Inhibition of hepatitis C virus replication by semi-synthetic derivatives of glycopeptide antibiotics

Emerging Roles of Glycopeptide Antibiotics: Moving beyond Gram-Positive Bacteria

Glycopeptides, a class of cell wall biosynthesis inhibitors, have been the antibiotics of choice against drug-resistant Gram-positive bacterial infections. Their unique mechanism of action involving binding to the substrate of cell wall biosynthesis and substantial longevity in clinics makes this class of antibiotics an attractive choice for drug repurposing and reprofiling. However, resistance to glycopeptides has been observed due to alterations in the substrate, cell wall thickening, or both. The emergence of glycopeptide resistance has resulted in the development of synthetic and semisynthetic glycopeptide analogues to target acquired resistance. Recent findings demonstrate that these derivatives, along with some of the FDA approved glycopeptides have been shown to have antimicrobial activity against Gram-negative bacteria, Mycobacteria, and viruses thus expanding their spectrum of activity across the microbial kingdom. Additional mechanisms of action and identification of novel targets have proven to be critical in broadening the spectrum of activity of glycopeptides. This review focuses on the applications of glycopeptides beyond their traditional target group of Gram-positive bacteria. This will aid in making the scientific community aware about the nontraditional activity profiles of glycopeptides, identify the existing loopholes, and further explore this antibiotic class as a potential broad-spectrum antimicrobial agent.

Glycopeptides as Potential Interventions for COVID-19

Coronavirus disease 2019 (COVID-19), an infectious disease that primarily attacks the human pulmonary system, is caused by a viral strain called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The outbreak emerged from Wuhan, China, and later spread throughout the world. Until the first week of May 2020, over 3.7 million cases had been reported worldwide and more than 258,000 had died due to the disease. So far, off label use of various drugs has been tried in many clinical settings, however, at present, there is no vaccine or antiviral treatment for human and animal coronaviruses. Therefore, repurposing of the available drugs may be promising to control emerging infections of SARS-COV2; however, new interventions are likely to require months to years to develop. Glycopeptides, which are active against gram-positive bacteria, have demonstrated significant activity against viral infections including SARS-COV and MERS-COV and have a high resemblance of sequence homology with SARS-COV2. Recent in vitro studies have also shown promising activities of aglycon derivative of glycopeptides and teicoplanin against SARS-COV2. Hydrophobic aglycon derivatives and teicoplanin, with minimal toxicity to human cell lines, inhibit entry and replication of SARS-COV2. These drugs block proteolysis of polyprotein a/b with replicase and transcription domains. Teicoplanin use was associated with complete viral clearance in a cohort of patients with severe COVID-19 symptoms. This review attempts to describe the activity, elucidate the possible mechanisms and potential clinical applications of existing glycopeptides against corona viruses, specifically SARS-COV2.

COVID-19 Therapeutic Options Under Investigation

Since its emergence in China in December 2019, COVID-19 has quickly spread around the globe causing a pandemic. Vaccination or the development of herd immunity seems the only way to slow down the spread of the virus; however, both are not achievable in the near future. Therefore, effective treatments to mitigate the burden of this pandemic and reduce mortality rates are urgently needed. Preclinical and clinical studies of potential antiviral and immunomodulatory compounds and molecules to identify safe and efficacious therapeutics for COVID-19 are ongoing. Two compounds, remdesivir, and dexamethasone have been so far shown to reduce COVID-19-associated death. Here, we provide a review of the potential therapeutic agents being considered for the treatment and management of COVID-19 patients.

Reprogramming of the Antibacterial Drug Vancomycin Results in Potent Antiviral Agents Devoid of Antibacterial Activity

Influenza A and B viruses are a global threat to human health and increasing resistance to the existing antiviral drugs necessitates new concepts to expand the therapeutic options. Glycopeptide derivatives have emerged as a promising new class of antiviral agents. To avoid potential antibiotic resistance, these antiviral glycopeptides are preferably devoid of antibiotic activity. We prepared six vancomycin aglycone hexapeptide derivatives with the aim of obtaining compounds having anti-influenza virus but no antibacterial activity. Two of them exerted strong and selective inhibition of influenza A and B virus replication, while antibacterial activity was successfully eliminated by removing the critical N-terminal moiety. In addition, these two molecules offered protection against several other viruses, such as herpes simplex virus, yellow fever virus, Zika virus, and human coronavirus, classifying these glycopeptides as broad antiviral molecules with a favorable therapeutic index.

Main trends in the design of semi-synthetic antibiotics of a new generation

This review summarizes main advances achieved by Russian researchers in the synthesis and characterization of semi-synthetic antibiotics of a new generation in the period from 2004 to 2019. The following classes of compounds are considered as the basis for modification: polycyclic antibacterial glycopeptides of the vancomycin group, classical macrolides, antifungal polyene macrolides, the antitumour antibiotic olivomycin A, antitumour anthracyclines and broad-spectrum antibiotics, in particular, oligomycin A, heliomycin and some other. Main trends in the design of modern anti-infective and antitumour agents over this period are considered in relation to original natural antibiotics, which have been independently discovered by Russian researchers. It is shown that a new type of hybrid structures can, in principle, be synthesized based on glycopeptides, macrolides and other antibiotics, including heterodimers containing a new benzoxaborole pharmacophore. The review addresses the influence of the length of the spacer between two antibiotic molecules on the biological activity of hybrid structures. A combination of genetic engineering techniques and methods of organic synthesis is shown to be useful for the design of new potent antifungal antibiotics based on polyenes of the amphotericin B group. Many new semi-synthetic analogues exhibit important biological properties, such as a broad spectrum of activity and low toxicity. Emphasis is given to certain aspects related to investigation of a broad range of biological activity and mechanisms of action of new derivatives.

The bibliography includes 101 references.

Hydrophobic Derivatives of Glycopeptide Antibiotics as Inhibitors of Protein Kinases

As key regulators of cell signaling, protein kinases (PKs) are attractive targets for therapeutic intervention in a variety of diseases. Herein, we report for the first time the inhibitory activity of polycyclic peptides, particularly, derivatives of glycopeptide antibiotics teicoplanin and eremomycin, against a panel of 12 recombinant human protein kinases and two protein kinases (CK1 and CK2) isolated from rat liver. Several of the investigated compounds inhibited various PKs with IC50 values below 10 μM and caused >90% suppression of the enzyme activity at 10 µM concentration. Kinetic analysis of the protein kinase CK2α inhibition by the teicoplanin aglycon analogue (7) demonstrated the non-competitive mechanism of inhibition (with regard to ATP). Interestingly, the inhibitory activity of some investigated compounds correlated with the earlier described antiviral activity against HIV, HCV, and other corona- and flaviviruses.

Structure-activity relationship studies of lipophilic teicoplanin pseudoaglycon derivatives as new anti-influenza virus agents

Six series of semisynthetic lipophilic glycopeptide antibiotic derivatives were evaluated for in vitro activity against influenza A and B viruses. The new teicoplanin pseudoaglycon-derived lipoglycopeptides were prepared by coupling one or two side chains to the N-terminus of the glycopeptide core, using various conjugation methods. Three series of derivatives bearing two lipophilic groups were synthesized by attaching bis-alkylthio maleimides directly or through linkers of different lengths to the glycopeptide. Access to the fourth and fifth series of compounds was achieved by click chemistry, introducing single alkyl/aryl chains directly or through a tetraethylene glycol linker to the same position. A sixth group of semisynthetic derivatives was obtained by sulfonylation of the N-terminus. Of the 42 lipophilic teicoplanin pseudoaglycon derivatives tested, about half showed broad activity against influenza A and B viruses, with some of them having reasonable or no cytotoxicity. Minor differences in the side chain length as well as lipophilicity appeared to have significant impact on antiviral activity and cytotoxicity. Several lipoglycopeptides were also found to be active against human coronavirus.

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Multiple series of lipophilic teicoplanin pseudoaglycon derivatives were prepared.

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Alkyl or aryl chains were coupled to the N-terminus by various conjugation methods.

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The activity of new antibiotic derivatives was evaluated against influenza viruses.

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Half of the 42 derivatives showed high activity against influenza A and B viruses.

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The length and lipophilicity of the side chains influence the antiviral activity.

Glycopeptide Antibiotics Potently Inhibit Cathepsin L in the Late Endosome/Lysosome and Block the Entry of Ebola Virus, Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

Ebola virus infection can cause severe hemorrhagic fever with a high mortality in humans. The outbreaks of Ebola viruses in 2014 represented the most serious Ebola epidemics in history and greatly threatened public health worldwide. The development of additional effective anti-Ebola therapeutic agents is therefore quite urgent. In this study, via high throughput screening of Food and Drug Administration-approved drugs, we identified that teicoplanin, a glycopeptide antibiotic, potently prevents the entry of Ebola envelope pseudotyped viruses into the cytoplasm. Furthermore, teicoplanin also has an inhibitory effect on transcription- and replication-competent virus-like particles, with an IC₅₀ as low as 330 nm. Comparative analysis further demonstrated that teicoplanin is able to block the entry of Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS) envelope pseudotyped viruses as well. Teicoplanin derivatives such as dalbavancin, oritavancin, and telavancin can also inhibit the entry of Ebola, MERS, and SARS viruses. Mechanistic studies showed that teicoplanin blocks Ebola virus entry by specifically inhibiting the activity of cathepsin L, opening a novel avenue for the development of additional glycopeptides as potential inhibitors of cathepsin L-dependent viruses. Notably, given that teicoplanin has routinely been used in the clinic with low toxicity, our work provides a promising prospect for the prophylaxis and treatment of Ebola, MERS, and SARS virus infection.

Teicoplanin inhibits Ebola pseudovirus infection in cell culture

There is currently no approved antiviral therapy for treatment of Ebola virus disease. To discover readily available approved drugs that can be rapidly repurposed for treatment of Ebola virus infections, we screened 1280 FDA-approved drugs and identified glycopeptide antibiotic teicoplanin inhibiting Ebola pseudovirus infection by blocking virus entry in the low micromolar range. Teicoplanin could be evaluated further and incorporated into ongoing clinical studies.

Dengue virus entry and trafficking: perspectives as antiviral target for prevention and therapy

ABSTRACT 

Dengue virus (DENV) is the etiological agent of the most important human viral infection transmitted by mosquitoes in the world. In spite of the serious health threat that dengue represents, at present there are no vaccine or antiviral agents available and treatment of patients consists of supportive therapy. This review will focus on the process of DENV entry into the host cell as a potential target for antiviral therapy. The recent advances in the knowledge of viral and cellular molecules and mechanisms involved in binding, internalization and trafficking of DENV into the host cell until virion uncoating are discussed, together with an overview of the strategies and compounds evaluated for development of antiviral agents targeted to DENV entry.

Flaviviruses, an expanding threat in public health: focus on dengue, West Nile, and Japanese encephalitis virus

The flaviviruses dengue, West Nile, and Japanese encephalitis represent three major mosquito-borne viruses worldwide. These pathogens impact the lives of millions of individuals and potentially could affect non-endemic areas already colonized by mosquito vectors. Unintentional transport of infected vectors (Aedes and Culex spp.), traveling within endemic areas, rapid adaptation of the insects into new geographic locations, climate change, and lack of medical surveillance have greatly contributed to the increase in flaviviral infections worldwide. The mechanisms by which flaviviruses alter the immune and the central nervous system have only recently been examined despite the alarming number of infections, related deaths, and increasing global distribution. In this review, we will discuss the expansion of the geographic areas affected by flaviviruses, the potential threats to previously unaffected countries, the mechanisms of pathogenesis, and the potential therapeutic interventions to limit the devastating consequences of these viruses.

Artemisinin analogues as potent inhibitors of in vitro hepatitis C virus replication

We reported previously that Artemisinin (ART), a widely used anti-malarial drug, is an inhibitor of in vitro HCV subgenomic replicon replication. We here demonstrate that ART exerts its antiviral activity also in hepatoma cells infected with full length infectious HCV JFH-1. We identified a number of ART analogues that are up to 10-fold more potent and selective as in vitro inhibitors of HCV replication than ART. The iron donor Hemin only marginally potentiates the anti-HCV activity of ART in HCV-infected cultures. Carbon-centered radicals have been shown to be critical for the anti-malarial activity of ART. We demonstrate that carbon-centered radicals-trapping (the so-called TEMPO) compounds only marginally affect the anti-HCV activity of ART. This provides evidence that carbon-centered radicals are not the main effectors of the anti-HCV activity of the Artemisinin. ART and analogues may possibly exert their anti-HCV activity by the induction of reactive oxygen species (ROS). The combined anti-HCV activity of ART or its analogues with L-N-Acetylcysteine (L-NAC) [a molecule that inhibits ROS generation] was studied. L-NAC significantly reduced the in vitro anti-HCV activity of ART and derivatives. Taken together, the in vitro anti-HCV activity of ART and analogues can, at least in part, be explained by the induction of ROS; carbon-centered radicals may not be important in the anti-HCV effect of these molecules.

Intracytoplasmic trapping of influenza virus by a lipophilic derivative of aglycoristocetin

We report on a new anti-influenza virus agent, SA-19, a lipophilic glycopeptide derivative consisting of aglycoristocetin coupled to a phenylbenzyl-substituted cyclobutenedione. In Madin-Darby canine kidney cells infected with influenza A/H1N1, A/H3N2, or B virus, SA-19 displayed a 50% antivirally effective concentration of 0.60 μM and a selectivity index (ratio of cytotoxic versus antiviral concentration) of 112. SA-19 was 11-fold more potent than unsubstituted aglycoristocetin and was active in human and nonhuman cell lines. Virus yield at 72 h p.i. was reduced by 3.6 logs at 0.8 μM SA-19. In contrast to amantadine and oseltamivir, SA-19 did not select for resistance upon prolonged virus exposure. SA-19 was shown to inhibit an early postbinding step in virus replication. The compound had no effect on hemagglutinin (HA)-mediated membrane fusion in an HA-polykaryon assay and did not inhibit the low-pH-induced refolding of the HA in a tryptic digestion assay. However, a marked inhibitory effect on the transduction exerted by retroviral pseudoparticles carrying an HA or vesicular stomatitis virus glycoprotein (VSV-G) fusion protein was noted, suggesting that SA-19 targets a cellular factor with a role in influenza virus and VSV entry. Using confocal microscopy with antinucleoprotein staining, SA-19 was proven to completely prevent the influenza virus nuclear entry. This virus arrest was characterized by the formation of cytoplasmic aggregates. SA-19 appeared to disturb the endocytic uptake and trap the influenza virus in vesicles distinct from early, late, or recycling endosomes. The aglycoristocetin derivative SA-19 represents a new class of potent and broad-acting influenza virus inhibitors with potential clinical relevance.

An analogue of the antibiotic teicoplanin prevents flavivirus entry in vitro

There is an urgent need for potent inhibitors of dengue virus (DENV) replication for the treatment and/or prophylaxis of infections with this virus. We here report on an aglycon analogue of the antibiotic teicoplanin (code name LCTA-949) that inhibits DENV-induced cytopathic effect (CPE) in a dose-dependent manner. Virus infection was completely inhibited at concentrations that had no adverse effect on the host cells. These findings were corroborated by quantification of viral RNA levels in culture supernatant. Antiviral activity was also observed against other flaviviruses such as the yellow fever virus and the tick-borne encephalitis virus (TBEV). In particular, potent antiviral activity was observed against TBEV. Time-of-drug-addition experiments indicated that LCTA-949 inhibits an early stage in the DENV replication cycle; however, a virucidal effect was excluded. This observation was corroborated by the fact that LCTA-949 lacks activity on DENV subgenomic replicon (that does not encode structural proteins) replication. Using a microsopy-based binding and fusion assay employing DiD-labeled viruses, it was shown that LCTA-949 targets the early stage (binding/entry) of the infection. Moreover, LCTA-949 efficiently inhibits infectivity of DENV particles pre-opsonized with antibodies, thus potentially also inhibiting antibody-dependent enhancement (ADE). In conclusion, LCTA-949 exerts in vitro activity against several flaviviruses and does so (as shown for DENV) by interfering with an early step in the viral replication cycle.