Duchenne Action Month 2025: Looking Back at News and Expert Insights

According to Parent Project Muscular Dystrophy, Duchenne muscular dystrophy, which causes progressive muscle weakness, constitutes the most common form of muscular dystrophy in children. The condition primarily affects boys, with around 1 in 5,000 boys currently living with DMD. Although no cure for DMD is available, a number of new transformative treatment options are currently under development or have recently reached commercialization.

An important area of interest for new therapeutic development in DMD is cell and gene therapy, along with other advanced modalities such as RNA therapy. In honor of Duchenne Action Month, observed annually in September by the patient and clinician communities, and following up on World Duchenne Day, held every year on September 7, CGTLive® is taking a look back at some of our news and interviews on the topic of DMD from the past few months. Click the "READ MORE" buttons for more details and information about each item.

September 10, 2025 — Patients with Duchenne muscular dystrophy (DMD) treated with Avidity Biosciences' antibody-oligonucleotide conjugate delpacibart zotadirsen (also known as del-zota), which consists of an anti–transferrin receptor 1 (TfR1) antibody conjugated to an exon 44–skipping phosphorodiamidate-morpholino conjugate (PMO), have shown functional improvements.

The findings come from patients with DMD with exon 44 skipping (DMD44) treated in the phase 1/2 EXPLORE44 clinical trial (NCT05670730) and the phase 2 EXPLORE44OLE trial (NCT06244082). The group includes 12 ambulatory and 5 nonambulatory patients who have at least 1 year of follow-up. Results were compared with baseline and natural history data.

On the Performance of Upper Limb 2.0 (PUL2) test, patients treated with del-zota (n = 17) showed a 1.5-point improvement from baseline whereas natural history patients (n = 27) showed a 0.7-point decline from baseline. Avidity noted that for the patients treated with del-zota, similar improvements on PUL2 were seen for ambulatory and nonambulatory patients.

September 9, 2025 — Following the FDA’s public release of the full complete response letter (CRL) that it issued to Capricor Therapeutics for the company’s biologics license application (BLA) for deramiocel, an investigational allogeneic cardiosphere-derived cell therapy intended for the treatment of DMD cardiomyopathy, Capricor has responded by publishing its full response to the agency.

Capricor stated that it was not notified in advance by the FDA that the latter would be publishing the CRL publicly on its website. Furthermore, the FDA did not publish Capricor’s response to the CRL, which, according to the company, provides clarifications on the feedback received and insight on its proposed plans to address remaining issues. As such, Capricor published its response to the CRL on its own website.

“Transparency is vital in regulatory communications, especially when patients are waiting for therapies with the potential to alter the course of devastating diseases such as Duchenne muscular dystrophy,” Linda Marbán, PhD, CEO of Capricor, said in a statement. “Our focus remains on working closely with the FDA to resolve the outstanding issues and to advance deramiocel toward approval. While we respect the FDA’s process, we believe it is important that the public has visibility into both the CRL and our detailed written response submitted to the agency. We are now awaiting the official minutes from our recent Type A meeting with the FDA review team, expected to be issued later this quarter, which will help define the next steps in our regulatory pathway. Looking ahead, we expect top-line HOPE-3 data in the fourth quarter of 2025, and our discussions with the FDA have centered on how these data will inform and support the timing of our BLA resubmission.”

July 30, 2025 — The FDA has recommended that Sarepta Therapeutics remove its voluntary hold on United States shipments of DMD gene therapy delandistrogene moxeparvovec-rokl (marketed as Elevidys) for patients who are ambulatory.

In a press release announcing the recommendation, the FDA also stated that it has concluded its investigation of the death an 8-year-old boy who was treated with Elevidys in Brazil and died on June 7, 2025. The agency stated that it has deemed the boy’s death was not related to the Elevidys product.

Although the hold on shipments for Elevidys was voluntary, the FDA had informally requested that Sarepta suspend all shipments of the gene therapy product earlier in July. Initially, the company made a public statement that it would not be complying with the request, acknowledging that it had previously paused shipments to patients who are nonambulatory, but would continue to ship the product to patients who are ambulatory. The company justified its decision on the basis of a “comprehensive scientific interpretation of the data” that did not indicate any new or changed safety signals for Elevidys in ambulant patients.

July 23, 2025 — In recent years substantial progress has been made in the field of Duchenne muscular dystrophy (DMD) with the introduction of gene therapy and exon skipping therapies. Although these therapies provide transformative new treatment effects, however, they are not curative and leave room for improvement.In an interview with CGTLive®'s sister site, NeurologyLive®, Jeffrey Chamberlain, PhD, Professor of Neurology and Medical Genetics and McCaw Endowed Chair for Muscular Dystrophy at the University of Washington, discussed future avenues for improving DMD gene therapy and exon skipping. He drew attention various considerations, such as delivery vectors, the use of microdystrophin, and treatment timing.

May 19, 2025 — Sarepta Therapeutics’ delandistrogene moxeparvovec-rokl (marketed as Elevidys) is an FDA-approved gene therapy intended to treat DMD. A notable case study of a patient treated with Elevidys was presented by Ben Samelson-Jones, MD, PhD, an assistant professor of pediatric hematology at Perelman School of Medicine, University of Pennsylvania, and the associate director of clinical in vivo gene therapy at Children’s Hospital of Philadelphia (CHOP), at the American Society of Gene & Cell Therapy (ASGCT) 28th Annual Meeting, held May 13 to 17, 2024, in New Orleans, LA.

CGTLive® spoke with Samelson-Jones at the conference to learn about the case and its implications. Samelson-Jones pointed out that the case emphasizes the importance of conservative management.