Investigating Nucleoside Analogue Inhibition of Coronavirus Replication
Emerging viruses, such as coronaviruses (CoVs), continue to pose a threat to human health, and few countermeasures have been approved to treat these infections. Two CoVs have emerged to cause severe disease in humans within the last twenty years, and CoVs that are closely related to these two viruses continue to circulate in bats. Thus, new CoVs could emerge into humans to cause severe disease, emphasizing the importance of developing antivirals that broadly inhibit these viruses. This work has identified two compounds that potently inhibit CoVs: remdesivir (GS-5734) and β-D-N4-Hydroxycytidine (NHC; EIDD-1931). Both of these compounds are classified as nucleoside analogues, structural mimics of naturally occurring compounds that are required for viral replication. This work demonstrates that both of these compounds inhibit CoVs by targeting viral replication, though they do so by distinct mechanisms. In addition, remdesivir and NHC obtain only low-level resistance to the compounds after extended passage, suggesting a high barrier to resistance for both of these inhibitors. This low-level resistance in CoVs is associated with a fitness cost in the absence of drug. However, low-level resistance to one of these compounds does not broadly confer resistance to other nucleoside analogues, suggesting their potential to be used in combination to treat CoV infections. Overall, this work identifies two distinct nucleoside analogue inhibitors that potently inhibit CoVs and provide insight into CoV replication.