and orally active γ-secretase inhibitor with IC50s of 115 nM and 200 nM for total amyloid-β (Aβ) and Aβ42, respectively. DAPT inhibits the activation of Notch 1 signaling and induces cell differentiation. DAPT also induces autophagy and apoptosis. DAPT has neuroprotection activity and has the potential for autoimmune and lymphoproliferative diseases, degenerative disease and cancers treatment.