Antibody cocktail ‘rapidly’ prevents and treats COVID, study finds. Here’s how

Katie Camero
·4 min read

Editor’s note: This story is available in Spanish here.

New results from a multi-stage clinical trial show that a cocktail of special antibodies can reduce risks of developing symptomatic COVID-19 by 81% if someone is not already infected with the virus. And for those who still get infected, the drug can help clear the virus from their bodies faster and shorten the duration of their symptoms.

A separate trial found that the cocktail, called REGEN-COV, is also able to reduce people’s chances of developing coronavirus symptoms if dealing with an asymptomatic infection by 76% after three days, the American biotechnology company Regeneron announced Monday.

The cocktail was given emergency-use authorization by the Food and Drug Administration in November, and is currently being used to treat mild to moderate COVID-19 in adults and children at least 12 years old who face high risks for severe disease and who are not hospitalized; it was the same drug given to former President Donald Trump when he tested positive for coronavirus in October.

Researchers say these antibodies can help protect people from infection and disease alongside vaccinations, and may be particularly useful for those waiting to get their shots or for those with compromised immune systems who may not respond well to vaccines.

“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,” Dr. George Yancopoulos, president and chief scientific officer at Regeneron, said in a statement. “These Phase 3 data provide even more evidence that REGEN-COV… can change the course of COVID-19 infection in non-hospitalized patients” by effectively preventing asymptomatic patients from becoming symptomatic.

Participants in the late-stage trial were enrolled only if they didn’t have any COVID-19 symptoms, didn’t have coronavirus antibodies and lived with someone who tested positive within the past four days. People that tested negative were assigned to the “prevention trial” (1,505) and those who tested positive were put in the “treatment trial” (204).

All participants were then randomly given one dose of the antibody cocktail or a placebo administered via a subcutaneous injection, which is when a short needle delivers drugs into the tissue layer between the skin and muscle. The technique is typically used when drugs are given in small doses or need to be delivered quickly.

COVID-19 vaccines, for reference, are given intramuscularly, or in the muscle.

What the ‘prevention trial’ found

In addition to finding that the antibody cocktail reduced risks of developing symptomatic infections by 81% in people who were not infected, the trial found that the drug helped clear symptoms in one week, compared to three weeks in the placebo group, in those who did develop infections.

“These findings are very encouraging and suggest that REGEN-COV is highly effective at preventing symptomatic COVID-19 in household contacts of SARS-CoV-2 infected individuals,” Dr. Dan Barouch, co-principal investigator of the trial and director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, said in the statement. “The rapid and robust protection, together with the subcutaneous route of administration, support the practical utility of these antibodies in protecting against COVID-19 in multiple settings, including after high-risk exposures.”

Side effects occurred in 20% of the participants who received the cocktail and included fever, itchy skin, chills and abdominal pain. No one who got the drug was hospitalized. Two people who received the cocktail died, but their deaths were not caused by COVID-19 or the drug, according to the company.

What the ‘treatment trial’ found

The antibody cocktail was found to prevent people with asymptomatic infections from progressing to symptomatic ones by 76% after three days.

The researchers also learned that the drug cut the number of weeks patients experienced symptoms by 45% and reduced their viral load — the amount of virus in their body — by more than 90%. This means people treated with REGEN-COV may be less likely to spread the virus once infected.

Side effects similar to the other trial occurred in 34% of the participants. No one was hospitalized or died.

Pfizer COVID vaccine protects children — even more than adults, trial study finds

Pfizer is testing a pill that could be the first oral COVID treatment, company says

Arthritis drug reduces death, length of stay in hospitalized COVID patients, study says