The U.S. Food and Drug Administration (FDA) has extended its review of the Biologics License Application (BLA) for REGEN-COV (casirivimab and imdevimab), a monoclonal antibody therapy developed by Regeneron Pharmaceuticals, for the treatment of COVID-19 in non-hospitalized patients and as prophylaxis in certain individuals. The review period has been extended by three months, setting a new target action date of July 13, 2022.
The extension is attributed to ongoing discussions between Regeneron and the FDA regarding the potential use of REGEN-COV for pre-exposure prophylaxis. Regeneron has submitted additional data from its completed prophylaxis trial, which the FDA has accepted for review. The FDA considers this submission a Major Amendment to the BLA.
Current Status of REGEN-COV
REGEN-COV initially became available in the U.S. in November 2020 through the FDA's Emergency Use Authorization (EUA) process. However, in January 2022, the FDA amended the EUA to exclude its use in regions where infection or exposure is likely due to variants not susceptible to the treatment. As a result, REGEN-COV is currently not authorized for use in any U.S. states, territories, or jurisdictions.
Regeneron's Ongoing Efforts
Despite the current limitations, Regeneron remains committed to combating the COVID-19 pandemic. The company is actively developing next-generation antibodies that are effective against currently circulating variants of concern. A first-in-human clinical trial has been initiated for one of these next-generation antibodies.
REGEN-COV's Mechanism and Development
REGEN-COV (casirivimab and imdevimab) is a cocktail of two monoclonal antibodies specifically designed to block the infectivity of SARS-CoV-2, the virus responsible for COVID-19. The therapy was developed using Regeneron's proprietary VelocImmune and VelociSuite technologies. Regeneron collaborates with Roche, who is primarily responsible for development and distribution outside the U.S., where it is known as Ronapreve.
Authorized Uses and Limitations
Under the EUA, REGEN-COV was authorized for treating mild to moderate COVID-19 in adults and pediatric patients (12 years and older weighing at least 40 kg) with positive SARS-CoV-2 viral testing results who are at high risk for progressing to severe COVID-19, including hospitalization or death.
It was also authorized for post-exposure prophylaxis in individuals at high risk for progression to severe COVID-19 who are not fully vaccinated or are not expected to mount an adequate immune response to complete SARS-CoV-2 vaccination and have been exposed to or are at high risk of exposure to SARS-CoV-2.
However, REGEN-COV is not authorized for use in patients hospitalized due to COVID-19, requiring oxygen therapy due to COVID-19, or requiring an increase in baseline oxygen flow rate due to COVID-19 in those on chronic oxygen therapy. Monoclonal antibodies like REGEN-COV may be associated with worse clinical outcomes when administered to hospitalized patients requiring high flow oxygen or mechanical ventilation.
Next Steps
The FDA will continue to monitor conditions to determine whether the use of REGEN-COV in a geographic region aligns with the scope of authorization, considering available information on variant susceptibility and CDC regional variant frequency data.
