Single Injection of Monoclonal Antibodies Reduces Risk of Symptomatic SARS-CoV-2 Infection

One subcutaneous injection of REGEN-COV™—a combination of the monoclonal antibodies casirivimab and imdevimab from Regeneron Pharmaceuticals—reduced the risk for symptomatic SARS-CoV-2 infection by 81% among household contacts of infected persons, according to new phase 3 clinical trial results.

Regeneron conducted the trial in partnership with the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health (NIH). The company announced the new findings in an April 12, 2021 press release.

“These data suggest that REGEN-COV can complement widespread vaccination strategies, particularly for those at high risk of infection. Importantly, to date REGEN-COV has been shown in vitro to retain its potency against emerging COVID-19 variants of concern," said Myron S. Cohen, MD, director, Institute for Global Health & Infectious Diseases, University of North Carolina at Chapel Hill, who also leads monoclonal antibody efforts for the NIH-sponsored COVID Prevention Network, in the press release.

The double-blind, placebo-controlled trial analyzed the effect of REGEN-COV on uninfected individuals without anti-SARS-CoV-2 antibodies or any COVID-19-related symptoms, who lived in the same household as an individual who tested positive for SARS-CoV-2 within the prior 4 days.

The study enrolled 1505 individuals who were not infected with SARS-CoV-2 at baseline and randomized them to receive either 1 dose of REGEN-COV (1200 mg) or placebo, given subcutaneously.

Results showed that REGEN-COV “rapidly protected” household contacts from exposure, with 72% protection against symptomatic infections in the first week and 93% in subsequent weeks, according to the press release.

On average, individuals in the REGEN-COV cohort who experienced a symptomatic infection saw symptom resolution in 1 week (vs 3 weeks with placebo) and cleared the virus faster than those who received placebo, added the press release.

Adverse events (AE) occurred in 20% (n=265 out of 1311) of the REGEN-COV cohort and 29% (n=379 out of 1306) of the placebo cohort. The percentage of participants who experienced serious AEs was similar in both groups, occurring in 1% (n=10) of REGEN-COV and 1% (n=15) of placebo participants.

"The rapid and robust protection, together with the subcutaneous route of administration, support the practical utility of these antibodies in protecting against COVID-19 in multiple settings, including after high-risk exposures," said the study’s co-principal investigator Dan H. Barouch, MD, PhD, Director, Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Professor of Medicine, Harvard Medical School, in the same press release. "These antibodies may be particularly useful in individuals who are not yet vaccinated and may also have potential in those who are immunosuppressed and may not respond well to vaccines."

In November 2020, the US Food and Drug Administration (FDA) authorized the emergency use of casirivimab and imdevimab for use in patients aged ≥12 with confirmed SARS-CoV-2 and who are at high risk for progressing to severe COVID-19 (including adults aged ≥65 years or who have certain chronic conditions).

Regeneron is planning to share the present data with the FDA and request emergency use authorization expansion to include COVID-19 prevention for appropriate populations, according to the press release.