Ginkgolic acid and anacardic acid are specific covalent inhibitors of SARS-CoV-2 cysteine proteases.

In the urgent campaign to develop therapeutics against SARS-CoV-2, natural products have been an important source of new lead compounds. We herein identified two natural products, ginkgolic acid and anacardic acid, as inhibitors using a high-throughput screen targeting the SARS-CoV-2 papain-like protease (PLpro). Moreover, our study demonstrated that the two hit compounds are dual inhibitors targeting the SARS-CoV-2 3-chymotrypsin-like protease (3CLpro) in addition to PLpro. A mechanism of action study using enzyme kinetics further characterized the two compounds as irreversible inhibitors against both 3CLpro and PLpro. Significantly, both identified compounds inhibit SARS-CoV-2 replication in vitro at nontoxic concentrations. Our finding provides two novel natural products as promising SARS-CoV-2 antivirals.