Playing to Our Strengths

Our mission is to help build a body of research for future generations of boys with Duchenne Muscular Dystrophy. The MIS51ON clinical research study is researching the investigational use of a drug called eteplirsen, a medication designed to target Duchenne gene mutations amenable to exon 51 skipping. This study is seeking to determine if a higher dose of eteplirsen is also safe and/or effective in treating Duchenne.

For more information on the study, including additional inclusion/exclusion criteria and a current list of participating global study centers, visit and search “NCT03992430”.

You may also email to learn more.

Exon Skipping for Duchenne muscular dystrophy

The Genetics of Duchenne

Duchenne is a rare, life-shortening genetic disorder that affects boys and causes their muscles to break down and lose strength over time. Duchenne is caused by specific errors (mutations) in the gene that codes for dystrophin. Dystrophin is a protein that plays a key role in the function of muscle cells and protects them from damage as muscles contract and relax. These mutations in the dystrophin gene lead to a lack of dystrophin protein in muscles. Without enough dystrophin, muscles gradually grow weaker until they can’t move at all, and eventually breathing and heart function are lost.

What is Exon Skipping?

Commonly with Duchenne, one or more exons (parts of the gene) are missing, causing errors in the instructions for making dystrophin. This results in the body not being able to produce enough— or any—working dystrophin protein. The goal of exon skipping is to allow the body to make a shorter form of the dystrophin protein, which may help to improve muscle function.

The dystrophin gene is made up of exons that are linked together to provide instructions for making dystrophin. With 79 exons, the dystrophin gene is the largest in the body. Think of the exons on the dystrophin gene like a chain of puzzle pieces, each with a special connection that allows one piece to connect to another. In order to complete the chain, the connections between certain pieces must match.

exon skipping imageIn the image at right, you can see that exon 50 is missing. The result is that exons 49 and 51 are not able to connect because their connectors are different shapes and don’t fit together. In the dystrophin gene, this missing exon would prevent the body from being able to read the instructions for making the dystrophin protein.

By moving certain exons aside, we can potentially “skip over” them to find an exon with the right connector. The new chain would be shorter, but the pieces will be connected (and therefore able to better produce dystrophin). Just as we skipped over one of the pieces, eteplirsen is designed to skip over exon 51.

The result of this exon 51 skipping may help increase production of this shorter form of dystrophin and improve muscle function.

About the Study Drug (Eteplirsen)

The study drug (eteplirsen) is designed to potentially help address the gene mutation by skipping over exon 51 and allowing production of a shorter but functional dystrophin gene. Researchers are trying to learn if higher doses of eteplirsen (compared to the currently approved dose of 30 mg/kg in the United States and Israel) may potentially help improve your child’s muscle function and quality of life.

Who is Eligible to Participate?

Individuals may be eligible to participate in MIS51ON if they meet the following eligibility criteria:

  • Male, 4 to 13 years of age (inclusive)
  • Has been diagnosed with Duchenne with a gene mutation amenable to exon 51 skipping
  • Has never received any gene therapy or gene editing treatment. If previously received any other type of treatment for Duchenne, please discuss the specific treatment(s) with the study doctor.
  • Has been on a stable dose of oral corticosteroids for at least 12 weeks
  • Ambulatory, able to walk independently without assistive devices

Additional requirements for participation may apply and will be discussed with the study doctor during the Screening Visit. For a full list of eligibility criteria, please visit

Study Overview

The MIS51ON study will compare doses of the study drug eteplirsen in individuals with Duchenne who are amendable to exon 51 skipping.  MISSION will explore the use of a higher dose of the study drug eteplirsen and compare the safety and efficacy achieved to eteplirsen at 30mg/kg which is the current dose that is used in other clinical research studies and prescribed commercially in countries where eteplirsen is approved, such as the United States.  

MIS51ON will be conducted in two parts Part 1, an Open-label Dose Escalation Phase, and Part 2, a Double-blind Dose Finding and Comparison Phase.


The open-label dose escalation phase of the study evaluated the safety and tolerability of two higher doses (than previously tested) of the study drug eteplirsen in participants. Based on data generated from Part 1, both the 100mg/kg and 200mg/kg doses of eteplirsen were selected as the higher dose comparator for Part 2 of the study.   We thank those individuals who participated in PART 1 of the MIS51ON Study!  


Part 2 of MIS51ON is a double-blind, dose finding, and dose comparison study.  This part of the study will evaluate the safety and effectiveness of higher dose eteplirsen (100mg/kg or 200mg/kg), compared to the 30mg/kg dose of eteplirsen that is currently used in research studies and commercially.  

Part 2: Dose Finding Phase:

Participants enrolled during Part 2 Dose finding phase will be randomly assigned (like flipping a coin) to receive one of the three doses of study drug, eteplirsen at the 200mg/kg, 100mg/kg or 30mg/kg dose. Each participant will receive their assigned dose of the study drug in once weekly infusions.  
The Dose Finding phase will identify which of the higher doses (100 mg/kg or 200 mg/kg) most affects levels of dystrophin (a protein in the muscle) and will be selected to compare with the 30 mg/kg dose in the Part 2: Dose Comparison phase of the study.  All participants who complete the Dose Finding phase of the study will then move into the Dose Comparison phase of the study.

Part 2: Dose Comparison Phase:

Participants newly enrolled or continuing treatment during the Part 2 Dose Comparison phase will be assigned to the selected higher dose eteplirsen (selected in the Dose Finding phase) or 30mg/kg dose for the remainder of the study.  

Part 2 of MIS51ON will enroll a total of 144 participant and study drug infusions will be administered for up to 144 weeks. 

Receiving the Study Drug (Eteplirsen)

Your child will receive their assigned study drug dose once a week via an IV infusion (putting a needle into a vein in their arm). After each infusion, your child will be monitored for at least one hour and possibly up to three hours.

Study Activities and Procedures

Individuals interested in participating in the MIS51ION study will attend screening visits with a study doctor at a participating center. During the screening visits, the study doctor will assess eligibility by asking questions about health and completing several clinical tests (including a physical exam, blood and urine collection, functional movement assessments, and heart monitoring during the screening period to determine if they qualify as a participant for the MIS51ION study.

If an individual is qualified for participation in MIS51ON, they will be randomly assigned to the study drug eteplirsen at either the higher-dose or 30mg/kg dose.

For the first 12 weeks of the MIS51ON study, participants will receive a weekly dose of the assigned study drug and complete blood and urine assessments at the study center to help the study team and researchers monitor participant response to the drug.

Following Week 12, participants will still receive weekly visits infusions of the study drug and will be asked to provide urine samples. Additional clinical tests (including physical exam, blood collection, functional movement assessments, and heart monitoring at the study center will take place approximately every four weeks and will vary depending on the visit.

There are also two muscle biopsies involved in Part 2 of MIS51ON. One biopsy will take place when a participant begins the study, and the second biopsy will occur after taking the study drug at Week 24, Week 48, or Week 144 (depending on which dose group they were assigned to).

Is There a Cost to Participate?

If your child chooses to and is eligible to participate, you will not receive any payment, either directly or indirectly, for his participation. Sarepta Therapeutics will pay for the clinical research study costs. In addition, reasonable travel-related expenses (e.g., mileage, parking, overnight stays) may be covered (by reimbursement, not prepaid) for you in accordance with the travel policy for the clinical research study. Please speak with the study doctor and staff for more information.

Understanding Your Rights

Participating in the MIS51ON clinical research study is completely voluntary. Your child may choose to stop participating at any time and for any reason.

Study Participation

SareptAlly is a clinical trial patient matching service for Sarepta-sponsored studies. 

A Patient Navigator can help you understand your clinical trial options.  

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Frequently Asked Questions

  • Will all individuals enrolled in this study receive treatment with the study drug (eteplirsen)?

    Yes, all patients enrolled in this study will receive Eteplirsen . There is no placebo group for this study.

  • Are individuals who are currently or have previously been treated with Eteplirsen eligible for this study?

    Individuals who are currently or have previously been treated with Eteplirsen may be eligible for this study with no washout period.

  • How many males will be enrolled in this study and where is it being run?

    Up to 154 patients are planned to be enrolled in this study globally. 144 of these patients will be enrolled in the double-blind dose finding and comparison part of the study.

    For a full list of study locations please go to and search "NCT03992430".

  • Who determines eligibility to participate?

    The study doctor determines whether or not a patient meets all of the inclusion criteria (things that must be met to be eligible) and none of the exclusion criteria (things that must not be met to be eligible) for the study. The study doctor determines eligibility by performing evaluations and tests which give them information on if the patient meets the criteria.  

  • Are biopsies collected in this study?

    Yes, a total of 2 biopsies are collected in the Dose Finding and Dose Comparison (Part 2) part of the study. All Part 2 patients will undergo a muscle biopsy before taking any dose of Eteplirsen and then the patient will undergo one more biopsy at either week 24, week 48, or week 144 (depending on which dose group they were assigned to).

  • Why are biopsies being collected?

    This study will measure the change in the amount of dystrophin protein in muscle after 24, 48, and/or 144 weeks of treatment and will be a component in determining a single high dose of Eteplirsen. Because Eteplirsen is designed to increase levels of dystrophin in muscle, in order to show that exon skipping induced by Eteplirsen is working as intended is to test muscle directly. This cannot be studied by testing blood or urine, for example.

  • What risks are associated with this study?

    As with any clinical research study, there are potential risks and benefits to participating in the MIS51ON clinical research study. Your child’s health may improve, get worse, or not change at all. In addition, there are potential risks to taking the study drug and undergoing some of the study-related procedures.

    Your child’s health and safety is always the top priority of the study team. If the study doctor believes that study participation is no longer appropriate or may be placing your child in unnecessary risk, he or she will consult with you to discuss other potential options to consider.

    To understand what these risks are, please carefully read the Informed Consent Form and speak with the study doctor.

  • What are some benefits to being a part of this clinical study?

    While no benefit can be guaranteed from participation in the MIS51ON study, some benefits may include:

    • Contribute to what is currently known about the progression of Duchenne
    • Help others by contributing to medical research that may trigger the development of Duchenne therapies.

Still have questions? 

If you have further questions about the trial or participation, you may contact a Patient Navigator at

Trial Locations

For a full list of participating study centers, please visit and search "NCT03992430".

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