If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Infectious disease


Regeneron antibody cocktail could be used to prevent COVID-19

The company is asking the FDA to permit preventative use after clinical trials show that it prevents SARS-CoV-2 spread within households

by Megha Satyanarayana
April 14, 2021 | A version of this story appeared in Volume 99, Issue 14


An image of boxes containing the two antibodies in Regeneron's treatment.
Credit: Regeneron
Regeneron's COVID-19 antibody cocktail, made up of casivirimab and imdevimab, shows promise as a preventative in Phase 3 trials.

An antibody treatment created by Regeneron appears to prevent COVID-19 from spreading between people who live in the same household, according to clinical trial data the company released earlier this week.

Support nonprofit science journalism
C&EN has made this story and all of its coverage of the coronavirus epidemic freely available during the outbreak to keep the public informed. To support us:
Donate Join Subscribe

The antibody cocktail could become a much needed stopgap as vaccination efforts continue in the US, says Jeffrey Henderson, an infectious diseases specialist at Washington University School of Medicine. Vaccines take a while to teach the immune system how to respond to SARS-CoV-2, he says. The antibody cocktail can stop the virus from infecting cells almost immediately.

“That can be really relevant in states where not everyone is immunized and there is still a high prevalence, or increasing prevalence, of infection in the community,” he says.

Regeneron says it will ask the US Food and Drug Administration to expand the emergency use authorization it has for REGEN-COV, as the cocktail is called, beyond its current status as a treatment to include infection prevention. The two antibodies, casivirimab and imdevimab, can be given to people who have mild COVID-19. Regeneron has partnered with Roche to improve global access to the drug.

The Phase 3 trial, jointly run with the National Institute of Allergy and Infectious Diseases, included about 1,500 people who were not infected with SARS-CoV-2 but were living with someone who had been recently diagnosed. Half the people in the trial received a single injection of the antibodies; the other half received a placebo.

In the group of people who got the antibodies, the risk of infection dropped by 81%, Regeneron says. And among people in the trial who did get infected, those in the antibody group cleared their infections within a week, compared to 3 weeks for the placebo group.

While the antibodies don’t kill the virus in infected people, they attach to different parts of the virus’s spike protein, preventing it from infecting new cells, and, in theory, allowing the body’s immune system to focus its energy on cells that are already infected.

John Newman, a stock analyst with Canaccord Genuity, says in a report that the trial results for the Regeneron cocktail are encouraging, both as a treatment and as a preventative.

As a treatment, REGEN-COV and other COVID-19 antibody treatments are given as an infusion in the hospital. This requires a complex setup that involves infection-control measures, Henderson says. But as a preventative, the dose is cut in half, and it’s given as a subcutaneous injection, much like an insulin shot. REGEN-COV won’t take the place of vaccines, Henderson says. Injectable antibodies have short lifespans, and unlike natural antibodies, there is no “memory” in the immune system of how to make them. That’s what vaccines help do—train cells in the immune system to manage future infections themselves.

Timing is key, Henderson says. After a year of COVID-19 clinical trials, it seems that getting any drug, whether antibody or small molecule, into someone as early as possible yields the best results. “You need to get these antivirals on board—get them into the patient—early, as soon as possible, to see a substantial effect like this,” he says.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.