Structural Basis of Main Proteases of Coronavirus Bound to Bofutrelvir

Globally, the continuous spread and evolution of SARS-CoV-2, along with its variants, profoundly impact human well-being, health, security, and the growth of socio-economic. In the field of development of drugs against COVID-19, the main protease (M^pro) is a critical target as it plays a core role in the lifecycle of SARS-CoV-2. Bofutrelvir acts as a potent inhibitor of SARS-CoV-2 M^pro, demonstrating high efficacy and broad-spectrum antiviral activity. Compared to therapies that require pharmacokinetic boosters, such as ritonavir, the monotherapy approach of Bofutrelvir reduces the risk of potential drug interactions, making it suitable for a wider patient population. However, further studies on the potency and mechanism of inhibition of Bofutrelvir against the M^pro of COVID-19 and its variants, together with other coronaviruses, are needed to prepare for the possibility of a possible re-emerging threat from an analogous virus in the future. Here, we reveal the effective inhibition of Bofutrelvir against the M^pro of SARS-CoV-2, SARS-CoV, and HCoV-229E through FRET and crystallographic analysis. Furthermore, the inhibitory mechanisms of Bofutrelvir against two SARS-CoV-2 M^pro mutants (G15S and K90R) were also elucidated through FRET and crystallographic studies. Through detailed analysis and comparison of these crystal structures, we identified crucial structural determinants of inhibition and elucidated the binding mode of Bofutrelvir to M^pros from different coronaviruses. These findings are hopeful to accelerate the development of safer and more potent inhibitors against the M^pro of coronavirus, and to provide important references for the prevention and treatment of similar viruses that may emerge in the future.