COVID-19 Antibody Therapy Reduces Deaths in Trial

Source: REUTERS/Brendan McDermid/File Photo

Regeneron’s antibody therapy cuts deaths by one-fifth in hospitalized patients suffering from severe COVID-19 and unable to evoke an immune response.

The Randomised Evaluation of COVID-19 Therapy (RECOVERY) trial first began in early 2020. The trial aimed to investigate the effectiveness of a COVID-19 antibody therapy developed by Regeneron pharmaceuticals. The treatment involved a combination of two monoclonal antibodies, casirivimab and imdevimab (REGN-COV2).

The body normally produces antibodies in response to foreign antigens present on bacteria and viruses. Upon binding to the antigen, they then destroy the pathogen. These antibodies can often survive in the body for months to years, providing protection against further infection. Scientists believe that antibodies produced in response to SARS-CoV-2 persist for 5-7 months in the body. Therefore, researchers have turned to monoclonal antibodies as a treatment for COVID-19. Monoclonal antibodies are synthetically formed and are specific to the foreign antigen.

Regeneron’s antibody cocktail, also called REGN-COV2, can attach to two different sites on the coronavirus spike protein. Thus, rendering the virus ineffective. Although the treatment received emergency use approval by the FDA in November 2020, this is the first large-scale trial to assess its effectiveness in reducing deaths in severe COVID-19.


The trial recruited over 9,000 patients hospitalized with COVID-19 between September 2020 and May 2021. The team of researchers then randomly allocated to a control group that only received the usual care, whereas the other group received the antibody therapy along with the usual care. Approximately one-third of these patients did not have an antibody response, also known as seronegative. Moreover, half of the patients did demonstrate an antibody response at baseline, and one-sixth had an unknown antibody status.

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

Professor Sir Peter Horby, chief investigator of the trial

Among those receiving the usual care, the seronegative group had almost twice as high 28-day mortality. This 28-day mortality was reduced by one-fifth in the seronegative patients from the antibody therapy group. Thus, resulting in six fewer deaths for every 100 seronegative patients. Furthermore, the seronegative group that received the antibody therapy had fewer hospitalization and lower chances of requiring a ventilator. However, researchers did not note any significant results in the seropositive group.

The preliminary results provide evidence for the use of antibody therapy in patients hospitalized with severe COVID-19.


Horby, Peter W, et al. “Casirivimab and Imdevimab in Patients Admitted to Hospital with COVID-19 (RECOVERY): a Randomised, Controlled, Open-Label, Platform Trial.” 2021, doi:10.1101/2021.06.15.21258542.


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