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FDA Okays Lower Dose, Injected Covid-19 Antibodies

Intradermal injection

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

4 June 2021. The Food and Drug Administration updated its emergency authorization for a dual-antibody Covid-19 therapy to allow for a lower and injectable dose. Regeneron Pharmaceuticals Inc. in Tarrytown, New York says FDA extended its authorization to increase supplies and ease administration of the company’s synthetic antibodies casirivimab and imdevimab, given together to treat Covid-19 infections in non-hospitalized patients.

FDA cleared the combination of casirivimab and imdevimab 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. At the time of authorization, casirivimab and imdevimab were given as an intravenous infusion in doses of 1,200 milligrams each, or 2,400 milligrams total.

Patients prescribed the antibody combination, now marketed by Regeneron as Regen-Cov, needed to receive their treatment at a hospital or clinic with the ability to provide intravenous infusions, which limited its availability. The updated authorization now calls for giving Regen-Cov in 1,200 milligram doses, 600 milligrams for each antibody, and as an intradermal or under-the-skin injection if infusions are not feasible. Intradermal injections can be given at doctors’ offices and outpatient clinics without infusion equipment. The lower dose also, in effect, doubles its supply.

Antibodies act against leading variants

Regeneron says FDA’s new Regen-Cov authorization is based on results of several clinical trials, including a late-stage study reported last month at a professional meeting. The findings from more than 4,500 participants show similar efficacy of the 1,200 and 2,400 milligram doses, defined as reduced risk of hospitalization, less time needed to resolve symptoms, and reduced viral load after seven days. In another trial, reported by Science & Enterprise in April, Regen-Cov given as an intradermal injection helps reduce the risk of symptomatic infections among household members of Covid-19 patients, and prevents individuals already infected with SARS-CoV-2 viruses from developing Covid-19 disease symptoms.

“Despite increased use of vaccines,” says George Yancopoulos, Regeneron’s president and chief scientist, in a company statement, “thousands of patients are still becoming infected in the U.S. every day, with many at high risk of serious complications from Covid-19. Unfortunately, to date only a fraction of patients eligible for antibody treatments have received them, which we hope will change based on this updated FDA authorization.”

The company says lab studies show the Regen-Cov antibodies also act against two of the more prominent SARS-CoV-2 viral variants, B.1.351 first identified in South Africa and P.1 first found in Brazil. World Health Organization now labels those variants Beta and Gamma respectively.

Regeneron develops synthetic antibodies that stimulate the immune system to prevent or treat infectious diseases. The company’s VelocImmune technology produces these human antibodies with genetically engineered mice. The engineered mice become living production lines, says the company, producing antibodies that respond as a human to a specific pathogen, while not affecting the rest of the animal. The antibodies are then retrieved and combined with human genetic properties for testing as therapies.

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