A Phase 2 Study to Evaluate the Safety, Efficacy, Pharmacokinetics and Pharmacodynamics of PF-06252616 in Duchenne Muscular Dystrophy

Inclusion Criteria:

1. Ambulatory boys age 6 to <16 years old (at the time of randomization), diagnosed with
DMD. Diagnosis must be confirmed in subject's medical history and by genetic testing
obtained during routine clinical care for diagnostic purposes as reported from an
appropriate regulated laboratory using a clinically validated genetic test (genetic
testing is not provided by the sponsor).

2. Subjects who are able to perform the 4 stair climb in > or = 0.33 but < or =1.6
stairs/second.

3. Subjects must be receiving glucocorticosteroids for a minimum of 6 months prior to
signing informed consent. There should be no significant change (>0.2 mg/kg) in dosage
or dose regimen (not related to body weight change) for at least 3 months immediately
prior to signing the informed consent and a reasonable expectation that dosage and
dosing regimen will not change significantly for the duration of the study.

4. Adequate hepatic and renal function on screening laboratory assessments.

5. No underlying disposition for iron accumulation on screening laboratory assessments.

6. Iron content estimate on the screening liver MRI is within the normal range.

Exclusion Criteria:

1. Subjects with known cognitive impairment or behavioral issues that would impede the
ability to follow instructions.

2. History of major surgical procedure within 6 weeks of signing the informed consent or
planned surgery during the study.

3. Any injury which may impact functional testing. Previous injuries must be fully healed
prior to consenting. Prior lower limb fractures must be fully healed and at least 3
months from injury date.

4. Presence or history of other musculoskeletal or neurologic disease or somatic disorder
not related to DMD including pulmonary and cardiac disease.

5. Compromised cardiac function (left ventricular ejection fraction <55% as determined on
a screening cardiac MRI or echocardiogram). Subjects may be receiving ACE (angiotensin
converting enzyme) inhibitors or beta blockers, ARB (angiotensin II receptor
antagonist) or aldosterone blocker/thiazide diuretic; however they must have initiated
treatment more than 3 months prior to screening to ensure stable therapy.

6. Evidence or history of clinically significant hematological, renal, endocrine,
pulmonary, gastrointestinal, cardiovascular (including uncontrolled hypertension),
hepatic, neurologic, or allergic disease (including drug allergies, but excluding
untreated, asymptomatic, seasonal allergies at time of dosing).

7. Documented history of iron overload including hemochromatosis, beta thalassemia major,
beta thalassemia intermedia or hemolytic anemia.

8. Unwilling or unable (eg, metal implants, requires sedation) to undergo examination
with closed MRI without sedation.

9. Participation in other studies involving investigational drug(s) for a minimum of 30
days or within 5 half lives (whichever is longer) prior to signing the informed
consent and/or during study participation.

10. Current or prior treatment with anti-myostatin, exon skipping, nonsense mutation
targeted therapies ever or more than 30 days of treatment with utrophin modifiers and
treatment with utrophin modifiers within 30 days prior ot signing the informed consent
and/or during study participation.

11. Current or prior treatment within the past 3 months with androgens or human growth
hormone.

12. Current treatment with immunosuppressant therapies (other than glucocorticoid
steroids), aminoglycosides (eg, gentamicin), multi vitamins with iron and iron
supplements and other investigational therapies (including idebenone).