Drug Repurposing Screens Reveal FDA Approved Drugs Active Against SARS-CoV-2

The novel coronavirus SARS-CoV-2 emerged in China at the end of 2019 and rapidly became a global pandemic. While there are a variety of experimental treatments currently in clinical trials, there is a dearth of approved therapeutics to treat COVID-19. Drug repurposing identifies existing therapeutics that have already been through testing in humans for new indications, and is particularly advantageous since they could be readily deployed. To this end, we screened a repurposing library of ~3,000 drugs for their antiviral activity against SARS-CoV-2 in a cell-based high-content assay. While screening in African Green Monkey Vero cells found only six antivirals, screening in the human hepatocyte Huh7.5 cells validated 23 drugs with activity against SARS-CoV-2 including: 6 protease inhibitors, 8 kinase inhibitors and two histone methyltransferase inhibitors. Since SARS-CoV-2 infects the lung epithelium, we used the human lung epithelial cell line Calu-3 and found that there are major differences in drug sensitivity and entry pathways used by SARS-CoV-2 in lung cells. While hydroxychloroquine and other quinolines are antiviral in Vero and Huh7.5 cells, they are inactive in Calu-3 cells. Moreover, the TMPRSS2 inhibitor camostat, has antiviral activity in Calu-3 cells but not in other cell types, suggesting that the entry pathway used in Vero and Huh7.5 cells is distinct from that used in lung cells. Entry in lung epithelial cells is pH-independent and requires TMPRSS2, while entry in Vero and Huh7.5 requires low pH and triggering by other proteases in the acidic endosomal compartment. Importantly, we found that 9 drugs were active in lung cells, 7 of which have been tested in humans. This includes 3 FDA approved drugs: Salinomycin, Dacomitinib and Cyclosporine. Moreover, we found that Cyclosporine targeting of Cyclophilin rather than Calcineurin is required, suggesting a strategy to treat SARS-CoV-2. These antivirals are active across diverse cell types, revealing essential host targets that have the potential for rapid clinical implementation. Funding: This study was supported by NIH, Dean’s Innovation Fund, Linda and Laddy Montague, and BWF.