SILVER SPRING, Maryland (Reuters) – U.S. advisers recommended against expanding the use of Johnson & Johnson’s blood thinner Xarelto as a way to reduce the risk of new heart attacks and strokes in people with heart problems.

A panel of outside experts to the Food and Drug Administration voted on Wednesday that the pill should not be approved for people with acute coronary syndrome.

J&J developed the drug in partnership with German drugmaker Bayer AG.

Xarelto is already approved for use to reduce the risk of blood clots in the legs and lungs of people who have had knee or hip replacement surgery. It is also approved to prevent strokes among people with a type of irregular heartbeat called atrial fibrillation.

But the companies wanted to expand its use to treat acute coronary syndrome, which refers to people who have heart attacks or chest pain, usually because of a blocked coronary artery.

About 1 million people in the United States are hospitalized each year after having an ACS episode, often a heart attack, according to researchers.

The trial tested Xarelto as an addition to aspirin, and other clot preventers like Bristol-Myers Squibb and Sanofi’s Plavix, which are typically used to treat the condition.

By a vote of 6 to 4, with one abstention, the panel said Xarelto looked promising but missing data could skew results. They were also concerned about bleeding risks.

“I want to see better evidence that this strategy of adding (Xarelto) …is robustly better for the patient,” said Dr. Steven Nissen, panel member and chairman of cardiovascular medicine at the Cleveland Clinic. “And I just wasn’t convinced.”

The FDA usually follows panel recommendations, although it is not required to, and a final decision is expected by the end of June.

“We appreciate the thoroughness of the committee’s review, and will ensure the questions raised today are addressed with the FDA,” said Paul Burton, a vice president with Janssen Research & Development, the J&J unit that markets Xarelto.

THREE-WAY RACE

Xarelto is one of three new medicines that offer potential advantages over older drugs to prevent strokes and other dangerous conditions caused by blood clots, in a market worth up to $10 billion in annual sales, according to Wall Street forecasts.

Investors have tried to bet on which of the three will become the dominant player in a race between Xarelto, Eliquis from Pfizer Inc and Bristol-Myers Squibb Co and Boehringer Ingelheim’s Pradaxa.

Pradaxa gained U.S. approval in 2010, while Eliquis is still under FDA review, with a decision expected by the end of June.

Xarelto’s rivals failed in treating patients with ACS, giving Bayer and J&J a potentially distinct market — although stroke prevention in atrial fibrillation is seen as the most lucrative use for the new drugs.

In a clinical trial of ACS, people who took a 2.5 milligram dose of Xarelto in addition to an aspirin and another anti-platelet medication had a 15 percent lower risk of having a stroke or dying from a heart attack than people just taking the other medicines, FDA reviewers said.

On the other hand, patients taking Xarelto had twice as much risk for a major fatal bleeding compared to the older drugs, while other kinds of bleeding were three times higher with Xarelto. But the overall rates were still low: only 0.1 percent of patients had fatal bleeding while taking the drug and 2 percent had some kind of bleeding.

The FDA advisers decided the balance between the heart benefits of Xarelto and its bleeding risks tilted against the drug because the company lost track of an average of 12 percent of patients during clinical trial. It was unclear how those patients fared while taking the medicine.

“Were there not questions about loss to follow-up and missing data, it would have been a yes,” said Allan Coukell, a pharmacist and the panel’s consumer representative, when explaining his ‘no’ vote on Xarelto.

J&J has said it expected some people to drop out of the final clinical trial since it enrolled about 15,500 patients and studied them for about 2 1/2 years, and the dropout rates were similar between people taking Xarelto and those on the older drugs, meaning the missing data should not impact the results.

(Reporting by Anna Yukhananov; Editing by Gary Hill, Tim Dobbyn, Leslie Gevirtz and Michael Perry)