A closely-watched experimental blood thinner developed by Bristol-Myers Squibb Co and Pfizer Inc proved superior to warfarin in preventing strokes in patients with dangerously irregular heart rhythms, according to data from a pivotal late stage trial.

The drug apixaban, which will be sold under the brand name Eliquis if approved, needed to show only non-inferiority to warfarin in stroke prevention to meet the primary goal of the Phase III trial.
But it showed superior efficacy to warfarin in patients with atrial fibrillation, according to initial data from the study released on Wednesday by the companies. This should help the drug compete with a pair of rivals in the highly lucrative market for millions of patients with the heart disorder.

The Bristol-Myers drug also showed superior efficacy in the key safety measure of major bleeding. But the companies did not reveal important overall bleeding data.

Full details of the study will be presented on August 28 at a major medical meeting in Europe.

The companies expect to submit applications seeking U.S. and European approval in the third or fourth quarter of this year.

Bristol-Myers shares rose 5 percent in extended trading, while Pfizer shares rose 2.3 percent.