Gene therapy may have the potential to cure Duchenne muscular dystrophy, but early results from clinical trials have not been as promising as researchers hoped. Research is ongoing.

Duchenne muscular dystrophy (DMD) is an inherited condition that causes muscle weakness, most often in children assigned male at birth. Symptoms get progressively worse over time, and there is no known cure.

A genetic mutation causes DMD. So, treatments that target the affected gene — known as gene therapy — might be able to help. A handful of gene therapies for DMD are currently in development.

This article explores how gene therapy works and whether it can effectively treat DMD.

Gene therapy is a relatively new treatment that repairs or replaces a genetic mutation to treat a medical condition.

DMD is linked to mutations in the dystrophin gene, one of the longest genes in the human genome. These mutations reduce your body’s ability to produce the dystrophin protein, which helps muscles keep their structure. Without dystrophin, your muscles start to waste away.

Gene therapy for DMD fixes or replaces the dysfunctional parts of the dystrophin gene so that it can make the correct protein. Having gene therapy during a specific window of time could theoretically stop the progression of DMD.

But most gene therapies are still in development. More research is needed to demonstrate their safety and long-term effectiveness.

Gene therapy drugs for Duchenne muscular dystrophy

In the summer of 2023, the Food and Drug Administration (FDA) awarded accelerated approval to delandistrogene moxeparvovec (Elevidys), a one-dose gene therapy drug from Sarepta Therapeutics. Delivered via a viral vector, Elevidys helps your body produce a shortened version of the dystrophin protein.

But the company recently announced the results of a 52-week randomized, placebo-controlled phase 3 clinical trial of Elevidys in 125 male children with DMD. Elevidys did not lead to a statistically significant improvement in symptoms, although it met some secondary measures.

Other gene therapies currently in development include fordadistrogene movaparvovec, a drug from Pfizer currently undergoing a phase 3 clinical trial.

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According to the FDA, Elevidys gene therapy can treat DMD in male children who meet the following eligibility criteria:

  • are 4–5 years old
  • are ambulatory (walking)
  • have a confirmed dystrophin gene mutation
  • do not have antibodies against the adeno-associated virus (AAV) rh74 vector
  • do not have a deletion in exon 8 or exon 9 of the dystrophin gene

Exons are regions of genes that code for a protein. The dystrophin gene has 79 exons.

In addition, children with DMD may have an increased chance of severe side effects if they have:

  • liver problems
  • mutations in exons 1–17 or 59–71 of the dystrophin gene

A healthcare professional will first check your child’s eligibility for gene therapy.

Your child will have to undergo blood tests to assess their liver function, platelet counts, and troponin-I levels. A few days prior to treatment, your child will receive a corticosteroid regimen to reduce the chance of an immune system reaction.

Healthcare professionals administer Elevidys as a one-time intravenous (IV) infusion. It takes 1–2 hours. After the treatment, your child will require weekly monitoring for side effects for 3 months or more.

It’s not clear how effective gene therapy is in treating DMD. It may vary from one drug to the next.

The data reported by Sarepta Therapeutics from the phase 3 clinical trial of Elevidys show that the drug fell short of its main effectiveness goal. Still, participants who received Elevidys showed the following improvements compared to a placebo:

  • a slight but not statistically significant improvement in movement compared to placebo
  • improvements in time to rise from the floor
  • improvements in timed 10-meter walking tests

Corticosteroids such as prednisone are the main treatment for DMD. These drugs reduce inflammation, allowing people with DMD to retain muscle function for longer than they otherwise would.

People with DMD need to take corticosteroids on a regular basis. This can cause serious long-term side effects. The medications are supportive, which means they can help ease symptoms but do not target the underlying cause of DMD.

In contrast, gene therapy is a one-time treatment that addresses the root cause of DMD. But its long-term effectiveness remains uncertain, and it carries a chance of serious side effects.

Recently-approved targeted therapies for DMD

The FDA has recently approved several other medications for DMD. Known as exon-skipping therapies, these drugs target specific genetic mutations. They include:

  • eteplirsen (Exondys 51)
  • golodirsen (Vyondys 53)
  • casimersen (Amondys 45)
  • viltolarsen (Viltepso)
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A one-time gene therapy treatment can cost several million dollars. Elevidys for DMD costs $3.2 million per dose. Your insurance may cover it since the drug now has FDA approval, but other gene therapy options may not be covered.

A 2022 study found that the direct cost of traditional DMD therapies could be as high as $2.3 million over 20 years of treatment.

We answer some of the most common questions about gene therapy for DMD below.

Can gene therapy cure Duchenne muscular dystrophy?

Some people have hailed gene therapy as a potential cure for DMD. While it shows Great potential, there is still a lot that we don’t know about its safety and effectiveness.

Is gene therapy FDA approved for Duchenne muscular dystrophy?

The FDA offered accelerated approval for Elevidys, the first-ever DMD gene therapy, in 2023. Accelerated approval is a program that speeds up the testing process for drugs that treat life threatening medical conditions.

Can gene therapy treat Becker muscular dystrophy or limb-girdle muscular dystrophy?

Gene therapies for other types of muscular dystrophy are in development, but as of yet, there is not enough research to show their effectiveness.

Gene therapy for DMD is an up-and-coming treatment that targets dystrophin gene mutations.

One gene therapy drug, delandistrogene moxeparvovec (Elevidys), received accelerated approval by the FDA in 2023. But a recent clinical trial suggests this drug isn’t as effective as medical professionals hoped.

Other treatments are currently undergoing testing. If your child has DMD, it may be helpful to ask your doctor about available treatments.