Sarepta Stock Down as FDA Seeks More Data from Rival Duchenne Drug

Xconomy Boston — 

Sarepta Therapeutics still awaits an FDA decision on its Duchenne muscular dystrophy drug. But the agency’s conclusion that another company working on a treatment for the muscle-wasting disease needs to submit more information is leading some observers to believe that approval chances for Cambridge, MA-based Sarepta’s drug are slim.

The FDA has informed Santhera Pharmaceuticals (SIX: SANN) that the Phase 3 trials it had filed for approval on its Duchenne drug are not enough, the Switzerland-based company said today. In addition to filing those results, Santhera said the agency asked the company to include in its application the results from a second late-stage study.

The second late-stage trial was already in the works, but Santhera planned that study to confirm the results of the earlier trial. Because data from the second trial aren’t expected until the second half of 2019, the FDA’s instructions effectively delay any decision on Santhera’s drug for at least three years.

Sarepta’s (NASDAQ: SRPT) stock price slid just 4.3 percent on the news, but some analysts have a dimmer outlook on the prospects of the Cambridge biotech’s drug, eteplirsen. Simos Simeonidis, an analyst at RBC Capital Markets, wrote in a research note that the news about Santhera’s drug makes a positive decision on Sarepta’s drug “even more unlikely.” He noted that Santhera studied its drug in a randomized, placebo-controlled trial that included 64 patients, compared to just 12 in Sarepta’s Phase 2b trial.

Duchenne affects an estimated 300,000 people worldwide and typically leads to the loss of the ability to walk in a patient’s teen years. Duchenne patients eventually die from complications, such as respiratory or heart failure. Eteplirsen isn’t a cure for Duchenne. Sarepta developed the drug to help patients create dystrophin—the protein they lack, which leads to the disease. Sarepta’s endpoint for its study was improvement in patients’ ability to walk under the treatment.

Based on its study results, Sarepta believed it could file for accelerated approval with a smaller sample of patients—despite FDA instructions that the company conduct a placebo-controlled trial. The small sample size of Sarepta’s study led a panel advising the FDA to vote 7-6 against recommending the drug’s approval on the basis that the company had not provided “substantial evidence from adequate and well-controlled studies.”

The Sarepta drug was due for an FDA decision by May 26, but as that deadline approached, the agency said it needed more time. Investors viewed that development as positive: Sarepta’s stock price rose, and the company used that increase as an opportunity to prepare a stock sale expected to raise more than $37 million.

But Simeonidis says the FDA’s earlier decisions on other Duchenne drugs suggest that the agency won’t be lenient or forgiving on treatments with weak data sets. He says FDA approval of the Sarepta drug would run counter to several indicators: rejections earlier this year of Duchenne drugs from BioMarin Pharmaceutical (NASDAQ: BMRN) and PTC Therapeutics (NASDAQ: PTCT); the FDA advisory panel’s vote against recommending approval; and the agency’s latest decision instructing Santhera to include the additional Phase 3 study results in the company’s application for its Duchenne drug.

Photo courtesy of Flickr user Joe Flintham via a Creative Commons license.