Infectious Disease Special Edition
The FDA revised the emergency use authorization for casirivimab and imdevimab (REGEN-COV, Regeneron) to allow their use as a post-exposure prophylaxis (PEP) for COVID-19 in adults and children 12 years of age and older, weighing at least 40 kg, who are at high risk for progression to severe COVID-19, including hospitalization or death.
The monoclonal antibody cocktail, casirivimab and imdevimab, is not authorized for pre-exposure prophylaxis, according to the FDA.
In individuals who require repeat dosing for ongoing exposure, casirivimab and imdevimab can also now be administered monthly. This new indication in people ages 12 and older is in addition to the previously granted authorization to treat nonhospitalized patients.
The cocktail is not a substitute for vaccination against COVID-19, the FDA said.
REGEN-COV should only be used as PEP for individuals who are:
- not fully vaccinated or who are not expected to mount an adequate immune response to complete SARS-CoV-2 vaccination (e.g., people with immunocompromising conditions, including those taking immunosuppressive medications), and
- have been exposed to an individual infected with SARS-CoV-2 consistent with close contact criteria per the CDC, or
- who are at high risk for exposure to an individual infected with SARS-CoV-2 because of occurrence of SARS-CoV-2 infection in other individuals in the same institutional setting (e.g., nursing homes or prisons).
Under the EUA for PEP, casirivimab and imdevimab can be administered by subcutaneous injection or IV infusion. For people who are not expected to mount an adequate immune response to vaccination and who have ongoing exposure to SARS-CoV-2 for more than four weeks, the initial 1,200-mg dose can be followed by subsequent repeat dosing of REGEN-COV 600 mg once every four weeks, for the duration of ongoing exposure.
Multiple analyses, including a recent publication in Cell, showed that casirivimab and imdevimab retains potency against the main variants of concern circulating within the United States, including delta (B.1.617.2; first identified in India), gamma (P.1; first identified in Brazil), and beta (B.1.351; first identified in South Africa) (Cell 2021;184:3949-3961.E11).
Another phase 3 study assessed the ability of casirivimab and imdevimab to prevent COVID-19 infection among household contacts of individuals infected with SARS-CoV-2. Casirivimab and imdevimab reduced the risk of symptomatic infections by 81% (P<0.001), with a 93% reduction of symptomatic infections after the first week, and no dose-limiting toxicities observed, which was the primary end point (N Engl J Med 2021 Aug 4 DOI: 10.1056/NEJMoa2109682).
The cocktail also remains authorized for the treatment of mild to moderate COVID-19 in adults and children with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.
The most common side effects were injection site reactions. The signs and symptoms of injection site reactions that occurred in at least 1% of subjects in the REGEN-COV group were skin redness (erythema), an uncomfortable, irritating sensation that creates an urge to scratch (pruritus), and ecchymosis (discoloration of the skin resulting from bleeding underneath, caused by bruising). There were no cases of severe hypersensitivity reactions or potentially life-threatening allergic reactions (such as anaphylaxis).
People who had a previous severe allergic reaction to REGEN-COV should not receive it again.