Phase 2 Study of EDG-5506 in Children and Adolescents With Duchenne Muscular Dystrophy Previously Treated With Gene Therapy (FOX)

A Phase 2 Study to Evaluate the Effect of EDG-5506 on Safety, Pharmacokinetics, and Biomarkers in Children and Adolescents With Duchenne Muscular Dystrophy Previously Treated With Gene Therapy

The FOX study is a 2-part, multicenter, Phase 2 study of safety, pharmacokinetics, and biomarkers in children and adolescents with Duchenne muscular dystrophy previously treated with gene therapy including a randomized, double-blind, placebo-controlled Part A, followed by an open-label part B.

Study Overview

• Status: Active, not recruiting
• Conditions: Duchenne Muscular Dystrophy
• Intervention / Treatment: Drug: Placebo; Drug: Sevasemten Dose 1; Drug: Sevasemten Dose 2; Drug: Sevasemten Dose 3

Detailed Description

FOX is a 2-part, multi-center, Phase 2 study to evaluate the effect of sevasemten (EDG-5506) on safety, pharmacokinetics and biomarkers of muscle damage in approximately 48 children and adolescents with Duchenne muscular dystrophy treated with oral, once-daily sevasemten. This study will have up to a 4-week Screening period, a 12-week randomized double-blind, placebo-controlled treatment period (Part A), followed by up to a 144-week open-label extension period (Part B).

Approximately forty-eight (48) participants aged 6 to 17, inclusive, will be randomized to sevasemten or placebo in a 2:1 ratio. Three dose cohorts (Cohort 1, Cohort 2 and Cohort 3) of approximately 12 participants each will be enrolled. Approximately 12 additional participants may be added to 1 of these cohorts.

After review of emerging data, the protocol was amended so all dose cohorts receive the same dose in Part B.

• Study Type: Interventional
• Enrollment (Actual): 43
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • California
    • Los Angeles, California, United States, 90095
      • UCLA Medical Center
    • Sacramento, California, United States, 95817
      • UC Davis Medical Center
  • Florida
    • Gainesville, Florida, United States, 32610
      • University of Florida
  • Massachusetts
    • Worcester, Massachusetts, United States, 01605
      • University of Massachusetts Memorial Medical Center
  • Missouri
    • St Louis, Missouri, United States, 63110
      • Washington University School of Medicine
  • North Carolina
    • Hillsborough, North Carolina, United States, 27278
      • Rare Disease Research
  • Ohio
    • Columbus, Ohio, United States, 43205
      • Nationwide Children's Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

• Aged 6 to 17 with a documented mutation on the DMD gene and phenotype consistent with DMD.
• Prior receipt of an AAV-based gene therapy (≥ 2 years after documented receipt of gene therapy administration or ≥ 3 years after randomization in a randomized study).
• Able to complete stand from supine in ≤ 8 seconds at the Screening visit and able to perform the 4-stair climb in < 10 seconds at the Screening visit.
• Body weight ≥ 15 kg at the Screening visit.
• Treatment with a stable dose of corticosteroids for a minimum of 6 months prior to the Baseline visit.

Key Exclusion Criteria:

• Medical history or clinically significant physical exam/laboratory result that, in the opinion of the investigator, would render the participant unsuitable for the study. This includes venous access that would be too difficult to facilitate repeated blood sampling.
• Screening visit cardiac echocardiography showing left ventricular ejection fraction (LVEF) < 40%.
• Receipt of an investigational drug (other than the AAV-based gene therapy per Inclusion criteria) within 30 days or 5 half-lives (whichever is longer) of the Screening visit in the present study.
• Receipt of an exon-skipping therapy within 6 months prior to the Screening visit.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cohort 1; Drug: Sevasemten Drug: Placebo	Drug: Placebo; Placebo is administered orally once per day; Drug: Sevasemten Dose 1; Sevasemten is administered orally once per day
Experimental: Cohort 2; Drug: Sevasemten Drug: Placebo	Drug: Placebo; Placebo is administered orally once per day; Drug: Sevasemten Dose 2; Sevasemten is administered orally once per day
Experimental: Cohort 3; Drug: Sevasemten Drug: Placebo	Drug: Placebo; Placebo is administered orally once per day; Drug: Sevasemten Dose 3; Sevasemten is administered orally once per day

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of adverse events during treatment with sevasemten or placebo	All participants	36 months
Severity of adverse events during treatment with sevasemten or placebo	All participants	36 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from Baseline in fast skeletal muscle troponin I	All participants	12 weeks
Change from Baseline in serum creatine kinase	All participants	12 weeks
Incidence of laboratory test-related treatment emergent adverse events	All participants	36 months
Pharmacokinetics as measured by steady state plasma concentration	All participants	36 months

Collaborators and Investigators

• Sponsor: Edgewise Therapeutics, Inc.
• Investigators: Study Chair: Sam Collins, MBBS, PhD, Edgewise Therapeutics, Inc.

Publications and helpful links

Helpful Links

• Sponsor Website

Study record dates

Study Major Dates

• Study Start (Actual): March 22, 2024
• Primary Completion (Estimated): March 1, 2027
• Study Completion (Estimated): March 1, 2027

Study Registration Dates

• First Submitted: October 20, 2023
• First Submitted That Met QC Criteria: October 20, 2023
• First Posted (Actual): October 25, 2023

Study Record Updates

• Last Update Posted (Estimated): November 6, 2025
• Last Update Submitted That Met QC Criteria: November 5, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Duchenne Muscular Dystrophy
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Nervous System Diseases; Muscular Diseases; Neuromuscular Diseases; Genetic Diseases, Inborn; Genetic Diseases, X-Linked; Muscular Disorders, Atrophic; Muscular Dystrophies; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Muscular Dystrophy, Duchenne
• Other Study ID Numbers: EDG-5506-215

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
• product manufactured in and exported from the U.S.: No