Oral Ifetroban in Subjects with Duchenne Muscular Dystrophy

Inclusion criteria:

1. Males 7 years of age and older with the diagnosis of DMD, defined as phenotypeconsistent with DMD and either positive genotype, first degree relative withpositive genotype, or confirmatory muscle biopsy.

2. Stable dose of oral corticosteroids for at least 8 weeks or has not receivedcorticosteroids for at least 30 days.

3. Stable cardiac function defined as change in left ventricular ejection fraction (LVEF) of < 15% and no heart failure admission over the last 12 months; LVEF 35% orgreater by cine cardiac magnetic resonance imaging (MRI) or echocardiography;myocardial damage in one or more left ventricular segments evident by lategadolinium enhancement allowed; concurrent angiotensin-converting enzyme inhibitors (ACEI), beta-blocker (BB) or angiotensin receptor blocker (ARB) therapy allowed (selection of which dictated by clinical care) if started three months or greaterfrom first dose of IMP without change in dose. Aldosterone receptor antagonists (eg.Spironolactone or eplerenone) allowed if started 12 months or greater from firstdose of Investigational Medicinal Product (IMP). No changes throughout the studyallowed, except in the event of a decline in left ventricular ejection fraction (LVEF) >5% following the baseline CMR as measured by a subsequent CMR at the samecenter. Should this occur, changes in cardiac medications are allowed on the study. a. Late-stage cohort: Subjects are eligible for the late-stage cohort if the subjecthas: i. LVEF 35%-45% by cine cardiac magnetic resonance imaging (MRI) orechocardiography or ii. historically documented LVEF 35%-45% by cine cardiacmagnetic resonance imaging (MRI) or echocardiography and if their baseline MRI isless than 50%.

4. Subjects aged 18 years and older, informed consent obtained directly. For subjectsages 7-17 years old (yo), both assent from the subject and permission from a parentor guardian.

Exclusion criteria:

1. Clinically significant illness other than DMD

2. Clinically significant laboratory abnormality not associated with DMD

3. Major surgery within six weeks prior to the first dose of study drug, or plannedsurgery during this study which would interfere with the ability to perform studyprocedures

4. Require antiarrhythmic therapy and/or initiation of diuretic therapy for managementof acute heart failure in the last 6 months

5. A LVEF of < 35% by Cardiac Magnetic Resonance Imaging (CMR) and/or fractionalshortening of < 15% based on echocardiography (ECHO) during screening

6. A known bleeding disorder or has received anticoagulant treatment within 2 weeks ofstudy entry

7. Allergy to gadolinium contrast or known renal insufficiency defined as abnormalcystatin C or creatinine above the upper limit of normal for age. The male serumreference ranges as follows:

• Age 7-9 years - 0.2-0.6 mg/dL

• Age 10-11 years - 0.3-0.7 mg/dL

• Age 12-13 years - 0.4-0.8 mg/dL

• Age 14-15 years - 0.5-0.9 mg/dL

• Age 16 years or older - 0.8-1.3 mg/dL

8. Non-MR compatible implants (e.g. neurostimulator, automatic implantablecardioverter-defibrillator [AICD])

9. Subjects who participated in a therapeutic clinical trial within 30 days or fivehalf-lives (whichever is longer) of study entry

10. Any other condition that could interfere with the subject's participation