Regeneron says monoclonal antibodies prevent Covid-19 in study

Regeneron said Tuesday that its monoclonal antibody cocktail prevented Covid-19 in a clinical trial.

The news, issued via a press release, mirrored similar news from Eli Lilly last week that its monoclonal antibody prevented symptomatic Covid-19 infections in nursing homes.

The results represent the first 400 volunteers from the study, which is being run by the National Institute of Allergy and Infectious Diseases (NIAID), and is continuing to enroll patients. The volunteers were at high risk of infection because they lived in the same household as a Covid-19 patient. Half the patients received a placebo, and the other half received 1.2 grams of casirivimab and imdevimab, Regeneron’s antibodies.


While eight of the 223 patients in the placebo group developed Covid symptoms and tested positive for the virus, none of the 186 patients who received the antibody did. Volunteers who received the antibody were also less likely to be asymptomatic carriers of the SARS-CoV-2 virus, which causes Covid-19. Twenty-three volunteers in the placebo group tested positive for the virus, compared to 10 in the antibody group, a 50% reduction.

It also appeared that infections in volunteers who received the antibody were less severe than those who did not, the company said. Infected volunteers in the placebo group had on average, more than 100-fold higher peak viral loads. Infections in the antibody group lasted no longer than a week, while 40% of the infections in the placebo group lasted three to four weeks.


Adverse events were less common among those who received the antibody cocktail, occurring at 18% in the placebo group and 12% in the antibody group. This was the result of the negative effects of the virus. Two percent of those in both groups had injection site reactions.

George Yancopoulos, Regeneron’s chief scientific officer, said in a statement that even with vaccines available, the antibody will be able help break the chain of infection, and may prove useful for individuals who are immunocompromised or unable to be vaccinated.

Regeneron was able to formulate the antibody so that it could be given as an injection, instead of being given intravenously. That would make the antibody much easier for health care workers to give.

The results have not been peer-reviewed or published in an academic journal.

Source: STAT