A potent inhibitor of γ-secretase that blocks the production of Aβ38, Aβ40, and Aβ42 with IC50 values of 12.0, 12.1, and 10.9 nM, respectively; also blocks Notch signaling (IC50 = 14.1 nM); modulates γ-secretase activity in vivo, altering Aβ levels in brain, cerebrospinal fluids, and plasma in a dose-dependent fashion.