Sarepta's shares drop as FDA advises against early filing for Duchenne muscular dystrophy drug eteplirsen

Shares in Sarepta Therapeutics fell as much as 57 percent Tuesday after the company said the FDA advised against seeking accelerated approval of its Duchenne muscular dystrophy (DMD) drug eteplirsen. The agency said that new clinical data and findings on the natural history of the disease raise "considerable doubt" about results from a Phase IIb study of eteplirsen.

"We are very disappointed with the FDA's decision to reconsider their openness to a potential NDA filing based on our current data and the resultant impact this change may have on our efforts to achieve an earlier approval of eteplirsen," remarked CEO Chris Garabedian. The company reported positive mid-stage results last year for the experimental exon-skipping compound and said in July that it planned to seek FDA approval in the first half of 2014.

However, Sarepta indicated Tuesday that at a meeting with the FDA last week, the regulator highlighted recent negative results from a Phase III study of GlaxoSmithKline and Prosensa's similar drug drisapersen in DMD. The agency said "the disconnect between increased expression of dystrophin and clinical efficacy for drisapersen...raises considerable doubt about the biomarker, and consequentially, its ability to reasonably likely predict clinical benefit." In the meeting, the FDA also questioned the robustness of the six-minute walk test data for eteplirsen.

Sarepta added that a request from the regulator to discuss, amongst other things, different clinical endpoints, along with questions about dystrophin as a biomarker and the need for a placebo-controlled study, will delay the initiation of dosing in the eteplirsen confirmatory study until at least the second quarter of 2014. "We do not fully understand, nor do we agree with the FDA’s new stance or with its comments," Garabedian said, noting "we believe this setback does not reduce the chance of ultimate approval of the drug." Garabedian indicated that Sarepta "will pursue a more traditional path to approval while we concurrently try to persuade the FDA to reconsider the potential of an early filing strategy."

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