Prosensa Starts Re-Dosing Drispersen in Duchenne Patients

James Radke

Prosensa is back in the clinical trial business. The company announced they have begun the re-dosing program for drisapersen in boys with Duchenne muscular dystrophy.

In September 2013, all dosing in the drisapersen clinical program was placed on hold following the disappointing initial evaluation of the phase 3, DEMAND III study. Subsequent analysis of the data as well as discussions with the U.S. Food and Drug Administration (FDA) led Prosensa to announce in June 2014 that they had received guidance for the FDA on how to best proceed using the existing data.

The company is now ready to start that process and for the first time since last September, a boy with Duchenne muscular dystrophy is being tested with the drug drisapersen.

Dr. Giles Campion, Prosensa's Chief Medical Officer said:

"We are very pleased that we have been able to keep our promise to commence re-dosing patients with drisapersen in the third quarter of this year, which is taking a staged approach."

"While we know the wait has been incredibly difficult for the boys (and their families), we have been working diligently on this achievement since regaining the rights to drisapersen and are grateful to all that have helped us in attaining this goal. While today is a major milestone for the Company, it is an even greater one for these first patients and their families, who have been anxiously awaiting drisapersen treatment since dosing was stopped almost one year ago.”

The re-dosing program in North America will include up to 72 patients across 14 sites who had participated in the drisapersen DEMAND V (Phase II) & DEMAND III (Phase III) studies. Eventually, the company plans to offer re-dosing to all participants in the earlier clinical trials.  How many of those patients are eligible or who have not switched over to another clinical trial (i.e., Sarepta’s eteplirsen) is not known.

Details of the re-dosing and any future trials by Prosensa are not known at press time but in their June press release, they noted that the FDA suggested at least two additional studies be conducted – a historically controlled trail and a randomized, placebo-controlled trial of another exon-skipping drug with a similar mechanism of action.

Travel Arrangements for Participants

Since drisapersen is administered once weekly subcutaneously, Prosensa plans to enable home-dosing where feasible and provide transport assistance to participants attending one of the clinical centers.  Prosensa is working with 1) Medical Research Network (MRN) to make home-dosing options available and 2) Greenphire to ease the logistics of traveling to a clinical center with minimal out-of-pocket expenses.

Hans Schikan, Prosensa's Chief Executive Officer  said:

"Given the weekly dosing regimen for drisapersen and the travel time and costs associated with these, we are pleased to collaborate with both Greenphire and MRN to ease the burden of this process to patients and their families.”

About Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is a progressive muscle disorder caused by the lack of functional dystrophin protein. Patients with Duchenne muscular dystrophy lose the ability to walk as early as age 10 and experience life-threatening lung and heart complications in their late teens and twenties.

There are an estimated 35,000 patients with Duchenne in the United States and Europe but the population has many subsets based on mutations of the dystrophin gene.

Both Sarepta’s eteplirsen or Prosensa’s drisaperson should be effective in the same 13% of the Duchenne population who would benefit from exon 51 skipping therapy (i.e., those with mutations near exon 51 of the dystrophin gene) while PTC Therapeutics’ ataluren should be effective in another 13% subset who have nonsense mutations in the dystrophin gene.

All three companies are starting, or have started, phase 3 confirmatory studies.

Image of racing greyhound courtesy of wikimedia commons.
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