Pharmacological Targeting of Tau Aggregates for Autophagic Removal

National Institute Of Neurological Disorders And Stroke

Investigators

Abstract

Tau aggregates are one of the most rigorous neuroanatomical signatures of Alzheimer's disease and related dementias (ADRD). This project seeks to de-risk a potential therapeutic strategy for ADRD by identifying novel drug candidates that eliminate Tau protein aggregates. Inspired by a recently developed technology in oncology research called ProTACs, which uses a targeted protein degradation approach to mark proteins for removal by proteasomes. Our strategy instead targets insoluble Tau protein aggregates for autophagic elimination. In the past year, we have performed drug screening to identify small molecule ligands of our protein of interest and validated binding compounds and determined the binding site of hit compounds. This compound binding site has been corroborated in structure-activity relationship and mutagenesis experiments. We worked with Dynabind to select the final set of Fip200 binding compounds for validation. We worked with the CRO Curia to synthesize a series of compounds off-DNA and with varying linkage chemistries between fragment library hits. Working with the lab of Nico Tjandra in NHLBI we tested the first round of these compounds using NMR to determine binding site of the compounds on Fip200 and we identified the site as a groove between the two monomer Claw domains. This is a promising site for targeting Fip200 to Tau aggregates as it may cause no negative consequences to the normal activity of Fip200. We used the orthogonal method Intrinsic Tryptophan Fluorescence (ITF) to validate these results. At the current stage we have an off-DNA Fip200 binder with affinity around 10 uM. We continue testing the new compounds created by Curia using ITF and NMR to map out the structural space and perhaps find higher affinity ligands. We are also creating fluorescent based probes to enable higher-throughput testing of our compounds. We will attempt to find crystallography conditions that enable us to solve high-resolution structures to optimize ligand. When successful we will engage with NCATS for SAR derivatization of the tool compounds. We tested 8 more potential starting point compounds from our DEL screen on DNA. Once we have a standalone ligand with a KD below 200 nM, we will link it to the halotag ligand to begin testing autophagy induction in our cell models. We have also begun synthesizing compounds off-DNA identified in our screens and validated their binding affinity. We have begun to test compounds in cellular models and developed methods to screen chemical derivatives of these compounds. We have identified a scaffold for our lead ligand to the protein of interest that avoids off-target effects. In the last year we have also initiated new screens to identify new classes of Binders to FIP200. We developed new high throughput assays (WAVE screen) to test a new series of derivatives of our existing ligand chemotypes. We are now working very effectively with NCATS/NHLBI - they have modeled binding modes of our ligands into the FIP200 pocket and designed compounds to optimize these structure based interactions. We have begin high-throughput testing of diverse compound classes using the WAVE screen. We would like to determine an optimal attachment points for connecting the FIP200 ligands to the tau targeting ligands. We plan to achieve improvements in potency and solubility with our next generation ligands.