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Antibodies Help Some Hospitalized Covid-19 Patients

Hospital room

(Fernando Zhiminaicela, Pixabay.

16 June 2021. Results from a clinical trial show a combination of two synthetic antibodies reduces deaths in hospitalized Covid-19 patients with no earlier immune response. The findings, released by Regeneron Pharmaceuticals Inc. in Tarrytown, New York and not peer-reviewed, are from a late-stage trial in the U.K. testing multiple therapies among hospitalized patients.

Health authorities up to now authorized several treatments for Covid-19 infections, but nearly all of those therapies are for non-hospitalized patients with mild to moderate symptoms.. The Recovery trial, short for Randomised Evaluation of Covid-19 Therapy, began in May 2020 to test a range of treatments among patients hospitalized in the U.K. with severe respiratory disease from their infections. A team led by researchers from University of Oxford is enrolling some 40,000 participants mainly in the U.K., but also Nepal and Indonesia.

The trial is run as a collection of smaller studies testing different therapies alone or in combination with hospitalized adults and children. One of the studies is testing Regeneron’s Covid-19 therapy called Regen-Cov, a cocktail of two monoclonal antibodies, synthetic proteins acting like antibodies to neutralize specific pathogens. The antibodies in this case are casirivimab and imdevimab designed to block infections from the SARS-CoV-2 virus. The two antibodies act against different parts of the protein covering the virus’s spike that penetrates and infects cells. The combination of two antibodies, says the company, limits the chance for a viral mutant or variant to escape neutralization.

Different results from patients with or without natural antibodies

Results from an early- and mid-stage trial testing the cocktail with hospitalized patients show the treatment reduces risks of death and need for mechanical ventilation more among patients with no previous natural antibodies from Covid-19 infections than patients who already have these antibodies. From these findings, the late-stage or phase 3 Recovery trial is looking specifically at differences in response to Regen-Cov among patients already with antibodies, called seropositive, and those without antibodies or seronegative.

Among Recovery trial participants in the U.K., 9,785 were randomly assigned to receive an 8,000 milligram infusion of Regen-Cov with the usual hospital care or the usual care alone, between September 2020 and May 2021. Among the 3,153 seronegative patients, the rate of death — the trial’s main efficacy measure — among those receiving Regen-Cov was 24 percent after 28 days, compared to 30 percent for patients receiving the usual hospital care alone, a statistically reliable difference. Adding in seropositive patients and those with unknown antibody status, the results show no difference between Regen-Cov recipients and non-recipients, 20 and 21 percent respectively.

FDA cleared Regen-Cov in November 2020 as a therapy for people age 12 and older with Covid-19 infections, mild to moderate symptoms not requiring hospitalization, and considered at high risk of progressing to severe illness. High risk individuals include those over 65, obese, pregnant, or having a chronic condition such as diabetes or heart disease. As reported by Science & Enterprise earlier this month, FDA updated the emergency use authorization or EUA to include lower doses injected under the skin, instead of infusions for non-hospitalized patients.

“Definitive phase 3 trials have now demonstrated,” says Regeneron president and chief scientist George Yancopoulos in a company statement, “that Regen-Cov can alter the course of Covid-19 infection from prevention, to very early infection, all the way through to when patients are on a ventilator in the hospital.” Yancopoulos adds, “We intend to rapidly discuss these results with regulatory authorities, including in the U.S. where we will ask for our EUA to be expanded to include appropriate hospitalized patients.”

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