A Study to Assess Vamorolone in Boys With Duchenne Muscular Dystrophy (DMD)

This study will evaluate the safety and tolerability of a new steroid-like medication called
vamorolone in boys with DMD ages ≥ 4 years and < 7 years. Enrolled participants will take the
study medication for 14 days followed by a 14 day follow-up period. The potential
effectiveness of vamorolone in treating DMD will also be explored.

Inclusion Criteria:

1. Subject's parent or legal guardian has provided written informed consent/Health
Insurance Portability and Accountability Act (HIPAA) authorization prior to any
study-related procedures;

2. Subject has a confirmed (by Central Genetic Counselor) diagnosis of DMD as defined as:

1. Dystrophin immunofluorescence and/or immunoblot showing complete dystrophin
deficiency, and clinical picture consistent with typical DMD, OR

2. Identifiable mutation within the DMD gene (deletion/duplication of one or more
exons) where reading frame can be predicted as 'out-of-frame', and clinical
picture consistent with typical DMD, OR

3. Complete dystrophin gene sequencing showing an alteration (point mutation,
duplication, other) that is expected to preclude production of the dystrophin
protein (i.e. nonsense mutation, deletion/duplication leading to a downstream
stop codon), with a typical clinical picture of DMD;

3. Subject is ≥ 4 years and < 7 years of age at time of enrollment in the study;

4. Subject is able to complete the Time to Stand Test (TTSTAND) without assistance, as
assessed at the Screening and Baseline Visits;

5. Clinical laboratory test results are within the normal range at the Screening Visit,
or if abnormal, are not clinically significant, in the opinion of the Investigator.
(Note: Serum gamma glutamyl transferase [GGT], creatinine, and total bilirubin all
must be ≤ upper limit of the normal range at the Screening Visit);

6. Subject has evidence of chicken pox immunity as determined by presence of IgG
antibodies to varicella, as documented by a positive test result from the testing
laboratory at the Screening Visit; and

7. Subject and parent/guardian are willing and able to comply with scheduled visits,
study drug administration plan, and study procedures.

Exclusion Criteria:

1. Subject has current or history of major renal or hepatic impairment, diabetes mellitus
or immunosuppression;

2. Subject has current or history of chronic systemic fungal or viral infections;

3. Subject has had an acute illness within 4 weeks prior to the first dose of study
medication;

4. Subject has used mineralocorticoid receptor agents, such as spironolactone,
eplerenone, canrenone (canrenoate potassium), prorenone (prorenoate potassium),
mexrenone (mexrenoate potassium) within 4 weeks prior to the first dose of study
medication;

5. Subject has evidence of symptomatic cardiomyopathy. [Note: Asymptomatic cardiac
abnormality on investigation would not be exclusionary];

6. Subject is currently being treated or has received previous treatment with oral
glucocorticoids or other immunosuppressive agents. [Notes: Past transient use of oral
glucocorticoids or other oral immunosuppressive agents for no longer than 3 months
cumulative, with last use at least 3 months prior to first dose of study medication,
will be considered for eligibility on a case-by-case basis. Inhaled and/or topical
corticosteroids prescribed for an indication other than DMD are permitted but must be
administered at stable dose for at least 3 months prior to study drug administration];

7. Subject has used idebenone within 4 weeks prior to the first dose of study medication;

8. Subject has an allergy or hypersensitivity to the study medication or to any of its
constituents;

9. Subject has severe behavioral or cognitive problems that preclude participation in the
study, in the opinion of the Investigator;

10. Subject has previous or ongoing medical condition, medical history, physical findings
or laboratory abnormalities that could affect safety, make it unlikely that treatment
and follow-up will be correctly completed or impair the assessment of study results,
in the opinion of the Investigator;

11. Subject is taking any other investigational drug currently or has taken any other
investigational drug within 3 months prior to the start of study treatment; or

12. Subject has previously been enrolled in the study.