The new trial, supported by England's National Health Service, is expected to begin in the first quarter of 2021 at multiple sites across the UK, the companies said in a joint statement.

Preclinical data suggested the companies' monoclonal antibody (mAb) has the ability to clear infected cells and the potential to enhance virus-specific T cell function, which could help treat and/or prevent infection.

This would become the second mAb from the Vir-GSK collaboration to be investigated as a potential COVID-19 treatment, with the first currently being assessed in two global late-stage studies.

"This study will be critical... as we work to understand whether the modifications we have made to this monoclonal antibody increase its potency and stimulate a T cell response to not only provide therapeutic benefits but also potentially confer a vaccine-like effect," Vir CEO George Scangos said.

GSK and Vir had set out in October to expand a trial of their first experimental COVID-19 antibody to 1,300 patients globally after initial use by a group of volunteers did not raise any safety concerns.

mAbs mimic natural antibodies generated in the body to fight off infection and can be synthesised in the laboratory to treat diseases in patients. Current uses include treatment of some types of cancers.

Other drugmakers testing mAbs as COVID-19 treatments include Regeneron Pharmaceuticals Inc, Eli Lilly, Roche and AstraZeneca.

GlaxoSmithKline is also working on a COVID-19 vaccine with Sanofi, but last month the French company said the shot showed an insufficient immune response in clinical trial results.

(Reporting by Muvija M and Pushkala Aripaka in Bengaluru; Editing by Saumyadeb Chakrabarty and Shailesh Kuber)