The FDA said that GlaxoSmithKline’s (GSK) and Vir Biotechnology’s sotrovimab should not be administered in areas where new SARS-CoV-2 variants are showing resistance to the COVID-19 antibody.

Sotrovimab has been shown in studies to be one of the few effective treatments against the Omicron variant and Vir has also claimed the antibody can offer protection against the new BA.2 subvariant derived from Omicron. But the FDA appears to be concerned that the antibody will not be effective for some emerging variants.

Sotrovimab is currently authorized for patients with mild-to-moderate COVID-19 at high risk of progressing to severe disease. However, the drug’s Emergency Use Authorization doesn’t cover hospitalized COVID-19 patients or those requiring supplemental oxygen.

The Biden administration signed contracts worth an estimated $1 billion in November 2021 for an unknown number of sotrovimab doses and announced plans in January to buy an additional 600,000 doses of the drug for an undisclosed amount.