Kinetic characterization and inhibitor screening for the proteases leading to identification of drugs against SARS-CoV-2

The coronavirus (CoV) disease (COVID-19), caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has claimed many lives worldwide and is still spreading since December 2019. The 3C-like protease (3CL^pro) and papain-like protease (PL^pro) are essential for maturation of viral polyproteins in SARS-CoV-2 life cycle and thus regarded as key drug targets for the disease. In this study, 3CL^pro and PL^pro assay platforms were established and their substrate specificities were characterized. The assays were used to screen collections of 1068 and 2701 FDA-approved drugs. After excluding the externally used drugs which are too toxic, we totally identified 12 drugs as 3CL^pro inhibitors and 36 drugs as PL^pro inhibitors active at 10 μM. Among these inhibitors, 6 drugs were found suppressing SARS-CoV-2 with EC₅₀ below or close to 10 μM. This study enhances our understanding on the proteases and provides FDA approved drugs for prevention and/or treatment of COVID-19.