Shares of the Tarrytown, NY company were up 1.06% to $554.00 at last check.
The company said the cocktail caused a 100% reduction in symptomatic infection and roughly 50% lower overall rates of infection, based on an analysis of about 400 participants in the trial who had a household member with COVID-19.
The two-antibody cocktail, REGEN-COV, includes casirivimab and imdevimab.
The U.S. Food & Drug Administration granted Emergency Use Authorization for REGEN-COV in November. Regeneron said it is supplying up to roughly 1.5 million doses of REGEN-COV for treatment of Covid-19 under the current EUA.
"These data using REGEN-COV as a passive vaccine suggest that it may both reduce transmission of the virus as well as reduce viral and disease burden in those who still get infected," George Yancopoulos, Regeneron's president and chief scientific officer, said in a statement.
Passive vaccines provide immediate short-term passive immunity. Traditional vaccines, on the other hand, activate the immune system to develop its own antibodies, which typically takes weeks, but provides longer-term active immunity.
Regeneron said there was one death and one COVID-19-related hospitalization in a placebo group, while there were no deaths or COVID-19 hospitalizations in the treatment group.
The company said it is collaborating with Roche to increase global supply of REGEN-COV. Regeneron is responsible for development and distribution of the treatment in the U.S., and Roche is primarily responsible for development and distribution outside the U.S.
The trial is being run jointly with the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.