Sarepta to seek approval for muscular dystrophy drug

The biotech plans to file early with the FDA even as the regulatory body may have some reservations about the limited amount of data.

By TheStreet Staff Jul 24, 2013 12:13PM

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Important and welcome news out Wednesday morning from Sarepta Therapeutics (SRPT). Following a meeting with Food and Drug Administration officials, the company intends to submit an application seeking the approval of eteplirsen for the treatment of Duchenne muscular dystrophy, an inherited disorder that involves muscle weakness and which affects boys and worsens quickly.


Sarepta will submit the approval filing in the first half of 2014, the company said Wednesday.

But shares of the biotech plunged nearly 15% Wednesday morning to $39.55 after the news.


Here's how Sarepta described the decision to file in its press release this morning:

The decision to submit an NDA for eteplirsen in 2014 is based on productive interactions with the FDA in a meeting that occurred this week. That meeting was a follow-up to the FDA's review of two recently submitted summary documents that included data on dystrophin and clinical outcomes from the existing eteplirsen studies. The FDA stated in pre-meeting comments that the Agency is "open to considering an NDA based on these data for filing." The Agency, however, requested additional information related to the methodology and verification of dystrophin quantification. Sarepta believes the requests from the Agency can be addressed and incorporated into an NDA submission in the first half of 2014.

From this wording, it seems as if the FDA still has some reservations about the limited amount of eteplirsen data, but then, that's no surprise.


Expect the agency to convene an advisory panel to review the eteplirsen data. In fact, this FDA panel may get a chance to review two DMD drugs, since GlaxoSmithKline (GSK) and Prosensa (RNA) are likely to have their own drug, drisapersen, under FDA review at the same time.


Glaxo is expected to announce top-line results from a phase III study of drisapersen in the fall. If positive, an FDA approval filing will soon follow.


Sarepta's announcement Wednesday morning leaves open the possibility that eteplirsen could be granted full approval, and not just accelerated approval based on a surrogate endpoint. (In this case, the production of dystrophin, a protein responsible for proper muscle function.)


Here's what Sarepta said this morning:

The Agency would not commit to declaring dystrophin an acceptable surrogate endpoint under the CFR 314 Subpart H Accelerated Approval pathway prior to an NDA filing and commented that a decision by the Agency to file "the NDA would not indicate that we have accepted dystrophin expression as a biomarker reasonably likely to predict clinical benefit. A filing would only indicate that the question merits review, and that we deem the data to be reviewable.

As I've stated before, I don't expect the FDA to be comfortable enough with the limited dystrophin data to use it as the basis for eteplirsen's approval. But it could easily approve the drug instead based on the convincing and positive benefit observed in walking ability, measured by the six-minute walk test.


All in, Wednesday's latest development in the Sarepta story is as best as anyone could have hoped for. Sure, risks remain, but eteplirsen will be filed early and the drug has an excellent chance of being approved next year.


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