LONDON (BLOOMBERG) - AstraZeneca Plc's Covid-19 antibody cocktail was found to be 77 per cent effective in preventing symptomatic Covid-19 in high-risk people in a key trial that could expand the range of drugs available to vulnerable groups.

Results from AstraZeneca's study found no one in the trial who received the cocktail contracted severe Covid-19 or died in relation to the disease, the company said in a statement Friday (Aug 20).

The trial of 5,197 participants, which started in November, was looking at whether the drug could prevent infection in at-risk groups and took place in the US, UK, Belgium, France and Spain.

The outcome will be a big relief for AstraZeneca after another study testing whether the cocktail could prevent symptomatic Covid-19 in people explicitly exposed to the virus failed in June.

The findings may also salvage a deal with the US to purchase the drug. The US had ordered as many as 700,000 doses for delivery in 2021, the value of which was partly contingent on the failed trial.

AstraZeneca said in June it was in "ongoing" discussions with the US government and awaiting results of this latest study - named Provent - before deciding how to proceed.

"We need additional approaches for individuals who are not adequately protected by Covid-19 vaccines," Dr Mene Pangalos, executive vice-president of biopharmaceuticals research and development, said in a statement. "We are very encouraged by these efficacy and safety data in high-risk people."

Antibody drugs are viewed as a way to potentially protect people, such as cancer patients, who may not respond as well to vaccination, but the products are cumbersome to administer and scale-up is limited.

Trials for both prevention and treatment options against Covid-19 have seen mixed success.

GlaxoSmithKline Plc and Vir Biotechnology Inc received US emergency-use authorisation for their product in May after it showed it could keep at-risk patients from worsening, though an earlier trial for hospitalised patients failed.