An experimental Novartis AG drug to treat hospitalized acute heart failure patients reduced deaths by 37 percent compared with a placebo and appeared to be safe, according to data from a late stage clinical trial presented on Tuesday.

The drug, serelaxin, which is a form of a human hormone that relaxes blood vessels and eases stress on the heart and other organs, is considered one of the most important medicines in the Swiss drugmaker’s developmental pipeline.

“With a meaningful mortality benefit, we believe Serelaxin could represent a $2.5 billion (annual) sales opportunity,” Deutsche Bank analysts said in a research note prior to release of the final data at the American Heart Association scientific meeting in Los Angeles.

Novartis said it now planned to seek approval for serelaxin. In the study of 1,161 patients, the drug cut deaths from any cause at six months by 37 percent and led to a marked reduction in worsening of heart failure during hospitalization, researchers said.

Patients who received 48 hours of continuously infused serelaxin experienced more than 45 percent fewer episodes of worsening heart failure symptoms than those who got a placebo.

Novartis had previously disclosed that serelaxin met one of the study’s two primary goals measuring relief of dyspnea, or extreme shortness of breath - a common symptom of acute heart failure - and that it reduced deaths. But the company did not say by how much. By one measure, serelaxin led to a 19 percent improvement in dyspnea, researchers said.

The drug failed to hit a secondary goal of the study that combined cardiovascular death with need for reshospitalizations, but researchers felt the life saving benefit was more important.

“We did have a startling death benefit. One of the reasons there may have been an inability to show a decrease in hospitalizations is more patients were alive to be rehospitalized,” said Dr John Teerlink, one of the trial’s co-lead researchers.

The data showed that only 29 acute heart failure patients would have to be treated with serelaxin to prevent one cardiovascular death, said Teerlink, a cardiologist and heart failure specialist at the San Francisco VA Medical Center.

Doctors say there is an enormous need for a treatment for acute heart failure, with few available options for the condition in which the heart is unable to pump enough blood.

“If it was approved we would not only use it, there would be a mandate to use it because we don’t have anything for acute decompensated heart failure,” said Dr. Milton Packer, a prominent cardiologist from the University of Texas Southwest Medical Center in Dallas, who was not involved in the study.

“If that mortality finding is real, boy are we going to get excited,” said Packer, who has been a member of FDA advisory panels for heart drugs.

There are more than one million hospitalizations in the United States each year for acute heart failure and another million in Europe. About half of all patients die within five years of diagnosis, often as a result of acute episodes that require urgent hospital care.

TREATMENT BENEFITS

The study showed the Novartis drug also reduced the duration of time spent in intensive care units by almost half a day and cut the length of hospital stay by almost a full day.

There was no difference in serious side effects between the two groups, but there was a significant increase in kidney impairment in the placebo group, as the Novartis drug appears to prevent worsening of kidney function, researchers said.

Despite missing some of the pre-set end points, or goals, of the study, Novartis said it is likely to seek approval of the drug based on the trial results.

“We believe this is a strong set of data and have started discussions with the main regulatory agencies. Our filing strategy will be determined by the outcome of these discussions,” said Ameet Nathwani, Novartis’ global business franchise head for critical care.

Dr John McMurry of the University of Glasgow, who was on a panel to critique the study, said that if there were a second serelaxin trial that also showed a mortality benefit it would be hard for health regulators to ignore.

“I think the agent was beneficial. This drug is doing something good in terms of relief,” he said.

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By Bill Berkrot and Deena Beasley