‘It’s a vote for hope’: first gene therapy for muscular dystrophy nears approval, but will it work?

The road to gene therapies for genetic disorders has been long — and expensive — but the field could soon get some good news. On 22 June, the US Food and Drug Administration will decide whether to grant a fast-track approval to the first gene therapy for Duchenne muscular dystrophy (DMD), a genetic disorder that affects around 1 in 3,500 boys. Children with DMD can’t make a protein called dystrophin, resulting in progressive muscle degeneration and death in their twenties due to heart or respiratory failure.

The therapy, known as SRP-9001, is made by Sarepta Therapeutics based in Cambridge, Massachusetts. It would be the 13th gene therapy that the FDA has approved since 2017, and the first to target a prevalent genetic disease in children. The accelerated approval would allow the drug to reach the market before large clinical trials have been completed, on the basis of evidence that the therapy allows boys to make an engineered form of dystrophin.

The decision date was delayed late in May after FDA officials and advisers raised concerns about the strength of Sarepta’s...