Second muscular dystrophy drug approved by US FDA 

Sarepta Therapeutics has announced United States Food and Drug Administration (FDA) accelerated approval for a second Duchenne muscular dystrophy treatment.

Developed by Professors Sue Fletcher and Steve Wilton at the Perron Institute and University of Western Australia, Vyondys 53 is the second exon skipping therapy for Duchenne muscular dystrophy, the most common childhood form of muscle wasting.

Vyondys 53 (golodirsen) is an antisense oligomer treatment for patients with a confirmed gene mutation amenable to exon 53 skipping. Vyondys 53 received accelerated approval based on data showing increased dystrophin in patient muscle after treatment. Dystrophin is a protein that is essential in maintaining muscle fibre strength and stability. In the absence of dystrophin, muscle is susceptible to damage during normal activity, leading to loss of muscle and ultimately the ability to walk and breath.

Vyondys 53 can treat up to 8 per cent of Duchenne patients.

On receiving the positive news, Professor Fletcher said: “This means so much to the patients and those who have believed in us and supported this work for so many years.”

The first DMD drug granted accelerated approval, Exondys 51 (eteplirsen), is relevant to patients who require exon 51 skipping, and received accelerated approval by the US FDA in 2016. This breakthrough therapy was also pioneered by Professors Fletcher and Wilton at the Perron Institute and UWA, prior to their move to Murdoch University in 2013.

Billy Ellsworth, one of the participants in the initial US clinical trial, is still able to walk at almost 19 years of age after nine years of treatment with Exondys.

A third compound, Casimersen, also designed by the Wilton/Fletcher lab to treat an additional group of patients is in advanced trials.