The TEAD transcription factors (TEAD1-4) are critical effectors of the Hippo pathway, forming active nuclear complexes with transcriptional co-activators YAP/TAZ to regulate cell growth/apoptosis pathways and control fundamental processes such as organ size. The Hippo pathway is frequently dysregulated in cancer, and the presence of druggable binding sites on TEADs make them attractive targets for development of small molecule inhibitors or degraders to therapeutically block TEAD function. We exploited a Targeted Protein Degradation (TPD) strategy for TEADs, aiming for improved isoform specificity and higher potency to block TEAD/co-factor interactions.
In this work, we describe the development of heterobifunctional molecules to enable TEAD1 degradation, by targeting a druggable lipidic pocket on TEAD1 (palimotylation, or P-site) and recruiting E3 ligases from the Inhibitor of Apoptosis proteins (IAPs) family. We identify and mechanistically characterise three unique series of TEAD1 degraders, which we term IAP recruiting protein degraders (IPDs). We report a detailed toolkit for structural, biophysical and cellular profiling, including the development of a cellular target engagement assay for the lipid pocket of TEAD1, IAP/TEAD1 ternary complex formation assay. We also evaluate the proteasome dependency and E3 ligase dependency using E3 ligase cIAP1 and XIAP KO cell lines and functional downstream profiling including TEAD isoform specificity, cell proliferation and Hippo pathway modulation.
Overall, our study provides essential resources for detailed characterization of IAP-recruiting degraders and important tools and learnings for bifunctional degraders targeted to the lipid pocket of TEADs.