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Disclosures: O’Brien reports being an employee and shareholder at Regeneron Pharmaceuticals.
August 04, 2021
2 min read

Regeneron cocktail shows promise as post-exposure prophylaxis for COVID-19

Disclosures: O’Brien reports being an employee and shareholder at Regeneron Pharmaceuticals.
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A single subcutaneous dose of Regeneron’s antibody cocktail prevents symptomatic COVID-19 and reduces the incidence of asymptomatic SARS-CoV-2 infection, according to results from a study published today in The New England Journal of Medicine.

Researchers said the results show that the cocktail, REGEN-COV, has the potential to be used as long-term prophylaxis in individuals at risk for COVID-19.

Source: Adobe Stock.
Source: Adobe Stock.

Last week, the FDA expanded its emergency use authorization to allow the cocktail, which includes the monoclonal antibodies casirivimab and imdevimab, to be used for postexposure prophylaxis. Data from the study published today were part of the package supporting the expanded authorization, Meagan O’Brien, MD, the senior director of early clinical development and clinical experimental sciences at Regeneron, told Healio.

Meagan O'Brien

“Monoclonal antibodies such as REGEN-COV can play an important complementary role to vaccines in the postexposure prophylaxis setting by providing rapid protection for people at high risk for progression to severe COVID-19 when they are not fully vaccinated or are not expected to mount an adequate response to vaccination, and who have been exposed to a SARS-CoV-2-infected individual or are at high risk of exposure because of infection occurring in a shared institutional setting, such as in nursing homes or prisons,” O’Brien told Healio, noting that the cocktail is “not a substitute for vaccination against COVID-19 and is not authorized for pre-exposure prophylaxis to prevent COVID-19.”

O’Brien, and colleagues conducted a randomized, double-blind, placebo-controlled trial that enrolled 1,505 participants who had come into contact with a household member with a diagnosis of a SARS-CoV-2 infection in the last 96 hours and enrolled them in a 1:1 ratio to receive either a total dose of 1,200 mg of REGEN-COV (n = 753) or placebo (n = 752).

The trial consisted of a baseline screening and a 28-day efficacy assessment. It will conclude with a 7-month follow-up.

The mean age of participants was 42.9 years, 45.9% were male, 9.3% were Black and 40.5% identified as Hispanic or Latin American. The median household size of participants was three people. Of the 1,505 participants, 30.5% were at high risk for severe COVID-19.

Symptomatic COVID-19 developed in 11 of the 753 (1.5%) participants in the Regeneron group, and 59 of 752 (7.8%) in the placebo group (relative risk reduction [RRR], 81.4%; OR, 0.17).

Within the first week of the trial, nine participants in the Regeneron group (1.2%), and 32 participants in the placebo group (4.3%) had symptomatic COVID-19 (RRR, 71.9%). In weeks 2 to 4, two participants in the Regeneron group (0.3%) and 27 in the placebo group (3.6%) had symptomatic COVID-19 (RRR, 92.6%).

Overall, either asymptomatic or symptomatic COVID-19 developed in 36 participants in the Regeneron group (4.8%) and in 107 participants in the placebo group (14.2%; RRR, 66.4%; OR, 0.31).