A Study to Evaluate the Safety and Tolerability of PF-06939926 Gene Therapy in Duchenne Muscular Dystrophy

Inclusion Criteria:

- Diagnosis of Duchenne muscular dystrophy confirmed by medical history and genetic
testing

- Body weight between 15 and 50 kg

- Receipt of glucocorticoids for 6 months and a stable daily dose for at least 3 months
prior to study entry

- Ability to rise from floor within seven (7) seconds and ability to walk

- Ability to tolerate magnetic resonance imaging (MRI) without sedation and with no
contraindications to these procedures

- Ability to tolerate muscle biopsies under anesthesia with no contraindications to
these procedures

Exclusion Criteria:

- Receipt of live attenuated vaccination within 3 months prior or exposure to a systemic
antiviral and/or interferon therapy within 30 days prior to receipt of PF-06939926

- Prior exposure to any gene therapy agent, including exon-skipping and missense agents

- Exposure to other investigational drugs within 30 days or 5 half-lives, whichever is
longer

- Neutralizing antibodies (NAb) against adeno-associated virus, serotype 9 (AAV9) or
pre-existing anti-dystrophin T-cell response

- Compromised cardiac function as indicated by a left ventricular ejection fraction of
less than 55% on cardiac MRI

- Inadequate hepatic or renal function or risk factors for autoimmune disease on
screening laboratory assessments.