Solid Biosciences has shared a new letter to the Duchenne community providing updates on the development of SGT-003, the company’s investigational gene therapy for Duchenne.

Solid shared that the ongoing INSPIRE DUCHENNE Phase 1/2 clinical trial has dosed 53 patients ages 0 to 10 years old, including a 6-month-old child, who is the youngest known child dosed to date with a microdystrophin gene therapy. According to Solid, SGT-003 continues to be well tolerated and have a favorable safety profile. 

The company shared in May 2026 that it is moving forward with IMPACT DUCHENNE, a Phase 3 randomized, placebo-controlled clinical trial evaluating SGT-003. IMPACT DUCHENNE is currently enrolling patients at clinical sites in Australia and Canada, with clinical site expansion planned in the United States, United Kingdom and Europe in the coming months, subject to regulatory authorizations.

Solid indicated that together, INSPIRE DUCHENNE and IMPACT DUCHENNE are intended to support a potential accelerated approval in the U.S.. According to Solid, the company’s engagement with the U.S. Food & Drug Administration (FDA) remains ongoing, and the company expects to provide updates as regulatory discussions progress.

Kevin Flanigan, MD, from Nationwide Children’s Hospital and Principal Investigator in the Phase 1/2 INSPIRE DUCHENNE clinical trial, will be providing an overview of the SGT-003 development program at PPMD’s 2026 Annual Conference during the Gene Therapy: Today & Tomorrow session, taking place Friday, June 26, at 1:30 PM ET. This session will be recorded and made available to the public as soon as possible within two weeks of the live event.

Read Solid’s community letter:

Dear Duchenne Community,

As we come together for the annual Parent Project Muscular Dystrophy (PPMD) conference over the next several days, we want to begin by recognizing the strength, resilience and partnership of this community. We are grateful for the opportunity to connect with so many families, advocates and clinicians and to continue advancing this work together.

We are writing today to share an update on SGT-003, our investigational Duchenne gene therapy. Kevin Flanigan, MD, Robert F. and Edgar T. Wolfe Foundation Endowed Chair in Neuromuscular Research at Nationwide Children’s Hospital and Principal Investigator in our Phase 1/2 INSPIRE DUCHENNE clinical trial, will be providing an overview of our SGT-003 development program tomorrow at 1:30 PM ET during the Gene Therapy: Today & Tomorrow session. We encourage any families attending PPMD to tune into Dr. Flanigan’s presentation.

INSPIRE DUCHENNE Enrollment and Safety Update

We are pleased to share that 53 boys have been dosed with SGT-003 in the INSPIRE DUCHENNE clinical trial as of a June 22, 2026, enrollment cutoff. This includes patients across a broad pediatric age range from 0 to 10 years old, including a 6-month-old child. To our knowledge, this little boy is the youngest child dosed to date with a microdystrophin gene therapy. 

Safety remains a top priority for Solid, and we are encouraged by the profile observed to date. SGT-003 has continued to be generally well tolerated, and we have no observed cases of drug-induced liver injury (DILI), myocarditis, thrombotic microangiopathy (TMA) or atypical hemolytic uremic syndrome (aHUS).  Detailed safety as of a May 29, 2026, cutoff will be provided in Dr. Flanigan’s presentation.

All participants in the trial were treated using a steroid-only prophylactic immunomodulation regimen in tandem with SGT-003, a regimen design supported by rigorous safety monitoring with the intent to support tolerability while also minimizing treatment burden on patients and families.

As always, we remain committed to sharing safety information clearly and transparently so that families and clinicians can continue to make informed decisions.

Phase 3 Development and Global Program Advancement

As announced last month, we are now underway in IMPACT DUCHENNE, our Phase 3 randomized, placebo-controlled clinical trial evaluating SGT-003.

IMPACT DUCHENNE is currently enrolling patients at clinical sites in Australia and Canada, with clinical site expansion planned in the United States, United Kingdom and Europe in the coming months, subject to regulatory authorizations.

INSPIRE DUCHENNE and IMPACT DUCHENNE have been designed as part of an integrated clinical development program with the intention of supporting global regulatory authorizations, including potential accelerated approval in the United States. Together, these trials are intended to build a comprehensive understanding of SGT-003’s safety and biomarker profile, in addition to its clinical effect.

Our engagement with the U.S. Food & Drug Administration (FDA) remains ongoing, and we expect to provide an update as discussions progress.

Our Commitment to the Community

We are encouraged by our progress to date and remain focused on advancing SGT-003 thoughtfully, responsibly and with urgency.

We would like to express our deepest gratitude to the boys and families participating in clinical research. Your courage, trust and commitment make our work possible. We are equally grateful to the clinical teams and partners who support these efforts every day.

As we gather at PPMD this weekend and continue these important conversations, we remain fully committed to the Duchenne community and to our shared goal of advancing meaningful treatment options.

We are humbled and thankful for your ongoing partnership.

With gratitude,
Annie Ganot
Co-founder & Head of Patient Advocacy
Solid Biosciences