Discovery and development of small-molecule heparanase inhibitors

Maculopathy after long-term use of fondaparinux, a heparin mimetic and heparanase inhibitor

Purpose

To report maculopathy associated with the long-term use of fondaparinux, a heparin mimetic and inhibitor of the extracellular matrix enzyme, heparanase.

Observations

A 41-year-old woman receiving thrice weekly injections of fondaparinux as prophylaxis against deep vein thrombosis for 9 years noticed gray spots in her vision without metamorphopsias. On exam, there was bilateral altered macular pigmentation with speckled hyperpigmentation. Optical coherence tomography revealed irregular thickening of the retinal pigment epithelium. Blue autofluorescence photography demonstrated symmetric well-defined plaques of hyper-and hypoautofluorescence similar to those described in patients chronically treated with pentosan polysulfate (PPS). Review of 13 years of outside medical records confirmed no prior treatment with PPS. Two years before, optical coherence tomography (OCT) done as part of routine eye examination showed early pigmentary changes which were not felt to be clinically significant. Inherited retinal gene panel testing and mitochondrial DNA testing did not reveal pathogenic variants associated with pattern dystrophies. The maculopathy was attributed to fondaparinux due to a pharmacologic effect shared with PPS of heparanase inhibition. Thirteen months after stopping fondaparinux, there was a significant reduction in macular pigmentary changes and improvement in outer retinal abnormalities on OCT.

Conclusions and importance

Fondaparinux is structurally and functionally related to PPS, which is also a heparin mimetic and heparanase inhibitor. Both drugs are now associated with phenotypically similar disruptions of the macular retinal pigment epitheliopathy. Although used for different clinical indications, both fondaparinux and PPS are sulfated oligosaccharides related to heparin that bind and inhibit heparanase, a critical enzyme in the extracellular matrix. This case is relevant for research into pharmacologic uses of heparanase inhibitors and monitoring for retinal disease in patients treated with them.

Design Principle of Heparanase Inhibitors: A Combined In Vitro and In Silico Study

Heparanase (HPSE) is an enzyme that cleaves heparan sulfate (HS) side chains from heparan sulfate proteoglycans (HSPGs). Overexpression of HPSE is associated with various types of cancer, inflammation, and immune disorders, making it a highly promising therapeutic target. Previously developed HPSE inhibitors that have advanced to clinical trials are polysaccharide-derived compounds or their mimetics; however, these molecules tend to suffer from poor bioavailability, side effects via targeting other saccharide binding proteins, and heterogeneity. Few small-molecule inhibitors have progressed to the preclinical or clinical stages, leaving a gap in HPSE drug discovery. In this study, a novel small molecule that can inhibit HPSE activity was discovered through high-throughput screening (HTS) using an ultrasensitive HPSE probe. Computational tools were employed to elucidate the mechanisms of inhibition. The essential structural features of the hit compound were summarized into a structure-activity relationship (SAR) theory, providing insights into the future design of HPSE small-molecule inhibitors.

Chemical toolbox to interrogate Heparanase-1 activity

The development of a robust chemical toolbox to interrogate the activity of heparanase-1 (HPSE-1), an endo-β-d-glucuronidase and the only known enzyme that cleaves heparan sulfate (HS), has become critically important. The primary function of HPSE-1, cleaving HS side chains from heparan sulfate proteoglycans (HSPGs), regulates the integrity of the extracellular matrix (ECM) and the bioavailability of active, heparan sulfate-binding partners such as enzymes, growth factors, chemokines, and cytokines. HPSE-1 enzymatic activity is strictly regulated and has been found to play fundamental roles in pathophysiological processes. HPSE-1 is significantly overexpressed under various conditions including cancer, metastasis, angiogenesis, and inflammation, making HPSE-1 a promising therapeutic and diagnostic target. Chemical tools that can detect and image HPSE-1 activity in vitro and/or in vivo can help drive the discovery of novel and efficacious anti-HPSE-1 drugs, investigate the basic biology of HPSE-1, and help serve as a diagnostic tool in clinical applications. Here, we will give an overview of the common chemical tools to detect HPSE-1 activity and highlight the novel heparanase probes recently developed in our lab.

Investigation of inhibitory effect of sulfated chitosan oligomer on human heparanase enzyme: in silico and in vitro studies

Deaths from cancer are widespread worldwide and the numbers continue to increase day by day. During the disease progression of cancer in cells, many of its metabolic activities change. Increased heparanase enzyme release is just one example. Following heparanase enzyme activity, many molecules interact with the remodeling of glycosaminoglycan structures, which triggers the release of different enzymes, cytokines, and growth factors, including fibroblast growth factors (FGF1 and FGF2), vascular endothelial growth factor (VEGF), hepatocyte growth factor, transforming growth factor β and platelet-derived growth factor. These are the most important factors in metastasis due to the formation of new vascular structures caused by those elements. To reduce tumor growth and metastasis, various drugs have been designed by modifying chitosan and its derivatives. In this study, we used chitosan oligomer (A), sulfated chitosan oligomer (ShCsO) (B), heparin (C), phosphate monomer (D1) of PI-88 and sulfate monomer (D2) of PI-88 as heparanase inhibitors. We modified the chitosan oligomer with chlorosulfonic acid to synthesize ShCsO to investigate its inhibitory effects on human serum heparanase. Also examined were molecular docking; molecular dynamics (MD); adsorption, distribution, metabolism, elimination and toxicity (ADMET); and target prediction. ShCsO decreased enzyme activity at a concentration of 0.0001 mg/mL. The docking scores of A, B and C from in silico studies were -6.254, -6.936 and -6.980 kcal/mol, respectively, and the scores for the two different PI-88 monomers were -5.741 and -5.824 kcal/mol. These results show that ShCsO may be a potential drug candidate for treating cancer.