PTC Therapeutics Inc's marketing application for its muscle disorder drug was not sufficient to merit a review, the U.S. Food and Drug Administration said, pushing the company's stock down about 40 percent before the bell.

PTC's drug, translarna, is being evaluated in patients with Duchenne muscular dystrophy (DMD), a progressive degenerative disorder that hampers muscle movement and affects one in 3,600 newborn boys.

Patients with DMD lose the ability to walk as early as age 10 and experience life-threatening lung and heart complications in their late teens and twenties.

There is no FDA-approved therapy for the condition.

BioMarin Pharmaceutical Inc and Sarepta Therapeutics Inc are also developing drugs for DMD, but their experimental treatments target a different subset of patients.

The FDA rejected Biomarin's drug last month.

PTC Therapeutics' translarna targets DMD caused by nonsense mutations, which account for about 13 percent of all cases. This translates into roughly 7,000 boys globally, including about 2,000 in the United States and Canada.

In October, the company announced that translarna had failed to meet the main goal in a keenly watched late-stage study, but in a sub-group of patients with less advanced DMD, the effect of the drug was deemed clinically meaningful.

At the time the company had said data from all trials on the drug merited an U.S. marketing application.

The treatment is already being sold in the European Union.

(Reporting by Rosmi Shaji in Bengaluru; Editing by Savio D'Souza and Don Sebastian)