A small molecule multi-kinase inhibitor reduces influenza A virus replication by restricting viral RNA synthesis

Identification of small molecules capable of enhancing viral membrane fusion

Several approaches have been developed to analyze the entry of highly pathogenic viruses. In this study, we report the implementation of a Bimolecular Multicellular Complementation (BiMuC) assay to safely and efficiently monitor SARS-CoV-2 S-mediated membrane fusion without the need for microscopy-based equipment. Using BiMuC, we screened a library of approved drugs and identified compounds that enhance S protein-mediated cell-cell membrane fusion. Among them, ethynylestradiol promotes the growth of SARS-CoV-2 and Influenza A virus in vitro. Our findings demonstrate the potential of BiMuC for identifying small molecules that modulate the life cycle of enveloped viruses, including SARS-CoV-2.

1-Benzyl-3-cetyl-2-methylimidazolium Iodide (NH125) Is a Broad-Spectrum Inhibitor of Virus Entry with Lysosomotropic Features

Cellular kinases are crucial for the transcription/replication of many negative-strand RNA viruses and might serve as targets for antiviral therapy. In this study, a library comprising 80 kinase inhibitors was screened for antiviral activity against vesicular stomatitis virus (VSV), a prototype member of the family Rhabdoviridae. 1-Benzyl-3-cetyl-2-methylimidazolium iodide (NH125), an inhibitor of eukaryotic elongation factor 2 (eEF2) kinase, significantly inhibited entry of single-cycle VSV encoding a luciferase reporter. Treatment of virus particles had only minimal effect on virus entry, indicating that the compound primarily acts on the host cell rather than on the virus. Accordingly, resistant mutant viruses were not detected when the virus was passaged in the presence of the drug. Unexpectedly, NH125 led to enhanced, rather than reduced, phosphorylation of eEF2, however, it did not significantly affect cellular protein synthesis. In contrast, NH125 revealed lysosomotropic features and showed structural similarity with N-dodecylimidazole, a known lysosomotropic agent. Related alkylated imidazolium compounds also exhibited antiviral activity, which was critically dependent on the length of the alkyl group. Apart from VSV, NH125 inhibited infection by VSV pseudotypes containing the envelope glycoproteins of viruses that are known to enter cells in a pH-dependent manner, i.e. avian influenza virus (H5N1), Ebola virus, and Lassa virus. In conclusion, we identified an alkylated imidazolium compound which inhibited entry of several viruses not because of the previously postulated inhibition of eEF2 kinase but most likely because of its lysosomotropic properties.

Structural evidence of quercetin multi-target bioactivity: A reverse virtual screening strategy

The ubiquitous flavonoid quercetin is broadly recognized for showing diverse biological and health-promoting effects, such as anti-cancer, anti-inflammatory and cytoprotective activities. The therapeutic potential of quercetin and similar compounds for preventing such diverse oxidative stress-related pathologies has been generally attributed to their direct antioxidant properties. Nevertheless, accumulated evidence indicates that quercetin is also able to interact with multiple cellular targets influencing the activity of diverse signaling pathways. Even though there are a number of well-established protein targets such as phosphatidylinositol 3 kinase and xanthine oxidase, there remains a lack of a comprehensive knowledge of the potential mechanisms of action of quercetin and its target space. In the present work we adopted a reverse screening strategy based on ligand similarity (SHAFTS) and target structure (idTarget, LIBRA) resulting in a set of predicted protein target candidates. Furthermore, using this method we corroborated a broad array of previously experimentally tested candidates among the predicted targets, supporting the suitability of this screening approach. Notably, all of the predicted target candidates belonged to two main protein families, protein kinases and poly [ADP-ribose] polymerases. They also included key proteins involved at different points within the same signaling pathways or within interconnected signaling pathways, supporting a pleiotropic, multilevel and potentially synergistic mechanism of action of quercetin. In this context we highlight the value of quercetin's broad target profile for its therapeutic potential in diseases like inflammation, neurodegeneration and cancer.

Understanding the Multifaceted Role of Human Down Syndrome Kinase DYRK1A

The dual-specificity tyrosine (Y) phosphorylation-regulated kinase DYRK1A, also known as Down syndrome (DS) kinase, is a dosage-dependent signaling kinase that was originally shown to be highly expressed in DS patients as a consequence of trisomy 21. Although this was evident some time ago, it is only in recent investigations that the molecular roles of DYRK1A in a wide range of cellular processes are becoming increasingly apparent. Since initial knowledge on DYRK1A became evident through minibrain mnb, the Drosophila homolog of DYRK1A, this review will first summarize the scientific reports on minibrain and further expand on the well-established neuronal functions of mammalian and human DYRK1A. Recent investigations across the current decade have provided rather interesting and compelling evidence in establishing nonneuronal functions for DYRK1A, including its role in infection, immunity, cardiomyocyte biology, cancer, and cell cycle control. The latter part of this review will therefore focus in detail on the emerging nonneuronal functions of DYRK1A and summarize the regulatory role of DYRK1A in controlling Tau and α-synuclein. Finally, the emerging role of DYRK1A in Parkinson's disease will be outlined.

Chemical Space Mapping and Structure-Activity Analysis of the ChEMBL Antiviral Compound Set

Curation, standardization and data fusion of the antiviral information present in the ChEMBL public database led to the definition of a robust data set, providing an association of antiviral compounds to seven broadly defined antiviral activity classes. Generative topographic mapping (GTM) subjected to evolutionary tuning was then used to produce maps of the antiviral chemical space, providing an optimal separation of compound families associated with the different antiviral classes. The ability to pinpoint the specific spots occupied (responsibility patterns) on a map by various classes of antiviral compounds opened the way for a GTM-supported search for privileged structural motifs, typical for each antiviral class. The privileged locations of antiviral classes were analyzed in order to highlight underlying privileged common structural motifs. Unlike in classical medicinal chemistry, where privileged structures are, almost always, predefined scaffolds, privileged structural motif detection based on GTM responsibility patterns has the decisive advantage of being able to automatically capture the nature ("resolution detail"-scaffold, detailed substructure, pharmacophore pattern, etc.) of the relevant structural motifs. Responsibility patterns were found to represent underlying structural motifs of various natures-from very fuzzy (groups of various "interchangeable" similar scaffolds), to the classical scenario in medicinal chemistry (underlying motif actually being the scaffold), to very precisely defined motifs (specifically substituted scaffolds).

Repurposing Kinase Inhibitors as Antiviral Agents to Control Influenza A Virus Replication

Influenza A virus (IAV) infection causes seasonal epidemics of contagious respiratory illness that causes substantial morbidity and some mortality. Regular vaccination is the principal strategy for controlling influenza virus, although vaccine efficacy is variable. IAV antiviral drugs are available; however, substantial drug resistance has developed to two of the four currently FDA-approved antiviral drugs. Thus, new therapeutic approaches are being sought to reduce the burden of influenza-related disease. A high-throughput screen using a human kinase inhibitor library was performed targeting an emerging IAV strain (H7N9) in A549 cells. The inhibitor library contained 273 structurally diverse, active cell permeable kinase inhibitors with known bioactivity and safety profiles, many of which are at advanced stages of clinical development. The current study shows that treatment of human A549 cells with kinase inhibitors dinaciclib, flavopiridol, or PIK-75 exhibits potent antiviral activity against H7N9 IAV as well as other IAV strains. Thus, targeting host kinases can provide a broad-spectrum therapeutic approach against IAV. These findings provide a path forward for repurposing existing kinase inhibitors safely as potential antivirals, particularly those that can be tested in vivo and ultimately for clinical use.

Antiviral strategies against influenza virus: towards new therapeutic approaches

Influenza viruses are major human pathogens responsible for respiratory diseases affecting millions of people worldwide and characterized by high morbidity and significant mortality. Influenza infections can be controlled by vaccination and antiviral drugs. However, vaccines need annual updating and give limited protection. Only two classes of drugs are currently approved for the treatment of influenza: M2 ion channel blockers and neuraminidase inhibitors. However, they are often associated with limited efficacy and adverse side effects. In addition, the currently available drugs suffer from rapid and extensive emergence of drug resistance. All this highlights the urgent need for developing new antiviral strategies with novel mechanisms of action and with reduced drug resistance potential. Several new classes of antiviral agents targeting viral replication mechanisms or cellular proteins/processes are under development. This review gives an overview of novel strategies targeting the virus and/or the host cell for counteracting influenza virus infection.

Antiviral effects of inhibiting host gene expression

RNA interference (RNAi) has been used to probe the virus-host interface to understand the requirements for host-gene expression needed for virus replication. The availability of arrayed siRNA libraries has enabled a genome-scale, high-throughput analysis of gene pathways usurped for virus replication. Results from these and related screens have led to the discovery of new host factors that regulate virus replication. While effective delivery continues to limit development of RNAi-based drugs, RNAi-based genome discovery has led to identification of druggable targets. These validated targets enable rational development of novel antiviral drugs, including the rescue and repurposing of existing, approved drugs. Existing drugs with known cytotoxicity and mechanisms of action can potentially be re-targeted to regulate host genes and gene products needed by influenza to replicate. Drug repositioning is more cost-effective, less time-consuming, and more effective for anti-influenza virus drug discovery than traditional methods. In this chapter, a general overview of RNAi screening methods, host-gene discovery, and drug repurposing is examined with emphasis on utilizing RNAi to identify druggable genes that can be targeted for drug development or repurposing.