In the latest twist surrounding Sarepta Therapeutics (SRPT), the Food and Drug Administration has delayed a decision on whether to approve a drug for Duchenne muscular dystrophy until May 26. At the same time, the FDA accepted an unusual extra submission from the drug maker as a “major amendment” to documents that the agency and its outside experts will review.

The drug, known as eteplirsen, is designed to combat DMD, a rare disease that causes muscles in boys to stop working and eventually results in death because they can no longer breathe. Clinical data was supposed to have been reviewed last month at an FDA expert panel meeting in advance of a Feb. 26 deadline for approving the drug. But that was postponed due to a snow storm and has not been rescheduled.

Meanwhile, Sarepta took the uncommon step last month of submitting another nine-page document in order to rebut an FDA analysis of its drug. Typically, the agency will post on its web site a review of a drug by its own medical staffers prior to an expert panel meeting. The agency also posts documents from the drug company, but in this case, also accepted the after-the-fact Sarepta filing.

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Sarepta made this move because the FDA analysis indicated the clinical trial data failed to properly compare different patient groups and demonstrate how DMD boys responded to its drug. So in its amendment, Sarepta included still more data showing how 12 boys performed after taking eteplirsen for four years, as well as an analysis of boys not on the drug. A key measure is a six-minute walking test.

For months, though, FDA approval has been a matter of intense debate.

Although Sarepta argues its data demonstrates the boys improved, there was skepticism around the 12-patient sample size, which is particularly small. But the drug maker maintains the FDA should confer so-called accelerated approval. In such instances, a drug for treating serious conditions and that fills an unmet medical need is approved based on a surrogate endpoint.

With the FDA’s willingness to accept the added information from Sarepta, some hope the agency is signaling an openness to more thoroughly consider a wide range of data.

“It is encouraging that the FDA has accepted additional information from Sarepta,” said Debra Miller, who heads CureDuchenne, an advocacy group that raises money to invest in drug makers that are developing products to combat DMD. The organization also runs a venture philanthropy arm with small holdings in BioMarin Pharmaceutical (BMRN), whose DMD drug was rejected recently by the FDA.

“The Duchenne community definitely wants all relevant data to be considered.  We most likely will have to wait for the rescheduled (expert panel) meeting to learn how this new data will influence the opinions of the FDA and (panel) members, but we are hopeful that the patient-and-parent voice is considered as they reevaluate the submission,” she continued.

Parental hopes are riding on the Sarepta drug even more than before. Having rejected the BioMarin drug last month, another agency rejection would leave children without any treatment. Both drugs were designed using the same approach to treating boys with DMD and, therefore, would target the same patient population. There is currently no other medication for the disease.

One analyst suggested the FDA’s latest action may bode well, but only if regulatory standards can be met.

“FDA’s acceptance of the amendment is just another sign that the agency will be very open to evaluating all information about this program. I really think they want to approve any drug for DMD that meets their standards for approval and want to allow every opportunity for the company to make the case that it does,” RW Baird analyst Brian Skorney wrote us.

“If Sarepta wants to make a point-by-point rebuttal to the FDA reviewer’s assertions, the agency wants to give the company that chance. But it still always comes down to whether or not Sarepta can make that case. I don’t think the acceptance of (the additional information from the company) indicates whether or not Sarepta has been successful at making the case.”

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