Novel Benzazole Derivatives Endowed with Potent Antiheparanase Activity

Role of a Novel Heparanase Inhibitor on the Balance between Apoptosis and Autophagy in U87 Human Glioblastoma Cells

BACKGROUND

Heparanase (HPSE) is an endo-β-glucuronidase that cleaves heparan sulfate side chains, leading to the disassembly of the extracellular matrix, facilitating cell invasion and metastasis dissemination. In this research, we investigated the role of a new HPSE inhibitor, RDS 3337, in the regulation of the autophagic process and the balance between apoptosis and autophagy in U87 glioblastoma cells.

METHODS

After treatment with RDS 3337, cell lysates were analyzed for autophagy and apoptosis-related proteins by Western blot.

RESULTS

We observed, firstly, that LC3II expression increased in U87 cells incubated with RDS 3337, together with a significant increase of p62/SQSTM1 levels, indicating that RDS 3337 could act through the inhibition of autophagic-lysosomal flux of LC3-II, thereby leading to accumulation of lipidated LC3-II form. Conversely, the suppression of autophagic flux could activate apoptosis mechanisms, as revealed by the activation of caspase 3, the increased level of cleaved Parp1, and DNA fragmentation.

CONCLUSIONS

These findings support the notion that HPSE promotes autophagy, providing evidence that RDS 3337 blocks autophagic flux. It indicates a role for HPSE inhibitors in the balance between apoptosis and autophagy in U87 human glioblastoma cells, suggesting a potential role for this new class of compounds in the control of tumor growth progression.

Discovery and development of small-molecule heparanase inhibitors

Heparanase-1 (HPSE) is a promising yet challenging therapeutic target. It is the only known enzyme that is responsible for cleavage of heparan sulfate (HS) side chains from heparan sulfate proteoglycans (HSPGs), and is the key enzyme involved in the remodeling and degradation of the extracellular matrix (ECM). Overexpression of HPSE is found in various types of diseases, including cancers, inflammations, diabetes, and viral infections. Inhibiting HPSE can restore ECM functions and integrity, making the development of HPSE inhibitors a highly sought-after topic. So far, all HPSE inhibitors that have entered clinical trials belong to the category of HS mimetics, and no small-molecule or drug-like HPSE inhibitors have made similar progress. None of the HS mimetics have been approved as drugs, with some clinical trials discontinued due to poor bioavailability, side effects, and unfavorable pharmacokinetics characteristics. Small-molecule HPSE inhibitors are, therefore, particularly appealing due to their drug-like characteristics. Advances in the chemical spaces and drug design technologies, including the increasing use of in vitro and in silico screening methods, have provided new opportunities in drug discovery. This article aims to review the discovery and development of small-molecule HPSE inhibitors via screening strategies to shed light on the future endeavors in the development of novel HPSE inhibitors.

Complex Inhibitory Mechanism of Glycomimetics with Heparanase

Heparanase (HPSE) is the only mammalian endo-β-glucuronidase known to catalyze the degradation of heparan sulfate. Dysfunction of HPSE activity has been linked to several disease states, resulting in HPSE becoming the target of numerous therapeutic programs, yet no drug has passed clinical trials to date. Pentosan polysulfate sodium (PPS) is a heterogeneous, FDA-approved drug for the treatment of interstitial cystitis and a known HPSE inhibitor. However, due to its heterogeneity, characterization of its mechanism of HPSE inhibition is challenging. Here, we show that inhibition of HPSE by PPS is complex, involving multiple overlapping binding events, each influenced by factors such as oligosaccharide length and inhibitor-induced changes in the protein secondary structure. The present work advances our molecular understanding of the inhibition of HPSE and will aid in the development of therapeutics for the treatment of a broad range of pathologies associated with enzyme dysfunction, including cancer, inflammatory disease, and viral infections.

4-O-Substituted Glucuronic Cyclophellitols are Selective Mechanism-Based Heparanase Inhibitors

Degradation of the extracellular matrix (ECM) supports tissue integrity and homeostasis, but is also a key factor in cancer metastasis. Heparanase (HPSE) is a mammalian ECM-remodeling enzyme with β-D-endo-glucuronidase activity overexpressed in several malignancies, and is thought to facilitate tumor growth and metastasis. By this virtue, HPSE is considered an attractive target for the development of cancer therapies, yet to date no HPSE inhibitors have progressed to the clinic. Here we report on the discovery of glucurono-configured cyclitol derivatives featuring simple substituents at the 4-O-position as irreversible HPSE inhibitors. We show that these compounds, unlike glucurono-cyclophellitol, are selective for HPSE over β-D-exo-glucuronidase (GUSB), also in platelet lysate. The observed selectivity is induced by steric and electrostatic interactions of the substituents at the 4-O-position. Crystallographic analysis supports this rationale for HPSE selectivity, and computer simulations provide insights in the conformational preferences and binding poses of the inhibitors, which we believe are good starting points for the future development of HPSE-targeting antimetastatic cancer drugs.

Glioblastoma: Current Status, Emerging Targets, and Recent Advances

Glioblastoma (GBM) is a highly malignant brain tumor characterized by a heterogeneous population of genetically unstable and highly infiltrative cells that are resistant to chemotherapy. Although substantial efforts have been invested in the field of anti-GBM drug discovery in the past decade, success has primarily been confined to the preclinical level, and clinical studies have often been hampered due to efficacy-, selectivity-, or physicochemical property-related issues. Thus, expansion of the list of molecular targets coupled with a pragmatic design of new small-molecule inhibitors with central nervous system (CNS)-penetrating ability is required to steer the wheels of anti-GBM drug discovery endeavors. This Perspective presents various aspects of drug discovery (challenges in GBM drug discovery and delivery, therapeutic targets, and agents under clinical investigation). The comprehensively covered sections include the recent medicinal chemistry campaigns embarked upon to validate the potential of numerous enzymes/proteins/receptors as therapeutic targets in GBM.

Identification of Novel Potential Heparanase Inhibitors Using Virtual Screening

Heparanase (HPSE) is a mammalian endo-β-D-glucuronidase that cleaves heparan sulphate (HS) side chains of heparin sulphate proteoglycans (HSPG), a class of molecules composed of repeating polysulfated disaccharide units of glucosamine and hexuronic acid residues. HPSE controls the availability of growth factors, chemokines, lipoproteins and other bioactive molecules by degrading HS into smaller fractions, allowing the release of saccharide fragments that activate a plethora of signaling processes. HPSE overexpression has been correlated with tumor survival and metastasis as well as several diseases associated with chronic inflammation, including the ongoing COVID-19 pandemic caused by SARS-CoV-2. Thus, the search for molecules that could potentially inhibit HPSE has become increasingly relevant in the clinic. In this study, we have integrated a strategy that combines virtual screening and molecular docking of publicly available chemical databases to identify small compounds that can be developed into novel HPSE inhibitors. Structural rationalization of the interactions previously reported compounds led us to identify promising unexplored chemotypes. Here we show that these novel potential HPSE inhibitors present optimized in silico druggability and docking properties and may serve as pharmacological tools for the treatment of chronic and infectious diseases associated with chronic inflammation.

Synthesis of novel glycolipid mimetics of heparan sulfate and their application in colorectal cancer treatment in a mouse model

Heparan sulfate (HS) is a highly sulfated natural carbohydrate that plays crucial roles in cancer, inflammation, and angiogenesis. Heparanase (HPSE) is the sole HS degrading endoglycosidase that cleaves HS at structure‐dependent sites along the polysaccharide chain. Overexpression of HPSE by cancer cells correlates with increased tumor size and enhanced metastasis. Previously we have shown that a tetramer HS mimetic is a potent HPSE inhibitor displaying remarkable anticancer activity in vivo. Building on that work, we report the synthesis and testing of a novel library of single entity trimer glycolipid mimetics that effectively inhibit HPSE at low nanomolar concentrations. A lipophilic arm was introduced to assess whether an improvement of pharmacokinetics and plasma residence time would offset the reduction in charge and multivalency. Preclinical tests in a mouse syngeneic model showed effective tumor growth inhibition by the tetramer but not the trimer glycomimetic.

Structural Insights into Pixatimod (PG545) Inhibition of Heparanase, a Key Enzyme in Cancer and Viral Infections

Pixatimod (PG545), a heparan sulfate (HS) mimetic and anticancer agent currently in clinical trials, is a potent inhibitor of heparanase. Heparanase is an endo‐β‐glucuronidase that degrades HS in the extracellular matrix and basement membranes and is implicated in numerous pathological processes such as cancer and viral infections, including SARS−CoV‐2. To understand how PG545 interacts with heparanase, we firstly carried out a conformational analysis through a combination of NMR experiments and molecular modelling which showed that the reducing end β‐D‐glucose residue of PG545 adopts a distorted conformation. This was followed by docking and molecular dynamics simulations to study the interactions of PG545 with heparanase, revealing that PG545 is able to block the active site by binding in different conformations, with the cholestanol side‐chain making important hydrophobic interactions. While PG545 blocks its natural substrate HS from binding to the active site, small synthetic heparanase substrates are only partially excluded, and thus pentasaccharide or larger substrates are preferred for assaying this class of inhibitor. This study provides new insights for the design of next‐generation heparanase inhibitors and substrates.

Upregulation of ERK-EGR1-heparanase axis by HDAC inhibitors provides targets for rational therapeutic intervention in synovial sarcoma

BACKGROUND

Synovial sarcoma (SS) is an aggressive soft tissue tumor with limited therapeutic options in advanced stage. SS18-SSX fusion oncogenes, which are the hallmarks of SS, cause epigenetic rewiring involving histone deacetylases (HDACs). Promising preclinical studies supporting HDAC targeting for SS treatment were not reflected in clinical trials with HDAC inhibitor (HDACi) monotherapies. We investigated pathways implicated in SS cell response to HDACi to identify vulnerabilities exploitable in combination treatments and improve the therapeutic efficacy of HDACi-based regimens.

METHODS

Antiproliferative and proapoptotic effects of the HDACi SAHA and FK228 were examined in SS cell lines in parallel with biochemical and molecular analyses to bring out cytoprotective pathways. Treatments combining HDACi with drugs targeting HDACi-activated prosurvival pathways were tested in functional assays in vitro and in a SS orthotopic xenograft model. Molecular mechanisms underlying synergisms were investigated in SS cells through pharmacological and gene silencing approaches and validated by qRT-PCR and Western blotting.

RESULTS

SS cell response to HDACi was consistently characterized by activation of a cytoprotective and auto-sustaining axis involving ERKs, EGR1, and the β-endoglycosidase heparanase, a well recognized pleiotropic player in tumorigenesis and disease progression. HDAC inhibition was shown to upregulate heparanase by inducing expression of the positive regulator EGR1 and by hampering negative regulation by p53 through its acetylation. Interception of HDACi-induced ERK-EGR1-heparanase pathway by cell co-treatment with a MEK inhibitor (trametinib) or a heparanase inhibitor (SST0001/roneparstat) enhanced antiproliferative and pro-apoptotic effects. HDAC and heparanase inhibitors had opposite effects on histone acetylation and nuclear heparanase levels. The combination of SAHA with SST0001 prevented the upregulation of ERK-EGR1-heparanase induced by the HDACi and promoted caspase-dependent cell death. In vivo, the combined treatment with SAHA and SST0001 potentiated the antitumor efficacy against the CME-1 orthotopic SS model as compared to single agent administration.

CONCLUSIONS

The present study provides preclinical rationale and mechanistic insights into drug combinatory strategies based on the use of ERK pathway and heparanase inhibitors to improve the efficacy of HDACi-based antitumor therapies in SS. The involvement of classes of agents already clinically available, or under clinical evaluation, indicates the transferability potential of the proposed approaches.

Effect of heparanase inhibitor on tissue factor overexpression in platelets and endothelial cells induced by anti-β2-GPI antibodies

BACKGROUND

Anti-phospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity associated with the presence of "anti-phospholipid antibodies." Thrombosis may be the result of a hypercoagulable state related to activation of endothelial cells and platelets by anti-β2-glycoprotein I (β2-GPI) antibodies. Anti-β2-GPI antibodies induce a proinflammatory and procoagulant phenotype in these cells that, after activation, express tissue factor (TF), the major initiator of the clotting cascade, playing a role in thrombotic manifestations. Moreover, TF expression may also be induced by heparanase, an endo-β-D-glucuronidase, that generates heparan sulfate fragments, regulating inflammatory responses.

OBJECTIVES

In this study we analyzed, in human platelets and endothelial cells, the effect of a new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivative (RDS3337), able to inhibit heparanase activity, on signal transduction pathways leading to TF expression triggered by anti-β2-GPI.

METHODS

Platelets and endothelial cells were incubated with affinity purified anti-β2-GPI after pretreatment with RDS3337. Cell lysates were analyzed for phospho-interleukin-1 receptor-associated kinase 1 (IRAK1), phospho-p65 nuclear factor kappa B (NF-κB) and TF by western blot. In addition, platelet activation and secretion by ATP release dosage were evaluated.

RESULTS

IRAK phosphorylation and consequent NF-κB activation, as well as TF expression triggered by anti-β2-GPI treatment were significantly prevented by previous pretreatment with RDS3337. In the same vein, pretreatment with RDS3337 prevented platelet aggregation and ATP release triggered by anti-β2-GPI antibodies.

CONCLUSION

These findings support the view of heparanase involvement in a prothrombotic state related to APS syndrome, suggesting a novel target to regulate overexpression of procoagulant protein(s).

Anti-Tumoral Effects of a (1H-Pyrrol-1-yl)Methyl-1H-Benzoimidazole Carbamate Ester Derivative on Head and Neck Squamous Carcinoma Cell Lines

Nocodazole is an antineoplastic agent that exerts its effects by depolymerizing microtubules. Herein we report a structural analog of nocodazole, a (1H-pyrrol-1-yl)methyl-1H-benzoimidazole carbamate ester derivative, named RDS 60. We evaluated the antineoplastic properties of RDS 60 in two human head and neck squamous cell carcinoma (HNSCC) cell lines and we found that this compound significantly inhibited replication of both HNSCC cell lines without inducing any important cytotoxic effect on human dermal fibroblasts and human keratinocytes. The treatment of HNSCC cell lines with 1 μM RDS 60 for 24 h stopped development of normal bipolar mitotic spindles and, at the same time, blocked the cell cycle in G2/M phase together with cytoplasmic accumulation of cyclin B1. Consequently, treatment with 2 μM RDS 60 for 24 h induced the activation of apoptosis in both HNSCC cell lines. Additionally, RDS 60 was able to reverse the epithelial-mesenchymal transition and to inhibit cell migration and extracellular matrix infiltration of both HNSCC cell lines. The reported results demonstrate that this compound has a potent effect in blocking cell cycle, inducing apoptosis and inhibiting cell motility and stromal invasion of HNSCC cell lines. Therefore, the ability of RDS 60 to attenuate the malignancy of tumor cells suggests its potential role as an interesting and powerful tool for new approaches in treating HNSCC.

Computational Investigation Identified Potential Chemical Scaffolds for Heparanase as Anticancer Therapeutics

Heparanase (Hpse) is an endo-β-D-glucuronidase capable of cleaving heparan sulfate side chains. Its upregulated expression is implicated in tumor growth, metastasis and angiogenesis, thus making it an attractive target in cancer therapeutics. Currently, a few small molecule inhibitors have been reported to inhibit Hpse, with promising oral administration and pharmacokinetic (PK) properties. In the present study, a ligand-based pharmacophore model was generated from a dataset of well-known active small molecule Hpse inhibitors which were observed to display favorable PK properties. The compounds from the InterBioScreen database of natural (69,034) and synthetic (195,469) molecules were first filtered for their drug-likeness and the pharmacophore model was used to screen the drug-like database. The compounds acquired from screening were subjected to molecular docking with Heparanase, where two molecules used in pharmacophore generation were used as reference. From the docking analysis, 33 compounds displayed higher docking scores than the reference and favorable interactions with the catalytic residues. Complex interactions were further evaluated by molecular dynamics simulations to assess their stability over a period of 50 ns. Furthermore, the binding free energies of the 33 compounds revealed 2 natural and 2 synthetic compounds, with better binding affinities than reference molecules, and were, therefore, deemed as hits. The hit compounds presented from this in silico investigation could act as potent Heparanase inhibitors and further serve as lead scaffolds to develop compounds targeting Heparanase upregulation in cancer.

New classes of potent heparanase inhibitors from ligand-based virtual screening

Heparanase is a validated target in cancer therapy and a potential target for several inflammatory pathologies. A ligand-based virtual screening of commercial libraries was performed to expand the chemical space of small-molecule inhibitors. The screening was based on similarity with known inhibitors and was performed in several runs, starting from literature compounds and progressing through newly discovered inhibitors. Among the fifty-five tested compounds, nineteen had IC₅₀ values lower than 5 µM and some showed remarkable potencies. Importantly, tere- and isophthalamides derivatives belong to new structural classes of heparanase inhibitors and some of them showed enzyme affinities (61 and 63, IC₅₀ = 0.32 and 0.12 µM, respectively) similar to those of the most potent small-molecule inhibitors reported so far. Docking studies provided a comprehensive binding hypothesis shared by compounds with significant structural diversity. The most potent inhibitors reduced cell invasiveness and inhibited the expression of proangiogenic factors in tumour cell lines.

Heparanase Inhibitors in Cancer Progression: Recent Advances

BACKGROUND

An endo-β-glucuronidase enzyme, Heparanase (HPSE), degrades the side chains of polymeric heparan sulfate (HS), a glycosaminoglycan formed by alternate repetitive units of D-glucosamine and D-glucuronic acid/L-iduronic acid. HS is a major component of the extracellular matrix and basement membranes and has been implicated in processes of the tissue's integrity and functional state. The degradation of HS by HPSE enzyme leads to conditions like inflammation, angiogenesis, and metastasis. An elevated HPSE expression with a poor prognosis and its multiple roles in tumor growth and metastasis has attracted significant interest for its inhibition as a potential anti-neoplastic target.

METHODS

We reviewed the literature from journal publication websites and electronic databases such as Bentham, Science Direct, PubMed, Scopus, USFDA, etc., about HPSE, its structure, functions, and role in cancer.

RESULTS

The present review is focused on Heparanase inhibitors (HPIns) that have been isolated from natural resources or chemically synthesized as new therapeutics for metastatic tumors and chronic inflammatory diseases in recent years. The recent developments made in the HPSE structure and function are also discussed, which can lead to the future design of HPIns with more potency and specificity for the target.

CONCLUSION

HPIns can be a better target to be explored against various cancers.

Ultrasensitive small molecule fluorogenic probe for human heparanase

Heparanase (HPA) is a critical enzyme involved in the remodeling of the extracellular matrix (ECM), and its elevated expression has been linked with diseases such as various types of cancer and inflammation. The detection of heparanase enzymatic activity holds tremendous value in the study of the cellular microenvironment, and search of molecular therapeutics targeting heparanase, however, no structurally defined probes are available for the detection of heparanase activity. Here we present the development of the first ultrasensitive fluorogenic small-molecule probe for heparanase enzymatic activity via tuning the electronic effect of the substrate. The probe exhibits a 756-fold fluorescence turn-on response in the presence of human heparanase, allowing one-step detection of heparanase activity in real-time with a picomolar detection limit. The high sensitivity and robustness of the probe are exemplified in a high-throughput screening assay for heparanase inhibitors.

An efficient synthesis of novel di-heterocyclic benzazole derivatives and evaluation of their antiproliferative activities

A series of unsymmetrical nine di-heterocyclic compounds of benzazole derivatives were synthesized at one step via cyclization reaction. The compounds evaluated for in vitro cytotoxic activity against A549, A498, HeLa, and HepG2 cancer cell lines. The biological evaluation results show that 23, 26 and 29 exhibit better activity against HepG2 and HeLa cancer cell lines. Compound 23 also showed good activity against A549, and A498 cancer cell lines. The analogs were further performed molecular docking studies against human cytochrome P450 2C8 monooxygenase enzyme, calculated some theoretical quantum parameters, ADMET descriptor and molecular electrostatic potential analysis. The strategy applied in this research work may act as a perspective for the rational design of potential anticancer drugs. Communicated by Ramaswamy H. Sarma.

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.

Density Functional Theory Study on the Mechanism of Iridium-Catalyzed Benzylamine ortho C-H Alkenylation with Ethyl Acrylate

Iridium-catalyzed oxidative o-alkenylation of benzylamines with acrylates was enabled by the directing group pentafluorobenzoyl (PFB). Density functional theory calculations were performed to explore the detailed reaction mechanism. The calculated results reveal that N-deprotonation prior to C-H activation is favored over direct C-H activation. Moreover, C-H activation is reversible and not the rate-determining step, which has been supported by the experimental observation. The regio- and stereoselectivity of ethyl acrylate insertion are controlled by the steric effect and the carbon atom with a larger orbital coefficient of the π* antibonding orbital in the nucleophilic attack, respectively. The migratory insertion of ethyl acrylate is computationally found to be rate-determining for the whole catalytic cycle. Finally, the seven-membered ring intermediate IM11 undergoes a sequential N-protonation and β-H elimination with the assistance of AcOH, rather than β-H elimination and reductive elimination proposed experimentally, to afford the o-alkenylated product. IM11 is unable to directly cyclize through C-N reductive elimination because both sp³-hybridized N and C atoms are unfavorable for N-C reductive elimination. The origin of the directing group PFB preventing the product and intermediates undergoing aza-Michael addition has been explained.

Heparanase: A Potential Therapeutic Target in Sarcomas

Sarcomas comprise a heterogeneous group of rare malignancies of mesenchymal origin including more than 70 subtypes. They may arise in muscle, bone, cartilage and other connective tissues. Their high histological and genetic heterogeneity makes diagnosis and treatment very challenging. Deregulation of heparanase has been found in several sarcoma subtypes and high expression levels have been correlated with poor prognosis in Ewing's sarcoma and osteosarcoma. Altered expression of specific heparan sulfate proteoglycans and heparan sulfate biosynthetic enzymes has also been observed. Advances in molecular pathogenesis of sarcomas have evidenced the critical role of several heparan sulfate binding growth factors and receptor tyrosine kinases, highly interconnected with the microenvironment, in sustaining tumor growth and progression. Interference with heparanase/heparan sulfate functions represents a potential therapeutic approach in sarcoma. In this chapter, we summarize the current knowledge about the biological significance of heparanase expression and its potential as a therapeutic target in subtypes of both soft tissue and bone sarcomas. Particular emphasis is given to the involvement of heparan sulfate proteoglycans and their synthesizing and modifying enzymes in bone physiology and disorders leading up to the pathobiology of bone sarcomas. The chapter also describes the cooperation between exostin loss-of-function and heparanase upregulation in hereditary Multiple Osteochondroma syndrome as a paradigmatic example of constitutive alteration of the heparanase/heparan sulfate proteoglycan system which may contribute to progression to malignant secondary chondrosarcoma. Preclinical evidence of the role of heparanase as a promising therapeutic target in various sarcoma subtypes is finally resumed.

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.

Heparanase: A Challenging Cancer Drug Target

Heparanase has been viewed as a promising anti-cancer drug target for almost two decades, but no anti-heparanase therapy has yet reached the clinic. This endoglycosidase is highly expressed in a variety of malignancies, and its high expression is associated with greater tumor size, more metastases, and a poor prognosis. It was first described as an enzyme cleaving heparan sulfate chains of proteoglycans located in extracellular matrices and on cell surfaces, but this is not its only function. It is a multi-functional protein with activities that are enzymatic and non-enzymatic and which take place both outside of the cell and intracellularly. Knowledge of the crystal structure of heparanase has assisted the interpretation of earlier structure-function studies as well as in the design of potential anti-heparanase agents. This review re-examines the various functions of heparanase in light of the structural data. The functions of the heparanase variant, T5, and structure and functions of heparanase-2 are also examined as these heparanase related, but non-enzymatic, proteins are likely to influence the in vivo efficacy of anti-heparanase drugs. The anti-heparanase drugs currently under development predominately focus on inhibiting the enzymatic activity of heparanase, which, in the absence of inhibitors with high clinical efficacy, prompts a discussion of whether this is the best approach. The diversity of outcomes attributed to heparanase and the difficulties of unequivocally determining which of these are due to its enzymatic activity is also discussed and leads us to the conclusion that heparanase is a valid, but challenging drug target for cancer.

Tandem Double-Cross-Coupling/Hydrothiolation Reaction of 2-Sulfenyl Benzimidazoles with Boronic Acids

A new tandem palladium-catalyzed reaction involving a Suzuki-Miyaura coupling, a desulfenylative coupling, and a hydrothiolation of a triple bond is reported. Notably, the desulfenylative coupling occurs without copper(I) assistance and the hydrothiolation is totally regioselective and stereoselective. The overall process results in the double incorporation of the boronic acid and the reincorporation of the sulfenyl moiety into the product structure. Starting from 2-(bromobenzylsulfenyl)-1-propargyl benzimidazoles, the transformation led to variously substituted benzimidazoles bearing a stereodefined alkenyl sulfide.

Targeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds

Heparanase is an endoglycosidase involved in remodeling the extracellular matrix and thereby in regulating multiple cellular processes and biological activities. It cleaves heparan sulfate (HS) side chains of HS proteoglycans into smaller fragments and hence regulates tissue morphogenesis, differentiation, and homeostasis. Heparanase is overexpressed in various carcinomas, sarcomas, and hematological malignancies, and its upregulation correlates with increased tumor size, tumor angiogenesis, enhanced metastasis, and poor prognosis. In contrast, knockdown or inhibition of heparanase markedly attenuates tumor progression, further underscoring the potential of anti-heparanase therapy. Heparanase inhibitors were employed to interfere with tumor progression in preclinical studies, and selected heparin mimetics are being examined in clinical trials. However, despite tremendous efforts, the discovery of heparanase inhibitors with high clinical benefit and minimal adverse effects remains a therapeutic challenge. This review discusses the key roles of heparanase in cancer progression focusing on the status of natural, chemically modified, and synthetic heparanase inhibitors in various types of malignancies.

Iridium-Catalyzed Benzylamine C-H Alkenylation Enabled by Pentafluorobenzoyl as the Directing Group

The first iridium-catalyzed oxidative alkeynylation of benzylamines with acrylates enabled by a new directing group pentafluorobenzoyl has been developed. The reaction proceeded efficiently in the presence of silver acetate as oxidant and chlorobenzene as solvent. A good range of benzylamines could be selectively monoalkenylated without interfering with further aza-Michael addition. The kinetic isotope effect experiments showed that C-H activation is not the rate-limiting step. In addition, a five-membered iridacycle species was isolated and established as the possible key intermediate.

Novel Symmetrical Benzazolyl Derivatives Endowed with Potent Anti-Heparanase Activity

Heparanase is the only mammalian endo-β-d-glucuronidase involved in a variety of major diseases. The up-regulation of heparanase expression increases tumor size, angiogenesis, and metastasis, representing a validated target in the anti-cancer field. To date, only a few small-molecule inhibitors have been described, but none have gotten through pre-clinical development. Previously, we explored 2-(4-(4-(bromo-methoxybenzamido)benzylamino)phenyl) benzazole derivatives as anti-heparanase agents, proposing this scaffold for development of broadly effective heparanase inhibitors. Herein, we report an extended investigation of new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivatives, proving that symmetrical compounds are more effective than asymmetrical analogues, with the most-potent compound, 7g, being active at nanomolar concentration against heparanase. Molecular docking studies were performed on the best-acting compounds 5c and 7g to rationalize their interaction with the enzyme. Moreover, invasion assay confirmed the anti-metastatic potential of compounds 5c, 7a, and 7g, proving the inhibition of the expression of proangiogenic factors in tumor cells.