A new blood-thinning drug moved closer to U.S. approval on Monday, leading a pack of stroke-fighting medicines vying to compete in an estimated $10 billion a year market.

A U.S. advisory panel voted 9-0 to recommend clearance of Pradaxa, made by unlisted German drugmaker Boehringer Ingelheim, for preventing strokes in patients with a type of irregular heart beat.

The endorsement puts Pradaxa ahead of a possible competitors from partners Bayer and Johnson & Johnson, and Bristol-Myers Squibb Co and Pfizer.

The companies are racing to launch new oral anti-coagulant drugs to replace warfarin, a problematic 65-year-old medicine originally developed as rat poison.

Warfarin is the treatment of choice for people at high risk of stroke due to atrial fibrillation, a common form of irregular heart beat. But the drug interacts badly with food and other medicines, carries a high risk of bleeding and requires regular blood tests.

Members of the Food and Drug Administration advisory panel said Pradaxa clearly was safe and effective and some said it appeared to work better than warfarin.

Pradaxa is clearly superior in my mind, said University of Minnesota statistician James Neaton.

The FDA usually follows panel recommendations and a decision on Pradaxa is due by October 19.

If approved next month, Pradaxa would get a head start in a warfarin replacement market expected to be worth more than $10 billion a year and possibly as much as $20 billion. Bayer Chief Executive Werner Wenning recently put the opportunity at $12 billion to $15 billion.

At least eight potential warfarin replacements are currently being tested by major drugmakers.

FDA reviewers, in a preliminary analysis released last week, said they did not believe Pradaxa should be awarded a superiority claim and they backed approval only of a 150-milligram dose, not a 110-mg dose.

Although the higher dose proved better than warfarin in a pivotal clinical trial known as RE-LY, doctors and patients knew which drug they were getting. Study results usually are considered stronger if doctors and patients do not know which treatment is being given.

The advisory panel did not vote on which dose to recommend, but four members said they supported only the higher dose while six backed both doses to give doctors options. Winning approval of both doses could provide flexibility that could set Pradaxa apart from rivals.

The drug also would have a first-mover advantage if it reaches the market ahead of Xarelto, a rival drug being developed by Bayer and Johnson & Johnson and apixaban, the candidate from Bristol-Myers and Pfizer.

But pricing and doctors' perceptions of the medicines also will affect use.

Jefferies & Co analysts have projected apixaban to emerge as the class leader with eventual peak annual sales of $6.1 billion, compared with $5.2 billion for Xarelto and $4.6 billion for Pradaxa.

Other experimental oral anti-coagulants in development include Daiichi Sankyo edoxaban and Merck & Co's betrixaban.

An estimated 2.3 million Americans have atrial fibrillation, and the prevalence is expected to grow to 5.6 million by 2050 as the population ages, Boehringer said.

Dr. Christopher Corsico, Boehringer's U.S. medical director, said in statement the company was pleased with the panel's unanimous recommendation in favor of Pradaxa.

Boehringer, now controlled by great-grandchildren of the company's founder, suffered a setback in June when U.S. advisers rejected the company's experimental sex pill for women.

Pfizer