On Dec. 29, 2020, Regeneron announced encouraging initial data from an ongoing Phase 1/2/3 clinical trial of the Regeneron antibody cocktail, casirivimab and imdevimab, in hospitalized COVID-19 patients requiring low-flow oxygen.

The results passed the futility analysis (p<0.3 one-sided), as seronegative patients treated with the antibody cocktail had a lower risk of death or receiving mechanical ventilation (HR: 0.78; 80% CI: 0.51-1.2). The benefit was driven by results starting one week post-treatment, when the risk of death or receiving mechanical ventilation was reduced by approximately half with antibody cocktail treatment, based on a post-hoc analysis.