On Apr. 1, 2021, Arbutus Biopharma, X-Chem and Proteros Biostructures announced hat they had entered into a discovery research and license agreement focused on the discovery of novel inhibitors targeting the SARS-CoV-2 nsp5 main protease (Mpro).

The agreement was designed to accelerate the development of pan-coronavirus agents to treat COVID-19 and potential future coronavirus outbreaks.