UPDATE 1-US FDA panel backs Astellas-Cardiome heart drug

(Adds details from panel discussion, comments, context, byline)

By Kim Dixon

BELTSVILLE, Md., Dec 11 (Reuters) - An experimental intravenous drug developed by Astellas Pharma Inc (4503.T) and Cardiome Pharma Corp (COM.TO) merits approval for treating a potentially fatal heart ailment, a U.S. drug advisory panel said on Tuesday.

The Food and Drug Administration advisory panel voted 6-to-2 to recommend approval of the treatment, called vernakalant, for atrial fibrillation. With AF, the heart's upper chambers beat abnormally, putting them at risk for blood clots and strokes.

Japan's Astellas and Canada's Cardiome are seeking FDA clearance to sell intravenous vernakalant for acute treatment of atrial fibrillation. About 2.2 million Americans suffer from AF in the U.S., according to the American Heart Association.

The number is expected to rise as the population ages.

The FDA typically, though not always, takes the advice of these advisory panels.

The drug's risks include developing a dangerously slow heart beat, low blood pressure, excessive bleeding, and a rhythm disturbance that can be fatal.

But the panel said current treatments, including drugs, are fairly ineffective and carry their own dangers. Many patients undergo an electrical cardioversion, where the heart is electrically shocked, a procedure with risks such as putting a patient under anesthesia, and the potential for burns.

"It's a worthwhile addition to the armamentarium," despite its risks, said Dr. Michael Lincoff, a panel member and professor of medicine at the Cleveland Clinic, who voted for approval.

Most panel members conceded it is unclear how effective the drug is after a short period of time, because patients in the studies were allowed other treatments after the initial experimental drug treatment.

The companies are seeking use of the drug for patients who have had atrial fibrillation for up to a week, but the data do not support a benefit much past two days, panel members said.

"I think it should be clearly stated (on the drug's label) how low the efficacy is beyond 48 hours," Dr. Barry Massie, another panel member and chief of cardiology at the San Francisco Veteran's Administration Hospital said.

Several experts, even those who voted for the drug, worried that the drug would be used in patients who are too sick and run greater risk of adverse events and even death.

In one death very likely related to the drug in clinical trials, the patient's health status should have excluded him from the study, according to an FDA medical review.