COVID-19 caused by SARS-CoV-2 has continually been a serious threat to public health worldwide. Two orally available 4-fluoro-benzothiazole-containing small molecules, TKB245 and TKB248, specifically inhibit SARS-CoV-2 main protease (Mpro) activity and potently block SARS-CoV-2 infectivity and replication more effectively than nirmatrelvir, molnupiravir, and ensitrelvir. Both compounds also block Delta and Omicron variant replication in human-ACE2-knocked-in mice. Native mass spectrometry shows binding to dimer Mpro, promoting dimerization. X-ray crystallography reveals binding to Mpro's active site, forming a covalent bond with Cys-145. These compounds show potential as COVID-19 therapeutics.
