Sarepta apply for approval of Duchenne MD drug

Sarepta Therapeutics has issued a press release which gives an update on their plans for the development of exon skipping drug “eteplirsen”. Eteplirsen is a ‘molecular patch’ designed skip a portion of the dystrophin gene called ‘exon 51’. It has the potential to treat around 13 percent of boys with Duchenne muscular dystrophy – those with a mutation in the vicinity of exon 51.

In January Sarepta released encouraging results from 120 weeks of eteplirsen treatment in their Phase 2b clinical trial. The results indicate that the walking ability of the 10 boys participating in the study is still being stabilised. However, this is a very small study and the results will need to be confirmed in a larger phase 3 study which is currently being planned.

There has been a lot of discussion over whether eteplirsen might be eligible for accelerated, approval by the Food and Drug Administration (FDA) in the USA. An accelerated approval is usually granted to drugs that treat a serious disease with no treatment options, based on initial trial data. This would mean that the drug is made available prior to the completion of further clinical trials and could pave the way for a similar arrangement in other countries. Full approval would depend on the outcome of further trials and if the results of further trials are unconvincing the drug would be withdrawn from the market.

In November 2013 the FDA said that it would not consider an early approval for eteplirsen largely because the drug has only been tested on a small number of boys, however this new press release announces that the FDA has agreed to consider an application for accelerated approval, so Sarepta will file that application this year. This does not guarantee approval but it is encouraging that the FDA is agreeing to look at the application.

In the same press release it was explained that the FDA has also provided guidance to Sarepta on the design of further exon skipping clinical trials. This includes a trial to confirm the effectiveness of eteplirsen and studies to test the drug in boys that are too young or too old to participate in this trial. They will also start a trial of other exon skipping drugs which are designed for boys with mutations in other parts of the dystrophin gene. Sarepta plans to start all of these trials before the end of this year.

Edward Kaye, M.D., senior vice president and chief medical officer of Sarepta Therapeutics commented on the news:

“We are excited to have guidance from the FDA that allows us to move quickly into additional clinical trials with eteplirsen to confirm our current understanding of eteplirsen’s safety profile, its effect on dystrophin production, and its impact on clinical outcomes in DMD patients. We are particularly pleased that the FDA shares our interest in accelerating the clinical development of our follow-on exon-skipping drugs and we expect to initiate enrolment in this trial later this year.”

Further information

• Sarepta Therapeutics have a webpage called Skip Ahead with lots of useful information about exon skipping and how it works
• The MDA Duchenne muscular dystrophy factsheet contains more information about the condition including a research summary
Clinical trials – your questions answered
• You can get regular updates by becoming a friend of the MDA Facebook page

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Uploaded 3 July 2018