FDA changes course on Sarepta’s once-rejected muscular dystrophy drug

The Food and Drug Administration reversed its decision on a treatment for Duchenne muscular dystrophy from Sarepta Therapeutics (SRPT), approving a previously rejected drug without explaining what the problem was in the first place.

The therapy, called Vyondys 53, is approved to treat the roughly 8% of Duchenne patients whose disease results from a specific DNA error. In a clinical trial, Sarepta’s drug produced a small increase in an important muscle protein called dystrophin that is normally missing in children with Duchenne. The company has yet to demonstrate that Vyondys 53 can improve muscle function or slow the progression of the disease.

In August, Sarepta said the FDA rejected Vyondys 53 over the risk of infections related to infusion ports and kidney toxicity seen in animal experiments. The FDA’s approval announcement, issued Thursday night, made no mention of the prior rejection. In a separate statement, Sarepta said that it filed an appeal with the FDA and eventually resolved the agency’s outstanding concerns.

Sarepta said it will price Vyondys 53 “at parity” with its previous Duchenne treatment, Exondys 51, which is dosed based upon patients’ weight and can cost upward of $1 million per year.

Exondys 51, was approved in 2016, a controversial decision that divided FDA staff and sparked widespread concerns that there wasn’t enough evidence to prove the drug’s benefit. Sarepta promised to run a trial confirming Exondys 51’s effects, but the company has fallen years behind.

Vyondys 53 is meant to treat patients whose Duchenne is caused by an error in the DNA sequence known as exon 53. Exondys 51 is used to treat the 13% of patients with disease caused by an error in the DNA sequence known as exon 51. There are about 5,000 Duchenne patients in the U.S.

DECEMBER 12, 2019

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