Design, Synthesis, and Structure–Activity Relationships of Indoline-Based Kelch-like ECH-Associated Protein 1-Nuclear Factor (Erythroid-Derived 2)-Like 2 (Keap1-Nrf2) Protein–Protein Interaction Inhibitors

Abstract

The Keap1 (Kelch-like ECH-associated protein 1)-Nrf2 (nuclear factor erythroid 2-related factor 2)-ARE (antioxidant response element) pathway is the major defending mechanism against oxidative stresses, and directly disrupting the Keap1-Nrf2 protein–protein interaction (PPI) has been an attractive strategy to target oxidative stress-related diseases, including cardiovascular diseases. Here, we describe the design, synthesis, and structure–activity relationships (SARs) of indoline-based compounds as potent Keap1-Nrf2 PPI inhibitors. Comprehensive SAR analysis and thermodynamics-guided optimization identified 19a as the most potent inhibitor in this series, with an IC50 of 22 nM in a competitive fluorescence polarization assay. Further evaluation indicated the proper drug-like properties of 19a. Compound 19a dose-dependently upregulated genes and protein level of Nrf2 as well as its downstream markers and showed protective effects against lipopolysaccharide-induced injury in both H9c2 cardiac cells and mouse models. Collectively, we reported here a novel indoline-based Keap1-Nrf2 PPI inhibitor as a potential cardioprotective agent.

Deconstructing Noncovalent Kelch-like ECH-Associated Protein 1 (Keap1) Inhibitors into Fragments to Reconstruct New Potent Compounds

“…To date, several classes of small-molecule inhibitors have been designed to noncovalently inhibit the PPI of the Keap1 Kelch domain and the Nrf2 Neh2 motifs, ,− including several recently developed compounds. − However, the Neh2-binding pocket of the Keap1 Kelch domain is large (550–780 Å) and contains multiple arginine residues, thus representing a challenging target for drug development . This is reflected in the reported Keap1–Nrf2 PPI inhibitors, which generally have high molecular weights and contain carboxylic acids leading to poor cell and CNS permeability.…”

Discovery of MK-4688: an Efficient Inhibitor of the HDM2–p53 Protein–Protein Interaction

“…In general, the development of orally bioavailable, drug-like PPI inhibitors has been challenging. The large, flat, and hydrophobic surfaces inherent to the interface between proteins can lead to the design of inhibitors that are larger and more lipophilic than typical oral drugs. , These molecular properties have been associated with high doses and variable pharmacokinetics (PK) in the clinic, and a reduced probability of successfully reaching the market. − In recent years, there has been significant progress in the discovery of PPI inhibitors with increasing “drug-likeness” that highlights how specific features inherent to some PPI interfaces (hot spots) can lead to higher probability of success. ,− The HDM2–p53 interaction is primarily mediated through a hydrophobic interface, where residues Phe19, Trp23, and Leu26 located on an N-terminal α helix of p53 fit into known hydrophobic pockets on the HDM2 protein surface . Furthermore, it has been shown that inhibitors can interrupt the HDM2–p53 PPI by binding within these hot-spot hydrophobic pockets. − Despite this feature of the PPI interface, the pioneering HDM2 inhibitors in clinical development displayed high lipophilicity, a high molecular weight (MW), and required high doses for efficacy that limited their progression.…”

Biliverdin Reductase A Protects Lens Epithelial Cells against Oxidative Damage and Cellular Senescence in Age-Related Cataract

“…In response to oxidants, Nrf2 is released from Keap-1 and translocated into the nucleus. As a result, Nrf2 combined with ARE and promotes the transcription of various detoxification and antioxidant enzymes (e.g., HO-1, NADPH: quinone oxidoreductase 1 (NQO-1), glutamate-cysteine ligase-modifier subunits (GCLM), and SOD) [ 45 , 46 ]. Previously, we verified the cytoprotective role of Nrf2 via inhibiting endoplasmic reticulum stress in LECs [ 47 ].…”