Regeneron’s REGEN-COV antibody cocktail delivered by injection reduces the relative risk of infection by 66% after exposure to a close contact infected with the SARS-CoV-2 virus, the drugmaker reports.

For those who become infected, the illness is shorter and milder after receiving the monoclonal antibody shot as preventive therapy, the company said. 

The new data was released days after the Food and Drug Administration revised its emergency use authorization for REGEN-COV. The cocktail now can be used after exposure to the SARS-CoV-2 virus to prevent illness in people at high risk of poor outcomes. Previously, it was authorized for use in high-risk, unhospitalized people who already were ill.

Study participants were enrolled within 96 hours of exposure to a household contact with SARS-CoV-2 infection. Half received a total dose of 1,200 mg of REGEN-COV and half received a placebo, each administered by injection. None of the participants were already infected and none were immune to the disease, based on testing.

Symptomatic infection developed in 11 of 753 participants in the REGEN-COV group compared with 59 infections in the 752-participant placebo group, a relative risk reduction of 81%, the researchers reported in the New England Journal of Medicine. When both symptomatic and asymptomatic infections were taken into account, the relative risk reduction was 66%.

Infections milder, shorter

For those who became infected and developed symptoms, the treatment with REGEN-COV appeared to have additional benefits. For these participants, the median time for symptoms to resolve was two weeks shorter with REGEN-COV than with placebo. What’s more, the amount of time these participants carried a high viral load was shorter than in the placebo group, investigators said.

There also were no toxic effects that would require limiting the dose, Regeneron noted.

High viral transmission found among household members would be typical of congregate settings as well, including nursing homes, investigators said. The use of injection versus intravenous infusion could also be a game changer for healthcare settings, Regeneron noted. (Most current COVID-19 monoclonal antibody treatments are delivered as intravenous infusions.)   

“The use of REGEN-COV in such persons could decrease further spread and transmissibility of SARS-CoV-2 infection,” the company said. “Our trial also showed that subcutaneous administration of REGEN-COV was efficacious and had an acceptable safety profile; thus, it may provide substantial benefits because the healthcare resources necessary for an intravenous infusion may be avoided.”

Recent studies have also shown that REGEN-COV has maintained efficacy against emerging variants of concern, the company added.