Synthesis of a Heparan Sulfate Mimetic Library Targeting FGF and VEGF via Click Chemistry on a Monosaccharide Template

From Cancer to COVID-19: A Perspective on Targeting Heparan Sulfate-Protein Interactions

Heparan sulfate (HS) is a complex, polyanionic polysaccharide ubiquitously expressed on cell surfaces and in the extracellular matrix. HS interacts with numerous proteins to mediate a vast array of biological and pathological processes. Inhibition of HS-protein interactions is thus an attractive approach for new therapeutic development for cancer and infectious diseases, including COVID-19; however, synthesis of well-defined native HS oligosaccharides remains challenging. This has aroused significant interest in the development of HS mimetics which are more synthetically tractable and have fewer side effects, such as undesired anticoagulant activity. This account provides a perspective on the design and synthesis of different classes of HS mimetics with useful properties, and the development of various assays and molecular modelling tools to progress our understanding of their interactions with HS-binding proteins.

Design, synthesis and in vitro biological evaluation of a novel class of anti-adenovirus agents based on 3-amino-1,2-propanediol

Nowadays there is not an effective drug for the treatment of infections caused by human adenovirus (HAdV) which supposes a clinical challenge, especially for paediatric and immunosuppressed patients. Here, we describe the design, synthesis and biological evaluation as anti-adenovirus agents of a new library (57 compounds) of diester, monoester and triazole derivatives based on 3-amino-1,2-propanediol skeleton. Seven compounds (17, 20, 26, 34, 44, 60 and 66) were selected based on their high anti-HAdV activity at low micromolar concentration (IC₅₀ from 2.47 to 5.75 µM) and low cytotoxicity (CC₅₀ from 28.70 to >200 µM). In addition, our mechanistic assays revealed that compounds 20 and 44 might be targeting specifically the HAdV DNA replication process, and compound 66 would be targeting HAdV E1A mRNA transcription. For compounds 17, 20, 34 and 60, the mechanism of action seems to be associated with later steps after HAdV DNA replication.

Heparin Binding Proteins as Therapeutic Target: An Historical Account and Current Trends

The polyanionic nature and the ability to interact with proteins with different affinities are properties of sulfated glycosaminoglycans (GAGs) that determine their biological function. In designing drugs affecting the interaction of proteins with GAGs the challenge has been to generate agents with high binding specificity. The example to emulated has been a heparin-derived pentasaccharide that binds to antithrombin-III with high affinity. However, the portability of this model to other biological situations is questioned on several accounts. Because of their structural flexibility, oligosaccharides with different sulfation and uronic acid conformation can display the same binding proficiency to different proteins and produce comparable biological effects. This circumstance represents a formidable obstacle to the design of drugs based on the heparin scaffold. The conceptual framework discussed in this article is that through a direct intervention on the heparin-binding functionality of proteins is possible to achieve a high degree of action specificity. This objective is currently pursued through two strategies. The first makes use of small molecules for which in the text we provide examples from past and present literature concerning angiogenic factors and enzymes. The second approach entails the mutagenesis of the GAG-binding site of proteins as a means to generate a new class of biologics of therapeutic interest.

Chitosan sulfate inhibits angiogenesis via blocking the VEGF/VEGFR2 pathway and suppresses tumor growth in vivo

SCTS inhibits neovascularization by blocking the VEGF/VEGFR2 signal pathway and exerts anti-tumor effects.

Sustained release of a synthetic structurally-tailored glycopolymer modulates endothelial cells for enhanced endothelialization of materials

GAG-mimicking polymers were prepared by a novel method allowing close control of structure and can be used as potent synthetic bioactive modifiers to promote endothelialization of materials.

Heparin Mimetics: Their Therapeutic Potential

Heparin mimetics are synthetic and semi-synthetic compounds that are highly sulfated, structurally distinct analogues of glycosaminoglycans. These mimetics are often rationally designed to increase potency and binding selectivity towards specific proteins involved in disease manifestations. Some of the major therapeutic arenas towards which heparin mimetics are targeted include: coagulation and thrombosis, cancers, and inflammatory diseases. Although Fondaparinux, a rationally designed heparin mimetic, is now approved for prophylaxis and treatment of venous thromboembolism, the search for novel anticoagulant heparin mimetics with increased affinity and fewer side effects remains a subject of research. However, increasingly, research is focusing on the non-anticoagulant activities of these molecules. Heparin mimetics have potential as anti-cancer agents due to their ability to: (1) inhibit heparanase, an endoglycosidase which facilitates the spread of tumor cells; and (2) inhibit angiogenesis by binding to growth factors. The heparin mimetic, PI-88 is in clinical trials for post-surgical hepatocellular carcinoma and advanced melanoma. The anti-inflammatory properties of heparin mimetics have primarily been attributed to their ability to interact with: complement system proteins, selectins and chemokines; each of which function differently to facilitate inflammation. The efficacy of low/non-anticoagulant heparin mimetics in animal models of different inflammatory diseases has been demonstrated. These findings, plus clinical data that indicates heparin has anti-inflammatory activity, will raise the momentum for developing heparin mimetics as a new class of therapeutic agent for inflammatory diseases.

Identification of gallic acid based glycoconjugates as a novel tubulin polymerization inhibitors

A novel class of gallic acid based glycoconjugates were designed and synthesized as potential anticancer agents. Among all the compounds screened, compound 2a showed potent anticancer activity against breast cancer cells. The latter resulted in tubulin polymerization inhibition and induced G2/M cell cycle arrest, generation of reactive oxygen species, mitochondrial depolarization and subsequent apoptosis in breast cancer cells. In addition, ultraviolet-visible spectroscopy and fluorescence quenching studies of the compound with tubulin confirmed direct interaction of compounds with tubulin. Molecular modeling studies revealed that it binds at the colchicine binding site in tubulin. Further, 2a also exhibited potent in vivo anticancer activity in LA-7 syngeneic rat mammary tumor model. Current data projects its strong candidature to be developed as anticancer agent.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Synthesis and evaluation of β-hydroxytriazoles and related compounds as antitubercular agents

A new series of β-hydroxytriazoles were synthesized and evaluated as Mycobacterium tuberculosis inhibitors. Our strategy implied the synthesis of alkyne precursors through a Barbier reaction between benzaldehydes and propargyl bromide followed by click chemistry to afford substituted β-hydroxyl benzyltriazoles. These compounds are also key intermediates either for oxidation reactions leading to α,β-diketotriazoles or for elimination reactions affording styryl triazoles. Evaluation of all new compounds for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv resulted in compounds with MIC up to 7 μM.

Angiogenic growth factors interactome and drug discovery: The contribution of surface plasmon resonance

Angiogenesis is implicated in several pathological conditions, including cancer, and in regenerative processes, including the formation of collateral blood vessels after stroke. Physiological angiogenesis is the outcome of a fine balance between the action of angiogenic growth factors (AGFs) and anti-angiogenic molecules, while pathological angiogenesis occurs when this balance is pushed toward AGFs. AGFs interact with multiple endothelial cell (EC) surface receptors inducing cell proliferation, migration and proteases upregulation. On the contrary, free or extracellular matrix-associated molecules inhibit angiogenesis by sequestering AGFs (thus hampering EC stimulation) or by interacting with specific EC receptors inducing apoptosis or decreasing responsiveness to AGFs. Thus, angiogenesis results from an intricate network of interactions among pro- and anti-angiogenic molecules, EC receptors and various modulators. All these interactions represent targets for the development of pro- or anti-angiogenic therapies. These aims call for suitable technologies to study the countless interactions occurring during neovascularization. Surface plasmon resonance (SPR) is a label-free optical technique to study biomolecular interactions in real time. It has become the golden standard technology for interaction analysis in biomedical research, including angiogenesis. From a survey of the literature it emerges that SPR has already contributed substantially to the better understanding of the neovascularization process, laying the basis for the decoding of the angiogenesis "interactome" and the identification of "hub molecules" that may represent preferential targets for an efficacious modulation of angiogenesis. Here, the still unexploited full potential of SPR is enlightened, pointing to improvements in its use for a deeper understanding of the mechanisms of neovascularization and the identification of novel anti-angiogenic drugs.