Discovery of M Protease Inhibitors Encoded by SARS-CoV-2

Area of Science:

• Virology
• Drug Discovery
• Biochemistry

Background:

• The COVID-19 pandemic, caused by SARS-CoV-2, poses a significant global health challenge.
• The viral main protease (M^pro) is a critical therapeutic target for developing antiviral drugs.
• Picornavirus-like supercluster M^pro inhibitors offer a potential avenue for SARS-CoV-2 drug development.

Purpose of the Study:

• To evaluate the efficacy of GC376, a broad-spectrum M^pro inhibitor, against SARS-CoV-2.
• To investigate the inhibitory mechanism and potential for optimization of GC376 for human use.

Main Methods:

• In vitro assays to determine the half-maximum inhibitory concentration (IC₅₀) of GC376 against SARS-CoV-2 M^pro.
• Cell-based assays to measure the half-maximum effective concentration (EC₅₀) of GC376 against SARS-CoV-2 replication.
• Mass spectrometry to analyze the covalent modification of SARS-CoV-2 M^pro by GC376.
• Molecular docking to understand the binding interactions of GC376 within the M^pro active site.

Main Results:

• GC376 demonstrated potent inhibition of SARS-CoV-2 M^pro with an IC₅₀ of 26.4 ± 1.1 nM.
• GC376 effectively inhibited SARS-CoV-2 replication with an EC₅₀ of 0.91 ± 0.03 μM.
• Mass spectrometry revealed limited covalent modification of M^pro by GC376, suggesting room for improvement.
• Molecular docking provided insights into GC376's binding mode, guiding optimization strategies.

Conclusions:

• GC376 is a potent inhibitor of SARS-CoV-2 M^pro and exhibits antiviral activity.
• Further optimization of GC376 or its analogues is warranted for enhanced efficacy and covalent modification.
• Given its existing safety profile as a veterinary drug, expedited development of GC376 for human COVID-19 treatment is recommended.