Crystal Structure of SARS-CoV-2 Main Protease in Complex with the Non-Covalent Inhibitor ML188

Area of Science:

• Virology
• Structural Biology
• Drug Discovery

Background:

• Viral proteases are essential for viral maturation and are key targets for antiviral therapies.
• The SARS-CoV-2 pandemic necessitates the development of direct-acting antivirals (DAAs).
• The main protease (Mpro) of SARS-CoV-2 is a primary target for drug design, with many efforts focused on covalent inhibitors.

Purpose of the Study:

• To evaluate the efficacy of ML188, a non-covalent inhibitor of SARS-CoV-1 Mpro, against SARS-CoV-2 Mpro.
• To determine the crystal structure of ML188 in complex with SARS-CoV-2 Mpro.
• To explore the potential of ML188 as a scaffold for pan-coronavirus inhibitors.

Main Methods:

• Enzyme inhibition assays to determine the potency of ML188 against SARS-CoV-2 Mpro.
• X-ray crystallography to obtain the high-resolution structure of the ML188-SARS-CoV-2 Mpro complex.
• Structural comparison of the ML188-SARS-CoV-2 Mpro complex with the previously determined SARS-CoV-1 Mpro complex.

Main Results:

• ML188 demonstrated potent inhibition of SARS-CoV-2 Mpro with an IC50 of 2.5 µM.
• The crystal structure of ML188 bound to SARS-CoV-2 Mpro was determined at 2.39 Å resolution.
• Structural analysis revealed subtle differences between the SARS-CoV-1 and SARS-CoV-2 Mpro complexes despite high sequence identity.

Conclusions:

• Non-covalent inhibitors like ML188 are valuable complements to covalent inhibitors for targeting SARS-CoV-2 Mpro.
• ML188 serves as a promising scaffold for developing broad-spectrum antiviral agents against coronaviruses.
• This study represents a critical step towards designing effective DAAs for COVID-19 treatment.