Evaluation of the Inhibition Potency of Nirmatrelvir against Main Protease Mutants of SARS-CoV-2 Variants.

SARS-CoV-2 continues to pose a threat to public health. Main protease (M) is one of the most lucrative drug targets for developing specific antivirals against SARS-CoV-2 infection. By targeting M, peptidomimetic nirmatrelvir is able to inhibit viral replication of SARS-CoV-2 and reduce the risk for progression to severe COVID-19. However, multiple mutations in the gene encoding M of emerging SARS-CoV-2 variants raise a concern of drug resistance. In the present study, we expressed 16 previously reported SARS-CoV-2 M mutants (G15S, T25I, T45I, S46F, S46P, D48N, M49I, L50F, L89F, K90R, P132H, N142S, V186F, R188K, T190I, and A191V). We evaluated the inhibition potency of nirmatrelvir against these M mutants and solved the crystal structures of representative M mutants of SARS-CoV-2 bound to nirmatrelvir. Enzymatic inhibition assays revealed that these M variants remain susceptible to nirmatrelvir as the wildtype. Detailed analysis and structural comparison provided the inhibition mechanism of M mutants by nirmatrelvir. These results informed the ongoing genomic surveillance of drug resistance of emerging SARS-CoV-2 variants to nirmatrelvir and facilitate the development of next-generation anticoronavirus drugs.