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Gene therapy options for Duchenne muscular dystrophy

Gene therapy options for Duchenne muscular dystrophy

New Capabilities

Regenxbio trial success sets up a second submission to the FDA

May 14th, 2026: Regenxbio gene therapy clears pivotal trial

Overview

For three years, Sarepta Therapeutics has been the only company in the world selling a gene therapy for Duchenne muscular dystrophy. Regenxbio's trial result on May 14, 2026, sets up a second contender for U.S. Food and Drug Administration (FDA) approval.

Duchenne strips boys of dystrophin, the muscle protein their cells need to work. Sarepta's Elevidys, the existing treatment, has been linked to deaths in older, non-ambulatory patients. A second approved therapy would give doctors and families a choice.

Why it matters

Roughly 12,000 American boys have Duchenne; a second gene therapy doubles their treatment options after safety questions emerged about the first.

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Key Indicators

10,000–15,000
U.S. patients with Duchenne
Almost all are boys; most are diagnosed before age 5.
$3.2M
Elevidys list price
Per-patient cost of Sarepta's one-time gene therapy, billed in a single dose.
2
Gene therapy contenders
Sarepta's approved Elevidys plus Regenxbio's pending FDA submission.
Mid-20s
Typical age of death
Without an effective treatment, Duchenne is fatal in early adulthood from heart and lung failure.

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People Involved

Curran Simpson
Curran Simpson
Leading FDA submission for RGX-202
 Doug Ingram
Doug Ingram
Defending Elevidys against safety questions and new competition

Organizations Involved

Regenxbio
Regenxbio
Biotechnology company
Preparing FDA submission for RGX-202

Rockville, Maryland biotech that spun out of University of Pennsylvania gene therapy research and licenses its NAV adeno-associated virus (AAV) vector platform to other drugmakers.
Sarepta Therapeutics
Sarepta Therapeutics
Biotechnology company
Marketing Elevidys under restricted label

Cambridge, Massachusetts biotech that built its business around Duchenne treatments, including three exon-skipping drugs and the gene therapy Elevidys.
FDA Center for Biologics Evaluation and Research
FDA Center for Biologics Evaluation and Research
Federal regulatory agency division
Reviewing gene therapy approvals and safety

The U.S. Food and Drug Administration unit that reviews gene therapies, vaccines, and other biologic drugs.

Timeline

1986 May 2026

7 events Latest: May 14th, 2026 · 2 months ago
Tap a bar to jump to that date

  1. Regenxbio gene therapy clears pivotal trial

    Latest Clinical Trial

    Regenxbio announces RGX-202 met its primary endpoint in the pivotal AFFINITY DUCHENNE trial, clearing the way for an FDA submission.

  2. FDA's top gene therapy regulator resigns

    Personnel

    Peter Marks, the CBER director who approved Elevidys, resigns over policy disputes with the Department of Health and Human Services.

  3. Elevidys linked to patient deaths

    Safety

    Sarepta reports deaths from acute liver failure in non-ambulatory teens treated with Elevidys and voluntarily pauses dosing in that group.

  4. FDA expands Elevidys to all ages

    Regulatory

    FDA broadens the Elevidys label to cover ambulatory and non-ambulatory patients regardless of age, opening the drug to thousands more boys.

  5. Elevidys becomes first Duchenne gene therapy

    Regulatory

    FDA grants accelerated approval to Sarepta's Elevidys for ambulatory boys ages 4-5. List price: $3.2 million per one-time infusion.

  6. First Duchenne drug approved

    Regulatory

    FDA grants accelerated approval to Sarepta's Exondys 51, an exon-skipping drug, over the objections of agency reviewers who cited weak efficacy data.

  7. Dystrophin gene identified

    Science

    Researchers at Harvard pinpoint the gene that, when mutated, causes Duchenne. The discovery sets the target for every future Duchenne therapy.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

May 2019

Zolgensma approval for spinal muscular atrophy (2019)

FDA approved Novartis's Zolgensma, a one-time AAV gene therapy for spinal muscular atrophy in children under 2. At $2.1 million, it was the most expensive drug ever approved at the time. It used an AAV9 vector built on the Regenxbio NAV platform under license.

Then

Zolgensma joined Biogen's earlier antisense drug Spinraza, giving SMA families two treatment options where they had none in 2015.

Now

Roche's Evrysdi followed in 2020, and SMA shifted from a near-certain infant fatality to a manageable condition for many patients.

Why this matters now

The same script may now play out for Duchenne. A second gene therapy arrives a few years after the first, giving doctors a choice and pressuring the incumbent on price and safety.

December 2013 to 2017

Hepatitis C drug competition (2014-2017)

Gilead's Sovaldi launched in 2013 as a near-cure for hepatitis C, priced at $1,000 per pill or $84,000 per course. AbbVie's Viekira Pak launched the next year, followed by Gilead's own Harvoni and later Mavyret. Insurers and pharmacy benefit managers used the second entrant to negotiate steep rebates.

Then

Net prices fell more than 50% within three years of the first competitor launch.

Now

Hepatitis C cure rates climbed past 95% in treated patients, and the U.S. cleared most of its diagnosed backlog by the early 2020s.

Why this matters now

Drug competition routinely lowers prices and broadens access. A second approved Duchenne gene therapy gives insurers and Medicaid programs leverage that did not exist with one supplier.

June 2023

Elevidys accelerated approval debate (2023)

FDA's CBER division, then run by Peter Marks, approved Elevidys despite a divided advisory committee vote and objections from agency reviewers who said the efficacy data was thin. The approval was conditional, requiring a confirmatory trial.

Then

Sarepta launched at $3.2 million per dose, the highest list price ever for an FDA-approved drug at the time of approval.

Now

When Elevidys was later linked to patient deaths, the original approval decision came under renewed scrutiny and contributed to Marks's resignation in March 2025.

Why this matters now

Regenxbio's submission lands in a more skeptical FDA. Reviewers will weigh safety more heavily than they did three years ago, and the bar for accelerated approval may be higher.

Sources

(1)
STAT News