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Advances in Experimental Medicine and... 2020The heparan sulfate mimetic PI-88 (muparfostat) is a complex mixture of sulfated oligosaccharides that was identified in the late 1990s as a potent inhibitor of... (Review)
Review
The heparan sulfate mimetic PI-88 (muparfostat) is a complex mixture of sulfated oligosaccharides that was identified in the late 1990s as a potent inhibitor of heparanase. In preclinical animal models it was shown to block angiogenesis, metastasis and tumor growth, and subsequently became the first heparanase inhibitor to enter clinical trials for cancer. It progressed to Phase III trials but ultimately was not approved for use. Herein we summarize the preparation, physicochemical and biological properties of PI-88, and discuss preclinical/clinical and structure-activity relationship studies. In addition, we discuss the PI-88-inspired development of related HS mimetic heparanase inhibitors with improved properties, ultimately leading to the discovery of PG545 (pixatimod) which is currently in clinical trials.
Topics: Animals; Antineoplastic Agents; Glucuronidase; Heparitin Sulfate; Humans; Neoplasms; Neovascularization, Pathologic; Oligosaccharides; Structure-Activity Relationship
PubMed: 32274723
DOI: 10.1007/978-3-030-34521-1_19 -
Advances in Experimental Medicine and... 2020Heparanase is an endo-β-glucuronidase that cleaves at a limited number of internal sites the glycosaminoglycan heparan sulfate (HS). Heparanase enzymatic activity was... (Review)
Review
Heparanase is an endo-β-glucuronidase that cleaves at a limited number of internal sites the glycosaminoglycan heparan sulfate (HS). Heparanase enzymatic activity was first reported in 1975 and by 1983 evidence was beginning to emerge that the enzyme was a facilitator of tumor metastasis by cleaving HS chains present in blood vessel basement membranes and, thereby, aiding the passage of tumor cells through blood vessel walls. Due to a range of technical difficulties, it took another 16 years before heparanase was cloned and characterized in 1999 and a further 14 years before the crystal structure of the enzyme was solved. Despite these substantial deficiencies, there was steady progress in our understanding of heparanase long before the enzyme was fully characterized. For example, it was found as early as 1984 that activated T cells upregulate heparanase expression, like metastatic tumor cells, and the enzyme aids the entry of T cells and other leukocytes into inflammatory sites. Furthermore, it was discovered in 1989 that heparanase releases pre-existing growth factors and cytokines associated with HS in the extracellular matrix (ECM), the liberated growth factors/cytokines enhancing angiogenesis and wound healing. There were also the first hints that heparanase may have functions other than enzymatic activity, in 1995 it being reported that under certain conditions the enzyme could act as a cell adhesion molecule. Also, in the same year PI-88 (Muparfostat), the first heparanase inhibitor to reach and successfully complete a Phase III clinical trial was patented.Nevertheless, the cloning of heparanase (also known as heparanase-1) in 1999 gave the field an enormous boost and some surprises. The biggest surprise was that there is only one heparanase encoding gene in the mammalian genome, despite earlier research, based on substrate specificity, suggesting that there are at least three different heparanases. This surprising conclusion has remained unchanged for the last 20 years. It also became evident that heparanase is a family 79 glycoside hydrolase that is initially produced as a pro-enzyme that needs to be processed by proteases to form an enzymatically active heterodimer. A related molecule, heparanase-2, was also discovered that is enzymatically inactive but, remarkably, recently has been shown to inhibit heparanase-1 activity as well as acting as a tumor suppressor that counteracts many of the pro-tumor properties of heparanase-1.The early claim that heparanase plays a key role in tumor metastasis, angiogenesis and inflammation has been confirmed by many studies over the last 20 years. In fact, heparanase expression is enhanced in all major cancer types, namely carcinomas, sarcomas, and hematological malignancies, and correlates with increased metastasis and poor prognosis. Also, there is mounting evidence that heparanase plays a central role in the induction of inflammation-associated cancers. The enzymatic activity of heparanase has also emerged in unexpected situations, such as in the spread of HS-binding viruses and in Type-1 diabetes where the destruction of intracellular HS in pancreatic insulin-producing beta cells precipitates diabetes. But the most extraordinary recent discoveries have been with the realization that heparanase can exert a range of biological activities that are independent of its enzymatic function, most notably activation of several signaling pathways and being a transcription factor that controls methylation of histone tails. Collectively, these data indicate that heparanase is a truly multifunctional protein that has the additional property of cleaving HS chains and releasing from ECM and cell surfaces hundreds of HS-binding proteins with a plethora of functional consequences. Clearly, there are many unique features of this intriguing molecule that still remain to be explored and are highlighted in this Chapter.
Topics: Animals; Glucuronidase; Heparitin Sulfate; History, 20th Century; History, 21st Century; Humans; Neoplasms; Neovascularization, Pathologic
PubMed: 32274707
DOI: 10.1007/978-3-030-34521-1_3 -
British Journal of Pharmacology Jul 2023Heparanase is the only confirmed endoglycosidase that cleaves heparan sulfate (HS), a ubiquitous glycosaminoglycan with various essential roles in multiple pathological...
BACKGROUND AND PURPOSE
Heparanase is the only confirmed endoglycosidase that cleaves heparan sulfate (HS), a ubiquitous glycosaminoglycan with various essential roles in multiple pathological processes. Thus, the development of heparanase inhibitors has become an attractive strategy for drug discovery, especially in tumour therapy, in which HS mimetics are the most promising compounds. The various biological effects of heparanase also suggest a role for HS mimetics in many non-cancer indications, such as type 1 diabetes. However, the potential benefits of HS mimetics in obesity-related type 2 diabetes have not been elucidated.
EXPERIMENTAL APPROACH
In this study, we investigated muparfostat (PI-88), a developed HS mimetic currently enrolled in Phase III clinical trials, in obese mouse models and in vitro cultured murine hepatocytes.
KEY RESULTS
Daily administration of muparfostat for 4 weeks caused hyperlipidaemia and aggravated hepatic steatosis in obese mice models, but not in lean animals. In cultured hepatocytes, muparfostat did not alter lipid accumulation. Acute tests suggested that muparfostat binds to lipoprotein lipase in competition with HS on vascular endothelial cell surfaces, thereby reducing the degradation of circulating triglycerides by lipoprotein lipase and subsequent uptake of fatty acids into vascular endothelial cells and causing hyperlipidaemia. This hyperlipidaemia aggravates hepatic steatosis and causes liver injury in muparfostat-treated obese mice.
CONCLUSIONS AND IMPLICATIONS
The binding activity of HS mimetics to lipoprotein lipase should be investigated as an additional pharmacological effect during heparanase inhibitor drug discovery. This study also provides novel evidence for an increased risk of drug-induced liver injury in obese individuals.
Topics: Animals; Mice; Diabetes Mellitus, Type 2; Endothelial Cells; Fatty Liver; Heparitin Sulfate; Lipoprotein Lipase; Mice, Obese
PubMed: 36735592
DOI: 10.1111/bph.16047 -
The Journal of General Virology Oct 2017To establish the importance of virus-heparan sulfate (HS) interactions in virus infectivity, the poxvirus vaccinia virus (VACV) was used, as it binds HS and has both...
To establish the importance of virus-heparan sulfate (HS) interactions in virus infectivity, the poxvirus vaccinia virus (VACV) was used, as it binds HS and has both enveloped virus (EV) and non-enveloped mature virus (MV) forms. Initial studies showed that heparin inhibited plaque formation by both MV-rich WR and EV-rich IHD-J strains of VACV, with the EV-rich strain also losing trademark 'comet'-shaped plaques. However, using GFP-tagged EV and MV forms of VACV, based on IC values, heparin was 16-fold more effective at inhibiting the infectivity of the EV form compared to the MV form. Furthermore, 6- and -sulfation of the glucosamine residues of heparin was essential for inhibition of the infectivity of both VACV forms. Several low-molecular-weight HS mimetics were also shown to have substantial antiviral activity, with glycosidic linkages, chain length and monosaccharide backbone being important contributors towards anti-VACV activity. In fact, the -mannose-based sulfated oligosaccharide mixture, PI-88 (Muparfostat), was four-fold more active than heparin at inhibiting MV infections. Paradoxically, despite heparin and HS mimetics being potent inhibitors of VACV infections, removal of HS from cell surfaces by enzymatic or genetic means resulted in only a modest reduction in infectivity. It is unlikely that this paradox can be explained by steric hindrance, due to the low molecular weight of the HS mimetics (~1-2.5 kDa), with a more likely explanation being that binding of heparin/HS mimetics to free VACV initiates an abortive viral infection. Based on this explanation, HS mimetics have considerable potential as antivirals against HS-binding viruses.
PubMed: 28933686
DOI: 10.1099/jgv.0.000921 -
Glycobiology Oct 2018The heparan sulfate mimetic PI-88 is a complex mixture of sulfated oligosaccharides with anti-metastatic and anti-angiogenic activity due to its potent inhibition of...
The heparan sulfate mimetic PI-88 is a complex mixture of sulfated oligosaccharides with anti-metastatic and anti-angiogenic activity due to its potent inhibition of heparanase and heparan sulfate-dependent angiogenic growth factors. It was recently in Phase III clinical trials for postresection hepatocellular carcinoma. The major oligosaccharide constituents of PI-88 were prepared for the first time by sulfonation of individually purified phosphorylated oligosaccharides isolated from the PI-88 precursor. PI-88 and its components were subjected to detailed 1D and 2D NMR spectroscopic analysis. The spectra of the individual components greatly assisted the assignment of minor resonances in the 1H NMR spectrum of PI-88. The data also showed that the majority of the oligosaccharides in PI-88 are fully sulfated and that undersulfated species present are largely due to anomeric desulfation. The solution conformation of the phosphomannopentaose sulfate (major component) of PI-88 was then determined by a combination of molecular dynamics simulations and NOE measurements which may provide insights into its binding interactions with target proteins.
Topics: Carbohydrate Conformation; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Dynamics Simulation; Oligosaccharides
PubMed: 30053088
DOI: 10.1093/glycob/cwy068 -
Frontiers in Immunology 2020The heparan sulfate mimetic PG545 (pixatimod) is under evaluation as an inhibitor of angiogenesis and metastasis including in human clinical trials. We have examined the...
The heparan sulfate mimetic PG545 (pixatimod) is under evaluation as an inhibitor of angiogenesis and metastasis including in human clinical trials. We have examined the effects of PG545 on lymphocyte phenotypes and function. We report that PG545 treatment suppresses effector T cell activation and polarizes T cells away from Th17 and Th1 and toward Foxp3+ regulatory T cell subsets and . Mechanistically, PG545 inhibits Erk1/2 signaling, a pathway known to affect both T cell activation and subset polarization. Interestingly, these effects are also observed in heparanase-deficient T cells, indicating that PG545 has effects that are independent of its role in heparanase inhibition. Consistent with these findings, administration of PG545 in a Th1/Th17-dependent mouse model of a delayed-type hypersensitivity led to reduced footpad inflammation, reduced Th17 memory cells, and an increase in FoxP3+ Treg proliferation. PG545 also promoted Foxp3+ Treg induction by human T cells. Finally, we examined the effects of other heparan sulfate mimetics PI-88 and PG562 on lymphocyte polarization and found that these likewise induced Foxp3+ Treg but did not reduce Th17 numbers or improve delayed-type hypersensitivity in this model. Together, these data indicate that PG545 is a potent inhibitor of Th1/Th17 effector functions and inducer of FoxP3+ Treg. These findings may inform the adaptation of PG545 for clinical applications including in inflammatory pathologies associated with type IV hypersensitivity responses.
Topics: Angiogenesis Inhibitors; Animals; Bone Marrow Cells; Dendritic Cells; Forkhead Transcription Factors; Heparitin Sulfate; Humans; Hypersensitivity; Lymphocyte Activation; Lymphocytes; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Oligosaccharides; Primary Cell Culture; Saponins; T-Lymphocytes; T-Lymphocytes, Regulatory; Th17 Cells
PubMed: 32117279
DOI: 10.3389/fimmu.2020.00132 -
World Journal of Gastroenterology Aug 2014To demonstrate that administering heparanase inhibitor PI-88 at 160 mg/d is safe and promising in reducing hepatocellular carcinoma (HCC) recurrence for up to 3 year... (Observational Study)
Observational Study Randomized Controlled Trial
AIM
To demonstrate that administering heparanase inhibitor PI-88 at 160 mg/d is safe and promising in reducing hepatocellular carcinoma (HCC) recurrence for up to 3 year following curative resection.
METHODS
A total of 143 patients (83.1% of the 172 participants in the phase II study) participated in the follow-up study. Of these patients, 50 had received no treatment, 48 had received 160 mg/d PI-88, and 45 had received 250 mg/d PI-88 during the phase II trial. Safety parameters and the following efficacy endpoints were investigated: (1) time to recurrence; (2) disease-free survival; and (3) overall survival.
RESULTS
PI-88 at 160 mg/d delayed the onset and frequency of HCC recurrence, and provided a clinically significant survival advantage for up to 3 years after treatment compared with those of the control group: (1) the recurrence-free rate increased from 50% to 63%, and (2) time to recurrence at the 36th percentile was postponed by 78%. The efficacy of administering PI-88 at 250 mg/d was confounded by a high dropout rate (11 out of 54 patients). Additionally, subgroup analyses of patients with (1) multiple tumors or a single tumor ≥ 2 cm; and (2) hepatitis B or C revealed that administering PI-88 at 160 mg/d conferred the most significant survival advantage (56.8% improvement in disease-free survival, P = 0.045) for patients with both risk factors for recurrence.
CONCLUSION
Administering PI-88 at 160 mg/d is a safe and well-tolerated dosage that may confer significant clinical benefits for patients with HCC.
Topics: Adult; Aged; Antineoplastic Agents; Carcinoma, Hepatocellular; Chemotherapy, Adjuvant; Disease-Free Survival; Drug Administration Schedule; Enzyme Inhibitors; Female; Glucuronidase; Humans; Liver Neoplasms; Male; Middle Aged; Oligosaccharides; Risk Factors; Survival Analysis; Taiwan; Time Factors; Treatment Outcome
PubMed: 25170226
DOI: 10.3748/wjg.v20.i32.11384 -
Molecules (Basel, Switzerland) May 2021A convergent synthetic route to a tetrasaccharide related to PI-88, which allows the incorporation of a fluorescent BODIPY-label at the reducing-end, has been developed....
A convergent synthetic route to a tetrasaccharide related to PI-88, which allows the incorporation of a fluorescent BODIPY-label at the reducing-end, has been developed. The strategy, which features the use of 1,2-methyl orthoesters (MeOEs) as glycosyl donors, illustrates the usefulness of suitably-designed BODIPY dyes as glycosyl labels in synthetic strategies towards fluorescently-tagged oligosaccharides.
Topics: Antineoplastic Agents; Boron Compounds; Glycosylation; Oligosaccharides; Spectrometry, Fluorescence; Staining and Labeling; Stereoisomerism
PubMed: 34068920
DOI: 10.3390/molecules26102909 -
Antimicrobial Agents and Chemotherapy Feb 2016Herpes simplex virus (HSV) and many other viruses, including HIV, initiate infection of host cells by binding to glycosaminoglycan (GAG) chains of cell surface...
Herpes simplex virus (HSV) and many other viruses, including HIV, initiate infection of host cells by binding to glycosaminoglycan (GAG) chains of cell surface proteoglycans. Although GAG mimetics, such as sulfated oligo- and polysaccharides, exhibit potent antiviral activities in cultured cells, the prophylactic application of these inhibitors as vaginal microbicides failed to protect women upon their exposure to HIV. A possible explanation for this failure is that sulfated oligo- and polysaccharides exhibit no typical virucidal activity, as their interaction with viral particles is largely electrostatic and reversible and thereby vulnerable to competition with GAG-binding proteins of the genital tract. Here we report that the cholestanol-conjugated sulfated oligosaccharide PG545, but not several other sulfated oligosaccharides lacking this modification, exhibited virucidal activity manifested as disruption of the lipid envelope of HSV-2 particles. The significance of the virus particle-disrupting activity of PG545 was also demonstrated in experimental animals, as this compound, in contrast to unmodified sulfated oligosaccharide, protected mice against genital infection with HSV-2. Thus, PG545 offers a novel prophylaxis option against infections caused by GAG-binding viruses.
Topics: Administration, Intravaginal; Animals; Antiviral Agents; Disease Models, Animal; Female; Herpes Genitalis; Herpesvirus 2, Human; Lipids; Mice, Inbred C57BL; Oligosaccharides; Saponins; Virion
PubMed: 26643323
DOI: 10.1128/AAC.02132-15 -
Carbohydrate Research Jun 2022Convergent synthetic routes to PI-88 tetra- and pentasaccharide-component analogues, have been developed featuring regioselective glycosylations of mannose-polyol...
Convergent synthetic routes to PI-88 tetra- and pentasaccharide-component analogues, have been developed featuring regioselective glycosylations of mannose-polyol n-pentenyl glycosides (NPG) acceptors with 1,2-methyl orthoesters (MeOE) glycosyl donors.
Topics: Antineoplastic Agents; Glycosides; Mannose; Oligosaccharides
PubMed: 35461048
DOI: 10.1016/j.carres.2022.108557