Broad Target Screening Reveals Abundance of FKBP12-Based Molecular Glues in Focused Libraries

Competitive (nondegradative) molecular glues represent a promising drug modality that remains underexplored primarily due to the lack of adequate hit identification approaches. In this study, we screened our historically grown FKBP-focused library containing >1000 drug-like molecules to identify FKBP-assisted molecular glues targeting a diverse panel of 57 proteins. In addition to establishing a robust and generalizable screening approach, we discovered three novel FKBP-dependent molecular glues targeting PTPRN, BRD4BD2, and STAT4. Our results demonstrate that molecular glues are more common than previously thought and that they can be identified by repurposing existing focused libraries. An optimized, highly cooperative FKBP12-BRD4BD2 glue demonstrated the involvement of the BD2 pocket and exhibited selectivity over the closely related BD1 domain. Our results underscore the value of FKBP12-assisted molecular glues to target challenging proteins with the potential for high selectivity.