Extension Study of Drisapersen in DMD Subjects

This is a phase IIIb, multi-centre, open-label extension study in male subjects with DMD who
have previously been treated with drisapersen.

This study aims to enroll up to approximately 220 subjects. The primary dosing arm is
drisapersen 6 mg/kg as subcutaneous (SC) injection(s) once a week. All subjects starting with
subcutaneous injections will receive a loading dose of twice weekly 6mg/kg drisapersen for
the first three weeks of treatment. This study does not have a minimum duration of
participation. Subjects will have varying times of study participation depending on when they
enter from one of the eligible studies and will be permitted to continue the study until such
a time that they withdraw based on protocol-defined criteria, or BioMarin stops the study.
Subjects naïve to treatment are not eligible for participation in this study

For subjects who have previously experienced significant safety or tolerability issues in one
of the eligible studies, or who experience these during this study, there is the potential of
an alternate intermittent dosing arm. This will be agreed in advance with the Medical
Monitor.

For subjects who have previously experienced significant injection site reactions in an
earlier drisapersen study, or who experience similar reaction(s) during this study, there is
the potential to be dosed intravenously.

Inclusion Criteria:

1. Any subject who has been previously treated with an exon 51 skipping antisense
oligonucleotide (drisapersen or eteplirsen) and is not eligible for another ongoing
drisapersen study. Subjects who withdrew from the previous studies due to meeting
laboratory safety stopping criteria may be eligible to enroll if:

2. The laboratory parameters that led to stopping have resolved; benefit of further
treatment with drisapersen outweighs the risk to the individual subject; and following
consultation with the Medical Monitor.

3. Subjects with DMD mutation/deletion within the dystrophin gene and correctable by
drisapersen-induced DMD exon 51 skipping.

4. Male subjects age >5 at screening in whom the investigator considers treatment with
drisapersen is likely to lead to improvement or prevent worsening of the condition.

5. Continued use of glucocorticoids for a minimum of 60 days prior to study entry with a
reasonable expectation that the subject will remain on glucocorticoids for the
duration of this study. Changes to or cessation of glucocorticoids will be at the
discretion of the investigator conducting this study in consultation with the
subject/parent and Medical Monitor.

6. Willing and able to comply with all study requirements and procedures (with the
exception of those assessments requiring a subject to be ambulant, for those subjects
who have lost ambulation).

7. Able to give informed assent and/or consent in writing by the subject and/or
parent(s)/legal guardian (according to local regulations)

Exclusion Criteria:

1. Subjects who have previously been treated with drisapersen and who had a serious
adverse experience or who met safety stopping criteria that remains unresolved, which
in the opinion of the investigator could have been attributable to drisapersen. Once
resolved, subject may be eligible to enter the study following investigator
consultation with the Medical Monitor.

2. Use of anticoagulants, anti-thrombotics or antiplatelet agents within 28 days of the
first re-dosing of drisapersen. Chronic use of anticoagulants, anti-thrombotics or
antiplatelet agents is prohibited during the study. As needed dosing (pro re nata -
PRN) may be acceptable (except for aspirin) following discussion with the Medical
Monitor.

3. Participation in any investigational clinical trial within 3 months prior to start or
during this study (except for other drisapersen studies). If subjects have
participated in any other study within the last 6 months this should be discussed with
the Medical Monitor prior to start of this study.

4. History of significant medical disorder which may confound the interpretation of
safety data (e.g. current or history of renal or liver disease/impairment, history of
inflammatory illness)

5. Symptomatic cardiomyopathy. If subject has a left ventricular ejection fraction <45%
at start of this study, the investigator should discuss inclusion of subject in this
study with the Medical Monitor.

6. A platelet count under the lower limit of normal (LLN) at start of this study. A
re-test is possible at a later stage, and if within normal range, the subject may
enter the study.