Sarepta Therapeutics Inc said U.S. health regulators have asked for additional information on its experimental drug to treat a rare degenerative disease in boys.
Sarepta shares fell 12 percent in extended trading after closing at $39.24 on the Nasdaq on Monday.
The drugmaker said the U.S. Food and Drug Administration sought more information about the drug, eteplirsen, to consider early approval.
"We do not anticipate that the request for information by the FDA nor the delay of a few months on the definitive decision on the acceptability of an accelerated approval submission will have an impact on our ongoing activities," Chief Executive Chris Garabedian said on a conference call.
The company said in October that the drug significantly improved walking ability in a mid-stage trial for patients with Duchenne Muscular Dystrophy (DMD).
DMD is caused by mutation of the gene that helps produce dystrophin, a protein that plays a key role in muscle fiber function. The drug enables the production of dystrophin.
Sarepta said it was confident that the consistency of the dystrophin levels will be enough to determine that the drug needs a quicker approval.
The company said the FDA indicated that the safety data from the first few months of a yet-to-be-conducted late-stage study could be used to support approval of the drug.
The company said it intends to continue dosing patients in a late-stage study in the first quarter of 2014.
"The fact that the FDA is just asking for some further clarification which will all occur over the near term, within one quarter or so seems to be a positive," said William Blair & Company analyst Tim Lugo.
Nine of the 10 brokerages tracked by Thomson Reuters StarMine recommend buying Sarepta shares. Their mean price target is $42; five of the analysts rate the company a "strong buy.
(Reporting By Adithya Venkatesan in Bangalore; Editing by Maju Samuel and Steve Orlofsky)