FDA Approves Drug that Treats Duchenne Muscular Dystrophy

The Food and Drug Administration (FDA) has approved a drug that is a treatment for a specific type of Duchenne muscular dystrophy (DMD). The drug has been given accelerated approval in order to make it more quickly available to patients.

Muscular dystrophy refers to a group of more than 30 genetic diseases that cause progressive weakness and degeneration of the skeletal muscles that are used during voluntary movement. All forms of muscular dystrophy progressively grow worse as muscles degenerate and weaken. Many people who have muscular dystrophy eventually lose the ability to walk.

All forms of muscular dystrophy are genetically inherited and involve a mutation in one of the thousands of genes that are critical to muscle integrity. Many cases of muscular dystrophy occur from spontaneous mutations that are not found in the genes of either parent. Those mutated genes can be passed down to the offspring of a person who has muscular dystrophy.

Duchenne muscular dystrophy is caused by an absence of dystrophin, a protein that helps keep muscle cells intact. Symptoms onset is in early childhood, usually between the ages of 3 and 5. The disease primarily affects boys, but there are also rare cases where the disease has affected girls.

On September 19, 2016, the FDA approved Exondys 51 (eteplirsen) injection. It is the first drug to be approved to treat patients with Duchenne muscular dystrophy. The drug is specially indicated for patients who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping (which now affects about 13 percent of the population with DMD).

In other words, the drug is treatment for people who have a specific kind of Duchenne muscular dystrophy. This subset includes about 13% of all DMD patients, or about 1,300 to 1,900 patients in the United States.

Exondys 51 is made by a company called Sarepta Therapeutics, which is based in Cambridge, Massachusetts. The FDA is requiring Sarepta to conduct a clinical trial to confirm the drug’s clinical benefit. If the trial fails to verify clinical benefit, the FDA may initiate proceedings to withdraw approval of the drug.

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