Discovery of a Highly Promising Disulfide Derivative Scaffold as Inhibitor of SARS‐CoV‐2 main protease

The main protease (M pro ) of Severe Acute Respiratory Syndrome Coronavirus (SARS‐CoV‐2) represents a promising target for antiviral drugs aimed at combating COVID‐19. Consequently, the development of M pro inhibitor is an ideal strategy for combating the virus. In this study, we identified twenty‐two dithiocarbamates ( 1 a – h ), dithiocarbamate‐Cu(II) complexes ( 2 a‐hCu ) and disulfide derivatives ( 2 a – e , 2 i ) as potent inhibitors of M pro , with IC 50 value range of 0.09–0.72, 0.9–24.7, and 15.1–111 μM, respectively, through FRET screening. The enzyme kinetics, inhibition mode, jump dilution, and DTT assay revealed that 1 g may be a partial reversible inhibitor, while 2 d and 2 f‐Cu are the irreversible and dose‐ and time‐dependent inhibitors, potentially covalently binding to the target. Binding of 2 d , 2 f‐Cu , and 1 g to M pro was found to decrease the stability of the protein. Additionally, DTT assays and thermal shift assays indicated that 2 f‐Cu and 2 d are the nonspecific and promiscuous cysteine protease inhibitor. ICP‐MS implied that the inhibitory activity of 2 f‐Cu may stem from the uptake of Cu(II) by the enzyme. Cytotoxicity assays demonstrated that 2 d and 1 g exhibit low cytotoxicity, whereas 2 f‐Cu show certain cytotoxicity in L929 cells. Overall, this work presents two promising scaffolds for the development of M pro inhibitors to combat COVID‐19.