The gene therapy Elevidys (delandistrogene moxeparvovec-rokl), approved in the U.S. to treat people ages 4 and older with Duchenne muscular dystrophy (DMD), can be safely administered to boys with DMD as young as 2 years old, new data show.
A new analysis, which covered nine boys with DMD given the gene therapy at age 2, found no serious side effects from Elevidys. Data also indicate that the therapy is working as intended to restore production of the needed dystrophin protein — which acts much like a shock absorber in the body during movement — in the muscle cells of these youngsters.
“The safety of [Elevidys] in ambulatory patients aged [at least] 2 to [younger than] 3 years was manageable with appropriate monitoring and consistent with the known safety profile in older … patients” able to walk, the researchers wrote in a poster, which was presented at the 31st Annual Congress of the World Muscle Society (WMS), recently held in Hiroshima, Japan.
The team noted that, “given the irreversible muscle loss in DMD, gene therapy may have greater potential benefit when administered earlier in the disease course.” Still, the researchers noted that “the findings of these studies are limited by the relatively small sample size” involving these younger patients.
“Assessing functional outcomes over time will provide important context for interpreting the clinical benefit of the observed findings,” the researchers wrote.
The work was sponsored by Sarepta Therapeutics, which developed Elevidys and markets it in the U.S.
At the same conference, Sarepta also presented new analyses on the use of Elevidys in boys with DMD ages 8 to 12, with data suggesting the gene therapy slows the decline of motor function among preteens.
The “results presented at WMS 2026 fit within a broader and increasingly consistent body of evidence generated across the clinical development program,” Louise Rodino-Klapac, PhD, president of research and development and technical operations at Sarepta, said in a company press release detailing study findings in both older and younger DMD patients, all still able to walk.
“Seeing similar patterns emerge across ambulatory Duchenne populations reinforce that timely treatment with [Elevidys] has the potential to meaningfully change the trajectory of the disease,” Rodino-Klapac said. “We remain committed to following patients over time and publishing evidence to help inform treatment decisions and advance care for the Duchenne community.”
New data comes from youngsters given Elevidys at age 2
Dystrophin is a protein that normally helps protect muscle cells from damage. People with DMD produce virtually no dystrophin, leading muscles to accumulate damage over time.
Elevidys is a one-time gene therapy designed to deliver a gene encoding a shortened version of dystrophin to muscle cells. The therapy has been approved in the U.S. since 2023 for treating DMD in certain patients.
The new analysis of toddler-age children covered nine boys who received Elevidys as part of a Phase 1b trial called ENDEAVOR (NCT04626674) or a Phase 2 trial called ENVOL (NCT06128564). Safety data showed some patients experienced vomiting, reduced appetite, and/or abnormal liver enzymes following treatment. None of the side effects were serious.
Overall, Elevidys’ safety profile in this analysis matches reports from boys 4 and older who can walk, the scientists noted.
The findings in younger children help us better understand the biological effects of treatment earlier in the disease course where preserving muscle may offer the greater opportunity for long-term benefit.
Analyses of muscle biopsies collected 12 weeks, or about three months, after Elevidys treatment showed that the youngsters were expressing the shortened version of dystrophin in their muscle cells, suggesting the therapy is working as expected.
“The findings in younger children help us better understand the biological effects of treatment earlier in the disease course where preserving muscle may offer the greater opportunity for long-term benefit,” said Craig McDonald, MD, coauthor of the study at the University of California Davis and an investigator in clinical trials of Elevidys.
McDonald noted that “measures of expression [protein production] provide important biological evidence,” but said “long-term functional outcomes remain the most meaningful way to understand the impact of treatment for patients and families.”
Sarepta noted that “continued follow-up will be important to understand longer-term outcomes” with Elevidys.
Gene therapy also may help DMD boys ages 8 and older, per new data
At the conference, researchers also shared new data on the gene therapy’s use in boys older than 8.
Although Elevidys is indicated for all ambulatory boys ages 4 and older, its approval was based mainly on data from youngsters ages 4 to 7. As such, there’s not much known about its effect in older ambulatory boys.
In the other poster presented at WMS 2026, scientists evaluated outcomes among 25 ambulatory boys with DMD given Elevidys between the ages of 8 and 12. These boys participated either in the ENDEAVOR trial or in a Phase 3 study called EMBARK (NCT05096221).
“The period between 8 and 12 years of age represents a critical phase of Duchenne when many boys transition from relative stability to progressive functional decline,” Rodino-Klapac noted.
Results from the Elevidys-treated boys were compared against data from nearly 100 boys with DMD in natural history studies. Several standardized motor function measures were assessed, including the time it takes to stand up from sitting, and the time it takes to run or walk 10 meters (about 33 feet).
Over two years, all of these measures tended to worsen in boys given Elevidys, the data showed. However, the researchers noted that the rate of decline was significantly slower than was seen in natural history studies.
According to McDonald, also a coauthor of that study, “the older ambulatory patient data demonstrate that [Elevidys] treatment can provide functional benefit that’s statistically significant at a stage when decline often becomes more pronounced.”
Safety data from 8- to 12-year-olds were consistent with the overall known profile of Elevidys. A few serious side effects were reported, including vomiting and liver damage, but all were managed, per the researchers.
“These findings help to address an important evidence gap regarding gene therapy for DMD in older ambulatory patients and support the use of [Elevidys] in ambulatory patients with DMD aged 8-12 years,” the team from that study concluded.
The post Approved Duchenne gene therapy may be safe for boys as young as 2 appeared first on Muscular Dystrophy News.