Efficacy, Safety, and Tolerability of Zeleciment Rostudirsen (DYNE-251) Administered Intravenously Every 4 Weeks in Ambulatory Participants With Duchenne Muscular Dystrophy (FORZETTO) (FORZETTO)

May 20, 2026 updated by: Dyne Therapeutics

A Phase 3, Randomized, Double-Blind, Placebo-Controlled Study to Investigate the Efficacy, Safety, and Tolerability of DYNE-251 Administered Intravenously in Ambulatory Male Participants 4 to 18 Years of Age With Duchenne Muscular Dystrophy Amenable to Exon-51 Skipping

The purpose of the study is to assess the efficacy, safety, and tolerability of zeleciment rostudirsen (DYNE-251) administered intravenously (IV) every 4 weeks to ambulatory Duchenne muscular dystrophy (DMD) participants, 4 to 18 years of age, with dystrophin mutations amenable to exon 51 skipping.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

The study consists of three periods: a Screening period (up to 6 weeks), a Placebo-Controlled Period (72 weeks) and an open-label Long-Term Extension Period (96 weeks).

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
90

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child
  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Ambulatory male with confirmed diagnosis of DMD and with a mutation in the dystrophin gene characterized by exon deletion amenable to exon 51 skipping .
  • Rise From Floor (RFF) time must be < 10 seconds for both screening assessments .
  • Receiving a stable daily or weekend dosage of glucocorticoids for at least 24 weeks prior to randomization with the expectation of maintaining a stable dose during the Placebo-Controlled Period of the study (unless dose adjustment is required by weight change)

Exclusion Criteria:

  • Receipt of ongoing immunosuppressive therapy (other than glucocorticoids) within 12 weeks prior to randomization
  • Use of any pharmacologic treatment (other than glucocorticoids) that may have an effect on muscle strength or function within 12 weeks prior to randomization
  • Any change in prophylaxis/treatment for congestive heart failure (CHF) within 12 weeks prior to randomization
  • Receipt of eteplirsen within 1 week prior to randomization
  • Receipt of alternative exon-skipping or dystrophin-modifying therapy or zeleciment rostudirsen within 24 weeks prior to randomization
  • Receipt of givinostat within 12 weeks prior to randomization
  • Receipt of gene therapy at any time

Note: Other inclusion or exclusion criteria may apply

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Placebo-Controlled Period: Zeleciment Rostudirsen (DYNE-251)
Participants will be randomized to receive zeleciment rostudirsen, once every 4 weeks (Q4W) for up to 72 weeks.
Drug: Zeleciment Rostudirsen (DYNE-251)
Administered by IV infusion
Placebo Comparator: Placebo-Controlled Period: Placebo
Participants will be randomized to receive placebo, Q4W for up to 72 weeks.
Drug: Placebo
Administered by IV infusion
Experimental: Open-Label Long-Term Extension Period: Zeleciment Rostudirsen (DYNE-251)
All participants who complete the Placebo-Controlled Period of the study will receive zeleciment rostudirsen administered Q4W for up to 96 weeks.
Drug: Zeleciment Rostudirsen (DYNE-251)
Administered by IV infusion

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Rise From Floor (RFF) velocity
Time Frame: Baseline, Week 73
Baseline, Week 73

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
RFF (Rise From Floor) velocity
Time Frame: Baseline, up to Week 169
Baseline, up to Week 169
Stride Velocity 95th Percentile (SV95C)
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
North Star Ambulatory Assessment (NSAA) Total Score
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
10-Meter Walk/Run (10MWR) Velocity
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
4-Stair Climb (4SC) velocity
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
Functional Composite score
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
Forced Vital Capacity (FVC)
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
Patient Global Impression of Severity (PGI-S)
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
Outcome of Patient Global Impression of Change (PGI-C)
Time Frame: Week 73, up to Week 169
Week 73, up to Week 169
Blood Creatine Kinase (CK) levels
Time Frame: Baseline, Week 73, up to Week 169
Baseline, Week 73, up to Week 169
Incidence of participants With Treatment-Emergent Adverse Events (TEAEs)
Time Frame: Through study completion, up to Week 173
Through study completion, up to Week 173
Maximum Observed Plasma Drug Concentration of DYNE-251 (Cmax)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Time to Maximum Observed Plasma Drug Concentration of DYNE-251 (tmax)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Area Under the Plasma Drug Concentration-Time Curve From Time 0 to the Last Quantifiable Concentration of DYNE-251 in Plasma (AUC-tlast)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Area Under the Plasma Drug Concentration Versus Time Curve From Time 0 (Dosing) Extrapolated to Time Infinity of DYNE-251 (AUC∞)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Apparent Terminal Phase Elimination Rate Constant of DYNE-251 in Plasma (λz)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Apparent Terminal Elimination Half-Life of DYNE-251 in Plasma (t½)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Total Body Clearance (CL) of DYNE-251
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Volume of Distribution at the Terminal Phase of DYNE-251 in Plasma (Vz)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Volume of Distribution at Steady State of DYNE-251 in Plasma (Vss)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169
Incidence of Participants With Antidrug Antibodies (ADAs)
Time Frame: Through study completion, up to Week 169
Through study completion, up to Week 169

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Dyne Therapeutics

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 1, 2030

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 1, 2032

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 20, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 20, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 27, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 27, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 20, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • DYNE251-DMD-301
  • 2025-524096-23-00 (Ctis)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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