UPDATE 1-Sanofi drug keeps heart patients out of hospital

(Adds Sanofi comment, further quotes, analyst sales forecasts, background)

By Ben Hirschler

LONDON, May 15 (Reuters) - Patients with a common heart arrhythmia are less likely to end up in hospital if given Sanofi-Aventis's (SASY.PA: Quote, Profile, Research) experimental drug Multaq, scientists said on Thursday.

The news boosts the chances of success for the product, which the French drugmaker plans to submit for marketing approval in the third quarter and sees as a potential blockbuster.

It is a rare piece of good news for the world's third biggest drugmaker, which has suffered a series of pipeline and patent setbacks recently. Sanofi shares (SNY.N: Quote, Profile, Research) rose 2 percent in New York after the news.

Multaq reduced hospitalisations in people with atrial fibrillation by 25 percent, although it did not result in a statistically significant fall in total mortality, according to results of a 4,628-patient clinical study presented at the American Heart Rhythm Society meeting in San Francisco.

The primary endpoint of the study was cardiovascular hospitalisation or death from any cause, where there was a reduction of 24 percent.

Dr. Stuart Connolly, director of cardiology at Canada's McMaster University and one of the trial investigators, told Reuters the findings showed Multaq was a promising new drug.

"Although it hasn't shown a reduction in mortality ... keeping people out of hospital is a very important outcome," he said in a telephone interview.