The Food and Drug Administration has accepted for Priority Review the Biologics License Application (BLA) for REGEN-COV® (casirivimab and imdevimab) for the treatment of COVID-19 in nonhospitalized patients and as prophylaxis in certain individuals.

REGEN-COV consists of 2 potent, virus-neutralizing antibodies that bind noncompetitively to the receptor binding domain of the SARS-CoV-2 spike protein, thereby blocking its interaction with the host cell. 

The BLA submission is supported by data from two phase 3 trials ( Identifier: NCT04425629, NCT04452318) that included more than 6000 patients. The efficacy and safety of REGEN-COV was evaluated as a treatment for nonhospitalized patients with COVID-19, and to prevent symptomatic infections in asymptomatic household contacts of SARS-CoV-2 infected individuals.

Among nonhospitalized patients with COVID-19, results showed that treatment with REGEN-COV 1200mg and 2400mg significantly reduced the risk of hospitalization or death by 70% (P =.002) 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).

Findings from the prophylaxis trial showed that REGEN-COV reduced the risk of symptomatic SARS-CoV-2 infection development by 81.4% compared with placebo (P <.0001). REGEN-COV was also associated with a 66.4% reduction in symptomatic and asymptomatic infections overall.

A Prescription Drug User Fee Act target date of April 13, 2022 has been set for the application.

REGEN-COV is currently 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.

REGEN-COV is also authorized for use for postexposure prophylaxis of COVID-19 in individuals (12 years of age and older weighing at least 40kg) who are at high risk for progression to severe COVID-19, including hospitalization or death. 

The Company expects to submit a second BLA later this year for REGEN-COV for the treatment of hospitalized patients due to COVID-19. 


  1. FDA accepts REGEN-COV® (casirivimab and imdevimab) for Priority Review for treatment and prophylaxis of COVID-19. News release. Regeneron Pharmaceuticals, Inc. Accessed October 14, 2021.
  2. Weinreich DM, Sivapalasingam S, Norton T, et al. REGEN-COV antibody combination and outcomes in outpatients with COVID-19. N Engl J Med. Published online September 29, 2021. doi:10.1056/NEJMoa2108163
  3. O’Brien MP, Forleo-Neto E, Musser BJ, et al. Subcutaneous REGEN-COV Antibody Combination to Prevent COVID-19. N Engl J Med. Published online September 23, 2021. doi:10.1056/NEJMoa2109682