Duchenne muscular dystrophy is a genetic condition that prevents the body from making dystrophin, a protein that muscles need to stay strong and function well. To help restore some of the dystrophin missing in individuals with Duchenne, a gene therapy called Delandistrogene moxeparovec (also known as SRP-9001) was developed by Sarepta Therapeutics. Gene therapy works by delivering specific genetic instructions into the body to make a shorter version of the protein dystrophin.
To deliver these instructions into the body, gene therapies use a carrier (also called a vector) in this case, one called rAAVrh74. However, some boys with Duchenne already have antibodies (natural defenses) against this carrier, which means their immune system would block the therapy before it could work, making them ineligible to receive this treatment.
This study explored a possible solution: using an antibody-cleaving enzyme (a specialized protein) called imlifidase to temporarily reduce those antibodies, potentially allowing these boys with antibodies the opportunity to benefit from this specific type of gene therapy.
The study design included boys aged 4–9 years with Duchenne and elevated rAAVrh74 antibodies (5 participants, all in Spain). Participants received 1 or 2 doses of imlifidase. If antibody levels dropped sufficiently, they were approved to receive SRP-9001 gene therapy. Muscle biopsies were used to measure gene delivery and dystrophin production. The study also monitored side effects of both treatments.
Participants received one or two doses of imlifidase. If their antibody levels dropped enough, they then received the SRP-9001 gene therapy. Muscle biopsies were used to check whether the therapy successfully delivered the genetic instructions and whether dystrophin was being produced. The study also monitored participants for any side effects from both treatments.
In October 2025, the study was stopped earlier than planned when the sponsor decided to redirect resources toward other research priorities. Because of this, the full planned analyses were not completed and results are not available. While the study did not reach its planned completion, it contributed to understanding how to potentially expand gene therapy eligibility for Duchenne patients with pre-existing antibodies. The participants’ involvement has helped inform future research directions.
At Defeat Duchenne Canada, we know that access to treatment is everything. This study represents exactly the kind of research that moves the field forward. It asked difficult questions and searched for ways to reach boys with specific antibodies who are currently left out. While this study did not reach its finish line, the knowledge gained and the commitment of every family who participated contributes to the path toward better options for all Canadians living with Duchenne.
If you would like additional information, please visit Sarepta’s Plain Language Summary below.
If you have questions for Sarepta about this study or the decision to halt the study, please email them at [email protected].
Want to know more about Duchenne Research?
Scientists and medical experts have been tirelessly pursuing diverse approaches to defeat Duchenne muscular dystrophy. From tackling the root cause to alleviating symptoms, the field of research is vast and promising. Explore the various strategies being developed and tested, and gain insights into the future of muscular dystrophy treatment: