Regeneron's antibody cocktail is effective in preventing Covid infection, study shows
An employee works in a lab at the Regeneron Pharmaceuticals Westchester campus in Tarrytown, New York, U.S. September 17, 2020.

Regeneron Pharmaceuticals said on Tuesday its antibody cocktail was effective in preventing Covid-19 in people exposed to those infected with the new coronavirus, based on interim results from a late-stage study.

The two-antibody cocktail, REGEN-COV, caused a 100% reduction in symptomatic infection and roughly 50% lower overall rates of infection, based on an analysis of about 400 participants in the trial who had a household member with Covid-19.

Regeneron said it would discuss the interim results with U.S. health regulators to potentially expand the antibody cocktail's current emergency use authorization (EUA). Full data from the trial is expected early in the second quarter

The U.S. Food and Drug Administration in November granted EUA to the antibody cocktail for the treatment of mild to moderate Covid-19 in adults and children.

The current trial tested REGEN-COV for use as a passive vaccine, which involves directly delivering virus-fighting antibodies into the body unlike traditional vaccines in which the receiver's immune system is activated to develop its own antibodies.

REGEN-COV may be able to provide immediate passive immunity to those at high risk of infection, in contrast to active vaccines that take weeks to provide protection, the company said.

"These data using REGEN-COV as a passive vaccine suggest that it may both reduce transmission of the virus as well as reduce viral and disease burden in those who still get infected," said George Yancopoulos, president and chief scientific officer of Regeneron.

The drugmaker also expects REGEN-COV to help people who respond poorly to vaccination.

During the trial, jointly run by Regeneron and the National Institute of Allergy and Infectious Diseases, one death and a Covid-19 related hospitalization were reported among those who received placebo, but there was no such incident in the treatment group, the company said.

REGEN-COV is also being studied in two late-stage hospitalized patient trials and a late-stage trial for the treatment of non-hospitalized patients.