A Phase III Double-blind, Randomized, Placebo-Controlled Study Assessing the Efficacy, Safety and Tolerability of Idebenone in Patients With Duchenne Muscular Dystrophy Receiving Glucocorticoid Steroids

• Male patients with a 35% ≤ FVC ≤ 80% of predicted value at Screening and at Baseline and who, in the opinion of the investigator are in the respiratory function decline phase.

• Minimum 10 years old at Screening.

• Signed and dated Informed Consent Form.

• Documented diagnosis of DMD (severe dystrophinopathy) and clinical features consistent of typical DMD at diagnosis (i.e. documented delayed motor skills and muscle weakness by age 5 years). DMD should be confirmed by mutation analysis in the dystrophin gene or by substantially reduced levels of dystrophin protein (i.e. absent or \<5% of normal) on Western blot or immunostaining.

• Chronic use of systemic glucocorticoid steroids for DMD related conditions continuously for at least 12 months prior to Baseline without any dose adjustments on a mg/kg basis in the last 6 months (only dose adjustments determined by weight changes are allowed).

• Ability to provide reliable FVC values at Screening and Baseline, and reproducible within 15% (relative change) at Baseline compared to Screening.

• Patients assessed by the Investigator as willing and able to comply with the requirements of the study, possess the required cognitive abilities and are able to swallow study medication.

• Patients who prior to Screening have been immunized with 23-valent pneumococcal polysaccharide vaccine or any other pneumococcal polysaccharide vaccine as per national recommendations, as well as annually immunized with inactivated influenza vaccine.