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Antibody Cocktail Prevents Covid-19 Disease Symptoms

Intradermal injection

Intradermal injection (British Columbia Institute of Technology, Wikimedia Commons,

12 Apr. 2021. A clinical trial shows two synthetic antibodies given together reduce the risk of symptomatic infections among household members of Covid-19 patients. Other findings from the trial show the antibody cocktail, made by Regeneron Pharmaceuticals Inc. in Tarrytown, New York, helps prevent individuals already infected with SARS-CoV-2 viruses from developing Covid-19 disease symptoms. The results are released by Regeneron and are not peer reviewed.

In the trial, Regeneron tested its antibody therapy for Covid-19, code-named Regen-Cov, as a preventive drug against SARS-CoV-2 infections. Regen-Cov is a combination of the company’s synthetic antibodies casirivimab and imdevimab authorized by the Food and Drug Administration in November 2020 as a treatment for non-hospitalized Covid-19 patients with mild to moderate symptoms.

The company designed the casirivimab and imdevimab cocktail to be given as an intravenous 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. Notably, Regeneron reformulated Regen-Cov for the trial to be given as an injection under the skin, instead of an infusion as given as a therapy.

The late-stage clinical trial enrolled 3,750 participants without Covid-19 symptoms at 134 sites mainly in the U.S., all household contacts of people with Covid-19 infections. The study, conducted with National Institute of Allergy and Infectious Diseases, or NIAID, at National Institutes of Health, includes participants in different age groups randomly assigned to receive 1,200 milligrams of Regen-Cov or a placebo.

Among participants in the trial are 1,505 individuals without SARS-CoV-2 infections, divided almost evenly between Regen-Cov or placebo recipients. The results show, after 29 days, 11 Regen-Cov recipients or 1.5 percent developed SARS-CoV-2 infections, compared to 59 placebo recipients, or 7.8 percent. When calculated in terms of infection risk, Regen-Cov recipients show an 81 percent lower risk than placebo recipients.

No Regen-Cov recipients hospitalized

In addition, Regen-Cov recipients who developed Covid-19 symptoms cleared their symptoms in 1.2 weeks on average, compared to 3.2 weeks for placebo recipients. And infected Regen-Cov recipients experienced high viral loads for less than three days on average, compared to nine days for those receiving a placebo.

Also among participants in the trial are 204 participants with recent SARS-CoV-2 infections, but not exhibiting Covid-19 symptoms, randomly assigned to receive Regen-Cov or a placebo. Among Regen-Cov recipients, 29 percent later developed Covid-19 symptoms, compared to 42 percent of placebo recipients, a 31 percent lower risk of symptoms, and a difference large enough for statistical reliability. None of the Regen-Cov recipients required hospitalization for their symptoms, while six of the placebo group were hospitalized.

Among the 1,505 non-infected participants, adverse events were reported in 20 percent of Regen-Cov and 29 percent of placebo recipients, with one percent of each group reporting serious adverse effects. In the group of 204 SARS-CoV-2 infected participants, about one-third (34%) of Regen-Cov recipients, and nearly half (48%) of placebo recipients experienced adverse effects, with none of the Regen-Cov and three percent of placebo group rated as serious.

Regeneron says among the non-infected participants, 41 percent are of Hispanic origin and nine percent are Black Americans, with 31 percent having at least one high-risk factor of severe Covid-19 disease, such as obesity or age 50 and over. Among the infected participant sample, 35 percent are of Hispanic origin five percent are Black, and 32 percent exhibit at least one high-risk severe disease factor.

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