Letter to the Duchenne Community: IGNITE DMD Phase I/II Clinical Trial and 2022 Priorities

Dear Duchenne Community,

As we embark on a new year, we are pleased to share an update on IGNITE DMD, our ongoing Phase I/II clinical trial, as well as progress in expanding our pipeline of Duchenne treatments. Earlier this week we shared this announcement and provided a business update at the Annual JP Morgan Healthcare Conference this morning.

IGNITE DMD Phase I/II Clinical Trial for SGT-001

We continue to work with urgency and scientific rigor to advance SGT-001. We are pleased to share that we successfully dosed the ninth patient in the IGNITE DMD study in November 2021 utilizing our updated risk mitigation strategy and second-generation manufacturing process. We plan to continue dosing in 2022, employing these strategies to enhance patient safety. We look forward to sharing additional expression via immunofluorescence and Western blot, functional, pulmonary and patient reported outcomes data from the clinical trial in the first half of this year.

SGT-003

We also shared pre-clinical data on SGT-003, next-generation Duchenne microdystrophin gene transfer program that utilizes a rationally designed AAV-based vector to deliver the same proprietary and differentiated nNOS containing microdystrophin construct that is incorporated into SGT-001.

The additional data on SGT-003 demonstrates increased protein expression and more targeted biodistribution compared to AAV9 in DMD mdx mice. The data reflected multiple-fold increases in skeletal and cardiac muscle biodistribution with decreased levels in the liver to ultimately improve safety.