* Xarelto 21 pct more effective than warfarin in study
* Lower risk of intracranial hemorrhages seen with Xarelto
* Hemorrhagic stroke reduced by 41 pct, vs warfarin
* J&J says formal trial lacks bias seen in Pradaxa study
By Ransdell Pierson
CHICAGO, Nov 15 (Reuters) - A once-daily pill being developed by Bayer AG BAYGn.DE and Johnson & Johnson JNJ.N is considerably better able to prevent strokes than standard treatment, and with less risk of brain hemorrhages and bleeding-related deaths, researchers said on Monday.
The fuller picture for the new drug, Xarelto, could boost Wall Street global sales forecasts for the product -- already as high as $5 billion a year -- and make it a tougher-than-expected competitor for an up-and-coming crop of new blood clot preventers that must be taken twice a day.
Xarelto was 21 percent better able than the widely used but problematic drug warfarin to reduce strokes caused by a form of irregular heartbeat called atrial fibrillation that is common among the elderly.
Two weeks ago, the drugmakers announced general findings from the 14,000-patient trial called ROCKET AF, including that Xarelto was at least as good as warfarin in preventing strokes and had a similar overall bleeding risk.
But researchers did not disclose until Monday its actual superior effectiveness, or its lower risk for intracranial bleeding and hemorrhagic stroke -- the most feared consequences of anti-clotting medicines.
Patients taking Xarelto were about one-third less likely to have intracranial bleeding, which includes strokes and other bleeding within the brain area. An estimated 41 percent reduced risk was seen for hemorrhagic stroke.
Bleeding into a critical organ was reduced by 31 percent, while the risk of fatal bleeding was cut in half. But Xarelto patients had bigger drops in hemoglobin and required more blood transfusions, the other two components of major bleeding. (Reporting by Ransdell Pierson; Editing by Lisa Von Ahn)