Identification of Potent, Broad-Spectrum Coronavirus Main Protease Inhibitors for Pandemic Preparedness

The COVID-19 pandemic highlights the ongoing risk of zoonotic transmission of coronaviruses to global health. To prepare for future pandemics, it is essential to develop effective antivirals targeting a broad range of coronaviruses. Targeting the essential and clinically validated coronavirus main protease (M^pro), we constructed a structurally diverse M^pro panel by clustering all known coronavirus sequences by M^pro active site sequence similarity. Through screening, we identified a potent covalent inhibitor that engaged the catalytic cysteine of SARS-CoV-2 Mpro and used structure-based medicinal chemistry to develop compounds in the pyrazolopyrimidine sulfone series that exhibit submicromolar activity against multiple M^pro homologues. Additionally, we solved the first X-ray cocrystal structure of M^pro from the human-infecting OC43 coronavirus, providing insights into potency differences among compound–target pairs. Overall, the chemical compounds described in this study serve as starting points for the development of antivirals with broad-spectrum activity, enhancing our preparedness for emerging human-infecting coronaviruses.