Alzheimer’s disease (AD) is the most common cause of dementia and is the outcome of progressive brain cells death. Due to the disorder’s heterogeneity and in view of the variety of pathological mechanisms inducing the disease    we have undertaken an innovative – science based (Animal model) approach, which is presented here. Our unique approach is based on known genetic risk factors of AD and  hence  focuses on subpopulations of AD patients, which  share common genetic risk factors.

The allele ɛ4 of apolipoprotein E (apoE4) which is the most prevalent genetic risk factor for AD and is expressed by more than half of the patients is being studied in our lab and we found it, to be a promising therapeutic target.

A murine animal model which expresses  either apoE4 or the AD benign   form of this molecule apoE3 , mimics the  AD pathological effects of apoE4. ApoE is a lipoprotein and as such is composed of both protein and lipids. Importantly  human and animal model studies revealed  that apoE4 is hypo-lipidated  relative to apoE3 both in people and in  corresponding mice models
Furthermore, we have shown that activating the lipidating protein ABCA1 (ATP-binding cassette transporter ) in the mouse with an apoE derived peptide, reverses the hypolipidation of apoE4 in vivo and concomitantly counteracts the apoE4 driven pathological phenotype.

In view of these findings, we presently propose to undertake this approach and to counteract the pathological effects of apoE4 by developing ABCA1 agonists which by enhancing the efflux of cholesterol and phospholipids to   the lipid-poor apoE4 will  prevent the hypo-lipidation and will counteract its pathological effects.

OUR SOLUTION
• Our technology utilizes low molecular weight and brain permeable activators of ABCA1 to eliminate the AD related pathological effects of apoE4 by reversing the hypo-lipidation of apoE4 and rendering it similar to that of the AD benign isoform of this molecule apoE3.

• The proposed approach is based on  our  recently obtained findings that treatment  of apoE4 mice with a peptide agonist of the brain lipidating protein ABCA1 reverses both the hypolipidation and the pathological effects of apoE4.
OUR APPROACH
• The overall objective is to identify high affinity ABCA1 functional activators, which reverse the hypolipidation of apoE4. This is pursued by the following sequential steps.

• Phenotypic High-Throughput Screening (HTS) utilizing a cellular cholesterol efflux activation assay.

• An orthogonal assay to assess the extent  to which the HTS hits can reverse the apoE4 driven impaired digestion of senile plaques

• Cytotoxicity measurements

• Target recognition experiments, utilizing the microscale thermophoresis assay (MST), for assessing the extent to which the hits bind to ABCA1.
By utilizing these criteria, we identified 5 compounds which meet all of these criteria .Additional medicinal chemistry studies identified  two additional second
generation compounds  and    the  underlying structure of the lead compound

• In vivo studies directed at assessment of the extent to which intra-nasal application of the ABCA1 activators reverses the hypolipidation of apoE4 and counteracts its pathological effects in vivo..

APPLICATIONS
• Small druggable ABCA1 activators will be used for structure function studies directed at developing more efficacious lead compounds and at studying their mechanism of action.
• The lead compound will then be used for development of anti apoE4 related treatment of AD.
• The expected findings will also have important therapeutic implications on
atherosclerosis treatment where ABCA1 upregulation has been suggested as an
important untapped therapeutic target.

PRELIMINARY RESULTS

• High throughput Screening experiments followed by first generation medicinal chemistry led to the discovery of 7 compounds which fulfill all the functional activity requirements (e.g. activate the lipidation of apoE4, non toxicity, counteract the pathological effects of apoE4) and which
bind specifically to the extracellular domain of ABCA1.

• Analysis of the results led to the identification of a scaffold molecular structure whose activity is in the micromolar range which will serve as a template in
future medicinal chemistry experiments.

• In vivo studies utilizing apoE4 and apoE3 targeted replacement mice revealed that intra-nasal application of the leading hit N1 reverses the hypolipidation of apoE4 and counteracts its in vivo pathological effects in naïve mice as well as following inflammatory challenge

INTELLECTUAL PROPERTY: 
Application PCT/IL2021/050114: ApoE4 targeted therapy of Alzheimer’s disease based on activation of the lipidating transporter ABCA1