The Avidimer Platform - a molecular toolbox to accelerate proximity research and drug discovery

Project Summary / Abstract The identify of small molecules or biologics that induce proximity of two targets is a promising and rapidly growing modality in drug discovery. The premise has led to an explosion of new companies focused on proximity, including targeted protein degradation mechanisms, stabilization of complexes, and modification regulation. However, the commercial toolbox to enable success is largely lacking. One of the challenges is that most high- throughput screening methodologies utilized for molecular glues, including DNA encoded libraries and affinity selection mass spectrometry, do not inform on ternary complex formation, requiring costly and time consuming validation assays. Traditional proximity assays such as HTRF and AlphaLISA rely on the availability of suitable affinity reagents or require the incorporation of tags that can impact binding and protein behavior. They also require high protein concentrations, leading to a burden on protein expression and assay artifacts that impact data quality. The current challenge is to develop a molecular toolbox to enable the discovery of glues and other proximity inducers, including the discovery of novel affinity reagents and optimized high-throughput screening platform. Notably, the most common strategies for developing affinity reagents such as animal immunization are prone to batch-to-batch variability and motivation to move away from animals. This proposal describes the development of a novel application of phage display called the Avidimer Platform that reveals bispecific (two- site) binders to one or more protein targets. The Avidimer Platform solves two challenges: 1) the development of affinity reagents using a recombinant system to deliver a sustainable affinity reagent platform, eliminating batch-to-batch variability and data can be shared as a DNA sequence by email or a purified protein, and 2) the resulting Avidimer is a tool to enable HTS of molecular glues. This proposal aims to demonstrate the use of the Avidimer Platform to develop an Avidimer for a well-characterized model system and develop an assay for discovering glues. The proposal includes a benchmark against traditional glue screening methodologies. Importantly, the Avidimer Platform is flexible, and can be used for virtually any proximity inducing target and program and will have a significant overall impact on the proximity industry.