Discovery of novel Keap1-targeting hydrophobic tag (HyT) tethering degraders with potent Nrf2 activation activity

Targeted protein degradation has been emerging as a powerful strategy for modulating redox homeostasis. While CRBN-based PROTACs targeting Keap1 successfully promote Nrf2 activation, their translational potential is constrained by CRBN-associated resistance mechanisms and their large molecular size. Two series of hydrophobic tag-tethering degraders (HyTTDs) were designed based on the covalent Keap1 ligand CDDO. Degradation efficiency was evaluated in multiple cell lines, leading to the identification of NBE5, a norbornene-tag-containing degrader, as the most potent compound. NBE5 effectively degraded Keap1 and activated the Nrf2 antioxidant response. Mechanistic studies revealed a unique dual-pathway degradation process involving the ubiquitin-proteasome system and the autophagy-lysosome pathway. Our findings not only establish HyTTD as a viable degradation strategy for Keap1 but also identify NBE5 as a promising therapeutic candidate for redox-related pathologies such as inflammatory bowel disease.

Bardoxolone; Hydrophobic tag; Inflammatory bowel disease; Keap1; Nrf2 activation; Targeted protein degradation.