On Dec. 7, 2021, Arbutus Biopharma, X-Chem, and Proteros announced that Arbutus had identified several molecules that inhibit the SARS-CoV-2 nsp5 main protease (Mpro), a validated target for the treatment of COVID-19 and potential future coronavirus outbreaks.

Upon achievement of this milestone, as part of their discovery and research agreement, Arbutus has obtained a worldwide exclusive license to the identified molecules.