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Regen-CoV for early treatment in people recently infected with SARS-CoV-2

Regen-CoV is the brand name of a combination of two antibodies that attack SARS-CoV-2. The antibodies are as follows:

  • casirivimab
  • imdevimab

Regeneron Pharmaceuticals, the developer of the antibodies, has conducted a placebo-controlled study in 204 adults who were diagnosed with SARS-CoV-2 infection but who had not yet developed symptoms.

Researchers divided participants into two groups, as follows:

  • Regen-CoV at a single dose of 1,200 mg (600 mg of each antibody) administered as four injections just under the skin – 100 people
  • injections of placebo just under the skin – 104 people

According to the company, at the start of the study, 32% of participants had “at least one known factor that put them at high risk of suffering severe consequences from COVID-19,” including obesity and older age.

Results

The proportion of participants who developed symptoms of COVID-19 three days after injections were distributed as follows:

  • Regen-CoV – 29%
  • placebo – 42%

These results suggest that Regen-CoV can reduce the risk of developing COVID-19 by 31% vs. placebo. This difference favouring Regen-CoV was statistically significant.

For participants who developed symptoms, Regen-CoV reduced the duration of symptoms by 45%.

Although the study was not designed to assess the risk of hospitalization, it is noteworthy that the distribution of participants who visited a hospital emergency department or were hospitalized after injections because of COVID-19 was as follows:

  • Regen-CoV – 0 people
  • placebo – 6 people

Hopefully Regeneron will release detailed results from this and other studies in the future to help regulatory agencies decide on the scope of its use.

Given the totality of clinical data with Regen-CoV, it is likely that this antibody will be in the news in the future.

—Sean R. Hosein

REFERENCES:

  1. Regeneron. Phase three treatment trial in recently infected asymptomatic patients showed Regen-CoV (casirivimab with imdevimab) significantly reduced progression to symptomatic COVID-19. Press release. 12 April 2021.
  2. Baum A, Ajithdoss D, Copin R, et al. RegenCOV2 antibodies prevent and treat SARS-CoV-2 infection in rhesus macaques and hamsters. Science. 2020 Nov 27;370(6520):1110-1115.
  3. Baum A, Fulton BO, Wloga E, et al. Antibody cocktail to SARS-CoV-2 spike protein prevents rapid mutational escape seen with individual antibodies. Science. 2020 Aug 21;369(6506):1014-1018.