An antibody cocktail that held out promise as a single shot to prevent the worsening of Covid in high-risk people with mild to moderate symptoms, has seen its use getting further restricted by the United States Food and Drug Administration against the Omicron variant.

The injectable antibody cocktail, Regeneron’s casirivimab and imdevimab is marketed globally by Swiss-drugmaker Roche, which sells it in India through Cipla. The drug had hit global headlines after it was given to former US President Trump when he was tested positive for Covid.

Indiscriminate use

The therapy, though, was recently in the eye of a storm in India, after virologist Dr Gagandeep Kang called out the indiscriminate use of this expensive drug. The therapy continues to get prescribed by some doctors, despite not being part of treatment guidelines against Omicron. The one-dose treatment costs a patient, close to ₹60,000.

The FDA said it was revising authorisations for two monoclonal antibody treatments – Eli Lilly’s bamlanivimab and etesevimab (given together) and REGEN-COV (casirivimab and imdevimab) – “to limit their use to only when the patient is likely to have been infected with or exposed to a variant that is susceptible to these treatments”.

Monoclonal antibodies are laboratory-made proteins that mimic the immune system’s ability to fight off harmful viruses such as SARS-CoV-2. And like other infectious organisms, the SARS-CoV-2 virus can mutate over time, resulting in certain treatments not working against certain variants such as Omicron, it added. At present, physicians are optimistic about Sotrovimab, a similar product from UK drugmajor GlaxoSmithKline.

A spokesperson for Roche (India) told BusinessLine that they had informed the Indian drug regulatory authority on the developments and posted the usage guidelines on their website.

“Similar to several other antibody treatments, Ronapreve does not retain efficacy against the Omicron variant. There is no data on the clinical use of RonapreveTM in patients infected with the Omicron variant,” said Roche. “However, Ronapreve remains highly effective against all other key circulating variants, including Delta and Delta Plus, and it would be key for patients with these other variants to have access to this treatment,” it added.

Physician’s predicament

Madhumitha R, Infection control specialist at MGM Healthcare, said: “If you look at the Indian data right now, it’s almost 80-85 per cent Omicron variant that is circulating, so the role of the current monoclonal antibodies that we have may not be effective. But we do have a lot of Delta variant roaming around, and it is very difficult to prove which is Delta and which is Omicron. In such a situation, when there is still a confusion that this could be Delta and the patient is at a higher risk of progression, then we may choose to give monoclonal antibodies..”

Subramanian Swaminathan, Director (Infectious Diseases), Gleneagles Global Health City, added: “Although we are continuing to use it (monoclonal antibodies) and seeing clinical benefits, we don’t have sequencing; so, I don’t know whether it is a case of Delta or Omicron or its sub variants like Ba.1, Ba.2. All I know is that my patient has Covid.”

“If we give monoclonal antibodies patients are starting to feel better within 24 hours, and we are noticing that even today, and we are not giving them anything other than monoclonal antibodies. So, it suggests to me that it has some amount of antiviral activity,” he added.