The trial, which was jointly run with the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), met its primary and key secondary endpoints, showing that REGEN-COV (1,200mg) administered subcutaneously reduced the risk of symptomatic infections by 81% in contacts of COVID-19 patients.
Those individuals who did experience a symptomatic infection also recovered faster: resolving symptoms in one week, compared to three weeks in the placebo group.
Regeneron is now looking to request EUA expansion to include COVID-19 prevention in certain populations.
From treatment to prevention
REGEN-COV (casirivimab with imdevimab) is a cocktail of two monoclonal antibodies (also known as REGN10933 and REGN10987) that was designed specifically to block infectivity of SARS-CoV-2.
The two antibodies bind non-competitively to the critical receptor binding domain of the virus's spike protein. In targeting the RCD, Regeneron says it can diminish the ability of mutant viruses to escape treatment and protects against spike variants that have arisen in the human population.
The antibody cocktail is currently authorized in the US under Emergency Use Authorization (EUA) as a treatment for mild to moderate COVID-19 in adults (as a higher 2,400mg IV dose), as well as pediatric patients aged 12+ who are at high risk of progressing to severe COVID-19.
The new trial, however, looked at the preventative role the antibody cocktail could play: testing it among people known to be in close contact with COVID-19 patients.
The double-blind trial covered 1,505 individuals without anti-SARS-CoV-2 antibodies, who lived in the same household as an individual who had tested positive within the prior four days. These received either a dose of REGEN-COV (1,200mg) or placebo, administered as subcutaneous injections. In the trial, 31% of participants had at least one factor that put them at high risk of suffering from severe COVID-19.
“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 Cohen, M.D., from the NIH-sponsored COVID Prevention Network (CoVPN) and is Director of the Institute for Global Health & Infectious Diseases at the University of North Carolina at Chapel Hill.
"Despite standard precautions to reduce transmission, nearly 10% of unvaccinated individuals living with an infected person developed symptomatic infections if they did not receive REGEN-COV. If authorized, convenient subcutaneous administration of REGEN-COV could help control outbreaks in high-risk settings where individuals have not yet been vaccinated, including individual households and group living settings."
Dan H. Barouch, M.D., Ph.D., co-principal investigator of the trial and Director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center and Professor of Medicine at Harvard Medical School, added: "These findings are very encouraging and suggest that REGEN-COV is highly effective at preventing symptomatic COVID-19 in household contacts of SARS-CoV-2 infected individuals.
"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. 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."
The REGEN-COV antibody could also help provide protection to unvaccinated people who are exposed to the virus, while the company is also looking at its potential in immunocompromised people who may not be able to be vaccinated.