Identification of broad-spectrum M^pro inhibitors: a focus on high-risk coronaviruses and conserved interactions

The COVID-19 pandemic underscores the urgent need to develop broad-spectrum antivirals against coronaviruses (CoVs) to prepare for future outbreaks. In this study, we presented a systematic approach to developing broad-spectrum M^pro inhibitors, with a focus on high-risk CoVs. We optimised S-217622 as a lead compound, with the goal of enhancing conserved interactions within the S1, S2, and S3/S4 pockets of M^pro, leading to significantly improved inhibitory potency against representative CoVs. Compound 25 exhibited submicromolar activity across all ten CoVs, with IC₅₀ values below 0.1 μM for six of them. The X-ray co-crystal structure of SARS-CoV-2 M^pro in complex with compound 25 revealed the structural basis of conserved interactions contributing to its broad-spectrum activity. This study demonstrates the feasibility of reinforcing conserved interactions to develop M^pro inhibitors with broad-spectrum activity and provides valuable strategies for combating future pandemics caused by unknown CoVs.