Monoclonal Antibody Receives Expanded Authorized Usage From FDA


With the FDA nod, Regeneron’s monoclonal antibody Regen-Cov (casirivimab and imdevimab) is authorized for the use of the therapy for post-exposure prophylaxis in certain people exposed to SARS-CoV-2 or who are at high risk of exposure to an infected individual.


The Food and Drug Administration (FDA) has expanded the Emergency Use Authorization (EUA) for the Regeneron monoclonal antibody Regen-Cov (casirivimab and imdevimab) to include post-exposure prophylaxis in people at high risk for progression to severe COVID-19, those who are not fully vaccinated or are not expected to mount an adequate response to vaccination, and have been exposed to a SARS-CoV-2 infected individual, or who are at high risk of exposure to an infected individual because of infection occurring in the same institutional setting (such as in nursing homes or prisons).

"Today's FDA authorization enables certain people at high risk of developing severe COVID-19 infection to access Regen-Cov if they have been exposed to the virus–the first time an antibody treatment has been authorized for this purpose," Regeneron President and Chief Scientific Officer George Yancopoulos, MD, PhD, said.

This is based off results from a phase 3 study showing an 81% reduced risk of symptomatic infections in close contacts of SARS-CoV-2 infected individuals. The study assessed the monoclonal antibody for post-exposure prophylaxis of COVID-19 in household contacts of individuals infected with SARS-CoV-2.

There were 1505 participants (753 casirivimab and imdevimab, 752 placebo) who were not infected (seronegative with a negative PCR test) when they entered the trial.

Results showed the therapy demonstrated:

  • In a post-hoc analysis in the subgroup of participants who met the criteria for high risk for progression to severe COVID-19 (570 casirivimab and imdevimab, 567 placebo), there was a 76% risk reduction in COVID-19 with casirivimab and imdevimab treatment compared to placebo (p<0.0001).
  • Reduced the risk of symptomatic infections by 62% in a broader group of asymptomatic participants, regardless of infection status, based on a post-hoc analysis (p<0.0001).

Adverse effects occurred in 20% of casirivimab and imdevimab participants and 29% in placebo participants. Injection site reactions (all mild to moderate) occurred in 4% (55) of casirivimab and imdevimab participants and 2% (19) of placebo participants. Hypersensitivity reactions occurred in 0.2% (2) of casirivimab and imdevimab participants, all of which were mild in severity.

With the rise in COVID-19 cases across the United States due mainly to the highly contagious Delta variant, the need for additional therapies may prove to a necessary complement to vaccines.

Back in June, Regeneron said it was planning to seek an expansion of its FDA EUA to include appropriate hospitalized patients.

The study’s results demonstrated that adding 8000 mg of casirivimab and imdevimab it reduced risk of death by 20% in patients hospitalized with COVID-19 who had not mounted their own immune response.

"Definitive phase 3 trials have now demonstrated that Regen-Cov can alter the course of COVID-19 infection from prevention, to very early infection, all the way through to when patients are on a ventilator in the hospital," Yancopoulos, said at that time.

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