AstraZeneca said a study of Brilinta/Brilique (ticagrelor) 90mg tablets twice daily, when compared to aspirin 100mg once daily in patients with acute ischaemic stroke or transient ischaemic attack (TIA), had shown the drug had not met its primary efficacy endpoint of preventing repeat attacks within 90 days.
Fewer people who took AstraZeneca's drug in the trial had a recurrent stroke, heart attack or died than those on aspirin, but the difference was not statistically significant.
AstraZeneca's executive vice-president of global medicine development and chief medical officer, Sean Bohen, said: "We will present the full analysis of the trial results, including subgroups, at a forthcoming stroke congress and will engage with regulatory agencies on the interpretation of the data."
The so-called Socrates trial evaluated the efficacy and safety of 90-day treatment with Brilinta/Brilique versus aspirin for the prevention of major vascular events in patients over 40 years-old with an acute ischaemic stroke.
Shares in AstraZeneca fell 3.5p to 3911.5p.