Sarepta Therapeutics has cleared a huge regulatory hurdle after US regulators agreed to a full review of its Duchenne muscular dystrophy drug eteplirsen, pushing its stock upwards in after-hours trading.

Crucially, eteplirsen has been assigned Priority Review status - designated to drugs that offer benefit over existing therapies, or provide a treatment where no adequate therapy exists - which means a decision on the file should be reached by February 26 next year.

The company is seeking permission to market the drug for patients with the rare degenerative neuromuscular disorder who are amenable to exon 51 skipping, which equates to around 13% of the total DMD population.

Eteplirsen addresses the underlying cause of DMD by enabling the production of a functional dystrophin protein, and clinical studies have demonstrated a broadly favourable safety and tolerability profile as well as efficacy for the drug, says Sarepta.

Investors will be particularly thrilled with the news as the drug’s path has not been a smooth one, with reports of tense relations between the firm and US Food and Drug Administration, a request by the regulator for more data last October, and resignation of chief executive Chris Garabedian earlier this year.

The FDA is also currently reviewing BioMarin’s experimental DMD drug drisapersen in the same setting, on which it is expected to make a decision by the end of the year.