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NCT Number: NCT07700225

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

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.

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Key information

Conditions

DM1 Congenital, Hereditary, and Neonatal Diseases and Abnormalities Genetic Diseases, Inborn Heredodegenerative Disorders, Nervous System Muscular Diseases Muscular Disorders, Atrophic Muscular Dystrophies Musculoskeletal Diseases Myotonia Myotonic Disorders Myotonic Dystrophy Myotonic Dystrophy 1 Myotonic Dystrophy Type 1 Myotonic Dystrophy Type-1 Myotonic Dystrophy, Type 1 (DM1) Myotonic Muscular Dystrophy Nervous System Diseases Neurodegenerative Diseases Neurologic Manifestations Neuromuscular Diseases Neuromuscular Manifestations Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–70 year

Sex eligibility

All sexes

Study type

Observational

Primary location

Virginia Commonwealth University

Richmond, Virginia, 23298, United States

Location status: Recruiting

Location contact

Jennifer Raymond

CONTACT

[email protected]

804-828-6318

Nicholas Johnson, MD

PRINCIPAL_INVESTIGATOR

About this study

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:

  • How do clinical measures, such as walking speed, hand function, and muscle strength, change over a multi-year period in people with DM1?
  • 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?

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

Primary outcomes

  1. 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.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. 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.

Study contacts

Contact information is provided by the study sponsor or research team.

Jennifer Raymond

CONTACT

[email protected]

804-828-6318

Ruby Langeslay

CONTACT

[email protected]

804-828-6318

Sponsors and collaborators

Lead sponsor

Virginia Commonwealth University

Other

Collaborators

  • Dyne Therapeutics
  • Myotonic Dystrophy Clinical Research Network (DMCRN)
  • Vertex Pharmaceuticals Incorporated

Registry information

Acronym: END-EXT

Important dates

Study start
2026
Primary completion
2032
Study completion
2032
First posted
Jul 13, 2026
Registry last updated
Jul 27, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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