Alzheimer’s disease (AD) is a progressive neurodegenerative disorder afflicting approximately 30 million patients globally. Despite the considerable research efforts for preventing, treating, or curing the disease, effective strategies remain lacking. Recent trends focused on cholesterol modulating mechanisms and neuro-energy regulatory pathways. Several genes regulating cholesterol homeostasis have been reported as risk factors or have been implicated in AD, including the cholesterol carrier apoE. It is well established that ApoE4 allele confers isoform dependent risk for late onset AD (LOAD). The apoE4 allele, also increases the probability of disease at an earlier age. In addition, apoE has been demonstrated with defining pathological lesions of Alzheimer's disease, including neurofibrillary tangles, neuritic plaques and all associated from improper cholesterol regulation and apoE lipidation process. LXR receptors are a subfamily of the super family of nuclear receptors that regulate cholesterol in highly active cells in the body including the liver, brain, and heart. LXRs upregulate the expression of cholesterol regulating genes including ApoE and genes involved in reverse cholesterol transport (RCT). Thus, targeting those with apoE alleles may prove beneficial. Germane to our studies is that ApoE is under the transcriptional regulation of LXR and thus LXR agonist may offer opportunity to regulate ApoE3-E4 levels.

Innovation of AU403. Previous LXR compounds have failed in clinical testing due to induction of hepatoxicity, elevated circulating levels of cholesterol and poor brain penetrance. AU403 was selected as our lead compound because it induces LXRβ activity with minimal LXRα activity. In addition we designed AU403 to display PPAR-delta (δ) and PPAR-alpha (α) agonism to help reduce lipid accumulation in the liver and in circulation. Thus, we have developed AU403 to follow Lipinski’s rule of 5 for improved solubility and membrane permeability, including robust LogQ (BB) values, CNS activity and MDCK cell permeability. AU-403, was designed with an emphasis on ADME using Schrodinger and GastroPlus modeling software. To validate LXR and PPAR activity, we compared the impact of full LXR and PPAR agonists with AU-403 using reporter activity assays, lipid accumulation in primary rat hepatocytes and 3T3-L1 adipocytes, reduction of inflammatory signaling in macrophages, and gene transcription in primary rat hepatocytes. In addition, chemical characterization was performed to determine absorptive properties using LogP and PAMPA based experimental procedures. AU-403 demonstrated the lack of lipid accumulation in hepatocytes. Reduced A levels in 3xTgAD mice and compatible absorptive properties for blood brain distribution, and desirable transcription of genes to avoid side effects. Our future aims will validate our in-silico models of ligand binding to LXR and PPAR as determined by x-ray crystallographic protein-ligand complexes, determine specificity for co-activator/co-repressor recruitment utilizing TR-FRET assays, and test the ability to mitigate deficits with insulin signaling and energy regulation in a model of AD.

Keywords: Alzheimers Disease, nuclear receptors, Drug Design