Sara Cherry - January 20, 2021

Sara Cherry, PhD, Professor of Pathology and Laboratory Medicine and Microbiology, Scientific Director, High-throughput Screening Core, Director, Program for Chemogenomic Discovery, University of Pennsylvania, "COVID-19: Using chemogenomics to discover antivirals"

This study is focused on identifying therapeutic drugs and their mechanism of action against SARS-CoV2 infection. The High-throughput cell-based screening was employed for the initial chemical screening and selected drug candidates are further characterized in various ways before the move to pre-clinical and clinical trials. A total of about 20,000 antiviral libraries were acquired from different sources. SARS-CoV2 permissive cell lines, Vero, Huh7.5 and Calu-3, were seeded in 384 well plate format and performed High-throughput cell-based screening against SARS-CoV2 and OC43 (for pan Corona antivirals to help the preparation of possible next pandemic situation). Selected candidates were further validated to confirm their toxicity and antiviral activity. In 2020, Initial screening was performed with more than 3,500 compounds (U Penn in house compounds) and identified 4 antiviral candidates with Vero, 23 with Huh7.5 and 9 with Calu-3 cells. Four 4 different antiviral drugs, Remdesivir, Hydroxychloroquine, Cathepsin inhibitor and Camostat (TMPRSS2 inhibitor), were applied to each cell line to investigate the cell-type-specific entry pathway of SARS-CoV2. Remdesivir blocked SARS-CoV2 infection in all 3 cell types without toxicity. Hydroxychloroquine and Cathepsin inhibitor blocked the viral infection on Vero cells and Huh7.5 cells indicate that the virus can penetrate the cell in cathepsin mediated acid-dependent protease pathway. Huh7.5 cell also similar pattern as Vero cells. In contrast, Camostat showed strong protective activity and high cell viability on Calu-3 against SARS-CoV2 infection indicating SARS-CoV2 enter the cell via TMPRSS2 dependent pathway. They suggested blocking the entry may not the best way to inhibit the infection in vivo since it shows the virus can enter the cells in multiple pathways and we don’t know which cells would be using which pathway under which conditions. Inhibition of Cyclosporin has blocked Coronavirus in respiratory cell culture system but not affected influenza virus suggesting the immune pathway is associated with Coronavirus infection specifically.

Alisporivir also showed antiviral activity in respiratory cell models and consider as potentially therapeutic. Lung epithelial-derived Calu-3 cell was chosen to re-screen 18,000 compounds and identified 250 antiviral candidates. Additional TMPRSS2 inhibitor, UK-371804, was found through spike protein recombinant cell screen assay. Moluprivavir, Tubercidin and Thioguanine were identified as Nucleoside-based antivirals. More nucleoside screening was carried out and identified more inhibitors that block nucleoside metabolic pathways to prevent SARS-CoV2 infection. EGFR inhibitors were screened to be identified since the virus activates the singling pathway for viral replication.