A potent, orally bioavailable inhibitor of γ-secretase that more potently inhibits the cleavage of APP to Aβ40 than signaling through Notch (IC50s = 0.30 and 58 nM, respectively); shows good pharmacokinetics in rats, dogs, and humans and passes the blood-brain barrier, reducing plasma, brain, and cerebrospinal fluid Aβ40 levels.