CHARACTERIZATION OF A SMALL-MOLECULE APP TRANSLATION INHIBITOR FOR ALZHEIMER’S DISEASE PREVENTION AND THERAPY

Abstract

Progressive accumulation of β-amyloid (Aβ) in the brain is a critical upstream event in Alzheimer's disease (AD) pathogenesis and considered as a prime target for disease-modifying therapy of AD. Aβ is generated during proteolytic cleavage of the amyloid precursor protein (APP) and substantial effort has been focused on targeting APP β- and γ-secretases to limit Aβ production. However, since biological effects of these enzymes are not solely limited to APP, undesired off target effects are one of the main drawbacks in the implementation of their inhibitors in clinical practice. As an alternative to inhibiting APP processing, Aβ production can also be reduced by lowering APP expression level through targeting its translation with a small molecule translational inhibitor. We characterized in vitro and in vivo properties of 2-[(pyridin-2-ylmethyl)-amino]-phenol (2-PMAP; MW=200.2 Da), which inhibitory effect on APP translation was identified through a small molecule screen. In CHO APP751WT and CHO APP751SW lines, 2-PMAP lowered in a dose-response manner the steady-state APP level and inhibited Aβx-40 and Aβx-42 production with a minimum effective concentration <0.5μM. Its effect on APP translation was highly specific <25μM concentration. 2-PMAP does not alter APP mRNA level, while its dose-dependent effect on APP translation was directly showed in pulse-chase studies, which also confirmed absence of 2-PMAP effect on APP maturation, processing, and degradation. 2-PMAP has no effect on APP cleavage as shown using specific functional assays of APP secretases. 2-PMAP is BBB penetrant after oral and intravenous dosing and when given systemically to APPSW/PS1dE9 AD transgenic mice it reduced levels of full length APP, APP C-terminal fragments (CTFs) and levels of soluble Aβx-40 and Aβx-42 in the brain. A chronic, four-month treatment of APPSW/PS1dE9 mice with 2-PMAP produced significant reduction in Aβ brain deposition and did not reveal any evidence of observable toxicity, while rescuing the mice from memory deficit. 2-PMAP is a small molecule therapeutic effectively ameliorating Aβ pathology through targeting APP translation. 2-PMAP is unlikely to evoke off target effects associated with APP secretases inhibition and provides additional benefit in lowering levels of cytotoxic APP CTFs.