On Aug. 4, 2021, Regeneron announced that the New England Journal of Medicine (NEJM) had published positive detailed results from a Phase 3 trial that assessed the ability of REGEN-COV (casirivimab and imdevimab) to prevent COVID-19 infection among household contacts of SARS-CoV-2 infected individuals.

The trial met its primary endpoint, reducing the risk of symptomatic infections by 81% (p<0.001), with a 93% reduction of symptomatic infections after the first week, and no dose-limiting toxicities observed.