Phenyl Bis-Sulfonamide Keap1-Nrf2 Protein–Protein Interaction Inhibitors with an Alternative Binding Mode

Abstract

Inhibitors of Kelch-like ECH-associated protein 1 (Keap1) increase the activity of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) by stalling its ubiquitination and degradation. This enhances the expression of genes encoding proteins involved in drug detoxification, redox homeostasis, and mitochondrial function. Nrf2 activation offers a potential therapeutic approach for conditions including Alzheimer’s and Parkinson’s diseases, vascular inflammation, and chronic obstructive airway disease. Non-electrophilic Keap1-Nrf2 protein–protein interaction (PPI) inhibitors may have improved toxicity profiles and different pharmacological properties to cysteine-reactive electrophilic inhibitors. Here, we describe and characterize a series of phenyl bis-sulfonamide PPI inhibitors that bind to Keap1 at submicromolar concentrations. Structural studies reveal that the compounds bind to Keap1 in a distinct “peptidomimetic” conformation that resembles the Keap1-Nrf2 ETGE peptide complex. This is different to other small molecule Keap1-Nrf2 PPI inhibitors, including bicyclic aryl bis-sulfonamides, offering a starting point for new design approaches to Keap1 inhibitors.

Advances and challenges in therapeutic targeting of NRF2

“…A recent independent assessment questioned the characterisation of more than half of 19 reported KEAP1-NRF2 PPI inhibitors [29], highlighting the need for careful selection of such compounds for use in mechanistic and translational studies. Curiously, the recently described phenyl bis-sulfonamide PPI inhibitors bind to KEAP1-Kelch in a distinct 'peptidomimetic' conformation that resembles the KEAP1-Kelch : NRF2-ETGE peptide complex [30]. In addition, small-molecule PPI inhibitors with in vitro affinities for KEAP1 in the nanomolar range have been identified using structure-based virtual screening [31].…”

Medicinal Chemistry Insights into the Development of Small-Molecule Kelch-Like ECH-Associated Protein 1-Nuclear Factor Erythroid 2-Related Factor 2 (Keap1–Nrf2) Protein–Protein Interaction Inhibitors

“…Most importantly, the cellular potency of 24 was also found to be superior to that of 9 , particularly with respect to the induction of the transcription of Nrf2-controlled genes at a concentration of 100 μM in NCM460D cells . Among the aforementioned Keap1–Nrf2 inhibitors, compound 20 was selected for further structural biology study due to its fresh Keap1-interactive skeleton and midnanomolar binding activity (ITC: K d = 0.50 μM) . With the aim of exploring the exact binding mode, the crystal complex of Keap1 with 20 was successfully obtained.…”

“…The following cell-based biological evaluation confirmed that 20 could markedly induce the enzyme activity of NQO1 and elevate the mRNA levels of Nrf2 downstream genes in Hepa1c1c7 cells. Additionally, SAR studies revealed that introduction of a m -methoxy substitution to the benzyloxy group was also tolerated, and this transformation caused a slight increase in the induction of NQO1 enzyme activity …”

The Role of Organosulfur Compounds as Nrf2 Activators and Their Antioxidant Effects

“…The addition of o -methyl group increases hydrophobic interactions and hydrophobic groups improve the Keap1–Nrf2 protein–protein interaction (PPI) inhibitory effect of sulfonamide derivatives [ 94 ]. Recently, Georgakopoulos et al [ 114 ] reported a non-electrophilic phenyl bis-sulfonamide ( 16 ) as an effective inhibitor of Keap1–Nrf2 protein–protein interaction having an alternative binding mode. Compound 16 binds and interacts with Keap1 cells and improves the expression of Nrf2-mediated genes such as NQO1, HO-1, and GST.…”