On Apr. 8, 2021, Oxford University announced that favipiravir was to be investigated in the UK as part of the Platform Randomised trial of Interventions against COVID-19 In older peoPLE (PRINCIPLE), the worldﾒs largest clinical trial of possible COVID-19 treatments for recovery at home and in other non-hospital settings.

Favipiravir is an antiviral drug which has been licenced in Japan since 2014 to treat influenza. It works by inhibiting a viral enzyme called RNA polymerase, preventing viral replication within human cells. This viral enzyme is common to several viruses, including SARS-CoV-2, which causes COVID-19.