Inhibitory effects and structural analysis of drug candidate PF-07817883 against coronaviral main proteases (Mpro) and SARS-CoV-2 Mpro mutants.

Main proteases (Mpros) are a class of conserved cysteine proteases found among coronaviruses, playing a key role in their replication. These properties make Mpros ideal targets for the screening and design of pan-coronavirus drugs. Recently, PF-07817883 (ibuzatrelvir) has been developed against SARS-CoV Mpro by optimizing PF-07321332 (nirmatrelvir), showing broad-spectrum inhibitory efficacy against coronaviral Mpros. In the present study, we revealed the crystal structures of Mpros from SARS-CoV-2, SARS-CoV, HCoV-NL63, and HCoV-229E, and several SARS-CoV-2 Mpro mutants bound to PF-07817883. Detailed structural analyses demonstrates key molecular determinants necessary for interaction and elucidates the binding patterns of PF-07817883 to different coronaviral Mpros. The potencies of PF-07817883 against these investigated Mpros were further evaluated through molecular dynamic simulation and Enzymatic Activity Inhibition Assay. It shows that both E166N and E166R mutants exhibiting a certain degree of resistance to PF-07817883, the E166N mutant shows a more substantial impact on enzyme activity. These data provide molecular insights into broad-spectrum inhibition against selected coronaviral Mpros by PF-07817883 and the similarities and differences of PF-07817883 when bound to various Mpros, which will push the development of novel antivirals with pan-Mpro inhibitory efficacy.