The Tarrytown, N.Y., pharmaceutical company's Phase 3 trial gave the drug to "recently infected" people who were asymptomatic.
"Regen-COV reduced the overall risk of progressing to symptomatic COVID-19 by 31% (primary endpoint), and by 76% after the third day," Regeneron said in a statement.
"The trial also demonstrated that Regen-COV shortened symptom duration and markedly reduced viral levels."
Regeneron said it will ask the U.S. Food and Drug Administration to expand the drug's authorization among people exposed to the virus who haven't yet been vaccinated.
This “could provide temporary stopgap protection as people await vaccines,” The company added.
“COVID-19 transmission often occurs via infected people who do not yet have symptoms, so it is critical that we rapidly diagnose and treat these individuals for their own health and to prevent transmission,” Katharine Bar, the co-principal investigator of the trial, said in a statement.
Bar is assistant professor of medicine for infectious diseases at the Hospital of the University of Pennsylvania.
Regen-COV is currently authorized to treat people infected with COVID-19 who have mild to moderate symptoms and are at high risk of developing severe disease because of factors including age or underlying conditions such as obesity, media reports say.
Regen-COV studies have shown a reduced “risk of hospitalization or death by about 70%,” Regeneron said.
Volunteers did not require “hospitalizations or emergency-room visits stemming from COVID-19 … compared with four volunteers in the placebo group,” the company added.
Additionally, those who did contract COVID-19 recovered in an average of 1.2 weeks compared to an average of 3.2 weeks in the placebo group.
Regeneron did not disclose how many volunteers tested positive for COVID-19 without showing symptoms but plans to in the future, a spokeswoman told The Wall Street Journal.
At last check Regeneron shares were trading 0.5% higher at $477.61.