The FDA has approved the Exondys 51 (eteplirsen) injection for patients with Duchenne muscular dystrophy (DMD).


Exondys 51 (Sarepta Therapeutics, Cambridge, Massachusetts) was granted accelerated approval and is indicated for patients with a confirmed mutation of the dystrophin gene amenable to exon 51 skipping, which affects about 13% of those with the disorder.

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DMD, the most common type of muscular dystrophy, is characterized by progressive muscle deterioration and weakness and is caused by an absence of dystrophin. Initial symptoms are usually observed between ages 3 and 5 and worsen over time. The disease is common in individuals without a known family history of the condition and primarily affects boys. DMD occurs in about 1 of 3,600 male infants worldwide.

Patients with DMD progressively lose their ability to perform activities independently and frequently require use of a wheelchair by their early teens. As the disease progresses, life-threatening heart and respiratory conditions can occur. Patients typically die in their 20s or 30s, although disease severity and life expectancy can vary.

The FDA concluded that data from the clinical trials “demonstrated an increase in dystrophin production that is reasonably likely to predict clinical benefit in some patients with DMD who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping.”

A clinical benefit of Exondys 51, including improved motor function, has thus far not been established. The FDA considered the potential risks associated with the drug, the life-threatening and debilitating nature of the disease in children, and the current lack of available therapy. The most commonly reported side effects in the clinical trials were balance disorder and vomiting.

The FDA is requiring Sarepta Therapeutics to conduct a clinical trial to confirm the drug’s clinical benefit. If the trial fails, the FDA could initiate proceedings to withdraw approval of the drug.


  1. The US Food and Drug Administration. FDA grants accelerated approval to first drug for Duchenne muscular dystrophy. Accessed September 22, 2016.