Dose-Titration and Open-label Extension Study of SRP-4045 in Advanced Stage Duchenne Muscular Dystrophy (DMD) Patients

This is a randomized, placebo-controlled dose-titration study to assess safety, tolerability,
and pharmacokinetics of 4 dose levels of SRP-4045 in genotypically confirmed advanced-stage
DMD patients with deletions amenable to exon 45 skipping.

After completion of the dose-titration portion of the study and SRP-4045 is determined to be
safe, all patients will be evaluated on open-label SRP-4045 for the duration of the study.

Safety, including adverse event monitoring, routine laboratory assessments, and cardiac
testing will be monitored through the duration of the dose-titration and open-label portions
of the study.

Clinical efficacy will be assessed at regularly scheduled study visits via quality of life
questionnaires and tests of pulmonary and upper extremity function through the duration of
the dose-titration and open-label portions of the trial.

Inclusion Criteria:

- Genotypically confirmed DMD (amenable to exon 45 skipping).

- Stable cardiac and pulmonary function.

- Limited or no ambulation.

- On a stable dose of oral corticosteroids for at least 24 weeks OR has not received
corticosteroids for at least 24 weeks.

Exclusion Criteria:

- Current or previous treatment with the experimental agents SMT C1100 (BMN-195) or
PRO045.

- Other experimental treatment in the past 12 weeks.

- If on cardiac medication, must be on a stable dose for the past 12 weeks.

- Major surgery within the past 3 months.

Other inclusion/exclusion criteria apply.