The US Food and Drug Administration (FDA) has restricted the use of Covid-19 antibody therapies from Regeneron and Eli Lilly, as they are unlikely to work against the Omicron variant.

The US agency revised the emergency use authorisations (EUA) for Lilly’s bamlanivimab plus etesevimab regimen, and Regeneron’s REGEN-COV, based on the recent data.

According to the data, the antibody therapies are highly unlikely to be active against the rapidly circulating Omicron variant, stated FDA.

The treatments are currently not approved in any US territories but may be authorised if they work against circulating new variants, reported Reuters.

Monoclonal antibodies are laboratory-made synthetic proteins that emulate the immune system in fighting against disease-causing pathogens.

Similar to other infectious organisms, SARS-CoV-2 would also mutate over time, making certain treatments ineffective against certain variants, such as Omicron.

According to data from Centres for Disease Control and Prevention (CDC), the Omicron variant accounts for more than 99% of cases in the US as of 15 January 2022.

It is highly questionable that Covid-19 patients currently requiring care are infected with a variant other than Omicron, hence the antibody treatments are restricted, said the FDA.

The move prevents patients from exposure to potential side effects from specific treatment agents that are unlikely to be effective in treating patients infected with the Omicron variant.

Last month, the US government had stopped the distribution of Regeneron and Lilly’s therapies, until new data proving their efficacy against Omicron, reported Reuters.

Recently, the Covid-19 Treatment Guidelines Panel at the National Institute of Health (NIH) has recommended against the use of bamlanivimab and etesevimab regimen and REGEN-COV.

The NIH panel’s decision was based on reduced activity against the Omicron variant and real-time testing to identify rare, non-Omicron variants is not routinely available.

Other therapies such as Paxlovid, sotrovimab, remdesivir, and molnupiravir are showing promise in treatment against the Omicron variant.

The treatments are authorised or approved to treat Covid-19 patients, who are at elevated risk for progression to severe disease, including hospitalisation or death.

The US FDA said that it would review emerging data on all Covid-19 therapies related to the potential impact of variants and revise the authorisations