The U.S. Food and Drug Administration (FDA) has granted accelerated approval to Elevidys (delandistrogene moxeparvovec), a gene therapy developed by Sarepta Therapeutics, for the treatment of Duchenne muscular dystrophy (DMD) in pediatric patients aged 4-5 years with a confirmed mutation in the DMD gene. This marks a significant advancement in treating this debilitating genetic disorder, addressing a critical unmet medical need.
Elevidys is designed to deliver a functional gene into the body, enabling the production of Elevidys micro-dystrophin, a truncated version of the dystrophin protein. Dystrophin, normally 427 kDa, is crucial for muscle cell stability. Elevidys micro-dystrophin is a smaller protein (138 kDa) containing selected domains of the native dystrophin protein. The therapy is administered as a single intravenous dose.
The approval was based on data from a clinical trial that demonstrated an increase in Elevidys micro-dystrophin expression in treated patients. The FDA has concluded that this increase is reasonably likely to predict clinical benefit in this patient population, specifically those without significant pre-existing antibody titers against the AAV rh74 vector or other contraindications based on the inclusion criteria of the clinical trials.
Current Treatment Landscape and Unmet Needs
Currently, most DMD treatments focus on managing symptoms rather than addressing the underlying genetic cause. These include corticosteroid medications to slow muscle weakness progression and antisense oligonucleotides (ASOs) to facilitate exon skipping for specific DMD gene mutations. However, ASOs are only applicable to a minority of DMD gene mutations and require repeated administration. Elevidys offers a potential one-time treatment that targets the root cause of the disease.
Clinical Trial Details and Ongoing Studies
The clinical trial leading to the accelerated approval involved a two-part study. In Part 1, patients were randomized to receive either Elevidys or a placebo and were followed for 48 weeks. Part 2 involved patients who received the placebo in Part 1 being treated with Elevidys, while those initially treated with Elevidys received a placebo. All patients were followed for an additional 48 weeks.
The primary objective of the study is to assess whether Elevidys improves physical function and mobility in ambulatory DMD patients with a confirmed mutation in the DMD gene. While the accelerated approval is based on micro-dystrophin expression, the FDA requires a confirmatory clinical trial to verify the gene therapy’s clinical benefit, including improved motor function. This trial is currently ongoing.
Expert Commentary
"Today’s approval addresses an urgent unmet medical need and is an important advancement in the treatment of Duchenne muscular dystrophy," stated Dr. Peter Marks, PhD, Director of the FDA’s Center for Biologics Evaluation and Research.
