The Food and Drug Administration (FDA) has authorized the use of REGEN-COV (casirivimab and imdevimab) 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 investigational agent was previously granted Emergency Use Authorization (EUA) for the treatment of mild to moderate COVID-19.

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 evidence supporting the EUA for postexposure prophylaxis of COVID-19 was based on data from the phase 3 COV-2069 trial (ClinicalTrials Identifier: NCT04452318), which enrolled asymptomatic individuals who lived in the same household with a SARS-CoV-2 infected patient.

Individuals were randomly assigned to a single dose of casirivimab 600mg and imdevimab 600mg (n=753) or placebo (n=752) administered subcutaneously within 96 hours of collection of the index cases’ positive SARS-CoV-2 diagnostic test sample. The primary endpoint of the study was the proportion of individuals who developed RT-qPCR confirmed SARS-CoV-2 infection through day 29.

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Results showed that REGEN-COV reduced the risk of COVID-19 development by 81% in the primary analysis population (RT-qPCR negative and seronegative at baseline) compared with placebo (adjusted odds ratio [OR] 0.17; P <.0001). In a post-hoc analysis, a 62% reduction in risk was observed in the overall trial population (regardless of serology status at baseline) with REGEN-COV vs placebo (adjusted OR 0.35; P <.0001).

For postexposure prophylaxis, the authorized dose of REGEN-COV is casirivimab 600mg and imdevimab 600mg administered together either by subcutaneous injection or intravenous infusion. For individuals who remain at high risk of exposure for longer than 4 weeks, and who are not expected to mount an adequate immune response to COVID vaccination, repeat doses of casirivimab 300mg and imdevimab 300mg once every 4 weeks are appropriate for the duration of ongoing exposure.

Additional information on the use of REGEN-COV for postexposure prophylaxis can be found in the updated fact sheet.


  1. FDA authorizes REGEN-COV monoclonal antibody therapy for post-exposure prophylaxis (prevention) for COVID-19. News release.. Accessed August 2, 2021.
  2. FDA expands authorized use of REGEN-COV™ (casirivimab and imdevimab). News release.. Accessed August 2, 2021.
  3. REGEN-COV fact sheet for health care providers. Accessed August 2, 2021.

This article originally appeared on MPR

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