A Proximity-Driven Functional Screening Platform for the Discovery of Noninhibitory USP7 Ligand Enabling Targeted Protein Stabilization

Abstract Targeted protein stabilization by deubiquitinase-targeting chimeras (DUBTACs) has emerged as a promising therapeutic strategy for preserving the function of essential proteins. DUBTACs are bifunctional molecules that recruit deubiquitinating enzymes (DUBs) to remove ubiquitin chains from substrate proteins, thereby preventing their proteasomal degradation. A key requirement for DUBTACs development is the identification of ligands that bind DUBs without impairing their catalytic activity. However, such noninhibitory ligands are exceedingly rare. Here, we report a novel proximity-driven on-bead functional screening platform for the discovery of noninhibitory DUB ligands. Using this approach, we discovered a previously unreported noninhibitory ligand for USP7. Furthermore, we generated DUBTACs by conjugating this USP7 ligand to a CFTR-binding ligand. Our lead compound, WJ045, effectively stabilized CFTR protein levels in cells, demonstrating the potential of this platform for discovering DUB recruiters and facilitating the development of targeted protein stabilization therapeutics.