On Mar. 4, 2021, the National Institutes of Health (NIH) announced that the ACTIV-3 clinical trial evaluating the safety and efficacy of investigational therapeutics for COVID-19 in hospitalized patients, had closed enrollment in two sub-studies: one examining the investigational monoclonal antibody therapy VIR-7831, and another evaluating the investigational combination monoclonal antibody therapy containing BRII-196 and BRII-198.

The sub-studies were halted by the trial sponsor, the National Institute of Allergy and Infectious Diseases (NIAID), on Mar. 1, 2021, following an interim review and recommendation from the independent Data and Safety Monitoring Board (DSMB). There were no safety concerns with either therapeutic agent and no indication of harm in the therapeutic arms compared to the placebo arm.

VIR-7831 was developed through a partnership between GlaxoSmithKline (Brentford, United Kingdom) and Vir Biotechnology, Inc. (San Francisco). BRII-196 and BRII-198 are manufactured by Brii Biosciences (Durham, North Carolina and Beijing).