KEAP1/Nrf2 inhibitors(University of Copenhagen)

Nuclear factor-erythroid 2 related factor 2 (Nrf2) is a key regulator in cellular defense against oxidative stress. While flavonoids have been identified as Nrf2 activators by inhibiting Keap1-Nrf2 protein-protein interaction (PPI), their limited bioactivity presents significant challenges for therapeutic applications. To compensate for this shortcoming, 28 sulfonamide-flavonoid analogues targeting the Keap1-Nrf2 PPI were synthesized by a fragment-based approach. Among these, SG16, which incorporates a fluorine atom, exhibited potent Nrf2-activated capacity and notable anti-inflammatory properties. In AML12 hepatocytes, SG16 significantly enhanced the expression of antioxidant genes by promoting Nrf2 nuclear translocation. In an acute liver injury (ALI) mouse model, SG16 treatment led to a substantial, hundredfold upregulation of the cytoprotective gene HO-1 mRNA. Meanwhile, a dose-dependent decline in ALT, AST, and inflammatory cytokine levels was observed, reflecting improved liver function. Histopathological evaluations, including hematoxylin and eosin (HE) staining, TUNEL, myeloperoxidase (MPO) activity assessment, and F4/80 macrophage marker analysis, consistently demonstrated substantial attenuation of liver tissue damage following SG16 treatment. Moreover, Co-IP assays combined with experiments in Nrf2 knockout mice suggested that the novel sulfonamide-containing flavonoids are a promising class of Nrf2-targeted therapeutic candidates, warranting further exploration for oxidative stress-related disorders.

Inhibition of the protein-protein interaction between Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2) has been recognized as an attractive approach for treating oxidative stress-related diseases. Here, we present a new series of noncovalent Keap1-Nrf2 inhibitors developed by a conformational restriction strategy of our fluorenone-based compounds previously identified by fragment-based drug discovery. The design was guided by X-ray cocrystal structures, and the subsequent optimization process aimed at improving affinity, cellular activity, and metabolic stability. From the noncyclic compound 7 (K_i = 2.9 μM), a new series of tetrahydroisoquinoline-based Keap1 inhibitors with up to 223-fold improvement in binding affinity (57, K_i = 13 nM), better metabolic stability, and enhanced cellular activity was obtained. In addition, the compounds showed selectivity for the Keap1 Kelch domain across a panel of 15 homologous proteins. We thereby demonstrate the utility of cyclic rigidification in the design of potent and more drug-like Keap1-Nrf2 inhibitors.