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

Recruiting

Conditions

Intervention / Treatment

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

Interventional

Enrollment (Estimated)

90

Phase

  • 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 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

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
Intervention / Treatment
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

Outcome Measure
Time Frame
Rise From Floor (RFF) velocity
Time Frame: Baseline, Week 73
Baseline, Week 73

Secondary Outcome Measures

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

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)

June 1, 2026

Primary Completion (Estimated)

December 1, 2030

Study Completion (Estimated)

October 1, 2032

Study Registration Dates

First Submitted

May 20, 2026

First Submitted That Met QC Criteria

May 20, 2026

First Posted (Actual)

May 27, 2026

Study Record Updates

Last Update Posted (Actual)

May 27, 2026

Last Update Submitted That Met QC Criteria

May 20, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID 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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