Insights:Letter to the Duchenne Community: IGNITE DMD Phase I/II Clinical Trial and R&D Pipeline Development Update

Dear Duchenne Community,

This afternoon, we issued a press release providing updates on Solid’s business, including dosing as part of the IGNITE DMD Phase I/II clinical trial, and developments for our next generation gene therapy pipeline initiative SGT-003 and our collaboration with Ultragenyx. We are pleased to have made progress on these key strategic priorities and advance our mission of developing meaningful treatments for patients.

IGNITE DMD Clinical Trial Update

As previously reported, in April 2021, the eighth patient in IGNITE DMD, and fifth patient in the 2E14 vg/kg cohort, was treated with SGT-001. The patient experienced an SAE that was not unexpected and which we’re pleased to share has fully resolved.

Following dosing of two patients with our second-generation manufacturing process and clinical strategy, we conducted an extensive review of all clinical data, resulting in a strengthened risk mitigation plan including new patient management guidance which has been submitted to the FDA. Activities are underway to advance IGNITE DMD with the next patient dosing anticipated later this year.

No new drug-related safety findings have been identified in Patients 1 through 8 in post-dosing periods of 90-days to more than 3 years. We continue to follow dosed patients and collect data to support the potential benefit from dosing SGT-001.

R&D Pipeline Update

Preclinical activities progressed on our internally developed next-generation Duchenne microdystrophin gene transfer program, SGT-003, including proof of concept research; manufacturing, regulatory and clinical strategies; and development and validation of screening assays to support clinical dosing. We are targeting an IND submission for SGT-003 in early-2023.We’ve also made progress in our ongoing collaboration with Ultragenyx.

Upcoming Community Presentations

CureDuchenne FUTURES Conference: October 2021

Action Duchenne Annual Conference: November 2021

The team at Solid Biosciences would like to reiterate our continued dedication to the Duchenne community, and to express our gratitude for your unwavering support. The community has been the greatest driving force behind our dedication and commitment to advance meaningful treatments for patients.



Your Solid Biosciences Team