Study of Eteplirsen in DMD Patients

This is an open-label, multi-center study to evaluate the efficacy and safety of eteplirsen
in patients with genotypically confirmed Duchenne muscular dystrophy (DMD) with genetic
deletions amenable to exon 51 skipping (treated group), with a concurrent control arm of DMD
patients not amenable to exon 51 skipping (untreated group). Following primary efficacy
endpoints, dosing will continue to week 144 to evaluate the long term effects of eteplirsen.

Patients in the treated group will receive once weekly intravenous (IV) infusions of 30 mg/kg
Eteplirsen for 96 weeks, followed by a safety extension (not to exceed 48 weeks). Patients in
the untreated group will not receive treatment.

Clinical efficacy will be assessed at regularly scheduled study visits, including functional
tests such as the six minute walk test. Patients in the treated group will undergo a muscle
biopsy at Baseline and a second muscle biopsy over the course of the study. Patients in the
untreated group will not undergo muscle biopsy.

Safety, including adverse event monitoring and routine laboratory assessments, will be
continuously monitored for all patients.

Inclusion Criteria:

- Male 7-16 years old

- Diagnosed with DMD, genotypically confirmed

- Stable dose of corticosteroids for at least 24 weeks

- Have intact right and left alternative upper muscle groups

- Mean 6MWT greater than 300m (primary analysis on 300 to 450 meters)

- Stable pulmonary and cardiac function: predicted FVC equal to or greater than 50% and
LVEF of greater than 50%

Exclusion Criteria:

- Previous treatment with drisapersen or any other RNA antisense agent or any gene
therapy within the last 6 months

- Participation in any other DMD interventional clinical study within 12 weeks

- Major surgery within 3 months

- Presence of other clinically significant illness

- Major change in the physical therapy regime within 3 months

Other inclusion/exclusion criteria apply.