Orally active, potent γ-secretase inhibitor (IC50 = 12 nM). Inhibits Aβ40 and Aβ42 formation in vitro (IC50 values are 7.4 and 7.9 nM respectively) and reduces Aβ in the brain, plasma and cerebrospinal fluid in vivo. Exhibits no Notch toxicity. Brain penetrant.