What is monoclonal antibody therapy?

  • Monoclonal antibodies are directed against the COVID virus and prevents entry of virus into the cells of our body and limit the amount of virus in our body
  • The antibody Casirivimab and Imdevimab cocktail (“Antibody Cocktail”) is a medical product recommended for the use on the prescription of a medical specialist
  • The Antibody Cocktail remains efffective against many variants including delta, delta plus and earlier – alpha, beta and gamma but has reduced neutralising potency against omicron
  • The Antibody Cocktail may only be administered in settings in hospital settings wherein health care providers have immediate access to medications to treat an infusion reaction, such as anaphylaxis
  • The intravenous administration takes about 20 to 30 minutes. For the subcutaneous route, four syringes of 2.5 ml (2 each of Casirivimab & Imdevimab) need to be administered concurrently at four different sites on the abdomen or thigh
  • Patients should be monitored during the infusion and observed for least one hour after the completion of the infusion and 15-30 minutes after the subcutaneous injection

How does the monoclonal antibody work?

Casirivimab and Imdevimab in the antibody Cocktail are human immunoglobulin G-1 (IgG1) monoclonal antibodies produced by recombinant DNA technology in the lab. Monoclonal antibodies are proteins that mimic the immune system’s ability to fight off harmful pathogens such as viruses. Casirivimab and Imdevimab are monoclonal antibodies that are specifically directed against the spike protein of SARS-CoV-2, designed to block the virus’ attachment and entry into human cells. Casirivimab and Imdevimab cocktail remains efficacious against many variants including delta, however there is reduced neutralising potency against omicron.

High risk is defined at

Age ≥ 60 year
Cardiovascular disease, including hypertension
Chronic lung disease, including asthma
Type 1 or type 2 diabetes mellitus
Chronic kidney disease, including those on dialysis
Chronic liver disease
lmmunosuppressed, based on investigator’s assessment. Eg include: cancer treatment, bone marrow or organ transplantation, immune deficiencies, HIV (if poorly controlled or evidence of AIDS), sickle cell anemia, thalassemia, and prolonged use of immune-weakening medications.

“CDSCO approves Casirivimab and Imdevimab antibody therapy for restricted use in emergency situation for post-exposure prophylaxis”

Post exposure prophylaxis means taking medicine after exposure to the SARS-COV virus in order to prevent infection. The approval was based on the results of a large phase 3 study which showed that taking Casirivimab/Imdevimab within 96 hours of exposure to a person living in the same house infected with SARS COV-2 virus significantly reduced the risk of symptomatic infection by 81.4 %. Only 11 of 753 people exposed to the virus (1.5%) developed symptomatic infection compared to 59 of 752 (7.8%) participants who were given placebo. Among those who got infected despite taking antibody cocktail, symptoms resolved faster and the duration of high viral load was lower (NEJM 2021)**.

Antibody cocktail is indicated for restricted use in emergency situation for post-exposure prophylaxis of COVID-19 in adults (≥ 18 years) who are at high risk for progression to severe COVID-19, including hospitalization or death, and:

  • Are not fully vaccinated (as per approved schedule) or who are not expected to develop an adequate immune response to complete SARS-CoV-2 vaccination (for example, individuals with immune-compromising conditions including those taking immunosuppressive medications)
  • Have been exposed to an individual infected with SARS-CoV-2 i.e. having direct physical contact with the person, sharing eating or drinking utensils or being exposed to respiratory droplets from an infected person
  • Who are at high risk of 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 (for example, nursing homes, prisons)

The limitations of this authorized use include:

Post-exposure prophylaxis with CASIRIVIMAB & IMDEVIMAB is not a substitute for vaccination against COVID-19
CASIRIVIMAB & IMDEVIMAB is not authorized for pre-exposure prophylaxis for the prevention of COVID-19.
The antibody cocktail therapy is for those above the age of 65, home isolation patients having an oxygen saturation of 93% or require no oxygen support but are at risk of developing a severe form of the infection owing to comorbidities such as obesity, diabetes, liver disease, heart ailments, and chronic lung disease.” The therapy works effectively when administered within three-four days of contracting the infection, when the virus replicates and multiplies.
- Dr Jinendra Jain, Consultant Physician at Wockhardt Hospital
We have been admitting a lot of international travellers since the Omicron scare began and fitting candidates have received the cocktail therapy. We have observed beneficial results in almost all patients.
- Dr Smita Chavan, Deputy Dean, Seven Hills Hospital


O'Brien MP, Forleo-Neto E, Musser BJ, et al. Subcutaneous REGEN-COV Antibody Combination for Covid-19 Prevention.N Engl J Med. 2021 Aug 4.


NEJM: https://www.nejm.org/doi/full/10.1056/NEJMoa2109682

https://investor.regeneron.com/news-releases/news-release-d tails/phase-3-trial-showsrgen-covtm-casirivimab-imdevimab-antibody