Pfizer Clot Drug Beats Aspirin in Research, May Enter $10 Billion Market

Pfizer Inc.’s experimental blood thinner apixaban beat aspirin in a study that may open the door to a $10 billion-a-year market to prevent clots that cause strokes and deadly lung damage.

Patients who took the Pfizer drug were 54 percent less likely to have a stroke or damaging clot than those who took aspirin in a study of 5,600 patients who couldn’t use the standard therapy warfarin, researchers said today at the European Society of Cardiology conference in Stockholm. Apixaban and aspirin showed a similar risk of major bleeding, a feared side effect of blood thinners.

About half of the 2.2 million Americans with atrial fibrillation, an irregular heartbeat that increases the likelihood of clots, don’t take warfarin because of side effects or the need for constant monitoring, studies show. Today’s results leave “no competition for apixaban in the foreseeable future” for that group of patients and signal the drug could challenge warfarin, said lead investigator Stuart Connolly, of the Population Health Research Institute at McMaster University in Ontario, Canada.

“You can definitely conclude that apixaban is going to have a markedly improved safety profile compared to warfarin,” Connolly said in an interview in Stockholm. “You can also anticipate that apixaban is going to be at least as good as warfarin and probably better than warfarin in efficacy.”

Warfarin typically reduces the rate of stroke 40 percent more than aspirin, Larry Biegelsen, a New York-based analyst for Wells Fargo Securities, wrote in a note to investors on Aug. 30. That’s a lower rate than apixaban showed in today’s trial. Results from a larger 18,000-patient study comparing apixaban with warfarin in atrial fibrillation patients are expected early next year, Barbara Ryan, an analyst with Deutsche Bank in New York, said in a note to clients.

Replacing Warfarin

Pfizer, partnering with Bristol-Myers Squibb Co., is racing to challenge German drugmaker Boehringer-Ingelheim GmbH in the market for pills to replace warfarin. Crafted from rat poison 65 years ago, warfarin can cause fatal bleeding at high doses and leave patients vulnerable to clots if too little is given.

Aspirin is the only alternative now for irregular heartbeat patients for whom warfarin is too risky, Connolly said.

“This is a major advance for these patients,” the researcher said. “The effects are really important to individuals, and they’re going to be important to society.”

Atrial fibrillation means the heart doesn’t properly pump blood out of its upper chamber, allowing it to pool and clot, according to the American Heart Association. A stroke can result if part of that clot breaks off and gets lodged in the artery to the brain.

Trial Stopped

Pfizer and Bristol-Myers, both based in New York, stopped their Averroes study comparing apixaban to aspirin ahead of schedule in June, after an early analysis showed it cut the rate of strokes and certain clots. Both companies are looking for new drugs to plug a hole in revenue after their top-selling pills face generic competition.

Pfizer will start losing the majority of revenue next year for its cholesterol pill Lipitor, the top-selling drug in the world with $11.4 billion in sales last year. Meanwhile, Bristol- Myers is likely to face competition in the U.S. in 2012 for Plavix, the anti-clotting drug it markets with Sanofi-Aventis SA.

The companies may ask regulators to approve apixaban for irregular heartbeat patients on the basis of the Averroes trial alone, Seamus Fernandez, an analyst with Leerink Swann & Co., wrote in a note to investors on Aug. 30. The market for warfarin replacements may be worth $10 billion to $20 billion a year, Fernandez wrote in an earlier note.

Bayer Data

Apixaban may face competition from Xarelto, an anti-clot pill from Bayer AG and Johnson & Johnson, as well as from Boehringer Ingelheim’s Pradaxa. In a separate study released at the meeting in Stockholm today, Bayer said Xarelto was as safe and effective as the standard therapy of Sanofi-Aventis SA’s Lovenox plus warfarin at preventing blood clots in the lungs and legs.

Bayer has said it will issue data on how its blood thinner Xarelto matched up against warfarin at the American Heart Association’s meeting in November.

Meanwhile, the U.S. Food and Drug Administration is scheduled to review Pradaxa on Sept. 20. The blood thinner beat warfarin at preventing strokes in atrial fibrillation patients last year in a trial.

"These medications are going to change the practice in the United States," Ralph Brindis, president of the American College of Cardiology and a cardiologist at Oakland Medical Center, told journalists before today’s results were released. Being first to market in the U.S. "is huge," he said.

To contact the reporter on this story: Naomi Kresge in Stockholm at nkresge@bloomberg.net

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