Synthesis of a pseudo-disaccharide library and its application to the characterisation of the heparanase catalytic site

Structure-based lead optimization to improve potency and selectivity of a novel tetrahydroimidazo[1,2-a]pyridine-5-carboxylic acid series of heparanase-1 inhibitor

Heparanase-1 (HPSE1) is an endo-β-d-glucuronidase that is the only mammalian enzyme known to cleave heparan sulfate (HS) of heparan sulfate proteoglycans (HSPG), a key component of the glycocalyx layer of the vascular endothelium matrix. Inhibition of HPSE1 has therapeutic potential for cancer and proteinuric kidney diseases. We previously reported that 2 showed a moderate potency as an HPSE1 inhibitor and an issue of selectivity against exo-β-d-glucuronidase (GUSβ) and glucocerebrosidase (GBA) remained. A structure-based lead optimization of 2 using X-ray co-crystal structure analysis and fragment molecular orbital calculation resulted in 4e, which showed a more than 7-fold increase in HPSE1 inhibitory activity. The subsequent introduction of a methyl group into the 6-hydroxy group of 4e resulted in 18 with reduced inhibitory activities against GUSβ and GBA while maintaining the inhibitory activity against HPSE1. The inhibitory activities of 18 against serum HPSE1 in mice were significant and lasted for 4 h at doses of 3, 30, and 100 mg/kg. Compound 18 could be a novel lead compound for HPSE1 inhibitors with improved inhibitory activity against HPSE1 and increased HPSE1 selectivity over GUSβ and GBA.

Lead identification of novel tetrahydroimidazo[1,2-a]pyridine-5-carboxylic acid derivative as a potent heparanase-1 inhibitor

Heparanase-1 (HPSE1) is an endo-β-d-glucuronidase that cleaves heparan sulfate proteoglycans into short-chain heparan sulfates (HS). The inhibition of HPSE1 has therapeutic potential for proteinuric diseases such as nephrotic syndrome because increased HPSE1 expression is associated with the loss of HS in the glomerular basement membrane, leading to the development of proteinuria. The present study examined the generation of a lead compound focusing on chemical structures with a sugar moiety, such as glycosides and sugar analogs, taking their physical properties into consideration. Compound 10, an exo-β-d-glucuronidase (GUSβ) inhibitor, was found to have a weak inhibitory activity against endo-β-d-glucuronidase HPSE1. A structure-activity relationship study using the X-ray co-crystal structure of 10 and HPSE1 resulted in 12a, which showed a more than 14-fold increase in HPSE1 inhibitory activity compared with that of 10. Compound 12a could be a novel lead compound for the development of a potent HPSE1 inhibitor.

tert-Butyl(2-oxo-2H-pyran-5-yl)carbamate as the First Chameleon Diene Bearing an Electron-Donating Substituent

The 2(H)-pyran-2-one bearing electron-donating tert-butylcarbamate (BocNH-) group at the 5- position is a “chameleon” diene and undergoes efficient Diels–Alder cycloadditions with alkene dienophiles with both electron-rich and electron-deficient substituents. Cycloadditions afford the 5-substituted bicyclic lactone cycloadducts regardless of the electronic nature of the dienophile. However, cycloadditions with electronically matched electron-deficient dienophiles proceed faster than those with electronically mismatched electron-rich dienophiles.

Heparanase: Cloning, Function and Regulation

In 2019, we mark the 20th anniversary of the cloning of the human heparanase gene. Heparanase remains the only known enzyme to cleave heparan sulfate, which is an abundant component of the extracellular matrix. Thus, elucidating the mechanisms underlying heparanase expression and activity is critical to understanding its role in healthy and pathological settings. This chapter provides a historical account of the race to clone the human heparanase gene, describes the intracellular and extracellular function of the enzyme, and explores the various mechanisms regulating heparanase expression and activity at the gene, transcript, and protein level.

The Control of Heparanase Through the Use of Small Molecules

Despite the enormous progress made in recent years with antibodies, vaccines, antisense oligonucleotides, etc., the so-called "biological" approaches for tackling the control of various diseases, medicinal chemistry remains a bulwark to refer to for the development of new drugs. Also in the case of heparanase, medicinal chemistry has always been in the forefront to identify new inhibitors, through modification of natural macromolecules, e.g., sulfated polysaccharides like heparin, or of natural compounds isolated from bacteria or plants, or through rational design. In this chapter, the reader will find a detailed description of the most relevant small-molecule heparanase inhibitors reported so far in the scientific literature and in patent applications, with mention to the design strategy and to structure-activity relationships. Starting from heparanase inhibitors of natural origin and the attempts to improve their potency and selectivity, the reader will be guided through the major chemical classes of synthetic inhibitors, with representation of the structure of the most relevant compounds. The last paragraph is dedicated to a brief description of inhibitors that have reached clinical trials, highlighting their structure, mechanism, and improved derivatives.

Synthesis and Utility of 2,2-Dimethyl-2 H-pyrans: Dienes for Sequential Diels-Alder/Retro-Diels-Alder Reactions

The practical use of 2,2-dimethyl-2 H-pyrans as electron-rich dienes in sequential Diels-Alder/retro-Diels-Alder (DA/rDA) domino processes to generate aromatic platforms has been demonstrated. Different polysubstituted alkyl 2-naphthoates have been synthesized by the DA/rDA reaction of benzynes and 2,2-dimethyl-2 H-pyrans. The use of other activated alkynes allows the access of substituted alkyl benzoate derivatives.

Aspirin Inhibits Cancer Metastasis and Angiogenesis via Targeting Heparanase

Purpose: Recent epidemiological and clinical studies have suggested the benefit of aspirin for patients with cancer, which inspired increasing efforts to demonstrate the anticancer ability of aspirin and reveal the molecular mechanisms behind. Nevertheless, the anticancer activity and related mechanisms of aspirin remain largely unknown. This study aimed to confirm this observation, and more importantly, to investigate the potential target contributed to the anticancer of aspirin.Experimental Design: A homogeneous time-resolved fluorescence (HTRF) assay was used to examine the impact of aspirin on heparanase. Streptavidin pull-down, surface plasmon resonance (SPR) assay, and molecular docking were performed to identify heparanase as an aspirin-binding protein. Transwell, rat aortic rings, and chicken chorioallantoic membrane model were used to evaluate the antimetastasis and anti-angiogenesis effects of aspirin, and these phenotypes were tested in a B16F10 metastatic model, MDA-MB-231 metastatic model, and MDA-MB-435 xenograft model.Results: This study identified heparanase, an oncogenic extracellular matrix enzyme involved in cancer metastasis and angiogenesis, as a potential target of aspirin. We had discovered that aspirin directly binds to Glu225 region of heparanase and inhibits the enzymatic activity. Aspirin impeded tumor metastasis, angiogenesis, and growth in heparanase-dependent manner.Conclusions: In summary, this study has illustrated heparanase as a target of aspirin for the first time. It provides insights for a better understanding of the mechanisms of aspirin in anticancer effects, and offers a direction for the development of small-molecule inhibitors of heparanase. Clin Cancer Res; 23(20); 6267-78. ©2017 AACR.

Synthesis and conformational analysis of a simplified inositol-model of the Streptococcus pneumoniae 19F capsular polysaccharide repeating unit

Carbohydrate mimics have been studied for a long time as useful sugar substitutes, both in the investigation of biological events and in the treatment of sugar-related diseases. Here we report further evaluation of the capabilities of inositols as carbohydrate substitutes. The conformational features of an inositol-model of a simplified repeating unit corresponding to the capsular polysaccharide of Streptococcus pneumoniae 19F has been evaluated by computational analysis, and compared to the native repeating unit. The inositol mimic was synthesized, and its experimental spectroscopic data allowed for verification of the theoretical results.

Heparanase: a rainbow pharmacological target associated to multiple pathologies including rare diseases

In recent years, heparanase has attracted considerable attention as a promising target for innovative pharmacological applications. Heparanase is a multifaceted protein endowed with enzymatic activity, as an endo-β-D-glucuronidase, and nonenzymatic functions. It is responsible for the cleavage of heparan sulfate side chains of proteoglycans, resulting in structural alterations of the extracellular matrix. Heparanase appears to be involved in major human diseases, from the most studied tumors to chronic inflammation, diabetic nephropathy, bone osteolysis, thrombosis and atherosclerosis, in addition to more recent investigation in various rare diseases. The present review provides an overview on heparanase, its biological role, inhibitors and possible clinical applications, covering the latest findings in these areas.

Kinetic analysis and molecular modeling of the inhibition mechanism of roneparstat (SST0001) on human heparanase

Heparanase is a β-d-glucuronidase which cleaves heparan sulfate chains in the extracellular matrix and on cellular membranes. A dysregulated heparanase activity is intimately associated with cell invasion, tumor metastasis and angiogenesis, making heparanase an attractive target for the development of anticancer therapies. SST0001 (roneparstat; Sigma-Tau Research Switzerland S.A.) is a non-anticoagulant 100% N-acetylated and glycol-split heparin acting as a potent heparanase inhibitor, currently in phase I in advanced multiple myeloma. Herein, the kinetics of heparanase inhibition by roneparstat is reported. The analysis of dose-inhibition curves confirmed the high potency of roneparstat (IC₅₀ ≈ 3 nM) and showed, at higher concentrations, a Hill coefficient consistent with the engagement of two molecules of inhibitor. A homology model of human heparanase GS3 construct was built and used for docking experiments with inhibitor fragments. The model has high structural similarity with the recently reported crystal structure of human heparanase. Different interaction schemes are proposed, which support the hypothesis of a complex binding mechanism involving the recruitment of one or multiple roneparstat chains, depending on its concentration. In particular, docking solutions were obtained in which (i) a single roneparstat molecule interacts with both heparin-binding domains (HBDs) of heparanase or (ii) two fragments of roneparstat interact with either HBD-1 or HBD-2, consistent with the possibility of different inhibitor:enzyme binding stoichiometries. This study provides unique insights into the mode of action of roneparstat as well as clues of its interaction with heparanase at a molecular level, which could be exploited to design novel potential inhibitor molecules.