Discovery of 2-(furan-2-ylmethylene)hydrazine-1-carbothioamide derivatives as novel inhibitors of SARS-CoV-2 main protease

The COVID-19 posed a serious threat to human life and health, and SARS-CoV-2 M(pro) has been considered as an attractive drug target for the treatment of COVID-19. Herein, we report 2-(furan-2-ylmethylene)hydrazine-1-carbothioamide derivatives as novel inhibitors of SARS-CoV-2 M(pro) developed by in-house library screening and biological evaluation. Similarity search led to the identification of compound F8–S43 with the enzymatic IC(50) value of 10.76 μM. Further structure-based drug design and synthetic optimization uncovered compounds F8–B6 and F8–B22 as novel non-peptidomimetic inhibitors of M(pro) with IC(50) values of 1.57 μM and 1.55 μM, respectively. Moreover, enzymatic kinetic assay and mass spectrometry demonstrated that F8–B6 was a reversible covalent inhibitor of M(pro). Besides, F8–B6 showed low cytotoxicity with CC(50) values of more than 100 μM in Vero and MDCK cells. Overall, these novel SARS-CoV-2 M(pro) non-peptidomimetic inhibitors provide a useful starting point for further structural optimization.