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Study of DYNE-251 safety and effectiveness in patients with Duchenne muscular dystrophy who are candidates for exon 51 skipping treatment

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on Duchenne Muscular Dystrophy, a genetic condition that causes progressive muscle weakness. The research evaluates a new medication called DYNE-251, which is given through intravenous infusion. Some participants will receive DYNE-251 while others will receive a placebo solution.

The main purpose of this research is to test how safe DYNE-251 is and how well patients tolerate it when given multiple doses. The study will also measure the levels of a protein called dystrophin in muscle tissue after treatment. This protein is important because people with Duchenne Muscular Dystrophy don't make enough of it.

During the study, participants will receive regular infusions of either DYNE-251 or placebo. The treatment schedule will vary, with some participants receiving treatment every four weeks and others every eight weeks. The study includes various health checks and muscle tissue examinations to monitor how well the treatment is working. Doctors will track any changes in muscle function and strength throughout the study period.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    You will receive DYNE-251 or placebo (5% dextrose solution) through an intravenous infusion.

    The treatment will be administered either every 4 weeks or every 8 weeks, depending on your assigned group.

    Your glucocorticoid medication will continue at the same stable dose you have been taking.

  2. Step 2

    First muscle biopsy

    A sample of muscle tissue will be taken from your upper arm to measure baseline levels of dystrophin protein.

    This procedure will be performed before starting the treatment.

  3. Step 3

    Treatment monitoring at week 25

    A second muscle biopsy will be taken to measure changes in dystrophin protein levels.

    Blood tests will be conducted to monitor CK levels (an indicator of muscle health).

    Your physical function will be assessed using specific tests that measure upper limb strength and movement.

  4. Step 4

    Extended monitoring phase

    For participants receiving treatment every 8 weeks, an additional muscle biopsy will be performed at week 49.

    Regular assessments will continue up to week 145, including:

    Blood tests to monitor CK levels

    Tests to measure breathing function (forced vital capacity)

    Physical function tests for those who can walk

    Blood samples to check how the medication is processed by your body

  5. Step 5

    Safety monitoring

    Throughout the study, you will be monitored for any side effects or reactions to the treatment.

    Your heart function will be regularly assessed.

    Blood tests will check for antibodies against the study medication.

Who can join the trial?

8 criteria

  • Must be male between 4 and 16 years old at the time of providing consent
  • Must have a confirmed diagnosis of Duchenne muscular dystrophy with a specific genetic mutation that can be treated with exon 51 skipping
  • Must have an upper arm muscle group suitable for taking a tissue sample (biopsy)
  • Must have a Brooke Upper Extremity Scale score of 1 or 2 (this measures arm and shoulder function)
  • Can be either able to walk or not able to walk. If not able to walk, this must have occurred within the last 2 years
  • Must be taking glucocorticoids (steroid medications) at a stable dose for at least 12 weeks before starting the study
  • Must have good heart function, shown by:
    • Heart pumping strength (ejection fraction) of 50% or higher on ultrasound, or
    • Heart pumping strength of 55% or higher on MRI scan

Who cannot join the trial?

10 criteria

  • Male patients who are not between 4 and 17 years old
  • Female patients (study is only for male participants)
  • Patients who do not have a confirmed genetic diagnosis of Duchenne muscular dystrophy
  • Patients who cannot undergo multiple intravenous (IV) injections (injections into a vein)
  • Patients who cannot provide muscle tissue samples for dystrophin protein testing (dystrophin is a protein that helps keep muscle cells intact)
  • Patients who are currently participating in other clinical trials
  • Patients who cannot comply with study visits and procedures
  • Patients with any medical conditions that could interfere with study assessments
  • Patients who cannot provide informed consent or whose legal guardian cannot provide consent
  • Patients with known allergies to the study medication or its components
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Investigated drugs

DYNE-251 is a medication being studied for the treatment of Duchenne Muscular Dystrophy (DMD). It is administered through intravenous (IV) injection. This medication is designed to work specifically in patients whose DMD condition could be improved through a process called exon 51 skipping. The treatment aims to help the body produce dystrophin, a protein that is essential for proper muscle function and is typically lacking in patients with DMD.

What is already known about the treatment

DYNE-251 – An investigational drug administered intravenously (IV) that is being studied for the treatment of Duchenne muscular dystrophy (DMD) specifically in patients who can benefit from exon 51 skipping. This therapeutic compound is currently in clinical trials to evaluate its safety, tolerability, and effectiveness in increasing dystrophin protein levels in muscle tissue. DYNE-251 belongs to a class of treatments designed to modify gene expression through exon skipping, aiming to help produce a partially functional dystrophin protein in patients with specific genetic mutations. The medication represents a targeted approach to treating DMD, with ongoing research to determine its potential benefits and safety profile through multiple ascending dose studies.

Investigated diseases

Duchenne muscular dystrophy - A genetic disorder that causes progressive muscle degeneration and weakness. It primarily affects boys and typically becomes apparent in early childhood. The condition is characterized by gradual weakening of muscles, starting in the legs and pelvis, and later affecting the whole body. Children with this condition often have difficulty with basic movements like walking, running, and jumping. The muscle weakness progresses steadily over time, affecting different muscle groups throughout the body. The condition occurs due to mutations in the gene that produces dystrophin, a protein necessary for proper muscle function.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase I/IITrial ID2023-510351-31-00Protocol codeDYNE251-DMD-201Estimated enrolment75 patientsSponsorDyne Therapeutics Inc.

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