TY - JOUR T1 - Identifying SARS-CoV-2 Antiviral Compounds by Screening for Small Molecule Inhibitors of nsp5 Main Protease JF - bioRxiv DO - 10.1101/2021.04.07.438806 SP - 2021.04.07.438806 AU - Jennifer C Milligan AU - Theresa U Zeisner AU - George Papageorgiou AU - Dhira Joshi AU - Christelle Soudy AU - Rachel Ulferts AU - Mary Wu AU - Chew Theng Lim AU - Kang Wei Tan AU - Florian Weissmann AU - Berta Canal AU - Ryo Fujisawa AU - Tom Deegan AU - Hema Nagara AU - Ganka Bineva-Todd AU - Clovis Basier AU - Joseph F Curran AU - Michael Howell AU - Rupert Beale AU - Karim Labib AU - Nicola O’Reilly AU - John F.X Diffley Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/04/08/2021.04.07.438806.abstract N2 - The coronavirus 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread around the world with unprecedented health and socio-economic effects for the global population. While different vaccines are now being made available, very few antiviral drugs have been approved. The main viral protease (nsp5) of SARS-CoV-2 provides an excellent target for antivirals, due to its essential and conserved function in the viral replication cycle. We have expressed, purified and developed assays for nsp5 protease activity. We screened the nsp5 protease against a custom chemical library of over 5,000 characterised pharmaceuticals. We identified calpain inhibitor I and three different peptidyl fluoromethylketones (FMK) as inhibitors of nsp5 activity in vitro, with IC50 values in the low micromolar range. By altering the sequence of our peptidomimetic FMK inhibitors to better mimic the substrate sequence of nsp5, we generated an inhibitor with a subnanomolar IC50. Calpain inhibitor I inhibited viral infection in monkey-derived Vero E6 cells, with an EC50 in the low micromolar range. The most potent and commercially available peptidyl-FMK compound inhibited viral growth in Vero E6 cells to some extent, while our custom peptidyl FMK inhibitor offered a marked antiviral improvement.Competing Interest StatementThe authors have declared no competing interest. ER -