Prosensa Enrolls 100th Patient To Its Natural History Study Of Duchenne Muscular Dystrophy

Leiden, The Netherlands, Nov. 7, 2013 (GLOBE NEWSWIRE) -- Prosensa Holding N.V. (NASDAQ: RNA), the Dutchbiopharmaceutical company focusing on RNA-modulating therapeuticsfor rare diseases with high unmet need, today announced thesuccessful enrollment of the 100 th  patient intothe Natural History Study of Duchenne muscular dystrophy (DMD).

The goal of this observational study is tocharacterize DMD at various stages of progression using the samemeasures used in ongoing clinical studies, such as the "six minutewalk test." No medication is being tested in this study.

"The enrollment of the 100 th patientfor the Natural History Study reinforces our commitment todeveloping innovative treatment options for DMD," said Dr. GilesCampion, Prosensa's Chief Medical Officer. "This study will fostergreater understanding of the progression of this debilitatingdisease and will help explore new endpoints that could be used toexpedite drug development."

Dr. Brenda Wong, Director of the ComprehensiveNeuromuscular Center at Cincinnati Children's and one of thestudy's lead investigators, adds "this critical work on the naturalhistory of DMD represents an impactful milestone for patients andtheir families. Our findings may enable more efficient trial designfor follow-on programs and improved outcomes for patients."

Patients in the study are assessed every sixmonths for a period of three years to measure their muscle strengthand function, in addition to how the disease affects their qualityof life as the condition evolves over time. Investigators areobserving the patients as they perform various physical tests, andassess their quality of life through survey questions. Furthermore,certain biomarkers are measured through blood and urine samples toinvestigate a possible correlation to disease progression.

Prosensa and GlaxoSmithKline (GSK), who areboth funding the study, expect to enroll up to 250 DMDpatients into the study with any type of mutation in the DMD genebetween the ages of three and 18.  The study is beingconducted in 16 hospitals across 10 countries with 14 sites alreadyopen in the U.S. and Europe. Further information on the study canbe found here: www.ClinicalTrials.gov - StudyID: NCT01753804

Notes to editors

About Prosensa Holding N.V.

Prosensa (NASDAQ: RNA) is a Dutch biotechnology company engagedin the discovery and development of 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.

Prosensa's current portfolio includes six compounds for thetreatment of DMD, all of which have received orphan drug status inthe United States and the European Union. The compounds use aninnovative technique called exon-skipping to provide a personalizedmedicine approach to treat different populations of DMD patients.The company's lead investigational drug candidate, drisapersen,which is exclusively licensed to GlaxoSmithKline, is in PhaseIII clinical trials.

www.prosensa.com

About DMD

Duchenne muscular dystrophy (DMD) is a severely debilitatingchildhood neuromuscular disease that affects up to 1 in 3,500 boys.This rare disease is caused by mutations in the dystrophin gene,resulting in the absence or defect of the dystrophin protein. As aresult, patients suffer from progressive loss of muscle strength,often rendering them wheelchair-bound before the age of 12. Fewpatients survive the age of 30.

Forward Looking Statements

This press release contains certainforward-looking statements.  All statements, other thanstatements of historical facts, contained in this press release,including statements regarding our strategy, future operations,future financial position, future revenues, projected costs,prospects, plans and objectives of management, are forward-lookingstatements. The words "anticipate," "believe," "estimate,""expect," "intend," "may," "plan," "predict," "project," "target,""potential," "will," "would," "could," "should," "continue," andsimilar expressions are intended to identify forward-lookingstatements, although not all forward-looking statements containthese identifying words. Forward-looking statements in this pressrelease include statements around our exon -skipping drugcandidates and our collaboration with GlaxoSmithKline (GSK). Actualresults may differ materially from those projected or implied insuch 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 our views only as of today andshould not be relied upon as representing our views as of anysubsequent date. While we may elect to update these forward-lookingstatements at some point in the future, we specifically disclaimany obligation to do so, even if our views change.
CONTACT: Prosensa Holding N.V.         Celia Economides, Director IR & Corporate Communications         Phone: +1 917 941 9059         Email: c.economides@prosensa.nl

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