Inclusion Criteria:
1. Subject or 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;
2. Subject is a male and has a confirmed diagnosis of Becker dystrophy as defined as:
1. Identifiable mutation within the DMD gene (deletion/duplication of one or more exons), where reading frame can be predicted as 'in-frame', and clinical picture consistent with Becker dystrophy, OR
2. Complete dystrophin gene sequencing showing an alteration (small mutation, duplication, other) that is expected to allow production of an internally deleted dystrophin protein, with a typical clinical picture of Becker dystrophy;
3. Subject is ≥ 18 years of age and \<65 years of age at time of informed consent;
4. Subject is able to perform the timed run/walk 10 meters assessment (TTRW) in ≤ 30 sec at screening; assistive devices, cane or walker, are allowed.
5. Subject has an NSAA score ≤ 32 at screening.
6. 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). While AST and ALT can be elevated due to disease of muscle or liver, the study PI will review any increases of AST or ALT. If above upper limit of normal (ULN), then study PI will assess whether the increases are likely of muscle origin to determine inclusion.
7. Subject has not received oral glucocorticoids or other oral immunosuppressive agents for at least 3 months prior to first administration of study medication. \[Note: Inhaled and/or topical glucocorticoids are permitted if last use is at least 4 weeks prior to first administration of study medication or if administered at stable dose beginning at least 4 weeks prior to first administration of study medication and anticipated to be used at the stable dose regimen for the duration of the study\];
8. Subject has evidence of chicken pox immunity as determined by:
1. 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
2. Documentation, provided at the Screening Visit, that the subject has received 2 doses of varicella vaccine, with or without serologic evidence of immunity, with the second of the 2 immunizations given at least 14 days prior to first administration of study medication;
9. Subject is willing and able to comply with scheduled visits, study medication administration plan, and study procedures.
10. Subject agrees to use barrier contraception methods during his participation in this study and for 30 days after the tapering dose is completed.
Exclusion Criteria:
1. Subject has current or history of major renal or hepatic impairment, uncontrolled diabetes mellitus (defined as a diagnosis of diabetes with random glucose more than 1.5x ULN at screening and the patient has symptoms of polyuria or polydipsia) 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), or mexrenone (mexrenoate potassium) within 4 weeks prior to administration of study medication;
5. Subject has evidence of symptomatic cardiomyopathy \[Note: Asymptomatic cardiac abnormality on investigation would not be exclusionary unless cardiac ejection fraction is less than 40%\];
6. Subject has an allergy or hypersensitivity to the study medication or to any of its constituents;
7. Subject has severe behavioral or cognitive problems that preclude participation in the study, in the opinion of the Investigator;
8. 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;
9. Subject is taking (or has taken within 4 weeks prior to first dose of study medication) herbal remedies and supplements which can impact muscle strength and function (e.g., Co-enzyme Q10, creatine, etc);
10. Subject has been administered a live attenuated vaccine within 14 days prior to the first dose of study medication;
11. Subject is currently taking any other investigational drug or has taken any other investigational drug within 3 months prior to first dose of study medication; or
12. Subject has previously been enrolled in the VBP15-BMD-001 study or any other vamorolone study.
