Hepatitis C Virus Protease Inhibitors Show Differential Efficacy and Interactions with Remdesivir for Treatment of SARS-CoV-2 in Vitro

Antivirals targeting SARS-CoV-2 could improve treatment of COVID-19. We evaluated the efficacy of clinically relevant hepatitis C virus (HCV) NS3 protease inhibitors (PI) against SARS-CoV-2 and their interactions with remdesivir, the only antiviral approved for treatment of COVID-19. HCV PI showed differential potency in VeroE6 cell-based antiviral assays based on detection of the SARS-CoV-2 Spike protein. Linear PI boceprevir, telaprevir and narlaprevir had 50% effective concentrations (EC50) of {approx}40 M. Among macrocyclic PI simeprevir, paritaprevir, grazoprevir, glecaprevir, voxilaprevir, vaniprevir, danoprevir and deldeprevir, simeprevir had the highest (EC50 15 M) and glecaprevir the lowest (EC50 >178 M) potency. Acyclic PI asunaprevir and faldaprevir had EC50 of 72 and 23 M, respectively. ACH-806, an HCV NS3 protease co-factor NS4A inhibitor, had EC50 of 46 M. For selected PI, potency was similar in human hepatoma Huh7.5 cells. Selectivity indexes, based on antiviral and cell viability assays, were highest for linear PI. In combination with remdesivir, linear PI boceprevir and narlaprevir showed antagonism, while macrocyclic PI simeprevir, paritaprevir and grazoprevir showed synergism with drug reduction indexes of up to 27 for simeprevir. Treatment of infected cultures with equipotent concentrations (1-fold EC50) of HCV PI revealed minor differences in barrier to SARS-CoV-2 escape. Complete viral suppression was achieved treating with [≥]3-fold EC50 boceprevir or combination of 1-fold EC50 simeprevir with 0.4-fold EC50 remdesivir, not leading to significant viral suppression in single treatments. Considering potency, human plasma concentrations and synergism with remdesivir, simeprevir seemed the most promising compound for optimization of future antiviral treatments of COVID-19.