LAUSR

The severe acute respiratory syndrome coronavirus 2 main protease (SARS-CoV-2-Mpro) plays an essential role in viral replication, transcription, maturation, and entry into host cells. Furthermore, its cleavage specificity for viruses, but not humans, makes it a promising drug target for the treatment of coronavirus disease 2019 (COVID-19). In this study, a fragment-based strategy including potential antiviral quinazolinone moiety and glutamine- or glutamate-derived peptidomimetic backbone and positioned nitro functional groups was used to synthesize putative Mpro inhibitors. Two compounds, G1 and G4, exhibited anti-Mpro enzymatic activity in a dose-dependent manner, with the calculated IC50 values of 22.47 ± 8.93 μM and 24.04 ± 0.67 μM, respectively. The bio-layer interferometer measured real-time binding. The dissociation kinetics of G1/Mpro and G4/Mpro also showed similar equilibrium dissociation constants (KD) of 2.60 × 10−5 M and 2.55 × 10−5 M, respectively, but exhibited distinct association/dissociation curves. Molecular docking of the two compounds revealed a similar binding cavity to the well-known Mpro inhibitor GC376, supporting a structure−function relationship. These findings may open a new avenue for developing new scaffolds for Mpro inhibition and advance anti-coronavirus drug research.