Prosensa to Host Conference Call to Discuss Recent Drisapersen Data Presentations

Conference call and live webcast scheduled for 11:00 a.m. ET (5:00 p.m. CET)  Tuesday, October 8, 2013

LEIDEN, The Netherlands – October 3, 2013 – Prosensa Holding N.V. (NASDAQ: RNA), the Dutch biopharmaceutical company focusing on RNA-modulating therapeutics for rare diseases with high unmet need, will hold a conference call on Tuesday, October 8, 2013 at 11:00 a.m. ET / 5:00 p.m. CET to discuss recently-presented data on drisapersen, an investigational antisense oligonucleotide, for the treatment of Duchenne Muscular Dystrophy (DMD) patients with an amenable mutation, which is exclusively licensed to GlaxoSmithKline (GSK).

Prosensa Chief Executive Officer Hans Schikan will be joined by Giles Campion, Prosensa’s Chief Medical Officer & Senior Vice-President of Research and Development and Judith van Deutekom, Vice President of Drug Discovery to discuss the recently presented results from studies of drisapersen. These include results from DEMAND III (Phase III; DMD114044); DEMAND II (Phase II; DMD114117); DEMAND V (Phase II; DMD114876) and 177 week data from the Phase I/II extension study (DMD114673).

The data were presented at the DIA/FDA Oligonucleotide based Therapeutics Conference in Washington DC, the 18th World Muscle Society Congress in Asilomar, California and the 9th Annual Meeting of the Oligonucleotide Therapeutics Society in Naples, Italy, running from Sept 25-27, October 1-5 and 6-8, respectively.

In order to participate in the conference call, please dial 1-877 280 2342 (US domestic) and refer to conference ID 2579927. International dial-in numbers and an audio webcast can be accessed under “Events & Presentations” through the Investors & Media section of the Prosensa corporate website www.prosensa.com.

About drisapersen

Drisapersen, (previously GSK2402968/PRO051) an antisense oligonucleotide, which induces exon skipping of exon 51, is currently in late stage development for DMD.

GSK obtained an exclusive worldwide license to develop and commercialize drisapersen from Prosensa in 2009. Drisapersen has been designated orphan drug status in the EU, US and Japan. In June 2013, drisapersen was granted Breakthrough Therapy designation by the US Food and Drug Administration.

For more information regarding the ongoing clinical studies involving drisapersen visit www.clinicaltrials.gov.

 About DMD

Duchenne Muscular Dystrophy (DMD) is a severely debilitating childhood neuromuscular disease that affects up to 1 in 3,500 live male births. This rare disease is caused by mutations in the dystrophin gene, resulting in the absence or defect of the dystrophin protein.

Patients suffer from progressive loss of muscle function due to the absence or defect of the dystrophin protein, often making them use a wheelchair before the age of 12. Respiratory and cardiac muscle can also be affected by the disease. Few patients survive the age of 30.

 About exon skipping

The dystrophin gene is the largest gene in the body, consisting of 79 exons. Exons are small sequences of genetic code which lead to the manufacture of sections of protein. In DMD, when certain exons are mutated/deleted, the RNA cannot read past the fault. This prevents the rest of the exons being read, resulting in a non-functional dystrophin protein and the severe symptoms of DMD.

RNA-based therapeutics, specifically antisense oligonucleotides inducing exon skipping, are currently in development for DMD. This technology uses synthetic antisense oligonucleotides to skip an exon next to a deletion and thereby correct the reading frame, enabling the production of a novel dystrophin protein. Up to 13% of boys with DMD have dystrophin gene mutation/deletions amenable to an exon 51 skip.

About Prosensa Holding N.V.

Prosensa (NASDAQ: RNA) is a Dutch biotechnology company engaged in the discovery and development of RNA-modulating therapeutics for the treatment of genetic disorders. Its primary focus is on rare neuromuscular and neurodegenerative disorders with a large unmet medical need, including Duchenne muscular dystrophy, myotonic dystrophy and Huntington’s disease.

www.prosensa.com

Forward Looking Statements

This press release contains certain forward-looking statements.  All statements, other than statements 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-looking statements. The words “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “plan,” “predict,” “project,” “target,” “potential,” “will,” “would,” “could,” “should,” “continue,” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Forward-looking statements in this press release include statements around our exon -skipping drug candidates and our collaboration with GlaxoSmithKline (GSK). Actual results may differ materially from those projected or implied in such forward-looking statements.  Such forward-looking information involves risks and uncertainties that could significantly affect expected results.  These risks and uncertainties are discussed in the Company’s SEC filings, including, but not limited to, the Company’s Form 6-K containing this press release and certain sections of the Company’s Registration Statement on Form F-1. In addition, any forward-looking statements represent our views only as of today and should not be relied upon as representing our views as of any subsequent date. While we may elect to update these forward-looking statements at some point in the future, we specifically disclaim any 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