Risks of liver, cardiovascular or lung issues stemming from Sanofi's Multaq irregular heart beat drug mean its use should be restricted, Europe's drug regulator said on Thursday following a safety review.
The decision could raise further pressure on Sanofi to speed up the replenishment of a drug pipeline which has been drastically diminished after a top-to-bottom review.
Following a monthly meeting, the regulator's Committee on Medicinal Products for Human Use (CHMP) in London recommended the drug should only be prescribed "after alternative treatment options have been considered".
Patients taking Multaq, once touted as a blockbuster, are recommended to have their treatment evaluated by their doctor at their next scheduled appointment, the panel of the European Medicine's Agency said in a statement.
Nevertheless, the agency said that for some patients with non-permanent atrial fibrillation, Multaq was a useful option, adding that for them benefits outweighed the risks of using the drug.
Multaq, chemically known as dronedarone, should only be prescribed for certain heart disease cases including arrhythmia at varying intervals and some types of persistent atrial fibrillation following certain successful medical procedures, the panel said.
Atrial fibrillation is an abnormal heart rhythm in which the upper chambers of the heart beat in an uncoordinated manner. This can cause palpitations, shortness of breath and fatigue and raise the risk of more serious heart problems.
More and more people are suffering from the disease due to an increasingly ageing population.
EU and U.S. regulators in July widened their review into whether Multaq, approved for recent irregular heart beat patients, could cause some forms of cardiovascular disease. That came on top of a probe into possible ties between Multaq and liver failure.
The broadened review was prompted by Sanofi's decision to halt a late-stage clinical trial using Multaq in long-term sufferers, when it saw a "significant" rise in cardiovascular disorders such as heart attacks and strokes.
Before the latest problems, many analysts saw Multaq's potential annual sales exceeding $1 billion. Consensus forecasts currently point to sales of around $570 million in 2016, according to Thomson Reuters Pharma.
"It no longer is a flagship product," a Paris-based analyst who declined to be named said. "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 euros from 500 million by 2016.
Sanofi shares closed 3.2 percent lower at 46.50 euros, underperforming a 2.2 percent drop in the wider health index .
Some analysts had feared an outright withdrawal of Multaq from the market.
In a statement, Sanofi's Chief Medical Officer Jean-Pierre Lehner called the panel's opinion "significant" because it left the door open for use in some treatments.
The twice-daily 400 mg tablet won EU marketing approval in November 2009 for use in patients with non-permanent irregular heart beat.
(Reporting by Caroline Jacobs; Editing by Christian Plumb, James Regan and Jane Merriman)