On 21 Nov 2020, the United States Food and Drug Administration (US-FDA) has given a EUA for casirivimab and imdevimab to be given together for treating mild to moderate COVID-19.

It has been advocated for adults and pediatrics (age: 12 years or more, weight: at least 40 kgs/about 88 pounds) having positive results of direct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral testing and who are at elevated risk for advancing to severe COVID-19 infection. This includes patients aged 65 years or more or who have specific chronic illnesses.

Casirivimab and imdevimab given together were found to minimize COVID-19-associated hospitalization or emergency room visits in patients at elevated risk for disease advancement within 28 days after therapy in comparison with placebo.

Both the antibodies are particularly directed against the spike protein of SARS-CoV-2 and are designed to impede the attachment of the virus and its entrance into the human cells. The EUA was issued based on the data from a randomized, double-blind, placebo-controlled trial in 799 non-hospitalized adult patients suffering from mild to moderate COVID-19 symptoms.

Of these participants, 266 subjects were given a single intravenous infusion of 2400 mg casirivimab and imdevimab (1200 mg of each), 267 subjects were given 8000 mg casirivimab and imdevimab (4000 mg of each), and 266 subjects were given a placebo, within 3 days of getting a positive SARS-CoV-2 viral test. The time-weighted mean alteration in viral load from baseline was the primary outcome parameter.

On the 7th day, the viral load reduction was found to be greater in patients given casirivimab and imdevimab compared to patients given a placebo. The most vital efficacy proof of this combo was illustrated from the secondary outcome of medically attended visits linked to coronavirus, specifically emergency room visits and hospitalizations within 28 days after therapy.

For individuals at elevated risk for disease advancement, hospitalizations and emergency room visits were found to occur in 3% of patients receiving casirivimab and imdevimab in comparison with 9% in individuals receiving placebo. The impact on viral load, minimization in hospitalizations, and emergency room visits were found to be comparable in patients administered with either of the two doses.

The possible treatment-emergent adverse effects include flushing, anaphylaxis, infusion-associated reactions, chills, hives, itching, and fever. The efficacy and safety of this investigational COVID-19 therapeutic approach continue to be assessed. Both these antibodies must be given together by intravenous infusion and this combination is not authorized for individuals who are hospitalized or need oxygen due to COVID-19 infection.

The recommended dilution instructions for casirivimab and imdevimab for intravenous infusion is depicted in the following table:

A benefit of the combination of casirivimab and imdevimab has not been demonstrated in hospitalized COVID-19 patients. These antibodies may be linked with worse clinical outcomes when given to hospitalized COVID-19 individuals needing mechanical ventilation or high flow oxygen supplementation.

The EUA of these antibodies yields health care providers another potential tool to tackle the pandemic. Authorizing these monoclonal antibodies may aid outpatients to prevent hospitalization and minimize the overburden on the medical care system.