Sarepta drug future hinges on FDA panel

Austin McNary (in the wheelchair) and his brother Max have take eteplirsen.

Sarepta Therapeutics Inc. and families of children suffering from Duchenne muscular dystrophy will have to wait longer than expected for word on whether the Cambridge company's experimental treatment for the disease can move forward.

The Food and Drug Administration postponed a Friday meeting of an outside advisory committee because of the snowstorm bearing down on Washington, D.C. A new date has not yet been set. The FDA frequently relies on the views of such outside panels, made up of medical experts, when deciding whether to approve a new drug.

Sarepta and a group of advocates for Duchenne therapies will use the delay to hone their presentations to the advisory panel, including the company's rebuttal of a briefing document issued by the FDA staff last week. The staffers on Jan. 15 questioned the methodology of Sarepta's research and the benefits of its drug candidate, eteplirsen, in a small clinical study, news that sent the company's stock down by more than half.

"We're optimistic that the data will show that this will be a safe and effective treatment for muscular dystrophy patients," said Dr. Laura Hagerty, scientific program officer for the Muscular Dystrophy Association, who had been scheduled to address the advisory committee Friday. "We know it's the FDA's job to do the review. We encourage them to keep our families in the forefront of their minds, and to get therapies in the hands of patients as soon as possible."

In recent years, scientists have improved their understanding of Duchenne muscular dystrophy, a muscle-wasting genetic disorder that affects roughly one in every 3,500 boys. There is still no approved treatment on the market, but more than two dozen experimental drugs are in clinical trials and more under preclinical development.

There had been high hopes for the first two drug candidates to come up for FDA review: treatments developed by Sarepta and BioMarin Pharmaceutical Inc. of Novato, Calif.. Both were granted expedited review by the regulatory agency. The two are chemically distinct but target the same genetic mutation, which affects about 13 percent of Duchenne patients.

Both are so-called exon-skipping drugs, meaning they act by splicing out sections of defective genetic code to help boost the creation of missing muscle protein in patients.

Hopes for a speedy approval were dashed last week, however. First the FDA rejected BioMarin's experimental drug, drisapersen, saying the company would have to conduct additional studies to prove its effectiveness. Then the agency's briefing document on Sarepta's eteplirsen pointed to a number of inconsistences in the data generated to show clinical benefits in a company trial involving a dozen patients.

Sarepta responded with its own detailed point-by-point rebuttal and called for flexibility in evaluating drugs for unmet needs of small patient populations.

"The need for innovative and flexible approaches to FDA review . . . increases as more rare-disease therapies are being developed where the contextual knowledge of patients and their diseases often evolves in parallel with clinical development," the company wrote in its rebuttal.

FDA officials don't discuss their staff review of drug candidates during an approval process, a spokeswoman said. Sarepta executives didn't respond to a request to discuss eteplirsen.

Some industry analysts say the FDA may still approve the Sarepta drug, despite the staff’s misgivings, if the advisory committee concludes it is safe and offers some benefits to patients. Many patients and their families, who had been disappointed by the ruling on BioMarin’s drug and the briefing document, are expected to testify before the advisory panel.

Sarepta's shares closed down 9.8 percent Thursday to $11.96.