AAN releases Evidence in Focus Article on new gene therapy for Duchenne muscular dystrophy

To help neurologists, clinicians and families understand the current evidence for a new gene therapy for Duchenne muscular dystrophy called delandistrogene moxeparvovec, the American Academy of Neurology (AAN) has issued an Evidence in Focus article, published May 14, 2025, online in Neurology^®.

AAN Evidence in Focus articles highlight the strength of the current evidence for new therapies for neurological conditions. Their purpose is not to provide recommendations for practice, but rather to provide an overview of the available data and a framework to support care. This article reviews evidence available for the efficacy and safety of delandistrogene moxeparvovec.

Duchenne muscular dystrophy, which primarily affects those of male sex, is an inherited genetic condition that causes muscle weakness. Symptoms usually appear between the ages of two and four and become more severe over time. People with this disease are missing a protein called dystrophin that helps maintain muscle health.

Delandistrogene moxeparvovec is a one-time gene therapy infusion approved by the Food and Drug Administration in June 2024 for use in those age four and older. The therapy uses a disabled virus to inject a miniaturized version of the gene that makes a small form of dystrophin into the muscle cells.

"While the prognosis for individuals with Duchenne muscular dystrophy has improved in recent decades thanks to corticosteroids and supportive care, significant functional limitations persist for those affected by the condition," said author Maryam Oskoui, MD, of McGill University in Quebec, Canada, and a Fellow of the American Academy of Neurology. "Recent advances in genetic therapies for this disease have brought hope to many, with several gene replacement therapies currently being evaluated in clinical trials, and one-delandistrogene moxeparvovec-already approved by the FDA. This Evidence in Focus article offers a timely and objective overview of the existing data and explores key clinical considerations surrounding the use of delandistrogene moxeparvovec. However, it is important to acknowledge that evidence supporting its potential effectiveness and safety remains limited."

The Evidence in Focus article states that both Class I studies of delandistrogene moxeparvovec failed to meet their primary outcome measures related to motor function, a person's ability to control movements.

Research showed the therapy may possibly slow the decline of other measures of motor function by a small amount. However, the article states it is difficult to know how much of this benefit is due to the gene therapy and how much may additionally be influenced by the high dose steroid medications that are taken with the therapy.

The article highlights that neurologists and other clinicians treating people with Duchenne muscular dystrophy should be aware of the limitations of this treatment and the need to monitor and counsel patients for side effects including muscle inflammation and related muscle pain and weakness, heart inflammation, low blood platelet count, liver injury and possible death.

Based on the current research, it has yet to be determined whether the therapy will extend a person's life or improve their quality of life. The therapy does not cure Duchenne muscular dystrophy.

Those considering this gene therapy should ask their doctor if insurance will pay for the treatment. The one-time infusion costs $3.2 million, not including other costs related to the infusion in the hospital and the close follow-up required.

"Additional clinical studies that closely follow people receiving this treatment are essential to determine the short- and long-term effectiveness of delandistrogene moxeparvovec and to inform the understanding of the benefits and risks of this therapy across a person's lifetime," said author James J. Dowling, MD, PhD, of the University of Pennsylvania in Philadelphia, and a member of the American Academy of Neurology.

The article was developed with financial support from the American Academy of Neurology.