Design, Synthesis and Biological Evaluation of 1,4-Benzenesulfonamide Derivatives as Glyoxalase I Inhibitors

Background

Glyoxalase system is one of the defense cellular mechanisms that protect cells against endogenous harmful metabolites, mainly methylglyoxal (MG), through conversion of cytotoxic methylglyoxal into the non-toxic lactic acid. Glyoxalase system comprises of two enzymes glyoxalase I, glyoxalase II, and a catalytic amount of reduced glutathione. Cancerous cells overexpress glyoxalase I, making it a target for cancer therapy. Many studies have been conducted to identify potent Glx-I inhibitors.

Methods

Aiming to discover and develop novel Glx-I inhibitors, a series of 1,4-benzenesulfonamide derivatives were designed, synthesized, and biologically evaluated in vitro against human Glx-I enzyme. Seventeen compounds were designed based on the hit compound that was obtained from searching the National Cancer Institute (NCI) database. The synthesis of the target compounds (13-29) was accomplished utilizing an azo coupling reaction of aniline derivatives and activated substituted aromatic compounds. To understand the binding mode of the active compounds at the active site of Glx-I, docking studies were performed.

Results

Structure activity relationship (SAR) studies were accomplished which led to the identification of several compounds that showed potent inhibitory activity with IC50 values below 10 μM. Among the compounds tested, compounds (E)-2-hydroxy-5-((4-sulfamoylphenyl)diazenyl)benzoic acid (26) and (E)-4-((8-hydroxyquinolin-5-yl)diazenyl) benzenesulfonamide (28) displayed potent Glx-I inhibitory activity with IC50 values of 0.39 μM and 1.36 µM, respectively. Docking studies of compounds 26 and 28 were carried out to illustrate the binding mode of the molecules into the Glx-I active site.

Conclusion

Our results show that compounds 26 and 28 displayed potent Glx-I inhibitory activity and can bind the Glx-I well. These findings should lead us to discover new classes of compounds with better Glx-I inhibition.

Chemoproteomic Profiling of a Pharmacophore-Focused Chemical Library

Pharmacophore-focused chemical libraries are continuously being created in drug discovery programs, yet screening assays to maximize the usage of such libraries are not fully explored. Here, we report a chemical proteomics approach to reutilizing a focused chemical library of 1,800 indole-containing molecules for discovering uncharacterized ligand-protein pairs. Gel-based protein profiling of the library using a photo-affinity indole probe 1 enabled us to find new ligands for glyoxalase 1 (Glo1), an enzyme involved in the detoxification of methylglyoxal. Structure optimization of the ligands yielded an inhibitor for Glo1 (9). Molecule 9 increased the cellular methylglyoxal levels in human cells and suppressed the osteoclast formation of mouse bone marrow-derived macrophages. X-ray structure analyses revealed that the molecule lies at a site abutting the substrate binding site, which is consistent with the enzyme kinetic profile of 9. Overall, this study exemplifies how chemical proteomics can be used to exploit existing focused chemical libraries.

Recent advances in the discovery and development of glyoxalase I inhibitors

Glyoxalase I (GLO1) is a homodimeric Zn²⁺-metalloenzyme that catalyses the transformation of methylglyoxal (MG) to d-lacate through the intermediate S-d-lactoylglutathione. Growing evidence indicates that GLO1 has been identified as a potential target for the treatment cancer and other diseases. Various inhibitors of GLO1 have been discovered or developed over the past several decades including natural or natural product-based inhibitors, GSH-based inhibitors, non-GSH-based inhibitors, etc. The aim of this review is to summarize recent achievements of concerning discovery, design strategies, as well as pharmacological aspects of GLO1 inhibitors with the target of promoting their development toward clinical application.

Targeting Metalloenzymes for Therapeutic Intervention

Metalloenzymes are central to a wide range of essential biological activities, including nucleic acid modification, protein degradation, and many others. The role of metalloenzymes in these processes also makes them central for the progression of many diseases and, as such, makes metalloenzymes attractive targets for therapeutic intervention. Increasing awareness of the role metalloenzymes play in disease and their importance as a class of targets has amplified interest in the development of new strategies to develop inhibitors and ultimately useful drugs. In this Review, we provide a broad overview of several drug discovery efforts focused on metalloenzymes and attempt to map out the current landscape of high-value metalloenzyme targets.