Leveraging SARS-CoV-2 Main Protease (M^pro) for COVID-19 Mitigation with Selenium-Based Inhibitors

The implementation of innovative approaches is crucial in an ongoing endeavor to mitigate the impact of COVID-19 pandemic. The present study examines the strategic application of the SARS-CoV-2 Main Protease (M^pro) as a prospective instrument in the repertoire to combat the virus. The cloning, expression, and purification of M^pro, which plays a critical role in the viral life cycle, through heterologous expression in Escherichia coli in a completely soluble form produced an active enzyme. The hydrolysis of a specific substrate peptide comprising a six-amino-acid sequence (TSAVLQ) linked to a p-nitroaniline (pNA) fragment together with the use of a fluorogenic substrate allowed us to determine effective inhibitors incorporating selenium moieties, such as benzoselenoates and carbamoselenoates. The new inhibitors revealed their potential to proficiently inhibit M^pro with IC₅₀-s in the low micromolar range. Our study contributes to the development of a new class of protease inhibitors targeting M^pro, ultimately strengthening the antiviral arsenal against COVID-19 and possibly, related coronaviruses.