NOTE: Some edits were made (10/27/12) after eagle eyed commenter Richard Trent pointed out some flaws in my summary which I have tried to correct below.
Sarepta Pharamaceuticals recently released data about a very small trial of eteplirsen in boys with Duchenne muscular dystrophy. This medication operates by inactivating an “off switch” in the gene for dystrophin. Dystrophin is the muscle protein affected in Duchenne and Becker muscular dystrophy. Defects in the protein result in muscle breakdown, worsening muscle strength, breathing and heart problems, and eventually death. The only current treatment is oral corticosteroid therapy, which has significant side effects, including weight gain, mood problems, and decreased growth.
The trial in 12 boys with the disease showed promise in increasing a measure called the six-minute walk test. Boys on the higher dose of the drug had a 5% improvement in the distance that they could walk compared to boy not on the medication. Boys who were in the placebo arm had an approximately 17% decline. (They also received the study drug halfway through the trial, without apparent benefit).
This is great news, but I think that we have to take it with a bit of caution, for several reasons.
- Twelve patients is a very small trial, even for a relatively rare disorder like Duchenne.
- The benefit seen was relatively modest.
- Patients in the lower dose group did not see a benefit although the levels of dystrophin in the muscles of these boys increased substantially. These boys were excluded from the analysis but the FDA may not agree with this. Moreover, this lack of a dose-response is concerning to me as it raises the possibility that these effects may disappear in a larger trial.
The New York Times has a good article summarizing these results. Here is a reaction from the Jett Foundation which supports our clinic. You can find my recommendations for the care of boys with muscular dystrophy under ten. Here is a remembrance of a patient who died from this terrible disease.
