Aryl Aldehyde-Anchored Small Molecules Recruit FBXO22 for Targeted Degradation of NSD2.

Targeted protein degradation (TPD) has emerged as a transformative strategy in drug discovery, yet the repertoire of E3 ligase recruiters remains limited. Here, we report the discovery of an aldehyde-anchored PROTAC that covalently engages the E3 ligase FBXO22 to induce degradation of the histone methyltransferase NSD2 and CDK12. Competitive electrophile screening identified a phenyl aldehyde warhead as optimal, with SAR studies revealing that degradation is highly sensitive to the steric and electronic environment of the aldehyde moiety. The lead degrader, T9, effectively and selectively induces NSD2 degradation across multiple cancer cell lines. Mechanistic investigations confirmed that degradation is dependent on FBXO22, the ubiquitin-proteasome system, and the neddylation pathway, with mutagenesis identifying Cys326 as the critical residue for covalent engagement. This work establishes a stable covalent ligand for FBXO22, expanding chemical space of PROTAC design by introducing an accessible aldehyde-based E3 ligase ligand with broad potential for protein degradation.