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

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

• Dystrophin immunofluorescence and/or immunoblot showing complete dystrophin deficiency, and clinical picture consistent with typical DMD, OR
• 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
• 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;
• Subject is ≥ 4 years and < 7 years of age at time of enrollment in the study;
• Subject is able to complete the Time to Stand Test (TTSTAND) without assistance, as assessed at the Screening and Baseline Visits;
• 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);
• 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
• Subject and parent/guardian are willing and able to comply with scheduled visits, study drug administration plan, and study procedures.

Exclusion criteria

• Subject has current or history of major renal or hepatic impairment, diabetes mellitus or immunosuppression;
• Subject has current or history of chronic systemic fungal or viral infections;
• Subject has had an acute illness within 4 weeks prior to the first dose of study medication;
• 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;
• Subject has evidence of symptomatic cardiomyopathy. [Note: Asymptomatic cardiac abnormality on investigation would not be exclusionary];
• 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];
• Subject has used idebenone within 4 weeks prior to the first dose of study medication;
• Subject has an allergy or hypersensitivity to the study medication or to any of its constituents;
• Subject has severe behavioral or cognitive problems that preclude participation in the study, in the opinion of the Investigator;
• 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;
• 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
• Subject has previously been enrolled in the study.