Sarepta stock dives as FDA again asks for more data on muscular dystrophy drug eteplirsen

Shares of Sarepta Therapeutics plunged Monday after the company said regulators want more data about its muscular dystrophy treatment eteplirsen before they will consider approving the drug.

The Food and Drug Administration asked for three years of data on patients who participated in one study of the drug, an independent review of an important result, and more information about the drug's safety. Sarepta says the FDA wants to have further discussions and could impose more requirements later on. The company plans to file for approval of the drug again by mid-2015.

Sarepta Therapeutics Inc. shares lost $7.32, or 31.1 percent, to $16.24 in morning trading.

Eteplirsen is intended to treat Duchenne muscular dystrophy, a fatal genetic disease that causes increasing muscle weakness. It affects one of every 3,500 boys worldwide and the company says patients usually die before the age of 30. The drug is designed to address the cause of the disease by allowing the body to produce a functional dystrophin protein, which plays a key role in muscle fiber function. It is Sarepta's most advanced experimental drug and the company has asked the FDA for expedited approval.

Sarepta said Monday that the FDA wants to see the results from an independent review of patients' dystrophin levels as well as 168 weeks of clinical data from that pivotal trial.

In early 2013 the Cambridge, Massachusetts, company said the FDA asked for more information about the drug. At the time, analyst Kimberly Lee said the company's studies may be too small, as a key clinical trial involved only 12 patients. Lee added that the FDA did not seem convinced that increasing patients' dystrophin levels would lead to a clinical benefit.