WASHINGTON - AstraZeneca Covid-19 antibody drug is no longer authorised for use in the US, regulators said on Thursday, as it’s unlikely to work against strains of the virus that are now dominant across the country. 

Astra’s drug, called Evusheld, was authorised in December 2021 to prevent Covid-19 infection in high-risk people, but has been rendered less effective by the virus’ mutations.

At this point, fewer than 10 per cent of the variants currently circulating in the US appear to be responsive to Astra’s treatment, the US Food and Drug Administration said in a statement. 

In the meantime, Astra said in a statement that it’s testing a next-generation long-acting antibody to prevent Covid-19 in immune-compromised people, and aims to make the drug available in the second half of 2023, pending regulatory approval.

In early lab studies, the next-gen antibody was effective against all Covid-19 variants tested, the company said, including those that have thwarted other drugs.

“About 2 per cent of the global population is considered at increased risk of an inadequate response to Covid-19 vaccination and could benefit from monoclonal antibodies for Covid-19 protection,” the company said.

Earlier this month, the agency warned Evusheld was unlikely to work against the rapidly spreading XBB.1.5 variant, which has grown to account for almost half of the country’s Covid-19 cases, but the drug remained on the market until now. 

This hasn’t just been a problem for Astra’s antibody.

A US National Institutes of Health panel had recommended against using any monoclonal antibodies to treat or prevent Covid-19 in high-risk people because of the drugs’ waning effectiveness.

Evusheld was the last antibody treatment left on the market after the FDA revoked other drugs’ authorisations due to variants.

Covid-19 antibody drugs made by Eli Lilly & Co, Regeneron Pharmaceuticals Inc and a partnership between GSK Plc and Vir Biotechnology Inc have all been pulled from the market as well. BLOOMBERG