Gene therapy with delandistrogene moxeparvovec (Elevidys) helped slow or stabilize Duchenne muscular dystrophy (DMD) in young boys over two years, allowing many to maintain abilities that typically worsen with time, according to a study published recently in Neurology and Therapy.
In this large phase 3 study, boys who received the one-time infusion showed better movement and strength than similar children who did not receive the therapy, with no new safety problems emerging in the second year.
“These sustained results suggest the potential of delandistrogene moxeparvovec to persistently address the underlying cause of DMD and help slow muscle damage over extended periods of time,” said the study’s authors.
Delandistrogene moxeparvovec is designed to address the root cause of DMD — the lack of functional dystrophin — by enabling the body to produce micro-dystrophin, a shortened version of the protein.
What is dystrophin?
Dystrophin is the protein that mutates and leads to DMD. It is found in small quantities in muscle cells, where its role is to protect the cell from daily damage.
When it mutates, it causes muscle cell degeneration and inflammation, leading to damage in the tissue of the bones, lungs and heart.
The EMBARK trial enrolled 125 ambulatory boys aged 4 to younger than 8 years. In the first part of the study, 64 boys received the gene therapy as a single intravenous dose, while others initially received placebo and later crossed over.
Read more about therapies for DMD
At two years, treated boys performed significantly better than a carefully matched external comparison group drawn from previous DMD studies. On the North Star Ambulatory Assessment, a common measure of motor function, treated patients improved by 2.63 points on average, while the comparison group declined by 0.25 points. Boys who received gene therapy also stood up from the floor faster and completed a 10-meter walk or run more quickly, both signs linked to staying able to walk longer.
Importantly for families, none of the treated boys lost the ability to complete functional testing during the two-year follow-up. Muscle biopsies from a subset of patients showed that the therapy continued to produce micro-dystrophin and place it correctly in muscle cells more than a year after treatment, suggesting durability of the biological effect.
Safety remained consistent with earlier findings. Most side effects occurred within the first 90 days after infusion and were manageable with monitoring and treatment. Between years one and two, no treatment-related deaths or study withdrawals occurred, and no serious immune-related complications were seen in the EMBARK participants.
For patients and caregivers, these results suggest that receiving gene therapy early may help preserve strength and daily function during a critical period of childhood. While longer follow-up is needed to know how lasting the benefits will be, the findings offer cautious optimism that gene therapy can meaningfully slow the course of DMD.
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