Regeneron’s COVID-19 Antibody Cocktail Works as 'Passive Vaccine'

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When therapeutic antibodies for COVID-19 were authorized, it was typically to treat the disease, not necessarily prevent it. Most of the companies developing them, however, knew it was possible for antibodies to be used as short-term prevention, for example, when someone in a household is diagnosed, giving the other people in the household therapeutic antibodies. They typically will act as a passive vaccine for several months.

Regeneron Pharmaceuticals announced positive initial data from its ongoing Phase III trial of its antibody cocktail, REGEN-COV, as a passive vaccine to prevent COVID-19 in people at high risk of infection from household exposure. The trial is being run with the U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH).

Exploratory analysis found that the cocktail demonstrated 100% prevention of symptomatic infection in the 400 patients that could be evaluated. There was also about a 50% lower overall rate of infection, symptomatic and asymptomatic. The lower number of infections in the group on the cocktail were all asymptomatic, with decreased peak virus levels and a short duration of viral shedding, suggesting they were less likely to spread the disease.

The data also showed that in the placebo group, on average infections had a 100-fold higher peak viral load. In the cocktail group, infections lasted no more than one week, while about 40% in the placebo cohort lasted three to four weeks.

On January 21, Eli Lilly reported similar results in its own COVID-19 antibody, bamlanivimab, which was tested in nursing home facilities. Their Phase III BLAZE-2 COVID-19 prevention trial also conducted in partnership with NIAID and the COVID-19 Prevention Network (CoVPN) tested the antibody in 965 people who had tested negative for the virus at baseline.

The Regeneron study also found that adverse events occurred more frequently in the placebo group, 18% placebo compared to 12% on REGEN-COV. The company indicates this was driven by the increased rate of COVID-19 infections in the placebo group. In the placebo group, there was one death and one COVID-19-related hospitalization, while there were no deaths or hospitalizations in the REGEN-COV cohort. About 2% of the participants in both groups had injection site reactions.

“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 while still get infected,” said George D. Yancopoulos, president and chief scientific officer of Regeneron. “Even with the emerging availability of active vaccines, we continue to see hundreds of thousands of people infected daily, actively spreading the virus to their close contacts. The REGEN-COV antibody cocktail may be able to help break this chain by providing immediate passive immunity to those at high risk of infection, in contrast to active vaccines which take weeks to provide protection.”

In addition, people who are immunocompromised or otherwise unable to respond well to an active vaccine may be good choices for the antibody treatments.

David Weinreich, executive vice president and Head of Global Clinical Development at Regeneron, also noted that the cocktail was given as injections rather than an infusion, making it more convenient and efficient for patients and healthcare providers.

“It’s notable that the few infections that did occur after receiving REGEN-COV were all asymptomatic and associated with markedly lower viral load and duration of viral shedding, potentially reducing transmission,” Weinreich said. “We look forward to seeing the full dataset early next quarter and will discuss the current results with regulatory authorities, including the potential to expand the Emergency Use Authorization.”

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