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Antibody Therapy Shown to Prevent Covid-19 Disease

Global Covid-19

(Gerd Altmann, Pixabay)

26 Jan. 2021. Clinical trial results show a combination of synthetic antibodies designed to treat Covid-19 infections can also prevent contracting the disease. Interim findings from the trial, not peer-reviewed, were revealed today by biotechnology company Regeneron Pharmaceuticals Inc. in Tarrytown, New York.

The study is testing Regeneron’s cocktail of two synthetic antibodies, casirivimab and imdevimab, among household or family members of people already infected with Covid-19. These individuals are considered at high risk of the disease, and the trial aims to determine if the antibody combination can also serve as a passive vaccine, one that provides quick, short-term protection against Covid-19 disease symptoms, if not infections.

Regeneron originally designed the casirivimab and imdevimab cocktail as a Covid-19 therapy, given as a single infusion for neutralizing the SARS-CoV-2 virus responsible for Covid-19 infections. The antibodies attach to separate receptor binding domains of the SARS-CoV-2 spike protein that enters and begins infecting cells. In November 2020, FDA granted an emergency use authorization for the antibody cocktail to treat individuals with Covid-19 infections and mild to moderate symptoms, age 12 and older, but not hospitalized. As reported by Science & Enterprise earlier this month, the U.S. Department of Health and Human Services is buying up to 1.25 million more doses of the therapy, for $2.63 billion.

The late-stage clinical trial is enrolling 2,450 healthy individuals, but close household contacts of people with Covid-19 infections, conducted with National Institute of Allergy and Infectious Diseases, or NIAID, at National Institutes of Health. Participants in different age groups are randomly assigned to receive the casirivimab and imdevimab cocktail or a placebo, as an injection under the skin. As a therapy, the cocktail is usually given as an intravenous infusion.

Shorter infection times, lower disease burden

The early results reported today are from 409 participants, 186 receiving casirivimab and imdevimab, and 223 placebo recipients. Of the 186 antibody cocktail recipients, 10 became infected with Covid-19, compared to 23 of the 223 placebo recipients. Moreover, none of those receiving casirivimab and imdevimab developed symptomatic infections, compared to eight placebo recipients.

Antibody cocktail recipients, says Regeneron, also experienced shorter infection periods, about one week on average, while infections in 40 percent of placebo recipients lasted three to four weeks. In addition, none of the nine infected recipients of casirivimab and imdevimab experienced high viral loads, while 13 of 21 infected placebo recipients had high viral loads. And placebo recipients had, on average, 100 times the peak viral load of the antibody cocktail recipients.

Also among infected participants, says the company, those receiving casirivimab and imdevimab, now branded as REGEN-COV, experienced less viral shedding, as well as shorter times with Covid-19 symptoms. Antibody cocktail recipients shed their virus for nine weeks, while placebo recipients continued to shed their virus for 44 weeks. And, those infected and receiving the placebo report symptoms for 18 weeks, compared to none for infected antibody cocktail recipients.

Adverse effects during the trial occurred more with placebo recipients (18%)  than casirivimab and imdevimab (12%), which Regeneron attributes to higher infection and disease rates in the placebo group. Injection site reactions occurred equally (2%) in antibody cocktail and placebo recipients. One death occurred among participants, a placebo recipient.

“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,” says George Yancopoulos, president and chief scientist at Regeneron in a company statement. “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.”

Regeneron’s antibody therapy is the second Covid-19 treatment shown to also provide disease protections. Clinical trial results reported last week by Science & Enterprise, show the synthetic antibody bamlanivimab, made by AbCellera Biologics and Eli Lilly & Co., lowers the risk of symptomatic Covid-19 infections among long-term care residents and staff.

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