FDA staffers throw cold water on Sanofi's Lemtrada hopes

If you're a drug developer, which 6 words do you never, ever want to see in an FDA review of a potential new product? The 6 words applied to Sanofi's ($SNY) multiple sclerosis treatment Lemtrada: "serious and potentially fatal safety issues."

In advance of next week's advisory panel meeting on the drug, FDA staff reviewers flagged links between Lemtrada and autoimmune disorders, thyroid disease, cancer and other maladies. That means the drug is too risky to approve unless it really works, and works well, the agency staffers said.

Unfortunately for Lemtrada, reviewers weren't convinced of its efficacy, either. The staff review questioned whether Sanofi's trial data was adequate to prove that the drug works. Together with the safety questions, that could be a death knell for Lemtrada in the U.S.--and the U.S. would be Sanofi's most lucrative market for the drug.

In the aftermath of its patent-cliff sales crash, Sanofi has been counting on Lemtrada to help revive its fortunes. The French drugmaker bet big on the drug as the centerpiece of its $20 billion acquisition of Boston-based Genzyme in 2011. Sanofi wasn't without its doubts, however; as a hedge, the company negotiated a deal pegging part of the investor payoff to Lemtrada's approval and eventual success in the marketplace. 

The signs were promising, at least in Europe, where the drug won approval earlier this year. Analysts have said the drug could build up to almost $700 million in sales by 2017. But the FDA review could change that. If the agency's panel of outside experts agrees, then Lemtrada may never hit the U.S. market. If it does win approval, then its prescribed use could be sharply restricted.

MS patients are often willing to take risks for the promise of effective treatment. Other drugs for the disorder do come with the potential for serious harm; Biogen Idec's ($BIIB) Tysabri, for example, can trigger a potentially fatal brain infection, progressive multifocal leukoencephalopathy. Novartis' ($NVS) Gilenya, the first oral treatment to hit the market, carries the risk of heart rate abnormalities that can be fatal, particularly after a patient's first dose.

Still, the review on Lemtrada sounds ominous: "The certainty of the risks of potentially lifelong hypothyroidism, serious infusion reactions, melanoma and other malignancies, Graves's ophthalmopathy and other autoimmune disorders, and prolonged increased susceptibility to infection may not be balanced by the uncertainty that exists in the limited evidence of the potential clinical benefits from clinical trials that were not well-controlled," FDA drug reviewer John Marler wrote (as quoted by Bloomberg).

Plus, the FDA has approved other new options, including Sanofi's pill Aubagio and Biogen's wildly successful Tecfidera. So, MS patients do have a wider range of alternatives than ever before. The question now is whether the agency will be willing to add Lemtrada and its risks to the mix.

- read the Bloomberg story

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