AstraZeneca said on Friday (August 20) its antibody therapy met the main goal of preventing COVID-19.
That was the conclusion of a late-stage study.
It puts the British drugmaker on track to potentially offer an alternative to vaccines for people with weakened immune systems.
The company said the cocktail of two types of antibodies were initially discovered by Vanderbilt University Medical Center.
AstraZeneca said the combination reduced by 77% the risk of developing symptomatic COVID-19.
It added that more than 75% of the participants had chronic conditions, including some linked to a diminished immune response to vaccination.
The Anglo-Swedish drugmaker is also working on repurposing existing drugs to fight the virus.
An AstraZeneca executive said the prospect of offering a new treatment to prevent COVID-19 could position the British drugmaker as a supplier of both vaccines and drugs which guard against the infectious disease.