The US health regulator has revised the emergency use authorisations for Covid-19 antibody treatments from Regeneron and Eli Lilly to limit their use, as the drugs are unlikely to work against the Omicron coronavirus variant.

The Food and Drug Administration (FDA) said the treatments are currently not cleared for use in any US states or territories, but may be authorised in certain regions if they work against potential new variants, Reuters reported.

The agency highlighted other therapies that are expected to be effective against Omicron, including a rival antibody drug from GlaxoSmithKline and Vir Biotechnology as well as recently authorised antiviral pills from Pfizer and Merck & Co.