Long-Term Survival and Myocardial Function Following Systemic Delivery of Delandistrogene Moxeparvovec in DMD^MDX Rats

Delandistrogene moxeparvovec is a gene transfer therapy for Duchenne muscular dystrophy (DMD) that uses an adeno-associated viral vector to deliver a micro-dystrophin transgene to skeletal and cardiac muscle. This study evaluated the long-term survival and cardiac efficacy of delandistrogene moxeparvovec in a DMD-mutated (DMD^MDX) rat model of DMD-related cardiomyopathy. DMD^MDX male rats, aged 21-42 days, were injected with 1.33 × 10¹⁴ viral genomes/kilogram (vg/kg) delandistrogene moxeparvovec and followed for 12, 24, and 52 weeks. Ambulation was recorded via the Photobeam Activity System, whereas echocardiograms, cardiomyocyte contractility, calcium handling, and histological analysis of fibrosis were used to evaluate cardiac disease at 12-, 24-, and 52-weeks post-treatment. A separate cohort of rats was used to assess the impact of delandistrogene moxeparvovec on survival. Treatment with delandistrogene moxeparvovec extended median survival in DMD^MDX rats to >25 months versus the 13-month median survival in saline-control-treated DMD^MDX rats. Compared with saline control, delandistrogene moxeparvovec therapy elicited statistically significant improvements across cardiac parameters approaching wild-type values with additional benefits in mobility, histopathology, and fibrosis observed. Transgene expression was maintained up to >25 months and micro-dystrophin expression was broadly distributed across skeletal and cardiac muscle. Taken together, these findings demonstrate long-term cardiac efficacy and improved survival following delandistrogene moxeparvovec treatment in DMD^MDX rats.