New monoclonal antibody treatment for outpatients with COVID-19

Casirivimab/imdevimab will be the second monoclonal antibody treatment authorized for OUTpatients with COVID-19....

Casirivimab/imdevimab will be the second monoclonal antibody treatment authorized for OUTpatients with COVID-19. This combination will be an alternative to bamlanivimab as a single-dose IV infusion. And more are in the works. These "mabs" block SARS-CoV-2 from entering cells.

Evolving evidence suggests bamlanivimab may not be effective against certain viral variants, but so far, variants still seem susceptible to casirivimab/imdevimab. For now, anticipate limited use of either mab, due to logistical challenges in administering the infusions to COVID-19 positive outpatients.

Know which patients are suitable for treatment with casirivimab/imdevimab. This includes COVID-19 positive outpatients who are age 12 or older, with mild to moderate symptoms, and at high risk of severe complications (age 65 or older, BMI 30 or higher, etc). Keep in mind that about 30 outpatients would need to receive a single 1,200 mg/1,200 mg dose of casirivimab/imdevimab to prevent one COVID-19-related hospitalization or all-cause death. And be aware that early data suggest that higher doses of casirivimab/imdevimab may reduce mortality in patients HOSPITALIZED with COVID-19 who have a negative antibody test. But casirivimab/imdevimab isn't authorized for patients hospitalized with COVID-19, so for now, don't recommend it in these cases.

Educate that rare hypersensitivity reactions can occur, so monitoring is needed for at least 1 hour after the infusion. Reinforce that patients still need to self-isolate, since mab treatments aren't a cure and don't prevent spread of infection. Defer COVID-19 vaccination for at least 90 days after either mab, they may interfere with the vaccine immune response.

References

IDSA (2021). Monoclonal Antibodies. [online] Available at: https://www.idsociety.org/covid-19-real-time-learning-network/therapeutics-and-interventions/monoclonal-antibodies.
BC Centre of Disease Control. (2021). Clinical Reference Group SBAR: Therapies for COVID-19. [online] Available at: www.bccdc.ca/Health-Professionals-Site/Documents/Therapies_for_COVID-19.pdf.
Weinreich DM, Sivapalasingam S, et al. REGN-COV2, a Neutralizing Antibody Cocktail, in Outpatients with Covid-19. N Engl J Med. 2021 Jan 21;384(3):238-251.