Inhibitor of γ-secretase; causes a reduction in Aβ40 and Aβ42 levels in human primary neuronal cultures (IC50 values are 115 and 200 nM for total Aβ and Aβ42 respectively) and in brain extract, cerebrospinal fluid and plasma in vivo. Does not effect APPα and APPβ levels. Blocks Notch signaling in hybrid human-mouse fetal thymus organ culture (FTOC). Activity causes neural cells to commit to neuronal differentiation.