GSK and Prosensa announce primary endpoint not met in Phase III study of drisapersen

UPDATE AS OF 10/4/13: We received the following Q&A from GSK today, addressing many of the community's questions. Click here.

Today we learned that GSK’s phase III study of the exon 51 skipping drug drisapersen failed to show a statistically significant improvement in the six-minute walk test compared to placebo (Read the official press release and GSK's statement, below). We know that all of those families around the world who participated in this study are particularly devastated—it’s not at all trivial to participate in a trial like this. I think it is also pretty fair to say that the GSK staff involved in this study are devastated as well. 


GSK will address the Duchenne community via Webinar on October 15th in collaboration with PPMD, CureDuchenne, Action Duchenne, and UPPMD. Details will be forthcoming and you will have the opportunity to submit your questions.


This is not the first time this community has experienced a heart-wrenching set back and, unfortunately, it probably won’t be the last. Currently 42% of all phase III trials fail, largely due to lack of efficacy. Given the resources and time required to conduct a phase III study, this rate of failure is not sustainable in rare disease. PPMD is committed to improving the quality of drug candidates for Duchenne to the extent that it is possible to do so. Ultimately, though, a phase III trial is an experiment and we won’t know the answer until we do the experiment. 


For all of those families participating in any type of clinical research you should know that you are heroes in this fight against Duchenne. We lost a battle, not the war. 

GSK Statement

Dear Patient Group Representative,

I hope this message finds you well.

I am writing to share some disappointing news about our Phase III study of drisapersen in patients with Duchenne Muscular Dystrophy – we recently completed analysis of the data and did not see a statistically significant difference in 6 Minute Walk Distance between patients who received drisapersen and those who received placebo. The study also included key assessments of motor function and unfortunately there was no treatment difference in these endpoints: 10-meter walk/run test, 4-stair climb and North Star Ambulatory Assessment. The safety profile in this study was generally consistent with what was seen in earlier trials and the most commonly reported adverse events included injection site reactions and proteinuria. No patients had thrombocytopenia in this study. We will be closely working with the patient advocacy community to arrange a webinar of the results to provide an opportunity for boys and their families to ask questions.

We believe there is value in evaluating these results in the context of the overall development programme and additional analyses are undergoing and planned to fully understand the results of this Ph III study. We will also be consulting with experts in the field before deciding on next steps for drisapersen. Until this work is complete, anticipated by year end, we are holding all dosing with drisapersen within ongoing studies. Although treatment dosing will be held, safety monitoring and other relevant assessments will continue. We have notified study investigators and are recommending that patients currently participating in ongoing drisapersen clinical studies contact their local clinical study team. You can find information regarding the ongoing clinical studies involving drisapersen, by visiting

GSK and Prosensa issued a press release to announce the results and I have attached the release for reference. We have submitted the study results for presentation at a forthcoming scientific meeting and will also be submitting a paper for publication in a scientific peer-review journal.

I appreciate that these results are not the outcome that any of us had hoped for and I would like to sincerely thank all those who participated in the study for their commitment. I have provided my contact information below, should you have any questions.

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Comment by Sharon Hesterlee on September 23, 2013 at 8:25pm

Ok, send us your questions for GSK...they are going to try to answer as many as possible right away (after we discussed the fact that October 15th was too long a wait).  Please send your questions to my regular email account at and send them ASAP.

Comment by Tapio on September 23, 2013 at 7:06pm

This has been very disappointing news to say the least.

Jack was in the study as well. He received 24 doses over 24 weeks (we assumed he was getting the real deal based on his injection site reactions), not long enough to see major changes, but we were pretty convinced positive things were happening. There seemed to be a plateauing of muscle weakening in general, and we were fairly convinced improvements were happening as well. I'll never forget the day he excitedly came running into our kitchen to tell us something and started hopping up and down. Hopping! We couldn't remember the last time seeing him do that.

It's been almost a year since his last dose and we've quietly been waiting since then for his extension trial to start up.

Instead we're hit with this news on Friday - Jack's 10th birthday, of all days.

What a kick to the gut.

Comment by Andrea Cleary on September 23, 2013 at 7:10am

I agree, Jason. The fights not over yet. And check out Tulika's post about GSK filing for trial modification with the EMA. No one seems sure exactly what it means right now, but something is brewing...

Comment by Jason Darienzo on September 22, 2013 at 9:28pm

I think the inclusion criteria GSK/Prosensa used were not narrow enought for the 6 minute walk test to be effective. When you look at Sarepta they picked patients that were older and closer to loosing ambulation.

I think there is a way foward for GSK/Prosensa in spite of this setback.

Comment by Timothy Rutt on September 21, 2013 at 11:56am

Our son Jacob Rutt has done very well on the drug -- at our end-of-trial evaluation, he scored significantly above his cohort group on the 6 minute walk test.  While he still can't run or bike, he's improved his walking and endurance.  We got a call from Dr. Craig McDonald @ UC-Davis Medical Center, who has been handling our trial and the continuation study he is currently in, and it was apparent that he was devastated as well.  

Comment by mehrzad haidari on September 21, 2013 at 1:59am

The main question for me is : how they received the Breakthrough  Therapy from FDA?

based on what results? in vitro/vivo or in DMD patients?

Comment by Andrea Cleary on September 20, 2013 at 8:10pm

I agree with you Tonya, the way they did this stinks. I read somewhere that they will update us on Monday. Makes for a great weekend doesn't it?

Comment by mehrzad haidari on September 20, 2013 at 2:20pm

Really  the most heart breaking news nowadays!

Comment by BrodysMom on September 20, 2013 at 2:07pm

I am sick about this news! Although Brody had a few of the side effects, he got so much stronger on the drug.  He was running, jumping, and alternating feet on stairs (which he has never done in his life)! My heart is broken :( 

Comment by Andrea Cleary on September 20, 2013 at 12:37pm

At the beginning of this week I almost left an update for you all on how my son is doing in this trial, but something inside me said "why bother?" and I deleted it. Now I know why.

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