GSK and Vir Biotechnology say the United States has signed contracts worth roughly $1 billion to secure the antibody-based Covid-19 treatment sotrovimab from them with supply expected by December 17, Reuters reports.

Britain's GSK said the deal brought the total number of doses secured of the treatment, branded Xevudy, to more than 750,000 globally, adding that the United States would have an option to buy additional doses through March 2022.

The companies did not specify how many doses the US government had signed up for.