A Study of SGT-003 Gene Therapy in Ambulant Males With Duchenne Muscular Dystrophy (IMPACT DUCHENNE)

A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled Study to Investigate the Efficacy of a Single Intravenous Dose of SGT-003 in Ambulant Males With Duchenne Muscular Dystrophy

This is a Phase 3, double-blind, placebo-controlled study with the primary objective of evaluating the efficacy of a single IV infusion of SGT-003 in pediatric ambulant male participants with DMD. The secondary objectives include the evaluation of additional efficacy and safety outcomes. The study will be divided into 2 parts. Participants will be randomized 1:1 to either SGT-003 in Part 1 followed by placebo in Part 2 or to placebo in Part 1 followed by SGT-003 in Part 2. Participants will continue to be monitored in long term follow up (LTFU) for at least 5 years from their SGT-003 dosing date.

Study Overview

• Status: Recruiting
• Conditions: Duchenne Muscular Dystrophy
• Intervention / Treatment: Drug: Placebo; Drug: SGT-003

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Solid Bio Clinical Trials; Phone Number: 6173374680; Email: clinicaltrials@solidbio.com

Study Locations

• Australia
  • New South Wales
    • Sydney, New South Wales, Australia
      • Recruiting
      • The Children's Hospital of Westmead
      • Principal Investigator: Michelle Lorentzos, MD
      • Contact: CHW CRC clinical trials team; Phone Number: (02) 7825 1387; Email: SCHN-ClinicalTrials@health.nsw.gov.au
• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada
      • Recruiting
      • BC Children's Hospital
      • Principal Investigator: Kathryn Selby, MD
      • Contact: Nela Martic; Phone Number: 6549 604-875-2345; Email: nmartic3@cw.bc.ca
• United States
  • Arkansas
    • Little Rock, Arkansas, United States, 72202
      • Not yet recruiting
      • Arkansas Children's Hospital
      • Contact: Amber Kellogg, RN; Email: KelloggA@archildrens.org
  • Texas
    • Flower Mound, Texas, United States, 75082
      • Not yet recruiting
      • Neurology Rare Disease Center
      • Contact: Jennifer Avelar, CRC; Email: Research@neuromdcenter.com
  • Virginia
    • Norfolk, Virginia, United States, 23510
      • Not yet recruiting
      • Children's Hospital of The King's Daughters
      • Contact: Jennifer Beachum, BSHS; Email: Proud.research@chkd.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Participant is ambulatory.
• Established clinical diagnosis of DMD and documented DMD gene mutation predictive of DMD phenotype.
• Negative for antibodies against adeno-associated virus.
• On a stable daily oral regimen of at least 0.5 mg/kg/day prednisone or 0.75 milligrams per kilogram per day (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.

Exclusion Criteria:

• 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.
• 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.

Other Inclusion/Exclusion criteria to be applied as per protocol.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: SGT-003 followed by Placebo; Enrolled participants will receive a single intravenous (IV) infusion of SGT-003 in Part 1 and a single IV infusion of matching Placebo in Part 2.	Drug: Placebo; IV infusion; Drug: SGT-003; Adeno-associated virus (AAV)-based gene therapy that delivers a codon-optimized and CpG island-minimized human 5-repeat microdystrophin (h-μD5)
Experimental: Placebo followed by SGT-003; Enrolled participants will receive a single intravenous (IV) infusion of matching Placebo in Part 1 and a single IV infusion of SGT-003 in Part 2.	Drug: Placebo; IV infusion; Drug: SGT-003; Adeno-associated virus (AAV)-based gene therapy that delivers a codon-optimized and CpG island-minimized human 5-repeat microdystrophin (h-μD5)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Change From Baseline in Time to Rise (TTR) from Supine Velocity (rise/s) at Day 540	Baseline, Day 540

Secondary Outcome Measures

Outcome Measure	Time Frame
Change From Baseline in Stride Velocity 95th Centile (SV95C) (m/s) at Day 540	Baseline, Day 540
Change From Baseline in North Star Ambulatory Assessment (NSAA) total score at Day 540	Baseline, Day 540
Cumulative Loss of Function in NSAA Items at Day 540	At Day 540
Change From Baseline in Microdystrophin Protein Levels by western blot (% of normal dystrophin) at Day 90	Baseline, Day 90
Change From Baseline in Microdystrophin Tissue Distribution by Immunofluorescence (% positive fibers) at Day 90	Baseline, Day 90
Change from baseline in Percent Predicted Forced Vital Capacity (FVC) at Day 540	Baseline, Day 540
Change from baseline in Percent Predicted Peak Expiratory Flow (PEF) at Day 540	Baseline, Day 540
Change from baseline in Percent Predicted Forced Expiratory Volume in 1 second (FEV1) at Day 540	Baseline, Day 540
Change from baseline in the Pediatric Outcomes Data Collection Instrument (PODCI) Global score at Day 540	Baseline, Day 540
Change From Baseline in 4-Stair Climb (4SC) Velocity (tasks/s) at Day 540	Baseline, Day 540
Change From Baseline in 10-meter Walk/Run (10MWR) Velocity (m/s) at Day 540	Baseline, Day 540
Number of Participants with Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs), Adverse Events of special interest (AESIs), and clinically significant changes in Electrocardiogram (ECG) and Echocardiography (ECHO)	From first dose up to Day 540

Collaborators and Investigators

• Sponsor: Solid Biosciences Inc.

Study record dates

Study Major Dates

• Study Start (Actual): October 22, 2025
• Primary Completion (Estimated): January 1, 2029
• Study Completion (Estimated): January 1, 2034

Study Registration Dates

• First Submitted: August 29, 2025
• First Submitted That Met QC Criteria: August 29, 2025
• First Posted (Actual): September 8, 2025

Study Record Updates

• Last Update Posted (Actual): June 2, 2026
• Last Update Submitted That Met QC Criteria: June 1, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Duchenne Muscular Dystrophy (DMD); SGT-003; adeno-associated virus (AAV); IMPACT DUCHENNE
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Nervous System Diseases; Muscular Diseases; Neuromuscular Diseases; Genetic Diseases, Inborn; Genetic Diseases, X-Linked; Muscular Disorders, Atrophic; Muscular Dystrophies; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Muscular Dystrophy, Duchenne; Substandard Drugs; Pharmaceutical Preparations; Counterfeit Drugs
• Other Study ID Numbers: SGT-003-301; 2025-522949-22 (EudraCT Number); 1013075 (Other Identifier: IRAS)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No