A Study to Assess Vamorolone in Boys Ages 2 to <4 Years and 7 to <18 Years With Duchenne Muscular Dystrophy (DMD)

Prior treatment

• If 2 to \<4 years of age, subject is currently being treated or has received previous treatment with oral glucocorticoids or other immunosuppressive agents \[Notes: Past transient use of oral glucocorticoids or other oral immunosuppressive agents for no longer than 1 month cumulative, with last use at least 3 months prior to enrollment, will be considered for eligibility on a case-by-case basis, unless discontinued for intolerance. Inhaled and/or topical glucocorticoids are permitted if last use is at least 4 weeks prior to enrollment or if administered at stable dose beginning at least 4 weeks prior to enrollment and anticipated to be used at the stable dose regimen for the duration of the study\];
• Subject has used idebenone within 4 weeks prior to enrollment;
• Subject is taking (or has taken within 4 weeks prior to enrollment) herbal remedies and supplements which can impact muscle strength and function (e.g., Co-enzyme Q10, creatine, etc);
• Subject is taking (or has taken within 3 months prior to enrollment) any medication indicated for DMD, including Exondys51, Exondys53, Exondys45, Viltepso and Translarna;
• Subject has been administered a live attenuated vaccine within 14 days prior to the first dose of study medication;
• Subject is currently taking any other investigational drug or has taken any other investigational drug within 3 months prior to enrollment;
• Subject has previously been enrolled in the VBP15-006 study or any other vamorolone study.

Other illness

• 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 a history of primary hyperaldosteronism;
• Subject has evidence of symptomatic cardiomyopathy \[Note: Asymptomatic cardiac abnormality on investigation would not be exclusionary\];
• Subject has an allergy or hypersensitivity to the study medication or to any of its constituents;

Lab values

• Subject has used mineralocorticoid receptor agents, such as spironolactone, eplerenone, canrenone (canrenoate potassium), prorenone (prorenoate potassium), or mexrenone (mexrenoate potassium) within 4 weeks prior to enrollment;
• 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;

Other

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

• Subject's parent(s) or legal guardian(s) has (have) provided written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization, where applicable, prior to any study-related procedures; participants will be asked to give written or verbal assent according to local requirements;
• Subject has a centrally confirmed (by TRiNDS central genetic counselor\[s\]) diagnosis of DMD, 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 clinical picture consistent with typical DMD;
• Subject is male, 2 to \<4 years or 7 to \<18 years of age at time of enrollment in the study;
• If 7 to \<18 years of age and currently taking standard of care glucocorticoids for treatment of DMD, subject has been taking standard of care glucocorticoids at stable dose for at least 3 months prior to enrollment in the study, and will continue the same stable dose regimen through the date of the Baseline Day -1 Visit. \[Note: Inhaled and/or topical glucocorticoids are permitted if last use is at least 4 weeks prior to enrollment or if administered at stable dose beginning at least 4 weeks prior to enrollment and anticipated to be used at the stable dose regimen for the duration of the study\];
• If 7 to \<18 years of age, and not currently glucocorticoid-treated, subject has not received oral glucocorticoids or other oral immunosuppressive agents for at least 3 months prior to enrollment. \[Note: Inhaled and/or topical glucocorticoids are permitted if last use is at least 4 weeks prior to enrollment or if administered at stable dose beginning at least 4 weeks prior to enrollment and anticipated to be used at the stable dose regimen for the duration of the study\];
• 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. \[Notes: Serum gamma glutamyl transferase (GGT), creatinine, and total bilirubin all must be ≤ upper limit of the normal range at the Screening Visit. An abnormal vitamin D level that is considered clinically significant will not exclude a subject from participating\];
• 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 local laboratory from blood collected during the Screening Period; OR
  • Documentation, provided at the Screening Visit, that the subject has had 2 doses of varicella vaccine, with or without serologic evidence of immunity; the second of the 2 immunizations must have been given at least 14 days prior to assignment to a dose group;
• Subject and parent(s)/guardian(s) are willing and able to comply with scheduled visits, study drug administration plan, and study procedures.