A Study to Assess Dystrophin Levels in Participants With Nonsense Mutation Duchenne Muscular Dystrophy (nmDMD)

Inclusion Criteria:

- Evidence of signed and dated informed consent/assent document(s) indicating that the
participant (and/or his parent/legal guardian) has been informed of all pertinent
aspects of the trial.

- Phenotypic evidence of duchenne muscular dystrophy (DMD) based on the onset of
characteristic clinical symptoms or signs (for example, proximal muscle weakness,
waddling gait, and Gowers' maneuver) and an elevated serum creatine kinase (CK).
Medical documentation of phenotypic evidence of DMD needs to be provided upon request
by the Sponsor's medical monitor.

- Documentation of the presence of a nonsense point mutation in the dystrophin gene as
determined by gene sequencing. Review and approval of documentation by sponsor or
designee is required prior to enrollment.

- Willing to undergo muscle biopsy.

Exclusion Criteria:

- Ongoing intravenous (IV) aminoglycoside or IV vancomycin therapy.

- Known contra-indication to muscle biopsy (such as bleeding or clotting disorders).

- Prior or ongoing therapy with ataluren.

- Known hypersensitivity to any of the ingredients or excipients of the study drug (for
example, refined polydextrose, polyethylene glycol 3350, poloxamer 407, mannitol 25C,
crospovidone XL10, hydroxyethyl cellulose, colloidal silica, magnesium stearate).

- Exposure to another investigational drug within 2 months prior to start of study
treatment, or ongoing participation in any interventional clinical trial.

- Requirement for daytime ventilator assistance or any use of invasive mechanical
ventilation via tracheostomy. Evening non-invasive mechanical ventilation such as use
of bilevel positive airway pressure (Bi-PAP) therapy is allowed.

- Elevated serum creatinine or cystatin C levels at screening.

- Prior or ongoing medical condition (for example, concomitant illness, psychiatric
condition, behavioral disorder), medical history, physical findings or laboratory
abnormality that, in the investigator's opinion, could adversely affect the safety of
the participant, makes it unlikely that the course of treatment or follow-up would be
completed, or could impair the assessment of study results.