Project description:SARS-CoV-2 virus mimics host mRNA by capping its viral RNA to promote replication and evade host immune sensing. SARS-CoV-2 NSP14 is the N7-guanosine methyltransferase (N7-MTase) responsible for RNA cap-0 formation. Targeting NSP14 for antiviral drug development is an under-explored but promising strategy. Here we conducted a high-throughput screening on natural products library derived from Chinese herbal medicine to discover Emodin as a SARS-CoV-2 NSP14 inhibitor. Exploring Emodin derivatives, Questin was identified with potent cellular inhibitory activity (EC50=249 nM) against SARS-CoV-2, which inhibits NSP14 in an RNA cap competitive manner, making it one the most potent anti-coronaviral natural products. Mechanistically, besides catalyzing viral RNA capping, NSP14 by itself could remodel host transcriptome such as enriching CREBBP, a key host factor in cellular cyclic AMP response pathway, to promote viral infection. As a result, targeting NSP14 by Questin significantly impairs viral Replication & Translation step and reverses host transcriptome remodeled by NSP14. We next validated Questin as a promising lead with significantly improved toxicity upon acute exposure in zebrafish larvae. Taken together, our study not only demonstrates Questin as a potent drug lead for clinical antiviral application, but also highlights multiple antiviral potentials of NSP14 as therapeutic target.
Project description:The emergence of SARS-CoV-2 variants and drug-resistant mutants underscores the urgent need for novel antiviral therapeutics. SARS-CoV-2 NSP14, an N7-guanosine methyltransferase, plays a critical role in viral RNA capping, enabling viral replication and immune evasion. While NSP14 has emerged as a promising drug target, its role in host-virus crosstalk and the cellular consequences of NSP14 inhibition remain poorly understood. Here, we present the identification and characterization of C10, a highly potent and selective first-in-class non-nucleoside inhibitor of the NSP14 S-adenosylmethionine (SAM)-binding pocket. C10 demonstrates robust antiviral activity against SARS-CoV-2, including its variants, with EC50 values ranging from 64.03 to 301.9 nM, comparable to the FDA-approved drug remdesivir in our cell-based assays. C10 also exhibits broad-spectrum activity against other betacoronaviruses and directly suppresses SARS-CoV-2 genomic replication. C10 specifically reversed NSP14-mediated alterations in host transcriptome and restored host cell cycle progression disrupted by NSP14. The antiviral efficacy of C10 was further validated in a transgenic mouse model of SARS-CoV-2 infection. Our findings highlight C10 as a promising candidate for the development of effective treatments against SARS-CoV-2 and its emerging variants. This study also uncovers a novel mechanism of NSP14 in SARS-CoV-2 pathogenesis and its therapeutic potential, providing insights that may extend to other viral capping methyltransferases.
Project description:The emergence of SARS-CoV-2 variants and drug-resistant mutants necessitates additional antivirals. SARS-CoV-2 NSP14 N7-guanosine methyltransferase is responsible for viral RNA capping, facilitating replication and evading immune detection. NSP14 has emerged as a promising drug target, but the role of NSP14 in host-virus crosstalk and the cellular effects of NSP14 inhibition are poorly understood. Here, we performed structure-based virtual screen to identify non-nucleoside inhibitors targeting NSP14 SAM-binding pocket. Hit to Lead optimization resulted in the development of C10 that potently inhibited SARS-CoV-2 and variants with the EC50 values from 64.03 to 301.9 nM, comparable to FDA-approved drug remdesivir in our cell-based model. C10 is a selective inhibitor of β-coronavirus NSP14 and directly suppresses SARS-CoV-2 replication, as demonstrated by a SARS-CoV-2 replicon system. C10 specifically reversed NSP14-mediated host transcriptome alterations and, phenotypically, restored host cell cycle progression disrupted by NSP14. The antiviral efficacy of C10 was further validated in a transgenic mouse model of SARS-CoV-2 infection. Our findings indicate C10 holds promise for developing effective treatments against SARS-CoV-2 and emerging variants, as well as uncover a novel pathogenic role of NSP14 beyond its function in viral RNA capping, which may be also adaptable to other viral capping methyltransferase.
Project description:The continued emergence of SARS-CoV-2 variants and persistent inflammatory complications of COVID-19 highlight the urgent need for therapeutics with both antiviral and anti-inflammatory properties. Despite intensive global efforts, no approved antiviral therapy with these dual functions has yet been developed, representing a significant gap in current COVID-19 treatment strategies. In this study, we identify BAY 11-7082 (BAY) as a dual–action compound that inhibits SARS-CoV-2 replication and the production of virus-induced proinflammatory cytokines and chemokines, including IL-6, IL-8, CXCL1, and CXCL2. BAY predominantly exerts its antiviral activity at the post-entry stage of the viral life cycle. Mechanistically, BAY potentially interacts with SARS-CoV-2 NSP14 and inhibits virus-induced phosphorylation and degradation of IκBα, suppressing NF-κB activation through the IKK-IκBα signaling axis. Furthermore, BAY exhibits potent antiviral activity against multiple SARS-CoV-2 variants of concern (VOCs). Collectively, these findings support the potential of BAY as a dual-action therapeutic candidate, combining antiviral and anti-inflammatory effects, against SARS-CoV-2 and its emerging variants.
Project description:The continued emergence of SARS-CoV-2 variants and persistent inflammatory complications of COVID-19 highlight the urgent need for therapeutics with both antiviral and anti-inflammatory properties. Despite intensive global efforts, no approved antiviral therapy with these dual functions has yet been developed, representing a significant gap in current COVID-19 treatment strategies. In this study, we identify BAY 11-7082 (BAY) as a dual–action compound that inhibits SARS-CoV-2 replication and the production of virus-induced proinflammatory cytokines and chemokines, including IL-6, IL-8, CXCL1, and CXCL2. BAY predominantly exerts its antiviral activity at the post-entry stage of the viral life cycle. Mechanistically, BAY potentially interacts with SARS-CoV-2 NSP14 and inhibits virus-induced phosphorylation and degradation of IκBα, suppressing NF-κB activation through the IKK-IκBα signaling axis. Furthermore, BAY exhibits potent antiviral activity against multiple SARS-CoV-2 variants of concern (VOCs). Collectively, these findings support the potential of BAY as a dual-action therapeutic candidate, combining antiviral and anti-inflammatory effects, against SARS-CoV-2 and its emerging variants.
Project description:Interplay between type I interferon (IFN) driven innate responses and viral antagonism strongly influences SARS-CoV-2 transmission and the COVID-19 disease course. Hence, variant adaptation includes diminished induction of IFN stimulated genes (ISG) and/or evasion of their effector functions. Exogenous IFN treatment “rewires” innate responses to drive virus elimination, yet therapeutic trials to date have been unremarkable. Resolving this paradox could translate to variant-agnostic innate immunotherapy. By contrast, oncolytic viruses (OV) exhibit profoundly attenuated innate antagonism, resulting in potent IFN responses despite the inherently immunosuppressive nature of tumour microenvironments. Moreover, OV only undergo lytic replication within innate-deficient malignant cells, and not in cells where sufficient innate responses exist. This, combined with previous studies showing that OV suppressed replication of underlying oncogenic viruses in tumours, we explored whether clinical grade oncolytic Orthoreovirus (Reo) superinfection could eliminate SARS-CoV-2 from immune-competent lung epithelial cell lines in the absence of toxicity. Reo exerted profound activation of innate responses, including when SARS-CoV-2 infection was already established, rewiring cells towards an antiviral state emulating that of Reo infection alone. Both intracellular and paracrine mechanisms induced ISG repertoires including multiple known anti-SARS-CoV-2 effectors, as well as others that remain unvalidated. Amongst these, we demonstrate the first direct evidence that MX2 and XAF1 restrict SARS-CoV-2 replication. Thus, with an excellent safety record, self-amplification, and respiratory tract tropism, we propose that Reo superinfection may provide a tractable alternative to recombinant cytokines for innate antiviral immunotherapy.
Project description:SARS-CoV-2 non-structural protein Nsp14 is a highly conserved enzyme necessary for viral replication. Nsp14 forms a stable complex with non-structural protein Nsp10 and exhibits exoribonuclease and N7-methyltransferase activities. Protein-interactome studies identified human sirtuin 5 (SIRT5) as a putative binding partner of Nsp14. SIRT5 is an NAD-dependent protein deacylase critical for cellular metabolism that removes succinyl and malonyl groups from lysine residues. Here we investigated the nature of this interaction and the role of SIRT5 during SARS-CoV-2 infection. We showed that SIRT5 stably interacts with Nsp14, but not with Nsp10, suggesting that SIRT5 and Nsp10 are parts of separate complexes. We found that SIRT5 catalytic domain is necessary for the interaction with Nsp14, but that Nsp14 does not appear to be directly deacylated by SIRT5. Furthermore, knock-out of SIRT5 or treatment with specific SIRT5 inhibitors reduced SARS-CoV-2 viral levels in cell-culture experiments. SIRT5 knock-out cells expressed higher basal levels of innate immunity markers and mounted a stronger antiviral response. Our results indicate that SIRT5 is a proviral factor necessary for efficient viral replication, which opens novel avenues for therapeutic interventions.
Project description:Despite the wide availability of several safe and effective vaccines that can prevent severe COVID-19 disease, the emergence of SARS-CoV-2 variants of concern (VOC) that can partially evade vaccine immunity remains a global health concern. In addition, the emergence of highly mutated and neutralization-resistant SARS-CoV-2 VOCs such as BA.1 and BA.5 that can partially or fully evade (1) many therapeutic monoclonal antibodies in clinical use underlines the need for additional effective treatment strategies. Here, we characterize the antiviral activity of GS-5245, Obeldesivir (ODV), an oral prodrug of the parent nucleoside GS-441524, which targets the highly conserved RNA-dependent viral RNA polymerase (RdRp). Importantly, we show that GS-5245 is broadly potent in vitro against alphacoronavirus HCoV-NL63, severe acute respiratory syndrome coronavirus (SARS-CoV), SARS-CoV-related Bat-CoV RsSHC014, Middle East Respiratory Syndrome coronavirus (MERS-CoV), SARS-CoV-2 WA/1, and the highly transmissible SARS-CoV-2 BA.1 Omicron variant in vitro and highly effective as antiviral therapy in mouse models of SARS-CoV, SARS-CoV-2 (WA/1), MERS-CoV and Bat-CoV RsSHC014 pathogenesis. In all these models of divergent coronaviruses, we observed protection and/or significant reduction of disease metrics such as weight loss, lung viral replication, acute lung injury, and degradation in pulmonary function in GS-5245-treated mice compared to vehicle controls. Finally, we demonstrate that GS-5245 in combination with the main protease (Mpro) inhibitor nirmatrelvir had increased efficacy in vivo against SARS-CoV-2 compared to each single agent. We also evalulate the effect of antiviral therapy on host gene expression using RNAseq and show that therapeutic intervention reduces host inflammatory response as compared to vehicle controls during acute SARS-CoV-2 infection. Altogether, our data supports the continuing clinical evaluation of GS-5245 in humans infected with COVID-19, including as part of a combination antiviral therapy, especially in populations with the most urgent need for more efficacious and durable interventions.