FDA Authorizes Lower Dose of COVID-19 Antibody Therapy REGEN-COV

REGEN-COV (casirivimab and imdevimab) is a cocktail of 2 monoclonal antibodies.

The Food and Drug Administration (FDA) has updated the Emergency Use Authorization (EUA) for REGEN-COV™ (casirivimab and imdevimab), lowering the dose to 1200mg from 2400mg, for the treatment of COVID-19. 

REGEN-COV is authorized for use to treat mild to moderate COVID-19 in adults and pediatric patients 12 years of age and older weighing at least 40kg with positive results of direct SARS-CoV-2 viral testing who are at high risk for progressing to severe COVID-19, including hospitalization or death. According to the National Institutes of Health (NIH) COVID-19 Treatment Guidelines, the use of REGEN-COV is strongly recommended in non-hospitalized COVID-19 outpatients at high risk for clinical progression.

The updated EUA is based on data from several clinical trials, including a randomized, double-blind, placebo-controlled phase 3 trial that assessed REGEN-COV 1200mg and 2400mg in 4567 high-risk outpatients with COVID-19. Results showed that treatment with REGEN-COV 1200mg and 2400mg, both administered intravenously (IV), significantly reduced the risk of hospitalization or death by 70% (P =.0024) and 71% (P <.0001), respectively, when compared with placebo. The duration of COVID-19 symptoms was shortened by an average of 4 days in both dose groups (median 10 days vs 14 days in the placebo arm).

The fact sheet for REGEN-COV has been updated with the removal of the previously authorized 2400mg IV dose. It also indicates that IV infusion is strongly recommended as a route of administration for REGEN-COV; however, subcutaneous injection is an alternative route of administration when IV infusion is not feasible and would lead to a delay in treatment. 

Additionally, REGEN-COV has shown to retain potency against the main variants within the US based on in vitro research, including the P.1 variant (first identified in Brazil, now classified by the World Health Organization [WHO] as Gamma) and the B.1.351 variant (first identified in South Africa, now classified by the WHO as Beta).

The Company expects to submit a full Biologics License Application for REGEN-COV in non-hospitalized outpatients with COVID-19 later this summer. REGEN-COV is also being investigated in the prevention of COVID-19, as well as in the treatment of certain hospitalized COVID-19 patient settings.


FDA authorizes lower 1,200 mg intravenous and subcutaneous dose of REGEN-COV™ (casirivimab and imdevimab) antibody cocktail to treat patients with COVID-19. [press release]. Tarrytown, NY: Regeneron Pharmaceuticals, Inc.; June 4, 2021.