Sarepta Therapeutics Inc. said the U.S. Food & Drug Administration wouldn't issue a decision on the company's muscular dystrophy drug by Thursday's deadline, raising expectations that the agency may approve a treatment that an advisory panel recommended to reject.

Shares of Sarepta surged 22% to $22.52 in premarket trading. The stock fell 44% the day after the panel's decision last month and hit a low of $8 in the days that followed.

Sarepta said Wednesday that the FDA notified it that the agency would work past the Thursday deadline and aim to complete its work "in as timely a manner as possible." The FDA isn't required to follow the advice of its advisory panels but generally does so.

A representative for the FDA confirmed that the agency had contacted Sarepta about the extended review, but the representative didn't comment on a new goal date or the timing of the decision. A Sarepta representative said the FDA didn't provide the company with any details of a timeline for a decision.

The FDA is reviewing Sarepta's new drug application for eteplirsen, a treatment for patients with the crippling genetic condition Duchenne muscular dystrophy. The disease, which has no effective treatments, destroys muscles and frequently kills patients by their 30s. It affects roughly one in every 3,500 boys world-wide.

The FDA's decision highlights the tension between the agency's requirement that a drug be proven to work and the need to find anything that might help people with a lethal disease that has no cure. In such cases, patients and their families are often willing to take big risks.

At the FDA panel hearing in April for eteplirsen, parents gave emotional testimonies about how they believed their children have benefited from the drug and that studies simply haven't proven it.

Despite the testimonies, the panel voted 7-3, with three abstentions, that the drug's data—which was based on a single, small study of 12 patients—wasn't enough for approval.

In November, the same panel concluded that clinical data were lacking on another muscular dystrophy drug from BioMarin Pharmaceutical Inc.

Thomas M. Burton contributed to this article.

Write to Lisa Beilfuss at lisa.beilfuss@wsj.com

(END) Dow Jones Newswires

May 25, 2016 09:25 ET (13:25 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.
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