Sarepta’s letter to the FSHD community

On March 25, 2026, Sarepta shared the following letter to the FSHD Community:

Dear Members of the FSHD Community,

We are reaching out today for the first time to briefly introduce Sarepta and share an important update.

Sarepta has been dedicated to developing meaningful therapies for rare diseases, having brought forward four therapies to treat Duchenne. It is our work in neuromuscular disease that inspired us to expand our scientific pursuits with a belief that we could make a meaningful difference in other neuromuscular diseases.

We are very excited to work closely with the FSHD community and to advance research together. Specifically, Sarepta is advancing, SRP-1001 (formerly known as ARO-DUX4) which is being developed to reduce the production of a protein called DUX4, believed to play a central role in FSHD.

Earlier today, we shared first-in-human clinical data from this program. While these results are early, we want to communicate them transparently and clearly:

• The treatment showed a favorable safety and tolerability profile in this initial study;
• We observed encouraging delivery of the therapy to muscle tissue;
• There was evidence of suppression of genes regulated by DUX4; and
• We saw a rapid reduction in creatine kinase (CK) levels, a commonly used indicator of muscle injury.

These findings represent early signals, and much more work remains ahead to understand what this therapy may ultimately mean for people living with FSHD.

You may hear terms like “single ascending dose (SAD)” in which the investigational therapy is administered once and “multiple ascending dose (MAD)” studies in which the investigational therapy is given chronically. These are early-stage clinical trials designed primarily to evaluate safety, understand how the therapy behaves in the body, and help determine appropriate dosing for future studies. While they are not designed to demonstrate clinical benefit, they are an essential first step in the development process.

We are encouraged by these initial results and are planning the next phase of clinical research. This upcoming trial will explore higher dose levels of SRP-1001 to better understand its potential effects on the disease.

We will continue to work with the FSHD advocacy community and share additional updates as the program progresses.

If you are living with FSHD, or supporting someone who is, please know that we are committed to listening and learning from you as our work continues. We recognize the strength, resilience, and advocacy within this community, as too many rare diseases do not have treatments.

Your perspectives are essential in shaping how we move forward, and we hope that this early work is the beginning of a strong partnership. We look forward to staying connected and continuing this conversation in the months ahead.

If you have any questions or would like to connect with us, please reach out at: advocacy@sarepta.com.

Sincerely,

Wendy Erler

Senior Vice President, Patient Affairs

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Sarepta also released a press release with more information about their current projects including SRP-1001. You can read the press release here.