FDA approves first drug for Duchenne muscular dystrophy

September 19, 2016

Even though an FDA panel recommended against approving a new drug to treat Duchenne muscular dystrophy in April, the agency granted accelerated approval to eteplirsen injection (Exondys 51, Sarepta Therapeutics) in mid-September.

Patients with Duchenne muscular dystrophy will have a clearer path to treatment with the accelerated approval of eteplirsen injection (Exondys 51, Sarepta Therapeutics).

“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,” said Janet Woodcock, director of FDA’s Center for Drug Evaluation and Research.

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FDA granted the approval after asking Sarepta for data from patient biopsies obtained in an ongoing, incomplete study of the drug.

However, a clinical benefit of Exondys 51, including improved motor function, has not been established. “In making this decision, the FDA considered the potential risks associated with the drug, the life-threatening and debilitating nature of the disease for these children and the lack of available therapy,” FDA said.

Exondys 51 is specifically indicated for patients who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping, which affects about 13% of DMD patients.

“Patients with a particular type of Duchenne muscular dystrophy will now have access to an approved treatment for this rare and devastating disease,” Woodcock said. “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.”

DMD, the most common type of muscular dystrophy, is a rare genetic disorder characterized by progressive muscle deterioration and weakness. DMD is caused by an absence of dystrophin, a protein that helps keep muscle cells intact. The first symptoms are usually seen between three and five years of age, and worsen over time.

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

The accelerated approval of Exondys 51 is based on the surrogate endpoint of dystrophin increase in skeletal muscle observed in some Exondys 51-treated patients. “FDA has concluded that the data submitted by the applicant 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,” the agency said.

Under the accelerated approval provisions, FDA is requiring Sarepta Therapeutics to conduct a clinical trial to confirm the drug’s clinical benefit. The required study is designed to assess whether Exondys 51 improves motor function of DMD patients with a confirmed mutation of the dystrophin gene amenable to exon 51 skipping. If the trial fails to verify clinical benefit, the FDA may initiate proceedings to withdraw approval of the drug.

The most common side effects reported by participants taking Exondys 51 in the clinical trials were balance disorder and vomiting.

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