On Jun. 16, 2021, the University of Oxford announced the Randomised Evaluation of COVID-19 Therapy (RECOVERY) trial demonstrated that the investigational antibody combination developed by Regeneron reduced the risk of death when given to patients hospitalised with severe COVID-19 who have not mounted a natural antibody response of their own.

The treatment used a combination of two monoclonal antibodies (casirivimab and imdevimab, known as REGEN-COV in the US) that bind specifically to two different sites on the coronavirus spike protein, neutralising the ability of the virus to infect cells.