Stroke Health Center

New Anticlotting Drugs in the Works

Sept. 1, 2010 (Stockholm, Sweden) -- Two experimental anticlotting drugs showed impressive results at preventing deadly blood clots, doctors say.

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

In one study of 5,600 patients who couldn't or wouldn't use warfarin, apixaban beat aspirin at preventing dangerous clots or strokes.

In the other study of more than 3,400 patients, the new pill Xarelto was as safe and effective as warfarin at dissolving potentially deadly blood clots in the legs and preventing new ones.

Both studies were presented at the European Society of Cardiology Congress.

Apixaban cut the risk of stroke by more than half compared with aspirin, says researcher Stuart Connolly, MD, of McMaster University in Hamilton, Ontario, Canada.

The rate of major bleeding, the key concern, was no higher among patients on apixaban, he says.

The late-stage phase III study was stopped early after apixaban's advantages became clear, Connolly tells WebMD.

Drawbacks of Warfarin

The study followed patients with atrial fibrillation (AF), a condition characterized by irregular heart rhythms. They're five times more likely to suffer a stroke than people without AF because their erratic heartbeats 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 AF.

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, with apixaban, Xarelto, and a third drug, Pradaxa, leading the pack. Other anticlotting drugs in development include edoxaban and betrixaban.

Apixaban Study

In the new study, apixaban reduced the rate of strokes or major clots by 54%. The annual rate of strokes in patients on apixaban was 1.6% vs. 3.6% for those on aspirin, Connolly says.

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.

The apixaban results were "truly impressive," Connolly says.

Apixaban is set to be reviewed by FDA advisers later this month.

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

The study was funded by Bristol-Myers Squibb and Pfizer, from which Connolly received research grants and consulting fees.