FDA Updates Casirivimab and Imdevimab COVID-19 EUA to Smaller Dose


The authorization change halves the required dose of the monoclonal antibody regimen, based on recent data.


The US Food and Drug Administration (FDA) has updated the Emergency Use Authorization (EUA) for casirivimab and imdevimab (REGEN-COV) to indicate its use at half the dose rate as previously authorized.

The update lowers the combination monoclonal antibodies to 1200 mg—600 mg casirivimab and 600 mg imdevimab—in the treatment of mild-to-moderate COVID-19 in patients ≥12 years old at risk of severe disease progression.

In addition, the FDA advised that the therapy regimen be primarily administered by intravenous infusion, with subcutaneous injections serving as an alternative in the event infusions are unfeasible and/or would delay treatment for time-sensitive cases.

The FDA updated this authorization based on findings from several assessments, the most recent being a phase 3 trial which observed casirivimab and imdevimab reduced hospitalization risk by 70% in hospitalized patients with COVID-19 at high risk of severe disease. The findings additionally observed consistent treatment efficacy at 1200 mg and 2400 mg doses.

To date, 9000-plus persons have received intravenous casirivimab and imdevimab via clinical trials conducted in both hospitalized and non-hospitalized settings. Pooled analyses of non-hospitalized patients show an infusion-related reaction rate of 0.2% (grade 2 or greater) among 4026 patients.

In trial participants to receive subcutaneous casirivimab and imdevimab, injection site reaction rates were 12% among 729.

In a statement accompanying the update, Regeneron president and chief scientific officer George D. Yancopoulos, MD, PhD, emphasized the continued need for efficacious COVID-19 therapies—15-plus months into the US outbreak.

"Despite increased use of vaccines, thousands of patients are still becoming infected in the U.S. every day, with many at high risk of serious complications from COVID-19,” Yancopolous said. “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.”

Regeneron anticipates a Biologics License Application (BLA) for casirivimab and imdevimab will be submitted to the FDA, for the indicated treatment of non-hospitalized outpatients with COVID-19, later this summer.

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