Hans Schikan, CEO

Prosensa Corporate Overview

Jefferies Healthcare Conference

London, UK

November 19, 2014

This presentation may contain statements that constitute “forward-looking statements” within themeaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of1934. Forward-looking statements are statements other than historical fact and may includestatements that address future operating, financial or business performance or Prosensa’s strategies orexpectations. In some cases, you can identify these statements by forward-looking words such as“may,” “might,” “will,” “should,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,”“projects,” “potential,” “outlook” or “continue,” and other comparable terminology. Forward-lookingstatements are based on management’s current expectations and beliefs and involve significant risksand uncertainties that could cause actual results, developments and business decisions to differmaterially from those contemplated by these statements. These risks and uncertainties include, but arenot limited to, the timing and conduct of clinical trials of drisapersen and Prosensa’s other productcandidates, plans to pursue research and development of product candidates for DMD and otherindications, the clinical utility of Prosensa’s product candidates, the timing or likelihood of regulatoryfilings and approvals, Prosensa’s intellectual property position, expectations regarding payments underProsensa’s collaborations and Prosensa’s competitive position. These risks and uncertainties alsoinclude those described under the captions “Risk Factors” and “Management’s Discussion and Analysisof Financial Condition and Results of Operations” in Prosensa’s Annual Report on Form 20-F and otherfilings with the Securities and Exchange Commission. Forward-looking statements speak only as of thedate they are made, and Prosensa does not undertake any obligation to update them in light of newinformation, future developments or otherwise, except as may be required under applicable law. All

forward-looking statements are qualified in their entirety by this cautionary statement.

Forward-Looking Statements

To develop innovative, RNA-modulating

therapeutics to fill unmet medical

needs for patients with rare genetic diseases

Our Mission

2

Rare disease company based in the Netherlands, listed on Nasdaq (RNA)

Largest pipeline and clinical program in Duchenne muscular dystrophy (DMD)

NDA submission under accelerated approval for drisapersen underway,

followed by MAA in EU for conditional approval

Orphan Drug status for 6 DMD compounds

FDA Breakthrough Therapy Designation for drisapersen

Solid intellectual property position

Management with extensive experience in commercializing orphan drugs

Cash position (Sept 30, 2014): EUR 62M; Cash burn (FY-2013): EUR 22M;

(H1-2014): EUR 12.7M; YE 2014 cash balance guidance: EUR 52-54M

Corporate Highlights

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4

Our Science - RNA Modulation

Technology platform enables us to design sequences of nucleotides that bind to specified regions of pre-mRNA which may induce exon skipping or exon inclusion, reduce mutated

toxic RNA or protein, remove specific protein domains or block protein expression

Indication Compound Discovery Pre-Clinical Phase I/II Phase III

Drisapersen

PRO044

PRO045

PRO053

PRO052

PRO055

PROSPECT

PRO289

PRO135

Duchenne

Muscular

Dystrophy

Huntington’s

Disease

Myotonic

Dystrophy

R&D - Largest Pipeline in DMD

13% of DMD patients

6% of DMD patients

8% of DMD patients

8% of DMD patients

4% of DMD patients

2% of DMD patients

5

Evolution of clinical symptoms of DMD

0 5 10 15 20 25 30

death

ventilation 24h

ventilation at night

very limited use of arms

wheelchair - skeletal deformity

walking problems

Age

X-linked, rare genetic disease

Rapid progression of muscle degeneration

75,000 patients in addressable populations

Severely debilitating and invariably fatal progressive neuromuscular disease

Duchenne Muscular Dystrophy (DMD)

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6MWT is a validated functional endpoint for DMD and other rare diseases

Age & baseline walking ability are important variables that determine decline in the ability to walk as measured by 6MWT*

Recent publication suggests clinically meaningful change in walking ability, as measured by 6MWT, to be in the range of 20-30 meters*

Creatine Kinase (CK) is a marker of muscle damage - DMD patients have elevated levels of CK in their blood serum

Prosensa has completed enrollment with 269 patients in an observational study to characterize the natural history and progression of DMD in addition to capturing potential biomarkers

* McDonald, Muscle & Nerve 2013

DMD Natural History and Endpoints

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6-M

inu

te W

alk

Dis

tan

ce,

m 700

100

200

600

500

400

300

5 10

Functional Outcome - 6MWT Conceptual Representation

Late intervention

Early intervention

Approx. age years

8

7

Based on natural history, DMD boys lose approximately 40-60 meters in 6MWT per year

Lead Compound - Drisapersen

20-mer Antisense Oligonucleotide (AON) with specific binding to exon 51 of dystrophin gene pre-mRNA

Administered by once weekly subcutaneous injection (6mg/kg)

May address up to 13% of all DMD patients

Granted orphan drug status in US, EU, Japan, Australia

Breakthrough Therapy designation granted by the FDA

NDA submission initiated under rolling review and Fast Track status

Issued patents include US patent expiring 2023; EU patent expiring 2021

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Study Phase Study design N Status

CLIN-02DMD114673

Phase I/II +Extension

Open label, repeat dose escalation (extension phase 6 mg/kg/wk intermittent);

12Complete; extension ongoing

DEMAND IDMD114118

Phase IPlacebo-controlled, pharmacokinetics/safety; single dose

20 Complete

DEMAND IIDMD114117

Phase IIExploratory placebo-controlled, dose regimen comparison; ex-US, 24/48 wks

53 Complete

DEMAND IIIDMD114044

Phase IIIRandomized, placebo-controlled, confirmatory study; global, 48 wks

186 Complete

DEMAND IVDMD114349

Phase II/III Extension

Open label, extension study for DEMAND II) & DEMAND III ; 96 wks

234 Closed

DEMAND VDMD114876

Phase IIExploratory placebo-controlled, dose-comparison; US only, 24 wks

51 Complete

DMD115501Phase II/IIIExtension

Open-label, extension study for US & Canadian subjects from DEMAND III, IV, V

72 Recruiting

Drisapersen Clinical Program

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More than 300 patients and over 450 patient treatment years in global clinical program

Overview of Supportive Studies + Analyses

*pb = placebo (DEMAND IV: pb/delayed treatment); dr = drisapersen 6 mg/kg; Tx difference on 6MWD; not all analyses shown11

Clinically meaningful treatment difference across program; DEMAND III outlier

Efficacy results up to 3.4 years (177 weeks) appear to show delay of disease progression

0

100

200

300

400

500

600

700

800

0 12 24 36 48 60 72 80 93 105 117 129 141 153 165 177

Dis

tan

ce w

alke

d (

m)

Weeks

Age at

week 177

13.7

14.3

11.4

10.9

12.6

9.3

13.3

15.4

13.0

14.8

Long Term Study DMD114673

8 weeks on – 4 weeks off

12

N=10

Mean age is 12.9 years at 177 wks

13

Dis

tan

ce w

alke

d (

m)

Weeks

Mean change from baseline: +33 m

[Median change from baseline: +64 m]

Mean change from baseline: -25 m

[Median change from baseline: +8 m]

Long-term data suggest stabilization on 6MWT

Ambulant boys: N=8

All boys: N=10

Long Term Study DMD114673

Study DesignΔ 6MWT

(m)SD (m)

Study(years)

N

McDonald 2010¹ Natural History -57 104 1 18

Ataluren 2010¹ Placebo arm -42 90 1 57

Mazzone 2011² Natural History -42 74 1 71

Goemans 2012¹ Natural History -38 96 1 19

McDonald 2013² Natural History -59 82 1 33

Mazzone 2013² Natural History -122 78-97 2 113⁴

Goemans 2013² Natural History -125 139 2 14

Pane, 2014³ Natural History -146 146 3 68

DMD patients lose approximately 40-60 m in 6MWD in 1 year, 150 m in 3 years

¹All ages; ²Age >7, ³Age ≥7, ⁴ All patients in study

Functional Outcome - 6 Minute Walk Test

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(11)

20

DEMAND II (DMD114117)

(25 week endpoint)

+32m (n=18)

DEMAND V(DMD114876)

(24 week endpoint)

+16m (n=18)

-11m (n=16)

Δ6MWD = +31mp=0.003

Δ6MWD = +27mp=0.069

Δ6MWD = +35mp=0.014

DEMAND II + DEMAND V(DMD114117 + DMD114876)

(post-hoc analysis 24/25 weeks)

-4m (n=18)

Drisapersen 6 mg/kg/weekPlacebo

Two placebo-controlled studies show treatment benefit on 6MWD

+20m (n=36)

-11m (n=34)

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Placebo Controlled Studies - 6MWD

Visit Treatment N nUnadjusted

mean baseline value (sd)

Adjustedmean (se)

Treatment difference

(m)95% CI P-value

All Subjects

Week 48

Placebo 61 59 348 (92) -53 (10)

Drisapersen 125 117 337 (96) -42 (7) +10 (-15,35) 0.415

≤ 7 years at baseline

Week 48

Placebo 29 29 383 (67) -25 (11)

Drisapersen 51 50 368 (65) -4 (9) +21 (-7,50) 0.131

> 7 years at baseline†

Week 48

Placebo 32 30 316 (101) -83 (16)

Drisapersen 74 67 316 (107) -76 (11) +7 (-29,43) 0.703

> 7 years at baseline, and baseline 6MWD ≥300m and ≤450m

Week 48

Placebo 15 14 351 (34) -67 (20)

Drisapersen 34 33 375 (42) -42 (13) +25 (22,72) 0.292

Model includes terms for Treatment, Visit, Treatment by Visit, Study, Baseline 6MWD and Baseline 6MWD by Visit

DEMAND III by Age and Baseline 6MWD

†Includes subjects >11 years of age: drisapersen, n=11; placebo, n=1

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What Happened in DEMAND III?

Variability

44 clinical trial sites, across 19 countries

Many centers new to DMD clinical trials

Difference in standards of care

Heterogeneity

Patient population was generally older, more heterogeneous & more advanced in their disease than inthe previous placebo controlled studies, as evidenced by baseline characteristics

1 in 4 pts was >7 yrs & <300m baseline 6MWT

+29%

Time sincediagnosis[months]

58

4745

DEMAND IIIDEMAND VDEMAND II

-21%

6MWD[meter]

337

396

428

+167%

Rise fromfloor time[sec]

12.3

5.04.6

+48%

4 stairs climb-ascent time[sec]

4.74.6

3.1

-18%

Musclestrength [lbs]

102

125124

Baseline characteristics in DEMAND III; boys were generally more advanced in disease

DEMAND III - More Advanced Disease

Drisapersen arm = 6 mg/kg/week; figure shows differences for drisapersen arm; similar baseline characteristics for placebo arm18

StudyMean change in

6MWD for continuous treatment (n)*

Mean change in 6MWD for placebo/delayed

treatment (n)*

Difference in change in 6MWD between

treatment arms (n)*

DEMAND IVall patients

–67 m (69) –113 m (44) +46 m (113)

DEMAND IVfeeder study DEMAND II

–5 m (17) –57 m (13) +52 m (30)

DEMAND IVfeeder study DEMAND III

–87 m (52) –136 m (31) +49 m (83)

DEMAND IV≤ 7 years of age

+8 m (31) –29 m (21) +37 m (52)

DEMAND IV>7 years of age† –128 m (38) –190 m (23) +62 m (61)

*Includes all subjects (21 subjects lost ambulation during DEMAND III; 13 subjects lost ambulation during DEMAND IV. Zero values were imputed

once the subject had lost ambulation; zero minus baseline value).

Long Term (96 weeks) - DEMAND IV

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Time (weeks)

PlaceboDrisapersen

Dri

sap

erse

n t

issu

e le

vel

(mg/

g)

Leaky muscle fibers in DMD promote

AON uptake

AONs enter nuclei, bind to exon 51 of DMD pre-mRNA,

and induce skipping

Exon 51 skipping results in novel dystrophin production

Improved muscle physiology and

structure

qRT-PCRTissue PK IFA CK

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Confirmed Mechanism of Action

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0 10 20 30 40 50

10,000

12,000

8,000

6,000

0

14,000

∆ in CK level between Drisapersen(6mg/kg/wk) and placebo

-4,045(p<0.001)

DEMAND III(at week 48)

DEMAND V(at week 24)

DEMAND II(at week 25)

-3,327(p=0.064)

-1,305(p=0.439)

CK levels [IU/L]¹

DEMAND III

DEMAND V²

DEMAND II

PlaceboDrisapersen 6mg

Week¹Preliminary analysis; ²Treatment duration 24 weeks

Muscle Pathology: Decrease in CK

Consistent decrease in Creatine Kinase (CK) across 3 placebo controlled studies

0

5

10

15

Semi-tendinosus

Bicep femoris

Vastus medialis

Vastus intermedius

Vastus lateralis

Rectus femoris

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Preliminary MRI data suggest reduced fat infiltration. Data are supportive for drisapersen-induced improved muscle pathology

Drisapersen 6mg/kg/week (n=5)Placebo (n=5)

DEMAND V: Change in apparent fat fraction from baseline [%] at 48 weeks in 6 muscle groups

Muscle Pathology: Reduced Fat Infiltration

Key Safety Data

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Drisapersen is generally well tolerated, with an adverse event (AE) profile consistent with that described previously for this class of molecule

59 SAEs reported on drisapersen, most considered unrelated: 15/59 SAEs were considered related or possibly related to drisapersen

In total 12 of >300 subjects have withdrawn permanently from treatment owing to AEs

Most commonly reported AEs include injection-site reactions and renal abnormalities (including subclinical proteinuria); cases of (moderate to severe) thrombocytopenia have been reported

FDA Guidance Letter received on June 2, following meeting on May 14. Regulatory pathway possible under accelerated approval on existing data

Rolling NDA submission underway with first module (>15,000 pages) submitted on October 10; next module in preparation, anticipated submission December

Regular interactions with FDA (meetings September and October); next meeting planned for January 2015, with submission of final module expected shortly thereafter

Two confirmatory post-approval studies were discussed with FDA in meeting on October 22; studies planned to start prior to anticipated approval

EMA - interactions ongoing, plan to file for conditional approval shortly after submission of file with FDA

Drisapersen Regulatory Update

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1. Open-label study of drisapersen with historical control

Prosensa’s fully enrolled Natural History Study (269 patients) may serve as a control

2. Randomized, placebo-controlled trial of another exon-skipping drug with a similar mechanism of action, directed at a different exon

PRO044 may serve this purpose

Both study designs discussed with FDA

Final protocols currently in preparation for submission to IRB’s

Anticipated start in Q1 and Q2 2015, resp.

Confirmatory Studies - FDA Guidance

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0%

20%

40%

60%

80%

100%

0 200 400 600 800 1000

% f

ibre

s

Fibre dystrophin intensity (a.u.)

Distribution dystrophin per fibre

cu

mu

lati

ve

%

Dystrophin Assessment Methodology

32

40

38

36

42

2

1

10

16

64

911

7

53

12

15

13

8

14

23

1817

21

20

22

30

19

24

2928272625

35

33

31

34

4443

41

39

37

47464549

48

Sensitive, reproducible and objective methodology for dystrophin analysis developed by Prosensa and published in peer-reviewed online journal (PLOS ONE)

Objective: measures dystrophin over the entire membrane of a fibre and is operator

independent

Reproducible: method verified across multiple samples and experiments

Sensitive: assesses dystrophin levels by immunofluorescence in muscle biopsies from

BMD & DMD patients

Dystrophin Expression is Variable

Demonstration of a pharmacodynamic effect requires comparison of 2 biopsies pre- and post-treatment, taken from the same muscle, & sampled from areas of similar disease state

Follow-on Exons Moving Forward

PRO044

Positive dystrophin response detected in 12 of 21 evaluable biopsies

Dose exposure modelling predicts effective dose range at 6-9 mg/kg i.v.

Safety findings consistent with known class safety profile; no drug-related SAEs

Dosing of first patients in extension study Q1 2015

Placebo-controlled study anticipated to start 1H 2015

PRO045Dose finding study ongoing; preliminary results expected in Q4 2014

PRO053

Dose finding study ongoing; preliminary results expected in Q1 2015

PRO052/PRO055/PROSPECT

Preclinical studies ongoing

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PROSPECT - Multiple Exon Skipping

Addresses rare mutations, initially in exon 10 to 40 region

Proof-of-concept obtained in multiple patient muscle cell cultures

Initial applicability between 5% and 20% of DMD patient population

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Q3-2014 Re-dose initial group of boys (US & EU)

Q4-2014 NDA rolling submission commenced with FDA

Q1-2015 Anticipated completion of NDA submission with FDA

Q1-2015 Expected MAA application for drisapersen with EMA

1H-2015 Initiation of two confirmatory studies to support potential accelerated approval for drisapersen

Key Milestones Drisapersen

Rare disease company based in the Netherlands, listed on Nasdaq (RNA)

Largest pipeline and clinical program in Duchenne muscular dystrophy (DMD)

NDA submission under accelerated approval for drisapersen underway,

followed by MAA in EU for conditional approval

Orphan Drug status for 6 DMD compounds

FDA Breakthrough Therapy Designation for drisapersen

Solid intellectual property position

Management with extensive experience in commercializing orphan drugs

Cash position (Sept 30, 2014): EUR 62M; Cash burn (FY-2013): EUR 22M;

(H1-2014): EUR 12.7M; YE 2014 cash balance guidance: EUR 52-54M

Corporate Highlights

31