EMA calls for limits on Sanofi's Multaq

European regulators have wrapped up their safety review on Sanofi's ($SNY) heart drug Multaq. The good news is the European Medicines Agency confirmed Multaq's benefits outweigh its risks. The bad news is the positive balance applies only to a limited population of patients with atrial fibrillation. And for a drug once considered a potential blockbuster, the limits amount to a big letdown.

The EMA now says Multaq should only be prescribed after "alternative treatment options have been considered." Certain patients--such as those with current or previous episodes of heart failure--shouldn't get it at all. And patients who do get it should have their treatment evaluated at their next doctor's appointment, the agency said.

The EMA had been reviewing Multaq in part because of reports of liver failure with the drug. Another factor was Sanofi's decision to stop a late-stage trial in patients with permanent AF after a "significant" increase in heart attacks and strokes in those using Multaq rather than the placebo was observed. U.S. regulators are still weighing the data.

Multaq's sales are now expected to peak at around $570 million in 2016, rather than beating $1 billion as originally projected, Reuters reports. Some analysts may decide to cut their forecasts further based on the EMA's decision, but it's not as severe as a few market-watchers had feared.

"It no longer is a flagship product," a Paris-based analyst told the news service. "This decision doesn't come as a surprise, it's nothing dramatic." The analyst said he would likely cut his sales estimate for the drug to some €400 million ($539 million) from €500 million by 2016.

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