TISSUE-SELECTIVE ABCA1 AGONISTS AS POTENTIAL ALZHEIMER'S DISEASE THERAPEUTICS: HIT-TO-LEAD OPTIMIZATION

Abstract

The apolipoprotein E (APOE) ε4 allele is the strongest known risk factor for sporadic Alzheimer's disease (AD), which accounts for over 95% of all AD cases. ApoE4-containing lipoproteins contain a lower lipid content, which decreases stability and contributes to loss of lipoprotein function. To correct these deficits and restore proper lipoprotein function, we have developed tissue-selective ABCA1 agonists (TSAAgs) that induce central nervous system expression of the cholesterol transport protein ABCA1, thereby increasing lipid content of apoE4-containing lipoproteins, with minimal impact on peripheral lipogenesis. TSAAgs also ameliorate additional aspects of AD, including neuroinflammation and insulin resistance. High-throughput screening (HTS) utilized CCF-STTG1 astrocytoma (primary screen) and HepG2 hepatocellular carcinoma cells (counterscreen) expressing luciferase response elements linked to ABCA1 and SREBP1c promoters, respectively. Novel structural analogs of HTS hits were generated via iterative chemical synthesis. In vitro analysis of analog activity included PCR/immunoblot for both lipid- and insulin-related genes, ELISA for inflammatory markers, and a fluorescent cholesterol efflux assay. Prioritized HTS hits – those demonstrating anti-inflammatory and insulin-sensitizing properties in addition to TSAAg activity – served as scaffolds to generate a library of structural analogs. Evaluation of this analog library in vitro established structure-activity relationships that identified compounds with improved TSAAg activity and guided further structural modification. These results demonstrated a proof-of-concept to develop TSAAgs possessing multifunctional therapeutic potential against Alzheimer's disease. Our study represents a novel strategy to develop small molecule drug candidates that target multiple aspects of AD pathology. Future in vivo experiments are proposed to establish pharmacokinetic profiles, determine magnitude and mechanisms of tissue-selective ABCA1 induction, and monitor alterations in peripheral lipogenesis. Finally, treatments in the EFAD mouse model will assess TSAAg effects on cognitive and pathological deficits. Successful completion of this project could result in establishment of TSAAg compounds as leads for further pharmaceutical development and human clinical testing.