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 <i>via</i> 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.