EIDD-2801  EIDD-2801 is an experimental antiviral drug which is orally active and was developed for the treatment of influenza. It is a prodrug of the synthetic nucleoside derivative N4-hydroxycytidine, and exerts its antiviral action through introduction of copying errors during viral RNA replication. Activity has also been demonstrated against coronaviruses including SARS, MERS and SARS-CoV-2. In April, May and June 2020, the drug was tested in a preliminary human study for "Safety, Tolerability, and Pharmacokinetics" in healthy volunteers in the UK and US. This was in preparation for study of its efficacy in the treatment of COVID-19.