FDA expanded the emergency use authorization (EUA) for the monoclonal antibody cocktail casirivimab and imdevimab, to include post-exposure prophylaxis (PEP) among certain people exposed to COVID-19, manufacturer Regeneron announced on Friday.

Casirivimab-imdevimab (REGEN-COV) is the first monoclonal antibody treatment that can be used either as a treatment for COVID-19 or after exposure but prior to a positive COVID-19 test, Regeneron said.

The new indication covers individuals ages 12 and older who were exposed to someone with the virus or who were exposed to the virus in an institutional setting.

In a phase III trial jointly sponsored by NIAID, the cocktail reduced the risk of symptomatic infections by 81% when used as PEP among household contacts of individuals with SARS-CoV-2.

Specifically, the therapy is for those at high risk of progressing to severe COVID-19 who either were not fully vaccinated or “not expected to mount an adequate response to vaccination,” as well as for those with a high risk of exposure, such as in nursing home or prison settings.

Not only that, but the cocktail could be administered monthly for those who “require repeat dosing for ongoing exposure,” Regeneron said. The EUA for the therapy as PEP means it can be administered by subcutaneous injection or intravenous infusion.

Regeneron expanded on the results of the phase III trial to support the expanded indication, which consisted of 1,500 seronegative participants, 753 randomized to REGEN-COV and 752 randomized to placebo. In addition to reducing the risk of symptomatic infection by 81%, a post-hoc analysis found a risk reduction of 76% among a subgroup of participants at high risk of severe COVID in the REGEN-COV group.

In a broader group of 2,378 asymptomatic participants, regardless of serology, a post-hoc analysis found a risk reduction of 62% in the REGEN-COV group.

Adverse events included mild to moderate injection site reactions in up to 4% of individuals receiving the treatment. Mild hypersensitivity reactions occurred in less than 1% of the REGEN-COV group.

Regeneron touted the cocktail’s potency against a variety of variants, including the Delta variant, and added that the therapy is not a substitute for vaccination, and is not authorized for COVID-19 pre-exposure prophylaxis.

Previously, the cocktail was authorized in November 2020 for non-hospitalized patients ages 12 and older who tested positive for SARS-CoV-2 and were at increased risk of progressing to severe COVID-19, including those ages 65 and older with chronic medical conditions.