Sarepta's Elevidys Shows Promise in Older DMD Patients, Addressing Previous Data Gaps

Sarepta Therapeutics has presented new data for its gene therapy Elevidys, demonstrating significant functional improvements in older children with Duchenne muscular dystrophy (DMD). The results, unveiled at the 2025 annual meeting of the American Society of Gene & Cell Therapy in New Orleans, address previous concerns about the therapy's efficacy in older and non-ambulatory patients.

Elevidys Demonstrates Efficacy in 8-9 Year Old DMD Patients

A post-hoc analysis of the Phase III EMBARK trial revealed that after one year of follow-up, patients aged 8 to 9 years treated with Elevidys showed a 0.37-point improvement in the North Star Ambulatory Assessment test. In contrast, patients in an external control arm, managed with stable doses of oral corticosteroids, experienced a 4.38-point decline. The resulting treatment effect of 4.75 points was deemed statistically significant.

Additionally, Elevidys-treated patients demonstrated significant improvements in other mobility tests, including time to rise and the 10-meter walk/run test. The gene therapy also resulted in sustained expression of the microdystrophin protein, Elevidys' genetic payload, for up to 64 weeks, suggesting durability of the treatment effect.

Safety Update and Recent Concerns

Sarepta provided a brief two-year safety update for Elevidys, noting that outcomes were consistent with prior experience from the clinical development program. Side effects were described as overall "manageable with appropriate monitoring."

However, the presentation comes in the wake of a recent patient death that raised concerns in the Duchenne space. In March, Sarepta announced that one patient on Elevidys treatment developed acute liver failure, which ultimately proved fatal. While liver toxicities were known potential side effects, this case represented a severity not previously reported for Elevidys. The company has committed to updating the therapy's label to reflect this risk, though changes have yet to be implemented as of the time of writing.

Implications for Elevidys' Future

These new results are expected to strengthen Elevidys' case, particularly in light of previous expert calls for more comprehensive data. In October 2024, Craig McDonald, chair of the Department of Physical Medicine & Rehabilitation at UC Davis Health, highlighted the need for data on older ambulatory patients in the skill-losing phase of the disease.

The latest findings, showing mobility improvements in 8- to 9-year-old patients after one year of follow-up, directly address this gap. According to Sarepta, these improvements indicate a "stabilization or slowing of disease progression," potentially expanding the therapy's applicability to a broader patient population.