First Treatment Approved for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe and disabling condition that typically affects boys. The disorder of progressive muscular weakness develops in young children and worsens quickly. Affected individuals lose the ability to run, walk, move their arms and hands, and eventually breathe. Patients typically die in their 20s or 30s.

DMD is caused by a mutation or error in the gene for dystrophin, which is an essential protein involved in muscle fiber function. It affects about 1 in every 3600 male babies born.

However, there is now an FDA-approved drug for this disease.

“In rare diseases, new drug development is especially challenging due to the small numbers of people affected by each disease and the lack of medical understanding of many disorders,” Janet Woodcock, MD, director of the FDA’s Center for Drug Evaluation and Research, said in a statement. “Accelerated approval makes this drug available to patients based on initial data, but we eagerly await learning more about the efficacy of this drug through a confirmatory clinical trial that the company must conduct after approval.”

But it’s not without controversy. The drug Exondys 51, developed by Sarepta Therapeutics, was tested in 12 boys in a trial. Ten of those boys were able to walk distances beyond what untreated patients would. They also tolerated the treatment for years without serious side effects. Common side effects were balance disorder and vomiting.

But when the FDA chose to approve the drug, it went against the recommendation of an advisory panel that voted against approval because there is a lack of hard evidence that Exondys 51 works.

Exondys 51 works in patients with a specific mutation in the DMD gene that is amenable to exon 51 skipping, according to Sarepta. An estimated 13% of people with DMD have mutations that can be addressed by Exondys 51.

As a condition of the FDA’s approval, Sarepta must conduct a clinical trial to confirm the drug’s clinical benefit.

The Muscular Dystrophy Association (MDA) applauded the FDA’s approval.

“For our families, therapy options can’t come soon enough,” Valerie A. Cwik, MD, MDA executive vice president and chief medical and scientific officer, said in a statement. “MDA is eager for this treatment to get into the hands of those whom it can help, forever grateful to our partners, supporters, and, most importantly, our families, who all helped turn hope into a treatment that can change the course of Duchenne.

Donations for this debilitating disease can be made to EndDuchenne.org.

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