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UPDATED: Sanofi gets mixed FDA blessing for MS drug Lemtrada

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After a scathing staff review, Sanofi ($SNY) walked away from an FDA panel with mixed messages on its long-delayed multiple sclerosis drug Lemtrada, as agency advisers said the injection wasn't too risky to approve but took issue with the drugmaker's trial design.

The FDA's Peripheral and Central Nervous System Drugs Advisory Committee unanimously agreed that Lemtrada's attendant safety concerns aren't enough to preclude approval, but the panel voted 11-6-1 that Sanofi's clinical trials were inadequate. As for indications, the committee voted 12-6 that Lemtrada provided substantial evidence of effectiveness in relapsing MS but split 14-2-2 against its benefits on disability. Furthermore, the panel voted 16-0 with two abstentions that Lemtrada should not be indicated as a first-line MS therapy.

That 12-6 effectiveness vote would seem to contradict the panel's views on Lemtrada's clinical data, and analysts aren't sure just what to make of the final tallies, Bloomberg reports. "Either (the trials) were adequate and proved something, or they were inadequate and proved nothing," Deutsche Bank's Mark Clark told the news service. Others figure the mixed signals can only be a bad sign for Sanofi: Leerink Swann's Seamus Fernandez said in a note he'd hardly be surprised if Lemtrada faced further delays, and Jefferies' Jeffrey Holford pegs the drug's chances of near-term approval at between 20% and 30%.

However murky those results, the panel's vote is something of a respite from the particularly harsh reception Lemtrada got from FDA staff reviewers, who chafed at its "serious and potentially fatal safety issues" and deemed it unapprovable unless it demonstrated "substantial clinical benefit." Agency staff also cast doubts on Sanofi's pivotal data, questioning the efficacy results of "trials that were not well-controlled."

In any case, Sanofi said it is pleased with the outcome, noting in a statement that the panel "clearly recognized the effectiveness of Lemtrada" in its unanimous safety vote. "The committee vote did acknowledge FDA's concerns around study design, but this appears not to have had an impact on the committee's votes of the effectiveness and safety profile of Lemtrada," Sanofi said.

Still, even if things work out for Lemtrada, analysts expect peak sales around $700 million a year, far below the drug's once-sky-high promise now that its many developmental delays have allowed rivals to creep in and grab MS market share. Oral therapies like Biogen Idec's ($BIIB) Tecfidera and Novartis' ($NVS) Gilenya lead the way among a new class of treatments, and most analysts figure Lemtrada, if approved, would be used only in advanced cases of MS.

Back in 2011, the once-a-year Lemtrada was a major bargaining chip in Genzyme's prolonged negotiations with Sanofi, helping the Boston biotech land a $20 billion price tag. After 25 years in development, the drug was already approved to treat B-cell chronic lymphocytic leukemia when Genzyme first got hold of it in 2004, but, seeing a more lucrative market in MS, the biotech took it off the cancer market and got to work on a new indication.

Lemtrada picked up European approval in September, at that point an encouraging sign that Sanofi would soon make U.S. landfall with its long-stalled MS drug.

- read the Bloomberg story

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