Gene therapy in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a severe X-linked myopathy caused by mutations in the DMD gene, resulting in the absence of functional dystrophin. Gene therapy seems to represent a rational therapeutic strategy, aiming to restore dystrophin expression through delivery of engineered microdystrophin constructs using adeno-associated virus (AAV) vectors. Preclinical studies in murine and canine models demonstrated robust dystrophin restoration, histological improvement, and functional benefit, supporting the transition to clinical trials. Over the past decade, five AAV-microdystrophin programs have entered large-scale human testing. In 2023, delandistrogene moxeparvovec (Sarepta/Roche) received accelerated approval from the U.S. Food and Drug Administration for ambulatory pediatric patients, marking the first regulatory authorization of a gene therapy for DMD. By contrast, fordadistrogene movaparvovec (Pfizer) showed encouraging biomarker results but was associated with immune-mediated serious adverse events, including thrombotic microangiopathy cases and patient deaths due to acute liver failure, ultimately leading to program discontinuation. Other investigational candidates-GNT0004 (Généthon), SGT-003 (Solid Biosciences), and RGX-202 (Regenxbio)-incorporate distinct promoter designs and microdystrophin cassettes and are currently in early- to mid-phase evaluation. Key issues include immunogenicity against AAV capsids and transgene products, durability of expression, and the need for re-dosing or combinatorial strategies. Gene therapy management also raises difficult economic and logistical challenges for healthcare systems. Balancing rapid patient access to potentially disease-modifying therapies with rigorous scientific and regulatory standards is essential to ensure safe and durable benefit for individuals with DMD.