New Drug Helps Patients With Atrial Fibrillation

Study Shows Apixaban Prevents Strokes in Patients With Abnormal Heart Rhythm

By Charlene Laino
WebMD Health News

Reviewed by Laura J. Martin, MD

Feb. 10, 2011 (Los Angeles) -- The experimental anti-clotting drug apixaban beat aspirin at preventing dangerous blood clots or strokes in people with the abnormal heart rhythm atrial fibrillation, according to final results of the so-called AVERROES trial.

The late-stage phase III study was stopped early after apixaban's advantages became clear, and early results were first reported in September 2010.

Today, the final results were presented at the American Stroke Association International Stroke Conference 2011 and simultaneously published online in The New England Journal of Medicine.

If approved, apixaban will offer an alternative to the old standby, warfarin, which many people can't or won't take.

In the study of about 5,600 patients with atrial fibrillation in which warfarin therapy was considered unsuitable, apixaban cut the risk of stroke by more than half compared with aspirin.

For every 1,000 patients treated with apixaban instead of aspirin for one year, 21 strokes, nine deaths, and 33 hospitalizations will be avoided, says Hans-Christoph Diener, MD, chair of the department of neurology at the University of Essen, Germany.

However, two of 1,000 patients will suffer a major bleed, he says. Diener, who presented the results here on behalf of the AVERROES investigators, consults for Bristol-Myers Squibb and Pfizer, which funded the study.

"The results of this trial will change medical practice," Diener tells WebMD.

Drawbacks of Warfarin

The study followed patients with atrial fibrillation (AF), a condition characterized by irregular heart rhythms. The majority of patients with atrial fibrillation are more likely to suffer a stroke than people without atrial fibrillation because their irregular heartbeats may allow blood to pool in an upper chamber of the heart. Pooled blood is more likely to form clots, which can travel to the brain and block blood flow, causing a stroke.

Warfarin is the usual treatment, but up to half of patients can't take it because of increased bleeding risk or drug interactions, or refuse to take it. If too much is given, you can suffer a dangerous bleed; take too little, and you're at risk for a deadly blood clot related to the atrial fibrillation.

Aspirin is the usual care in patients who cannot take warfarin, but it's less effective. So there's a race on to find a better alternative. The drug Pradaxa was recently approved by the FDA for such use. Apixaban and Xarelto have both proven effective in late-stage testing, although they have yet to gain approval for this use.

Apixaban is part of a class of new drugs called factor Xa inhibitors that interfere with the body's clotting mechanism.

Apixaban vs. Aspirin

Final results of the new study show apixaban reduced the rate of strokes or major clots by 55%. The annual rate of strokes or clots in patients on apixaban was 1.6% vs. 3.7% for those on aspirin.

The annual rate of major bleeding, including bleeds to the brain, was 1.2% for aspirin and 1.4% for apixaban, a difference so small it could have been due to chance.

Asked to comment on the AVERROES results, Robert J. Adams, MD, director of the Medical University of South Carolina Stroke Center in Charleston, says that while "it's a big breakthrough scientifically, its effect [in the real world] will probably be muted by a massive difference in price compared with aspirin.

"If not for such [a probable] difference in price, it would be a paradigm shift," he tells WebMD.

No price has been set for the drug in the U.S, according to a company spokesperson.

Findings of another study, in which apixaban is being pitted against warfarin, are due out in August.

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SOURCES: American Stroke Association International Stroke Conference 2011, Los Angeles, Feb. 7-11, 2011.Hans-Christoph Diener, MD, chair, department of neurology, University of Essen, Germany.Robert J. Adams, MD, director, Medical University of South Carolina Stroke Center, Charleston.Connolly, S.J. New England Journal of Medicine, published online, Feb. 10, 2011.

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