Monoacidic Inhibitors of the Kelch-like ECH-Associated Protein 1: Nuclear Factor Erythroid 2‑Related Factor 2 (KEAP1:NRF2) Protein–Protein Interaction with High Cell Potency Identified by Fragment-Based Discovery

KEAP1
is the key regulator of the NRF2-mediated cytoprotective
response, and increasingly recognized as a target for diseases involving
oxidative stress. Pharmacological intervention has focused on molecules
that decrease NRF2-ubiquitination through covalent modification of
KEAP1 cysteine residues, but such electrophilic compounds lack selectivity
and may be associated with off-target toxicity. We report here the
first use of a fragment-based approach to directly target the KEAP1
Kelch–NRF2 interaction. X-ray crystallographic screening identified
three distinct “hot-spots” for fragment binding within
the NRF2 binding pocket of KEAP1, allowing progression of a weak fragment
hit to molecules with nanomolar affinity for KEAP1 while maintaining
drug-like properties. This work resulted in a promising lead compound
which exhibits tight and selective binding to KEAP1, and activates
the NRF2 antioxidant response in cellular and in vivo models, thereby providing a high quality chemical probe to explore
the therapeutic potential of disrupting the KEAP1–NRF2 interaction.