Regeneron’s COVID-19 antibody drug prevents symptomatic infection by 81%, study finds

Applause as 104-Year-Old Coronavirus Patient Leaves Hospital

A 104-year-old woman who contracted coronavirus twice has been released from hospital to a round of applause in Tunja, Colombia. (Credit: Hospital San Rafael Tunja via Storyful)

TARRYTOWN, N.Y. - A COVID-19 antibody cocktail developed by U.S. drugmaker Regeneron offered strong protection against symptomatic infection when given to people living with someone else infected with the virus, the company said.

Regeneron on Monday shared clinical trial results, which found that its REGEN-COV treatment reduced the overall risk of developing symptomatic COVID-19 by 81%, compared to those who received a placebo.

In November, the drug received an emergency use authorization from the U.S. Food and Drug Administration to treat mild-to-moderate COVID-19 patients. The new findings suggest the treatment could offer another form of protection against the virus for those who have not received a vaccination.

Regeneron said it would ask the FDA to expand the drug’s emergency approval to allow it to be used for preventative purposes in "appropriate populations."

e1ce62bf-View of Corporate and Research and Development Headquarters

FILE - A view of Regeneron Pharmaceuticals, Inc. headquarters is shown on Oct. 2, 2020 in Tarrytown, New York. (Photo by Lev Radin/Pacific Press/LightRocket via Getty Images)

To date, 40% of the U.S. population has received at least one dose of a COVID-19 vaccine and nearly 22% are fully vaccinated against the virus. While current vaccines have become more available and have been shown to be both safe and effective, antibody drugs like this could help those who haven’t been inoculated for various reasons.

"With more than 60,000 Americans continuing to be diagnosed with COVID-19 every day, the REGEN-COV antibody cocktail may help provide immediate protection to unvaccinated people who are exposed to the virus, and we are also working to understand its potential to provide ongoing protection for immunocompromised patients who may not respond well to vaccines," said Dr. George D. Yancopoulos, Regeneron’s president and chief scientific officer.

Regeneron’s clinical trial enrolled more than 1,500 people who lived in the same household as an individual who tested positive for the virus within the prior four days. They were randomly assigned to receive either one dose of REGEN-COV or a placebo.

After about a month, 1.5% of volunteers who received the treatment had symptomatic COVID-19, compared with 7.8% of those who received a placebo. Regeneron said the treatment offered 72% protection against symptomatic cases within the first week and 81% protection by day 29.

The trial also showed that REGEN-COV, which is a combination of monoclonal antibodies casirivimab and imdevimab, shortened COVID-19 symptom duration and reduced viral levels, the company said in a statement.

What are antibodies?

Antibodies are Y-shaped proteins than bind to one's foreign invaders, like viruses, bacteria, fungi and parasites.

Antibodies are a crucial part of the body’s adaptive immune system that bind to and help eliminate a virus, but it takes several weeks after infection or vaccination for the most effective ones to form. Drugs like REGEN-COV are intended to help sooner by supplying concentrated doses of one or two antibodies that work best.

The drug was given as an experimental medicine to former President Donald Trump when he was sickened with the virus in October, prior to the FDA’s emergency use authorization.

This story was reported from Cincinnati.

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