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Published on: August 14, 2018
Targeting the Fusion Process of SARS-CoV-2 Infection by Small Molecule Inhibitors
Seung Bum Park1, Parker Irvin1, Zongyi Hu1
1Liver Diseases Branch, NIDDK, NIH, Bethesda, Maryland, USA.
Abstract:
Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a serious threat to global public health, underscoring the urgency of developing effective therapies. Therapeutics and, more specifically, direct-acting antiviral development are still very much in their infancy. Here, we report that two hepatitis C virus (HCV) fusion inhibitors identified in our previous study, dichlorcyclizine and fluoxazolevir, broadly block human coronavirus entry into various cell types. Both compounds were effective against various human-pathogenic CoVs in multiple assays based on vesicular stomatitis virus (VSV) pseudotyped with the spike protein and spike-mediated syncytium formation. The antiviral effects were confirmed in SARS-CoV-2 infection systems. These compounds were equally effective against recently emerged variants, including the delta variant. Cross-linking experiments and structural modeling suggest that the compounds bind to a hydrophobic pocket near the fusion peptide of S protein, consistent with their potential mechanism of action as fusion inhibitors. In summary, these fusion inhibitors have broad-spectrum antiviral activities and may be promising leads for treatment of SARS-CoV-2, its variants, and other pathogenic CoVs. IMPORTANCE SARS-CoV-2 is an enveloped virus that requires membrane fusion for entry into host cells. Since the fusion process is relatively conserved among enveloped viruses, we tested our HCV fusion inhibitors, dichlorcyclizine and fluoxazolevir, against SARS-CoV-2. We performed in vitro assays and demonstrated their effective antiviral activity against SARS-CoV-2 and its variants. Cross-linking experiments and structural modeling suggest that the compounds bind to a hydrophobic pocket in spike protein to exert their inhibitory effect on the fusion step. These data suggest that both dichlorcyclizine and fluoxazolevir are promising candidates for further development as treatment for SARS-CoV-2.
Insights
Two hepatitis C virus fusion inhibitors, dichlorcyclizine and fluoxazolevir, effectively block SARS-CoV-2 and its variants by inhibiting viral entry. These broad-spectrum antivirals show promise for treating COVID-19 and other coronavirus infections.
Area of Science:
- Virology
- Drug Discovery
- Molecular Biology
Background:
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a global health threat requiring new therapies.
- Antiviral drug development, particularly direct-acting antivirals, is crucial but still in early stages.
- Viral entry mechanisms, such as membrane fusion, are conserved and represent potential therapeutic targets.
Purpose of the Study:
- To investigate the antiviral potential of previously identified hepatitis C virus (HCV) fusion inhibitors against SARS-CoV-2.
- To determine if dichlorcyclizine and fluoxazolevir exhibit broad-spectrum activity against various human coronaviruses (CoVs) and their variants.
- To elucidate the mechanism of action of these compounds against SARS-CoV-2.
Main Methods:
- Utilized vesicular stomatitis virus (VSV)-based pseudotype assays to evaluate compound efficacy against CoV entry.
- Assessed antiviral activity in SARS-CoV-2 infection systems and against emerging variants like Delta.
- Employed cross-linking experiments and structural modeling to identify the binding site and mechanism of action.
Main Results:
- Dichlorcyclizine and fluoxazolevir demonstrated broad-spectrum inhibition of human CoV entry into diverse cell types.
- Both compounds were effective against SARS-CoV-2 and its variants, including the Delta variant.
- Mechanism studies indicated binding to a hydrophobic pocket near the S protein's fusion peptide, consistent with fusion inhibition.
Conclusions:
- Dichlorcyclizine and fluoxazolevir exhibit potent antiviral activity against SARS-CoV-2 and other pathogenic CoVs.
- These compounds act as fusion inhibitors by targeting the S protein, offering a potential therapeutic strategy.
- The broad-spectrum activity and efficacy against variants position these inhibitors as promising candidates for COVID-19 treatment development.
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