Targeting biologically relevant tau monomers and oligomers using a novel DEL drug discovery platform to treat Alzheimer’s disease and tauopathies

PROJECT SUMMARY Targeting biologically relevant tau monomers and oligomers using a novel DEL drug discovery platform to treat Alzheimer’s disease and tauopathies This Phase I SBIR project aims at the identification using our novel DNA-encoded library (DEL) drug discovery platform of small molecular weight compounds that can bind to the protein monomeric and/or oligomeric tau and modify its biology, ultimately blocking or reducing its toxicity. A number of neurodegenerative diseases such as Alzheimer’s disease (AD) and sporadic frontotemporal dementias (e.g., Pick’s disease), are called tauopathies because of the abnormal intracellular inclusions highly enriched in tau protein that characterize them. These inclusions or neurofibrillary tangles (NFTs) are believed to be the result of pathological misfolding of tau due to hyperphosphorylation and leading to oligomerization, fibrillization and involving spreading of soluble tau oligomers. Those facts together with the progression with age of tau pathology and the difficulty to target Aβ peptide oligomers make the identification of tau pathology inhibitors highly relevant and urgently needed for AD and all tauopathies in general. Tau drug discovery is hampered by the need of large amounts of mostly non-physiological tau protein (E. coli) for high-throughput screening (HTS), the need to use elaborated tau systems that are not HTS compatible to recapitulate tau biology, and the need for a clear tau biological activity to perform HTS drug screening. Our research strategy is to remove those limitations and identify tau binders using a DEL screening approach that will allow small amounts of a physiological/high quality protein target to be used with very large screening power (125 million entirely new proprietary compounds) and a binding-based assay that is activity-independent. The central hypothesis is that due to the very large number of compounds available to be tested and the inherent diversity, it will be possible to identify efficiently, in a cost- effective way, compounds that are high-affinity binders of tau oligomers and possibly protofibrils. DEL screening protocols have been generated and optimized focusing on minimizing the amount of protein tau to be used and on purifying tau from mammalian cells. These steps will ensure that a physiological tau version is used for screening and validation purposes. Screen duplicates used are increasing confidence and improve hits’ heuristic values determination. Aim 1 will be dedicated to finalizing DEL screening campaigns with monomeric tau. Tau will be expressed in mammalian cells, purified, aggregated, and immobilized on beads. Aim 1 will generate a list of 24-36 hits binding to monomeric tau and not found for oligomeric tau; specificity will be investigated. Physical binding of all candidate hits identified (up to 100) will be validated with two different methods. Aim 2 will include chemical synthesis of 18 additional new hits and intermediaries, structure activity relationship studies and in-silico docking. Importantly, Aim 2 will help identifying hit candidates that can affect tau’s biology and especially oligomerization and seeding. Altogether, this proposal will generate 3-5 compounds with 3-digit nanomolar range KD or lower and will represent a strong proof of concept fully validating Phase I and a robust starting point to initiate Phase II.