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Press Release.

Disclosures: Horby and Stevens report no relevant financial disclosures.
June 16, 2021
3 min read

Regeneron cocktail reduces risk for death in some hospitalized patients, study finds


Press Release.

Disclosures: Horby and Stevens report no relevant financial disclosures.
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Regeneron’s antibody cocktail reduced the risk for death by 20% in patients hospitalized with severe COVID-19 who had not mounted their own immune response, researchers from the phase 3 RECOVERY trial said Wednesday.

According to Regeneron, it was the first time a trial demonstrated that any antibody treatment improved survival in patients hospitalized with COVID-19. The company said it would share the phase 3 data with the FDA and request that the emergency use authorization (EUA) for the investigational cocktail of casirivimab and imdevimab — called REGEN-COV — be expanded to include “appropriate hospitalized patients.”

COVID data
Regeneron’s antibody cocktail of casirivimab and imdevimab reduced the risk for death by 20% in hospitalized patients with COVID-19 who had not mounted an immune response.
Source: Adobe Stock.

The original EUA was issued in November for patients aged 12 years or older with mild-to-moderate COVID-19. Earlier this month, the FDA authorized a lower dose of REGEN-COV, which Regeneron said may help more patients access the treatment.

The RECOVERY trial has been assessing numerous potential treatments for COVID-19 for more than a year. Based on early-stage trial results that indicated REGEN-COV may improve survival among hospitalized patients who were seronegative, RECOVERY investigators enrolled almost 9,800 hospitalized patients between Sept. 18, 2020, and May 22, 2021, and randomly assigned them to receive either usual care plus REGEN-COV 8,000 mg by IV infusion or usual care alone. Around one-third of the participants in the phase 3 trial were seronegative at baseline.

According to the investigators, 24% of seronegative patients who received the antibody cocktail died vs. 30% of seronegative patients who received usual care alone (rate ratio = 0.80; 95% CI, 0.7-0.91). “Thus, for every 100 such patients treated with the antibody combination, there would be six fewer deaths,” the investigators said.

The findings were published in press releases by Regeneron and the RECOVERY trial and posted online on the preprint server medRxiv, but they have not yet undergone peer review. Investigators said they will submit the findings to a leading peer-reviewed medical journal.

Peter Horby, PhD, professor of emerging infectious disease at the University of Oxford and joint chief investigator for the RECOVERY trial, called the results “very exciting.”

“The hope was that by giving a combination of antibodies targeting the SARS-CoV-2 virus we would be able to reduce the worst manifestations of COVID-19,” he said in a statement. “There was, however, great uncertainty about the value of antiviral therapies in late-stage COVID-19 disease. It is wonderful to learn that even in advanced COVID-19 disease, targeting the virus can reduce mortality in patients who have failed to mount an antibody response of their own.”

Seronegative patients who received the antibody cocktail also spent less time in the hospital compared with the usual care group (a median of 13 days vs. 17 days), and they were more likely to be discharged alive by day 28 (64% vs. 58%), among other positive clinical findings.

Michael Stevens

Michael Stevens, MD, MPH, FACP, FIDSA, FSHEA, a professor of internal medicine at Virginia Commonwealth University School of Medicine, said the findings “have the potential to significantly impact the management of seronegative patients who are hospitalized with COVID-19 by providing a therapeutic option that can reduce disease progression, length of stay and mortality.”

“We eagerly await release of these data after formal peer review, and review and recommendations by guidelines panels from organizations such as the Infectious Diseases Society of America and NIH will be of great benefit,” Stevens told Healio. “It will be critical as well to identify how antibody testing can be incorporated into routine clinical care as only seronegative patients were reported as benefiting from this monoclonal antibody combination therapy. The RECOVERY trial investigators should be applauded for all of their efforts during the pandemic to inform clinical practice across a wide number of potential therapeutics.”


Horby PW, et al. medRxiv. 2021;doi:10.1101/2021.06.15.21258542.

Press Release.

Recovery. Recovery trial finds Regeneron’s monoclonal antibody combination reduces deaths for hospitalized COVID-19 patients who have not mounted their own immune response. Accessed June 16, 2021.