A Study to Assess the Efficacy and Safety of MNK-1411 in Duchenne Muscular Dystrophy

Inclusion Criteria:

1. Participants must have a documented diagnosis of Duchenne Muscular Dystrophy (DMD)
confirmed by complete dystrophin deficiency (by immunofluorescence and/or immunoblot),
or identifiable mutation in the DMD gene where reading frame can be predicated as "out
of frame," or complete dystrophin gene sequencing consistent with DMD; AND in the
opinion of the Investigator, a typical clinical profile consistent with DMD.

2. Participants taking approved treatments for DMD (by a Health Authority) that target
dystrophin gene mutations (e.g., eteplirsen or ataluren) may be enrolled in the study
if they have been on a stable dose for 30 days prior to the first dose of study drug,
and plan to remain on that dose throughout the study.

Exclusion Criteria:

1. Participant has had previous systemic treatment with corticosteroids within 2 months
prior to the Screening Visit. Exception: In subjects who were down-titrated to a
physiological dose of corticosteroids (ie, 3mg/m2 of prednisone or deflazacort) a
maximum of 1 month of no greater than a physiological dose followed by 1 month
completely off corticosteroids prior to the Screening Visit will be acceptable for
study entry. Transient previous use of corticosteroids will be evaluated on a
case-by-case basis by the sponsor or designee. The use of topical or intra-articular
corticosteroids is permitted during the study

2. Participant is unable to complete the 10 meter Walk/Run test at the Screening and/or
Baseline Visit.

3. Participant has Type 1 or Type 2 diabetes mellitus.

4. Participant has a history of chronic active hepatitis including acute or chronic
hepatitis B, or acute or chronic hepatitis C.

5. Participant has a history of tuberculosis (TB) infection, any signs/symptoms of TB, or
any close contact with an individual with an active TB infection.

6. Participant has known immune compromised status (not related to disease/condition
under study), including but not limited to, individuals who have undergone organ
transplantation or who are known to be positive for the human immunodeficiency virus.