Novel spirothiazamenthane inhibitors of the influenza A M2 proton channel

Tackling Influenza A virus by M2 ion channel blockers: Latest progress and limitations

Influenza outbreaks cause pandemics in millions of people. The treatment of influenza remains a challenge due to significant genetic polymorphism in the influenza virus. Also, developing vaccines to protect against seasonal and pandemic influenza infections is constantly impeded. Thus, antibiotics are the only first line of defense against antigenically distinct strains or new subtypes of influenza viruses. Among several anti-influenza targets, the M2 protein of the influenza virus performs several activities. M2 protein is an ion channel that permits proton conductance through the virion envelope and the deacidification of the Golgi apparatus. Both these functions are critical for viral replication. Thus, targeting the M2 protein of the influenza virus is an essential target. Rimantadine and amantadine are two well-known drugs that act on the M2 protein. However, these drugs acquired resistance to influenza and thus are not recommended to treat influenza infections. This review discusses an overview of anti-influenza therapy, M2 ion channel functions, and its working principle. It also discusses the M2 structure and its role, and the change in the structure leads to mutant variants of influenza A virus. We also shed light on the recently identified compounds acting against wild-type and mutated M2 proteins of influenza virus A. These scaffolds could be an alternative to M2 inhibitors and be developed as antibiotics for treating influenza infections.

Bicyclic Isoxazoline Derivatives: Synthesis and Evaluation of Biological Activity

The application of non-planar scaffolds in drug design allows for the enlargement of the chemical space, and for the construction of molecules that have more effective target-ligand interactions or are less prone to the development of resistance. Among the works of the last decade, a literature search revealed spirothiazamenthane, which has served as a lead in the development of derivatives active against resistant viral strains. In this work, we studied the novel molecular scaffold, which resembles spirothiazamenthane, but combines isoxazoline as a heterocycle and cyclooctane ring as a hydrophobic part of the structure. The synthesis of new 3-nitro- and 3-aminoisoxazolines containing spiro-fused or 1,2-annelated cyclooctane fragments was achieved by employing 1,3-dipolar cycloaddition of 3-nitro-4,5-dihydroisoxazol-4-ol 2-oxide or tetranitromethane-derived alkyl nitronates with non-activated alkenes. A series of spiro-sulfonamides was obtained by the reaction of 3-aminoisoxazoline containing a spiro-fused cyclooctane residue with sulfonyl chlorides. Preliminary screening of the compounds for antiviral, antibacterial, antifungal and antiproliferative properties in vitro revealed 1-oxa-2-azaspiro[4.7]dodec-2-en-3-amine and 3a,4,5,6,7,8,9,9a-octahydrocycloocta[d]isoxazol-3-amine with activity against the influenza A/Puerto Rico/8/34 (H1N1) virus in the submicromolar range, and high values of selectivity index. Further study of the mechanism of the antiviral action of these compounds, and the synthesis of their analogues, is likely to identify new agents against resistant viral strains.

Heterocyclic Inhibitors of Viroporins in the Design of Antiviral Compounds

Ion channels of viruses (viroporins) represent a common type of protein targets for drugs. The relative simplicity of channel architecture allows convenient computational modeling and enables virtual search for new inhibitors. In this review, we analyze the data published over the last 10 years on known ion channels of viruses that cause socially significant diseases. The effectiveness of inhibition by various types of heterocyclic compounds of the viroporins of influenza virus, hepatitis С virus, human immunodeficiency virus, human papillomaviruses, coronaviruses, and respiratory syncytial virus is discussed. The presented material highlights the promise held by the search for heterocyclic antiviral compounds that act by inhibition of viroporins.

Alternative Experimental Models for Studying Influenza Proteins, Host-Virus Interactions and Anti-Influenza Drugs

Ninety years after the discovery of the virus causing the influenza disease, this malady remains one of the biggest public health threats to mankind. Currently available drugs and vaccines only partially reduce deaths and hospitalizations. Some of the reasons for this disturbing situation stem from the sophistication of the viral machinery, but another reason is the lack of a complete understanding of the molecular and physiological basis of viral infections and host-pathogen interactions. Even the functions of the influenza proteins, their mechanisms of action and interaction with host proteins have not been fully revealed. These questions have traditionally been studied in mammalian animal models, mainly ferrets and mice (as well as pigs and non-human primates) and in cell lines. Although obviously relevant as models to humans, these experimental systems are very complex and are not conveniently accessible to various genetic, molecular and biochemical approaches. The fact that influenza remains an unsolved problem, in combination with the limitations of the conventional experimental models, motivated increasing attempts to use the power of other models, such as low eukaryotes, including invertebrate, and primary cell cultures. In this review, we summarized the efforts to study influenza in yeast, Drosophila, zebrafish and primary human tissue cultures and the major contributions these studies have made toward a better understanding of the disease. We feel that these models are still under-utilized and we highlight the unique potential each model has for better comprehending virus-host interactions and viral protein function.

Design and synthesis of heteroaromatic-based benzenesulfonamide derivatives as potent inhibitors of H5N1 influenza A virus

Influenza A virus is an enveloped negative single-stranded RNA virus that causes febrile respiratory infection and represents a clinically challenging threat to human health and even lives worldwide. Even more alarming is the emergence of highly pathogenic avian influenza (HPAI) strains such as H5N1, which possess much higher mortality rate (60%) than seasonal influenza strains in human infection. In this study, a novel series of heteroaromatic-based benzenesulfonamide derivatives were identified as M2 proton channel inhibitors. A systematic investigation of the structure-activity relationships and a molecular docking study demonstrated that the sulfonamide moiety and 2,5-dimethyl-substituted thiophene as the core structure played significant roles in the anti-influenza activity. Among the derivatives, compound 11k exhibited excellent antiviral activity against H5N1 virus with an EC₅₀ value of 0.47 μM and selectivity index of 119.9, which are comparable to those of the reference drug amantadine.

A Robust Proton Flux (pHlux) Assay for Studying the Function and Inhibition of the Influenza A M2 Proton Channel

The M2 protein is an important target for drugs in the fight against the influenza virus. Because of the emergence of resistance against antivirals directed toward the M2 proton channel, the search for new drugs against resistant M2 variants is of high importance. Robust and sensitive assays for testing potential drug compounds on different M2 variants are valuable tools in this search for new inhibitors. In this work, we describe a fluorescence sensor-based assay, which we termed "pHlux", that measures proton conduction through M2 when synthesized from an expression vector in Escherichia coli. The assay was compared to a previously established bacterial potassium ion transport complementation assay, and the results were compared to simulations obtained from analysis of a computational model of M2 and its interaction with inhibitor molecules. The inhibition of M2 was measured for five different inhibitors, including Rimantadine, Amantadine, and spiro type compounds, and the drug resistance of the M2 mutant variants (swine flu, V27A, and S31N) was confirmed. We demonstrate that the pHlux assay is robust and highly sensitive and shows potential for high-throughput screening.

Synthesis and structure-activity relationship study of arylsulfonamides as novel potent H5N1 inhibitors

H5N1 virus, one subtype of highly pathogenic influenza A virus in human infection, has recently received attention due to its unpredictable and high mortality. In this study, a series of arylsulfonamide derivatives were identified as improved H5N1 inhibitors for the influenza treatment by systematic structure-activity relationship investigation. Among them, the most potent H5N1 inhibitor 3h exhibited excellent antiviral activity against H5N1 virus with EC₅₀ value of 0.006 μM and selectivity index 33543.3. Moreover, the molecular docking of 3h with M2 proton channel protein provides practical way for understanding the inhibition of H5N1 with this kind of compounds.

Cyclophilin A as a target in the treatment of cytomegalovirus infections

BACKGROUND

Viruses are obligate parasites that depend on the cellular machinery of the host to regenerate and manufacture their proteins. Most antiviral drugs on the market today target viral proteins. However, the more recent strategies involve targeting the host cell proteins or pathways that mediate viral replication. This new approach would be effective for most viruses while minimizing drug resistance and toxicity.

METHODS

Cytomegalovirus replication, latency, and immune response are mediated by the intermediate early protein 2, the main protein that determines the effectiveness of drugs in cytomegalovirus inhibition. This review explains how intermediate early protein 2 can modify the action of cyclosporin A, an immunosuppressive, and antiviral drug. It also links all the pathways mediated by cyclosporin A, cytomegalovirus replication, and its encoded proteins.

RESULTS

Intermediate early protein 2 can influence the cellular cyclophilin A pathway, affecting cyclosporin A as a mediator of viral replication or anti-cytomegalovirus drug.

CONCLUSION

Cyclosporin A has a dual function in cytomegalovirus pathogenesis. It has the immunosuppressive effect that establishes virus replication through the inhibition of T-cell function. It also has an anti-cytomegalovirus effect mediated by intermediate early protein 2. Both of these functions involve cyclophilin A pathway.

Design and expeditious synthesis of organosilanes as potent antivirals targeting multidrug-resistant influenza A viruses

The efficacy of current influenza vaccines and small molecule antiviral drugs is curtailed by the emerging of multidrug-resistant influenza viruses. As resistance to the only FDA-approved oral influenza antiviral, oseltamivir (Tamiflu), continues to rise, there is a clear need to develop the next-generation of antiviral drugs. Since more than 95% of current circulating influenza A viruses carry the S31N mutation in their M2 genes, the AM2-S31N mutant proton channel represents an attractive target for the development of broad-spectrum antivirals. In this study we report the design and synthesis of the first class of organosilanes that have potent antiviral activity against a panel of human clinical isolates of influenza A viruses, including viruses that are resistant to amantadine, oseltamivir, or both.