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HomeHealthEffective against other variants, Regeneron antibody cocktail fails to tackle Omicron: Study

Effective against other variants, Regeneron antibody cocktail fails to tackle Omicron: Study

The study, primarily involving researchers from the Frankfurt-based Goethe University, has not yet been peer-reviewed. It has been shared on the preprint portal medRxiv.

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New Delhi: A monoclonal antibody cocktail of casirivimab and imdevimab, which has been effective against all the other Covid-19 variants, failed to neutralise the Omicron variant of SARS-CoV-2 in laboratory experiments, say researchers from Germany.

The study, primarily involving researchers from the Frankfurt-based Goethe University, has not yet been peer-reviewed. It has been shared on the preprint portal medRxiv.

The antibody cocktail was approved for use under several brand names in a number of countries, including the US, the UK, Australia and Japan. It is marketed in the US by Regeneron as REGN-COV2 and was used to treat former US President Donald Trump.

The cocktail is approved under the brand name Ronapreve for medical use in Japan, the UK and Australia.

Monoclonal antibodies imdevimab and casirivimab — the two antibodies in the Regeneron drug — failed to neutralise Omicron, although it efficiently prevented Delta infection, the researchers said.

They also noted that since Omicron was resistant to casirivimab and imdevimab, SARS-CoV-2 genome sequencing of patients may be needed before monoclonal antibody treatments are started. 

The study also says that efficacy of vaccine-induced antibodies against Omicron was severely reduced. 

“In contrast to the currently circulating Delta variant, neutralisation efficacy of vaccine-elicited sera against Omicron was severely reduced, highlighting T-cell mediated immunity as essential barrier to prevent severe Covid-19,” the team said. 

However, the researchers added that people who were fully vaccinated, and had a history of Covid infection, may be better protected. 


Also Read: Monoclonal antibodies, the non-vaccines that promise to boost Covid immunity


‘Much-reduced in efficacy’

To evaluate the protective capacity of antibodies against the Omicron variant, the researchers conducted laboratory tests on blood serum obtained from people who had received various Covid vaccines. 

The team found that, compared to the Delta variant, blood serum from a double BNT162b2 (Pfizer-BioNTech)-vaccinated person had an 11.4-fold reduction in efficacy after six months against the Omicron variant. 

Even among those who had received three doses of the vaccines, there was a 24.5-fold reduction in efficacy against Omicron as compared to the Delta variant, the study says.

Blood serum from people double-vaccinated with the mRNA1273 (Moderna) vaccine showed a 20-fold reduction in efficacy against the Omicron variant, compared to Delta. 

For those who got a Pfizer-BioNTech booster dose after two doses of the Moderna vaccine, there was 22.7-fold reduction in the neutralisation capacity against the Omicron variant. 

Mutations and reinfection

The Omicron variant has over 30 mutations in the spike protein — the part of the virus that facilitates its entry into host cells. Since the spike protein is the first part of the virus that our body encounters, it is the target of most vaccines as well as antibody therapies.

Due to numerous mutations in this spike protein, the Omicron variant has raised concerns about whether existing antibody treatments or vaccines will continue to work against it. 

Changes in the spike protein also raise the possibility that people who have been previously infected and are thus assumed to have increased immunity against Covid are at possible risk of reinfection from the Omicron variant. 

Fifteen of the mutations are in the receptor-binding domain (RBD) of the spike protein — which is a major target of neutralising antibodies. 

(Edited by Saikat Niyogi)


Also Read: Monoclonal antibody treatment, given to Trump, fails against Covid variants — Guardian report


 

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