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

The main purposes of this study are to see if it is safe to use a new medication called vamorolone for more than two weeks in children with Duchenne muscular dystrophy (DMD), to see if vamorolone works for the treatment for DMD, and to see how any potential side effects compare to those seen in boys using steroids.

This study will evaluate if it is safe to use a new medication called vamorolone for more than two weeks in children with DMD, if boys with DMD who take the study medication have improved muscle function compared to boys with DMD in other studies who did not take any type of steroid, and to see if boys with DMD who take the study medication gain less weight compared to boys with DMD in a prior study who took another type of steroid called prednisone. Enrolled participants will take the study medication for 24 weeks.

Eligibility Criteria:
Inclusion Criteria:

1. Participant's parent or legal guardian has provided written informed consent/HIPAA authorization prior to any extension study-specific procedures;
2. Participant has previously completed study VBP15-002 up to and including the Week 4 Follow-up assessments within 8 weeks prior to enrollment; and
3. Participant and parent/guardian are willing and able to comply with scheduled visits, study drug administration plan, and study procedures.

Exclusion Criteria:

1. Participant had a serious or severe adverse event in study VBP15-002 that, in the opinion of the Investigator, was probably or definitely related to vamorolone use and precludes safe use of vamorolone for the subject in this study;
2. Participant has current or history of major renal or hepatic impairment, diabetes mellitus or immunosuppression;
3. Participant has current or history of chronic systemic fungal or viral infections;
4. Participant 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. Participant has evidence of symptomatic cardiomyopathy. \[Note: Asymptomatic cardiac abnormality on investigation would not be exclusionary\];
6. Participant 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. Participant has an allergy or hypersensitivity to the study medication or to any of its constituents;
9. Participant has severe behavioral or cognitive problems that preclude participation in the study, in the opinion of the Investigator;
10. Participant 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; or
11. Participant is currently taking any investigational drug, or has taken any investigational drug other than vamorolone within 3 months prior to the start of study treatment.

Note: Participants may be re-evaluated if ineligible due to a transient condition which would prevent the subject from participating