GS-441524 is the active prodrug of the broad-spectrum antiviral Remdesivir. GS-441524 is an adenosine nucleotide analog in viral RNA production. It is a nucleotide analog inhibitor of RNA-dependent RNA polymerases (RdRps). The compound interferes with the action of viral RNA polymerase and evades proofreading by viral exoribonuclease (ExoN), causing a decrease in viral RNA production (RNA synthesis arrest), either by terminating RNA chains or causing mutations. It inhibits MERS-CoV or SARS-CoV-infected HAE cultures (EC50=74nM and 69nM) and murine hepatitis virus (MHV) (EC50=30nM). In vivo, remdesivir (25 and 50 mg/kg) reduces lung viral titers and prevents weight loss in a mouse model of SARS-CoV infection. Remdesivir is used as a treatment for Ebola virus disease and Marburg virus infections and other single stranded RNA viruses such as respiratory syncytial virus, Junin virus, Lassa fever virus, Nipah virus, Hendra virus and the coronaviruses (including MERS and SARS viruses). Remdesivir is effective in the control of 2019-nCoV (COVID-19) infection in vitro. It now also has been studied as potential treatment of SARS-CoV-2 infections.