Regeneron said Monday it will ask the Food and Drug Administration to expand the emergency use authorization for its COVID-19 antibody cocktail after a clinical trial showed it is effective at preventing infections in people who have been exposed to the virus.

The New York-based drugmaker said in a news release that a Phase 3 trial found that a single 1,200-mg dose of REGEN-COV, which combines the monoclonal antibodies casirivimab with imdevimab, reduced the risk of symptomatic COVID-19 cases by 81% in people who live with someone recently infected by the virus.

The antibody cocktail offered 72% protection in the first week, and 93% in subsequent weeks, Regeneron said.

In November, the FDA authorized REGEN-COV for emergency use in treating patients with mild to moderate COVID-19. Regeneron said it will seek to expand that authorization for prevention use and also to be administered through a subcutaneous shot, rather than only by intravenous infusion. 

Regeneron’s antibody cocktail was one of the treatments given to former President Donald Trump when he was hospitalized with COVID-19 in October. He credited it for his quick recovery. 

The clinical trial, which was jointly run with the National Institute of Allergy and Infectious Diseases, studied 1,505 people who had no coronavirus antibodies and lived with someone who tested positive for COVID-19 in the previous four days.

After 29 days, 11 people who had been given REGEN-COV developed symptomatic COVID-19, compared to 59 in the placebo group. Those who received the drug and were infected, however, recovered quicker — within one week, compared to three weeks in the placebo group.

None of the participants who received the antibody cocktail were hospitalized or went to the emergency room because of COVID-19 during the 29 days, Regeneron said.

Dr. Myron Cohen, who leads the monoclonal antibody efforts for the COVID Prevention Network, said the drug could be used to complement vaccine efforts, particularly for those at high risk of infection. He added that REGEN-COV has been shown in vitro to be effective against emerging variants.

"Despite standard precautions to reduce transmission, nearly 10% of unvaccinated individuals living with an infected person developed symptomatic infections if they did not receive REGEN-COV,” Cohen said in the news release. “If authorized, 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."

Regeneron separately announced Monday that another Phase 3 clinical trial in people with asymptomatic COVID-19 found that REGEN-COV reduced the risk of progressing to symptomatic cases by 31% overall, and by 76% after the third day.