FDA Approves First Drug for Duchenne Muscular Dystrophy

The FDA today approved Exondys 51 (eteplirsen) injection for the treatment of patients with Duchenne muscular dystrophy, making it the first drug to receive approval to treat the condition.

Exondys 51 is specifically indicated for patients who have a mutation of the dystrophin gene amenable to exon 51 skipping, which affects 13% of patients with Duchenne muscular dystrophy, according to the FDA.

The disease is caused by a lack of dystrophin, and is characterized by muscle deterioration and weakness. Symptom onset can happen as young a 3-years-old, and worsens with age. It typically results in dependence on a wheelchair in the teens.

As the disease and symptoms progress, many patients face heart and respiratory conditions that can significantly shorten lifespan. Exondys 51 received accelerated approval because the drug could potentially treat a serious disease that currently does not have any effective treatments.

Approval was based on the surrogate endpoint of increased dystrophin in skeletal muscle in patients who received the drug, according to the FDA. The FDA said potential risks were considered, as well as the lack of treatment options for patient with this debilitating disease.

Findings from the study suggest that the drug can increase dystrophin production, and could potentially provide benefits for patients. However, improved motor function as a result of the drug has not been confirmed.

Sarepta Therapeutics will conduct clinical trials to confirm the benefit of the drug as part of accelerated approval requirements. This study will determine Exondys 51’s ability to improve motor function in patients with confirmed mutation of the dystrophin gene amenable to exon 51 skipping.

If the drug does not confirm clinical benefit, the FDA may withdraw approval. Common side effects from the drug include balance disorder and vomiting.

Along with accelerated approval, the drug was also granted fast track designation, priority review status, and orphan drug designation from the FDA.

Additionally, the drug manufacturer received a rare pediatric disease priority review voucher, which is a program that encourages the development of new drugs to treat and prevent rare pediatric diseases. The FDA said they have only given out 7 of these vouchers.

“Patients with a particular type of Duchenne muscular dystrophy will now have access to an approved treatment for this rare and devastating disease,” said Janet Woodcock, MD, director of the FDA’s Center for Drug Evaluation and Research. “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. 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.”