Prosensa Announces 48-Week Data From A U.S. Phase II Placebo-Controlled Study Of Drisapersen In 51 DMD Boys

Chicago, IL, March 17, 2014 (GLOBE NEWSWIRE) -- Prosensa Holding N.V. (NASDAQ: RNA), the Dutchbiopharmaceutical company focusing on RNA-modulating therapeuticsfor rare diseases with high unmet need, today reported encouraging48-week  data from its U.S.-based, Phase II placebo-controlledstudy (DMD114876 or DEMAND V) of its lead compound, drisapersen,for the treatment of Duchenne Muscular Dystrophy (DMD).

The results of this study indicate that,compared to placebo, boys in the higher-dose drisapersen group (6mg/kg once weekly) experienced stabilization and even improvementsin their muscle function and physical activity as measured by thesix-minute walk test (6MWT) for the 24-week treatment phase andmaintained this improvement during the 24-week follow-up period.Additionally, when evaluating the percent-predicted six-minute walkdistance (6MWD), a clinically meaningful treatment difference of5.2% was observed at week 24 and 4.8% at week 48.

Principal investigator, Craig M. McDonald, M.D.,Professor and Chair of Physical Medicine & Rehabilitation andProfessor of Pediatrics at the University of California, DavisSchool of Medicine, will report the 48 week results in a postersession (Abstract #50) today at the Muscular Dystrophy Association2014 Clinical Conference in Chicago, Illinois (March 16-19).

"Given the severity of the disease and the lackof disease modifying treatment options available, the results ofthis important study support the use of drisapersen at a dose of 6mg/kg once weekly in the treatment of boys with DMD eligible forexon 51 skipping" Dr. McDonald said. "The maintenance of theclinically meaningful treatment benefit in the 24-week follow-upphase is very encouraging evidence for the drug's ability toproduce prolonged stabilization of disease and may indicate that,at the 6 mg/kg once weekly dose, the drug has a long term treatmenteffect that helps delay disease progression in younger, less severeboys."

The study included 51 boys with DMD who were atleast five years old, still able to walk and stand up from thefloor without help in less than 15 seconds. As previously reported,boys in the group who received a 6mg/kg dose of drisapersen eachweek for the 24-week treatment period show a 27.1 meter improvementin the 6MWT (including a 16.1 m increase from baseline) over theboys in the placebo group at the end of the treatment period(p=0.069), indicating a clinically meaningful outcome for theprimary endpoint. This study compared 6mg/kg/week with 3mg/kg/weekand placebo and was not statistically powered to show a significantdifference between the arms. A clinically meaningful treatmentdifference of 27.9 m over placebo (p=0.177) was maintained for 24weeks after drisapersen administration ceased. This includes anoverall mean increase from baseline of 14.7 m. In the drisapersen 6mg/kg/week group, an improvement was seen in the percent-predicted6MWD of 5.2% (p=0.051) and 4.8% (p=0.154) when compared to placeboat weeks 24 and 48, respectively.

Drisapersen at weekly doses of 3 and 6mg/kg/week was generally well tolerated, although the majority ofsubjects treated with drisapersen reported injection-site reactions(none severe or serious). Renal abnormalities were common andoccurred both in the placebo and drisapersen groups.

"Our priority remains improving the lives andoutcomes of boys afflicted with this devastating disease. We areencouraged by these results, and are actively continuing with theanalysis of the total drisapersen data set, which includes 300patients and combined data representing 450 patient years to putthese results into context," said Hans Schikan, CEO of Prosensa."As we reported earlier this year, initial findings from furtheranalyses of the aggregate drisapersen data suggest that treatingearlier in DMD and treating longer shows a delay in the progressionof the disease."

A copy of the poster can be accessed (startingMarch 18) under "Events & Presentations" through the Investors& Media section of the Prosensa corporate website at

About Prosensa Holding N.V.

Prosensa (NASDAQ: RNA) is an innovativebiotechnology company engaged in the discovery and development ofribonucleic acid-modulating, or RNA-modulating, therapeutics forthe treatment of genetic disorders. Its primary focus is on rareneuromuscular and neurodegenerative disorders with a large unmetmedical need, including Duchenne muscular dystrophy, Myotonicdystrophy and Huntington's disease. Its clinical portfolio ofRNA-based product candidates is focused on the treatment ofDuchenne muscular dystrophy, or DMD. Each of its DMD compounds hasbeen granted orphan drug status in the United States and theEuropean Union. Its first product candidate, drisapersen, canaddress a variety of mutations in the dystrophin gene, such as adeletion of exon 50 or exons 48 to 50.

About DMD

DMD is one of the most prevalent rare geneticdiseases globally affecting up to 1 in 3,500 boys and is invariablyfatal. There is currently no approved disease-modifying therapy forDMD. The progressive muscle-wasting that characterizes this diseaseis caused by inadequate production of dystrophin, a proteinnecessary for muscle function, as a result of mutations in thedystrophin gene. The different mutations, which are mostlydeletions of one or more exons, found in the dystrophin gene resultin distinct sub-populations of DMD patients. Prosensa are designingproduct candidates to address several sub-populations using itsplatform technology.

Forward Looking Statement

This press release contains certainforward-looking statements. All statements, other than statementsof historical facts, contained in this press release, includingstatements regarding its strategy, future operations, futurefinancial position, future revenues, projected costs, prospects,plans and objectives of management, are forward-looking statements.The words "anticipate," "believe," "estimate," "expect," "intend,""may," "plan," "predict," "project," "target," "potential," "will,""would," "could," "should," "continue," and similar expressions areintended to identify forward-looking statements, although not allforward-looking statements contain these identifying words.Forward-looking statements in this press release include statementsaround its exon-skipping drug pipeline and financial position.Actual results may differ materially from those projected orimplied in such forward-looking statements. Such forward-lookinginformation involves risks and uncertainties that couldsignificantly affect expected results. These risks anduncertainties are discussed in the Company's SEC filings,including, but not limited to, the Company's Form 6-K containingthis press release and certain sections of the Company'sRegistration Statement on Form F-1. In addition, anyforward-looking statements represent its views only as of today andshould not be relied upon as representing its views as of anysubsequent date. While Prosensa may elect to update theseforward-looking statements at some point in the future, Prosensaspecifically disclaim any obligation to do so, even if its viewschange.
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