Small Molecules Abolish Detrimental Effects Of Apolipoprotein (Apo) E4 In Vitro By Inhibiting Domain Interaction And Correcting Structure

ApoE4, the major risk factor for Alzheimer's disease (AD), assumes a pathological conformation—intramolecular domain interaction. ApoE structure correctors that abolish domain interaction were identified by fluorescence resonance energy transfer (FRET) assay. Screening a ChemBridge library identified CB9032258 (a phthalazinone derivative, N‐(2‐hydroxy‐3,5‐dimethyl‐phenyl)‐2‐(3‐methyl‐4‐oxo‐3,4‐dihydro‐phthalazin‐1‐yl)‐acetamide) that reduces the FRET signal dose‐dependently (IC50: 4.2 μM). Chemical modification of CB9032258 yielded well‐defined structure‐activity relationships (e.g., N‐(4′‐cyano‐biphenyl‐3‐yl)‐2‐(3‐methyl‐4‐oxo‐3,4‐dihydro‐phthalazin‐1‐yl)‐acetamide and 4‐{4‐[2‐(3‐methyl‐4‐oxo‐3,4‐dihydro‐phthalazin‐1‐yl)‐acetylamino]‐benzyl}‐piperazine‐1‐carboxylic acid tert‐butyl ester) with enhanced FRET potencies (IC50: 23 and 116 nM, respectively). ApoE4 domain interaction decreases mitochondrial cytochrome c oxidase subunit 1 levels, reduces mitochondrial motility, and inhibits neurite outgrowth. The compounds restored function in apoE4‐expressing neurons by disrupting domain interaction and reversing apoE4 detrimental effects. ApoE4 structure correctors negate detrimental apoE4 effects in vitro and could be an AD therapeutic. Supported by Merck Research Laboratories.