A Study of SGT-003 Gene Therapy in Duchenne Muscular Dystrophy

Prior treatment

• Prior or ongoing medical condition, medical history, or physical finding that in the Investigator's opinion could adversely affect the safety of the participant, make it unlikely that the course of treatment or follow-up would be completed, or could impair the assessment of study results.
• Current or prior treatment with an approved or investigational gene transfer drug or gene editing therapy.
• Exposure to vamorolone, givinostat, approved or investigational dystrophin- or disease-modifying drugs (such as eteplirsen, golodirsen, casimersen, viltolarsen, and ataluren), or another investigational drug for any indication within 6 months or 5 half-lives, whichever is longer, prior to enrollment.
• Major surgery within 3 months prior to recruitment or planned surgery any time during this study that would have the potential to interfere with the ability or performance on outcome measures.

Other illness

• History of severe hypersensitivity reactions, including anaphylaxis, to the product or its components.
• Any active infection.
• Known liver disease, evidence of active viral hepatitis, or abnormal liver function.
• Pulmonary function predictive of or requiring the use of daytime ventilatory support outside of acute illnesses.

Other

• Established clinical diagnosis of DMD that is associated with any deletion variant or variant predicted not to express exons 1 to 11, exons 42 to 45, or exons 57 to 69, inclusive, of the DMD gene as documented by a genetic report.
• Sponsor employees and their family members are ineligible to participate in this study.
• Abnormal renal function
• Clinically significant abnormalities of coagulation
• Impaired cardiovascular function

• Participant 7 to <12 years of age.
• Participant is able to understand and comply with all study procedures as appropriate by age and has a parent(s) or legal guardian(s) (i.e., legally authorized representative [LAR]) who is (are) able to understand and comply with the study procedure requirements. Be willing to provide informed assent and have an LAR(s) who is (are) willing to provide written informed consent for the participant to participate in the study.
• If participant is of reproductive potential, participant and partner of childbearing potential are willing to use 2 highly effective forms of contraception for 12 months following study drug administration.
• Participant is ambulatory. Ambulatory is defined as “being able to walk without the use of an assistive device.”
• Established clinical diagnosis of DMD and documented dystrophin gene mutation predictive of DMD phenotype.
• Negative for AAV antibodies.
• On a stable daily oral regimen of at least 0.5 mg/kg/day prednisone or 0.75 mg/kg/day deflazacort for at least 6 months prior to entering the study, allowing for weight-based dose modifications in accordance with clinical practice.
• Meet 10-meter walk/run time criteria.
• Meet time to rise from supine criteria.
• Participant has bodyweight ≤50 kg
• Participant is genetically male.