About Regen-CoV

Regen-CoV is the name given to a combination of the following two antibodies:

  • casirivimab
  • imdevimab

The antibodies in Regen-CoV can bind or attach themselves to SARS-CoV-2. By binding to SARS-CoV-2, the antibodies in Regen-CoV can prevent this virus from infecting cells and turning them into mini-virus factories. Also, the antibodies in Regen-CoV can bind to cells of the body that are infected by SARS-CoV-2. By binding to these cells, the antibodies attract cells of the immune system, which then destroy the infected cells.

In lab experiments with cells and SARS-CoV-2, the antibodies in Regen-CoV, when used in combination, are effective against a range of variants of the virus, including the following:

  • alpha (B.1.1.7)
  • beta (B.1.351)
  • delta (B.1.617.2)
  • gamma (P.1)

These antibodies attack SARS-CoV-2 in lab experiments and in clinical trials with people. The antibodies were developed by Regeneron Pharmaceuticals in cooperation with Hoffmann-La Roche. The latter pharmaceutical company is the distributor of Regen-CoV in Canada and other countries. According to Roche, the combination of antibodies in Regen-CoV are authorized for use in Canada for “the treatment of mild-to-moderate coronavirus disease 2019 (COVID-19), confirmed by direct SARS-CoV-2 viral testing, in adults and adolescents (12 years of age and older weighing at least 40 kg) who are at high risk for progressing to hospitalization and/or death.”

Roche states that the antibodies in Regen-CoV are not meant to be used in the following people:

  • those who are hospitalized due to COVID-19
  • those who require oxygen therapy due to COVID-19
  • those on chronic oxygen therapy due to underlying non-COVID-19 related comorbidity who require an increase in baseline oxygen flow rate due to COVID-19

The antibodies in Regen-CoV are meant to be administered together via intravenous infusion over the course of one hour. It is possible that in the future Health Canada may approve an additional way of administering Regen-CoV—such as injecting the antibodies just under the skin (subcutaneous injection).

The Canadian government has negotiated the price of Regen-CoV and bulk purchased many doses. These have been distributed to provinces and territories and are available at no cost to the patient.

—Sean R. Hosein


  1. Hoffmann-La Roche. Health Canada grants Interim Order authorization for casirivimab and imdevimab for the treatment of mild-to-moderate COVID-19. Press release. 10 June 2021.
  2. Hoffmann-La Roche. Casirivimab and imdevimab for injection. Product monograph. 9 June 2021.
  3. Copin R, Baum A, Wloga E, et al. The monoclonal antibody combination REGEN-COV protects against SARS-CoV-2 mutational escape in preclinical and human studies. Cell. 2021 Jul 22;184(15):3949-3961.
  4. O’Brien MP, Forleo-Neto E, Musser BJ, et al. Subcutaneous REGEN-COV antibody combination to prevent Covid-19. New England Journal of Medicine. 2021 Sep 23;385(13):1184-1195.
  5. Austin D. Why do placebos work? Scientists identify key brain pathway. Science. 27 October 2021.