Sanofi to warn docs on Multaq patients' liver failure

Multaq may have hit a snag. The atrial fibrillation drug from Sanofi-Aventis, whose 2009 U.S. launch got off to a slow start, is the subject of an impending "Dear Doctor" letter to inform physicians about two patients with liver failure, CardioBrief reports.

No causal link between Multaq and the liver trouble has been found, the company says. But Sanofi plans to change Multaq's label and will recommend that doctors check patients' liver function before prescribing the drug, CardioBrief says.

There's been some argument over Multaq's risk-benefit profile; one study found that the drug was less effective than a rival drug, and recommended that it be restricted to second-line use, but a commentary in the same journal disagreed. French regulators initially were skeptical about its efficacy, but later upped its effectiveness assessment, and European regulators recommended it as a first-line treatment.

This new information isn't likely to settle lingering doubts. "[I]t is not clear whether the liver toxicity represents an idiosyncratic reaction or an expected side effect that can be mitigated by monitoring liver function tests," Dr. Sanjay Kaul told the news site. "Nonetheless, the news of acute liver failure adversely alters the already tenuous benefit-risk balance of this drug."

Multaq was Sanofi's first major new drug after a long drought, and the company has been counting on it to help fill the sales holes left by blockbuster drugs with expiring patents. Analysts estimate that Multaq could bring in $1.35 billion in annual sales by 2014, Reuters reports. Hoping to boost Multaq's prospects, the company began a new trial last year, aiming to show that the drug can stave off cardiovascular episodes, such as stroke and heart attack, in patients with permanent atrial fibrillation--a very tough patient group.

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