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Small Molecules Targeting 3C Protease Inhibit FMDV Replication and Exhibit Virucidal Effect in Cell-Based Assays
Sirin Theerawatanasirikul1, Varanya Lueangaramkul2, Achiraya Pantanam2
1Department of Anatomy, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.
Abstract:
Foot-and-mouth disease (FMD) is a highly contagious disease in cloven-hoofed animals, caused by the foot-and-mouth disease virus (FMDV). It is endemic in Asia and Africa but spreads sporadically throughout the world, resulting in significant losses in the livestock industry. Effective anti-FMDV therapeutics could be a supportive control strategy. Herein, we utilized computer-aided, structure-based virtual screening to filter lead compounds from the National Cancer Institute (NCI) diversity and mechanical libraries using FMDV 3C protease (3Cpro) as the target. Seven hit compounds were further examined via cell-based antiviral and intracellular protease assays, in which two compounds (NSC116640 and NSC332670) strongly inhibited FMDV, with EC50 values at the micromolar level of 2.88 µM (SI = 73.15) and 5.92 µM (SI = 11.11), respectively. These compounds could inactivate extracellular virus directly in a virucidal assay by reducing 1.00 to 2.27 log TCID50 of the viral titers in 0-60 min. In addition, the time-of-addition assay revealed that NSC116640 inhibited FMDV at the early stage of infection (0-8 h), while NSC332670 diminished virus titers when added simultaneously at infection (0 h). Both compounds showed good FMDV 3Cpro inhibition with IC50 values of 10.85 µM (NSC116640) and 4.21 µM (NSC332670). The molecular docking of the compounds on FMDV 3Cpro showed their specific interactions with amino acids in the catalytic triad of FMDV 3Cpro. Both preferentially reacted with enzymes and proteases in physicochemical and ADME analysis studies. The results revealed two novel small molecules with antiviral activities against FMDV and probably related picornaviruses.
Insights
Researchers identified two novel small molecules, NSC116640 and NSC332670, that effectively inhibit foot-and-mouth disease virus (FMDV) replication and protease activity. These compounds show promise as potential therapeutics for controlling FMDV outbreaks in livestock.
Area of Science:
- Veterinary Virology
- Drug Discovery
- Molecular Biology
Background:
- Foot-and-mouth disease (FMD) is a highly contagious viral illness affecting cloven-hoofed animals, causing significant economic losses globally.
- Current control strategies rely heavily on vaccination and culling, highlighting the need for novel therapeutic interventions.
- The FMD virus (FMDV) 3C protease (3Cpro) is a critical enzyme for viral replication and a potential drug target.
Purpose of the Study:
- To identify and characterize novel small molecules with anti-FMDV activity using computer-aided drug design.
- To evaluate the antiviral efficacy and mechanism of action of identified compounds against FMDV.
- To assess the potential of these compounds as supportive therapeutics for FMD control.
Main Methods:
- Structure-based virtual screening of NCI compound libraries against FMDV 3Cpro.
- Cell-based antiviral assays to determine EC50 values and selectivity indices (SI).
- Virucidal assays, time-of-addition studies, and enzymatic inhibition assays (IC50) to elucidate mechanisms.
- Molecular docking and ADME/physicochemical analyses to predict compound interactions and properties.
Main Results:
- Two compounds, NSC116640 and NSC332670, demonstrated potent FMDV inhibition with EC50 values of 2.88 µM (SI=73.15) and 5.92 µM (SI=11.11), respectively.
- Compounds effectively inactivated extracellular virus and inhibited viral replication at early stages of infection.
- Both compounds showed significant FMDV 3Cpro inhibition (IC50: 10.85 µM for NSC116640, 4.21 µM for NSC332670) with specific interactions in the catalytic triad.
Conclusions:
- NSC116640 and NSC332670 are novel small molecules with significant antiviral activity against FMDV.
- These compounds target the FMDV 3Cpro, offering a potential new therapeutic avenue for FMD control.
- Further investigation into these compounds could lead to effective treatments for FMD and related picornaviral infections.
