Covid vaccine-maker AstraZeneca has revealed it had hit a setback in trials of a treatment for the coronavirus.
The drug, made from a combination of two antibodies, failed its main goal to treat Covid-19 symptoms in exposed patients, AstraZeneca said in a statement.
The treatment has been undergoing phase 3 or final clinical trials to assess its safety and efficacy.
AstraZeneca said that 1,121 unvaccinated adults had been exposed to an infected person as part of the trial.
Treatment AZD7442 reduced the risk of developing symptoms by only 33%, which was "not statistically significant", it added.
The company is nevertheless continuing trials to assess whether the drug can prevent Covid or treat more severe symptoms.
The US government has funded the development of AZD7442 and has agreements to receive 700,000 doses.
Meanwhile, AstraZeneca's Covid vaccine, which was developed with the University of Oxford, continues to face safety doubts.
The jab has been suspended in several European countries over reports of rare blood clots.
A top official in the European Medicines Agency on Sunday suggested that it might be worth abandoning AstraZeneca's coronavirus vaccine for all age groups where alternatives are available.
However, a study from British health authorities showed yesterday that two doses of AstraZeneca/Oxford or rival Pfizer/BioNTech vaccines stopped the need for in-patient treatment in more than 90% of cases of the Delta variant.