Pharmacological characterization of the novel γ-secretase modulator AS2715348, a potential therapy for Alzheimer's disease, in rodents and nonhuman primates

γ-Secretase is the enzyme responsible for the intramembranous proteolysis of various substrates, such as amyloid precursor protein (APP) and Notch. Amyloid-β peptide 42 (Aβ42) is produced through the sequential proteolytic cleavage of APP by β- and γ-secretase and causes the synaptic dysfunction associated with memory impairment in Alzheimer's disease. Here, we identified a novel cyclohexylamine-derived γ-secretase modulator, {(1R*,2S*,3R*)-3-[(cyclohexylmethyl)(3,3-dimethylbutyl)amino]-2-[4-(trifluoromethyl)phenyl]cyclohexyl}acetic acid (AS2715348), that may inhibit this pathological response. AS2715348 was seen to reduce both cell-free and cellular production of Aβ42 without increasing levels of APP β-carboxyl terminal fragment or inhibiting Notch signaling. Additionally, the compound increased Aβ38 production, suggesting a shift of the cleavage site in APP. The inhibitory potency of AS2715348 on endogenous Aβ42 production was similar across human, mouse, and rat cells. Oral administration with AS2715348 at 1 mg/kg and greater significantly reduced brain Aβ42 levels in rats, and no Notch-related toxicity was observed after 28-day treatment at 100 mg/kg. Further, AS2715348 significantly ameliorated cognitive deficits in APP-transgenic Tg2576 mice. Finally, AS2715348 significantly reduced brain Aβ42 levels in cynomolgus monkeys. These findings collectively show the promise for AS2715348 as a potential disease-modifying drug for Alzheimer's disease.