Establishing Biomarkers and Clinical Endpoints in Myotonic Dystrophy Type 1 (END-DM1) Extension (END-EXT)

July 8, 2026 updated by: Virginia Commonwealth University
Myotonic Dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder that causes progressive disability and shortened life expectancy. It is characterized by progressive weakness and myotonia, which preferentially affects the craniofacial, hand, and distal leg muscles. Many patients also experience difficulties with cognition, cardiac arrhythmias, respiratory failure, or cataracts. Currently there is no treatment to slow progression or reverse the symptoms.

Study Overview

Status

Recruiting

Conditions

Detailed Description

The goal of this observational study is to characterize long-term disease progression over at least 4 years in at least 1,000 adults with myotonic dystrophy type 1 (DM1).

The main questions this study aims to answer are:

  1. How do clinical measures, such as walking speed, hand function, and muscle strength, change over a multi-year period in people with DM1?
  2. Can long-term changes in slowly progressive measures, like heart rhythms (ECG) and lung function (FVC), be accurately captured and used as biomarkers for the disease over time?

Study Type

Observational

Enrollment (Estimated)

1000

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 Backup

Study Locations

  • United States
    • Virginia
      • Richmond, Virginia, United States, 23298
        • Recruiting
        • Virginia Commonwealth University
        • Principal Investigator:
          • Nicholas Johnson, MD
        • Contact:

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

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

The study seeks to enroll at least 1000 men and women aged 18 to 70 with a positive genetic test for myotonic dystrophy type 1, a clinical diagnosis of myotonic dystrophy type 1, or a clinical diagnosis or positive genetic test for congenital myotonic dystrophy. based on research criteria. Few restrictions are placed on participation in the study because we aim to capture the full spectrum of disease severity.

Description

Inclusion Criteria:

  • Age 18 to 70 years (inclusive)
  • Written, voluntary informed consent must be obtained prior to any study procedures. In cases where a Legally Authorized Representative (LAR) provides consent, verbal assent will be obtained from the subject, as determined by the investigator and documented directly on the consent form. Capacity to consent will be determined by the neurologist at the Baseline visit and will be signed off on the Inclusion/Exclusion checklist.
  • Clinical diagnosis of DM1 based on research criteria or positive genetic test. The research criteria for clinical diagnosis of DM1 require myotonia, muscle weakness in a characteristic distribution, and history of similar findings in a first degree relative. Genetic testing confirmed the diagnosis of DM1 in > 99% of individuals who satisfied these criteria. OR A diagnosis of CDM, which is defined as children having symptoms of myotonic dystrophy in the newborn period (<30 days), such as hypotonia, feeding or respiratory difficulty, requiring hospitalization to a ward or to the neonatal intensive care unit for 3 days or more; and a genetic test suspicious of an expanded trinucleotide (CTG) repeat in the DMPK gene in the child or first degree relative. An expanded CTG repeat size in the child is considered greater than 200 repeats or E1-E4 classification (E1= 200-500, E2=500-1,000, E3=1,000-1,500, E4>1,500)

Exclusion Criteria:

  • Symptomatic renal or liver disease, uncontrolled diabetes or thyroid disorder, or active malignancy other than in situ skin cancer.
  • Current alcohol or substance use disorder.
  • Concurrent pregnancy or planned pregnancy during the course of the study.
  • Concurrent medical condition that would, in the opinion of the investigator or clinical evaluator. compromise performance on study measures.
  • Use of mexiletine or other anti-myotonia agents within 72 hours of any study visit.

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

Cohorts and Interventions

Group / Cohort
Myotonic Dystrophy Type 1 (DM1) Longitudinal Cohort
Participants with a clinical or genetic diagnosis of myotonic dystrophy type 1 (DM1) or congenital myotonic dystrophy (CDM). This cohort includes individuals transitioning from the parent study, Establishing Biomarkers and Clinical Endpoints in Myotonic Dystrophy Type 1 (END-DM1; NCT03981575), as well as newly enrolled participants.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Characterize the long-term disease progression- 10 meter walk/run
Time Frame: Baseline (0 months), every 12 months over four years
The 10-meter walk test (10MWT) is used in research to reliably measure gait speed, assessing functional mobility and detecting changes in walking performance over time. It is a highly reliable, quick, and cost-effective tool. . It is favored for its simplicity, speed, and ability to predict functional independence. A "good" score varies by age/condition, with healthy adults averaging over 1.2-1.4 m/s.
Baseline (0 months), every 12 months over four years
Characterize the long-term disease progression- vHOT
Time Frame: Baseline (0 months), every 12 months over four years
The Video Hand Opening Time (vHOT) is used in research as a practical, low-cost, and reliable quantitative tool to measure handgrip myotonia (delayed muscle relaxation) in Myotonic Dystrophy Type 1 (DM1) patients. It is particularly valuable for multicenter clinical trials because it allows for blinded, objective assessment of therapeutic responses. A "good" (healthy) score is generally as close to zero as possible.
Baseline (0 months), every 12 months over four years
Characterize the long-term disease progression- grip strength
Time Frame: Baseline (0 months), every 12 months over four years
Grip strength is used in research as a reliable, low-cost biomarker for overall muscle strength, aging, and mortality risk. A good score varies by age and sex, with healthy young adults often averaging over 40-45 kg (males) and 25-30kg (females).
Baseline (0 months), every 12 months over four years
Characterize the long-term disease progression- ECG
Time Frame: Baseline (0 months), every 12 months over four years
Electrocardiograms (ECGs/EKGs) are used in research for their non-invasive, cost-effective ability to track heart rhythm, diagnose cardiac conditions, and assess cardiovascular disease risk. In research, a "good" ECG score indicates normal sinus rhythm and intervals, such as a PR interval of 120-200 milliseconds and an RR interval of 0.6-1.2 seconds.
Baseline (0 months), every 12 months over four years
Characterize the long-term disease progression- FVC
Time Frame: Baseline (0 months), every 12 months over four years
Forced Vital Capacity (FVC) is crucial in research for diagnosing and tracking restrictive lung diseases (e.g., pulmonary fibrosis), assessing disease progression, and measuring treatment efficacy in clinical trials. A "good" or normal FVC is typically 80% or higher of the predicted value, based on a patient's age, height, sex, and ethnicity.
Baseline (0 months), every 12 months over four years
Characterize the long-term disease progression- DM1-Activ-c
Time Frame: Baseline (0 months), every 12 months over four years
The DM1-Activ-c (25-item) is a validated, Rasch-built, patient-reported outcome measure designed specifically to assess daily activity and participation in Myotonic Dystrophy Type 1 (DM1) patients. It is used in research for its high sensitivity to disease progression and therapeutic changes (responsiveness), making it a reliable primary endpoint for clinical trials to measure patient improvement. The DM1-Activ-c is scored on a scale from 0 to 100, where higher scores indicate better functional ability.
Baseline (0 months), every 12 months over four years

Collaborators and Investigators

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

Sponsor

Virginia Commonwealth University

Collaborators

Dyne Therapeutics
Myotonic Dystrophy Clinical Research Network (DMCRN)

Investigators

  • Principal Investigator: Nicholas Johnson, MD, Virginia Commonwealth University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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)

July 1, 2026

Primary Completion (Estimated)

December 1, 2032

Study Completion (Estimated)

December 1, 2032

Study Registration Dates

First Submitted

July 8, 2026

First Submitted That Met QC Criteria

July 8, 2026

First Posted (Actual)

July 13, 2026

Study Record Updates

Last Update Posted (Actual)

July 13, 2026

Last Update Submitted That Met QC Criteria

July 8, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • HM300000528 END-EXT

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

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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