Phase III Study of Idebenone in Duchenne Muscular Dystrophy (DMD)

Inclusion Criteria:

1. Patients 10 - 18 years of age at Baseline.

2. Signed and dated informed consent.

3. Documented diagnosis of DMD or severe dystrophinopathy and clinical featuresconsistent of typical DMD at diagnosis (i.e. documented delayed motor skills andmuscle weakness by age 5 years). DMD should be confirmed by mutation analysis in thedystrophin gene or by substantially reduced levels of dystrophin protein (i.e. absentor <5% of normal) on Western blot or immunostain.

4. Ability to provide reliable and reproducible repeat PEF within 15% of the firstassessment (i.e. Baseline vs. Screening).

5. Patients assessed by the investigator as willing and able to comply with therequirements of the study, possess the required cognitive abilities and are able toswallow study medication.

Exclusion Criteria:

1. Patients dependent on assisted ventilation at Screening and/or Baseline (defined asnon-invasive nocturnal ventilation, daytime non-invasive ventilation or continuousinvasive ventilation).

2. Patients with documented DMD-related hypoventilation for which assisted ventilation isneeded according to current standard of care guidelines (e.g. FVC< 30%) or is requiredin the opinion of the Investigator.

3. Patients with a percent predicted PEF > 80% at Baseline.

4. Patients unable to form a mouth seal to allow precise respiratory flow measurementsand mouth pressures.

5. Symptomatic heart failure (high probability of death within one year of Baseline)and/or symptomatic ventricular arrhythmias.

6. Participation in the previous Phase II or Phase II Extension study (SNT-II-001 orSNT-II-001-E) for idebenone.

7. Participation in any other therapeutic trial and/or intake of any investigational drugwithin 90 days prior to Baseline.

8. Use of carnitine, creatine, glutamine, oxatomide, or any herbal medicines within 30days prior to Baseline.

9. Use of coenzyme Q10 or vitamin E (if taken at a dose of 5 times above the dailyphysiological requirement) within 30 days prior to Baseline.

10. Any previous use of idebenone.

11. Any concomitant medication with a depressive or stimulating effect on respiration orthe respiratory tract.

12. Planned or expected spinal fixation surgery during the study period (as judged by theinvestigator).

13. Asthma, bronchitis/COPD, bronchiectasis, emphysema, pneumonia or the presence of anyother non-DMD respiratory illness that affects PEF.

14. Chronic use of beta-2 agonists or any use of other bronchodilating medication (e.g.inhaled steroids, sympathomimetics, anticholinergics). Please note: Chronic use if defined as a daily intake for more than 14 days.

15. Moderate or severe hepatic impairment or severe renal impairment.

16. Prior or ongoing medical condition or laboratory abnormality that in theInvestigator's opinion could adversely affect the safety of the subject. Please note: Patients who suffer from a severe, unstable condition including (but notlimited to) cancer, auto-immune diseases, haematological diseases, metabolic disordersor immunodeficiencies, and who are at risk of an aggravation unrelated to the studycondition, can only be included in the study if accepted in writing by the Sponsor'sMedical Monitor.

17. Relevant history of or current drug or alcohol abuse or use of any tobacco/marijuanaproducts/smoking

18. Known individual hypersensitivity to idebenone or to any of the ingredients/excipientsof the study medication

19. Systemic glucocorticoid therapy

20. Chronic use of systemic glucocorticoid therapy for DMD related conditions within 12 months of Baseline (the "12 month non-use period")

21. More than 2 rounds of acute systemic glucocorticoid burst therapy (of ≤2 weekduration) for non-DMD related conditions within the 12 month non-use period

22. Use of any round of systemic glucocorticoid burst therapy of longer than 2 weeksduration within the 12 month non-use period

23. Use of systemic glucocorticoid burst therapy less than 8 weeks prior to baseline