Regeneron’s antibody cocktail REGEN-COV offers sustained protection against COVID-19

Regeneron’s antibody cocktail REGEN-COV (casirivimab and imdevimab) has demonstrated sustained protection against infection by SARS-CoV-2, the coronavirus that causes COVID-19, over an eight-month period.

The data comes from a phase 3 study run jointly by Regeneron and the National Institute of Allergy and Infectious Diseases (NIAID) and builds on one-month data published in The New England Journal of Medicine in September.

The antibodies offered an 81.4% reduction in the risk of infection over one month, a level of protection equalled by the new analysis covering a follow-up period of between two and eight months.

“This new data demonstrates how a single dose of REGEN-COV can help protect people from COVID-19 for many months after administration,” said Dr Myron Cohen, director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill, who was involved in the trial. “These results demonstrate that REGEN-COV has the potential to provide long-lasting immunity from SARS-CoV-2 infection, a result particularly important to those who do not respond to COVID-19 vaccines, including people who are immunocompromised.”

The phase 3 placebo-controlled trial involved people who lived in the same household as someone who had tested positive for SARS-CoV-2 and were uninfected at the time of administration. REGEN-COV was given in a single dose that involved four subcutaneous injections and participants were tested weekly.

After the initial one-month period, an additional 45 symptomatic infections occurred. Of those, only seven were in the group that had received REGEN-COV, and 38 were in the placebo group. Over the eight-month trial, no one who received the drug was hospitalised, although six people on placebo were taken to hospital (no deaths occurred).

The trial allowed participants to become vaccinated once the primary efficacy treatment period (month 1) was complete. Vaccination rates were balanced, with 34.5% in the REGEN-COV group and 35.2% in the placebo group receiving at least one COVID-19 vaccine dose by the end of the eight-month assessment period.

“This data adds to the increasing body of evidence supporting the use of REGEN-COV to prevent COVID-19 in uninfected individuals, which may be especially useful for the many immunocompromised people who do not respond adequately to vaccines and remain 'prisoners of the pandemic',” said Regeneron president and chief scientific officer, Dr George Yancopoulos. “With infections still occurring despite widespread vaccination, the immunocompromised face an ongoing risk of encountering the virus during their daily lives. We intend to rapidly share this additional data with regulatory authorities to help those most in need of protection from COVID-19.”

REGEN-COV is currently used in the US to treat those at high risk of serious consequences from COVID-19 infection who are either already infected (non-hospitalised) or in certain post-exposure prophylaxis settings.