After one month, 1.5% of volunteers receiving REGEN-COV had symptomatic Covid-19 infections, compared with 7.8% of those who received a placebo, amounting to an 81% risk reduction, Regeneron said.
There weren't any hospitalizations or emergency-room visits stemming from Covid-19 among volunteers taking Regeneron's drug, compared with four volunteers in the placebo group, according to the company.
The antibody drug also appeared to help speed recovery among those who contracted Covid-19 symptoms. Volunteers who received the drug had symptoms for an average of 1.2 weeks, compared with an average of 3.2 weeks in the placebo group, the company said.
Regeneron didn't disclose how many volunteers tested positive for Covid-19 without showing symptoms but plans to in the future, a company spokeswoman said.
REGEN-COV is a cocktail of two monoclonal antibodies, molecules that mimic the antibodies naturally produced by the immune system to fight viruses and bacteria.
The FDA first cleared use of the drug in November under an emergency-use authorization, which a medication to be prescribed before it has completed the complete battery of testing required for a full approval.
The drug gained attention last October, after it was given to then-President Trump, who then praised the therapy's impact.
Yet REGEN-COV and a rival antibody drug made by Eli Lilly & Co. haven't been used as much health officials had expected, partly because they are given by intravenous infusion, which can be cumbersome for hospitals to administer.
In Regeneron's prevention study, volunteers were given the drug with simpler-to-use subcutaneous shots in which the drug is injected through the skin.
"Convenient subcutaneous administration of REGEN-COV could help control outbreaks in high-risk settings where individuals have not yet been vaccinated, including individual households and group living settings," said Myron Cohen, director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill. He helped lead the study on behalf of NIAID.
Write to Joseph Walker at joseph.walker@wsj.com
Copyright ©2020 Dow Jones & Company, Inc. All Rights Reserved. 87990cbe856818d5eddac44c7b1cdeb8