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Study on the Safety of VX-670 for Adults with Myotonic Dystrophy Type 1

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying Myotonic Dystrophy Type 1, a genetic disorder that affects muscle function. The study will evaluate a new treatment called VX-670, which is administered as a solution for injection or infusion. The purpose of the study is to assess the safety and tolerability of this treatment in adults with Myotonic Dystrophy Type 1.

The study is divided into two parts. In the first part, participants will receive single doses of VX-670 to determine how well it is tolerated. In the second part, both single and multiple doses will be given to further evaluate safety and tolerability. Some participants will receive a placebo, which is a substance with no active medication, to compare the effects of VX-670.

Throughout the study, participants will be closely monitored for any side effects or changes in their health. This will include regular check-ups, laboratory tests, and assessments of heart function using standard tests like electrocardiograms (ECGs). The study aims to gather important information about how VX-670 is processed in the body and its potential impact on muscle function in individuals with Myotonic Dystrophy Type 1.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Upon joining the study, an initial assessment is conducted to confirm eligibility. This includes verifying a clinical diagnosis of myotonic dystrophy type 1 (DM1) and ensuring the participant meets specific criteria such as age, body mass index, and genetic test results.

  2. Step 2

    Part a: single dose administration

    Participants receive a single dose of VX-670 solution, administered as an injection or infusion. The purpose is to evaluate safety and tolerability. Monitoring includes checking for any adverse effects, conducting laboratory tests, and performing electrocardiograms (ECGs).

  3. Step 3

    Part b: multiple dose administration

    Participants may receive multiple doses of VX-670 to further assess safety and tolerability. This phase also involves monitoring for adverse effects, laboratory tests, and ECGs. Additional assessments include measuring drug concentration in plasma and muscle tissue, and evaluating changes in muscle biopsy samples.

  4. Step 4

    Ongoing monitoring

    Throughout the trial, participants undergo regular monitoring to ensure safety. This includes tracking vital signs and using the Columbia Suicide Severity Rating Scale (C-SSRS) to assess mental health.

  5. Step 5

    Completion and follow-up

    Upon completion of the trial, a final assessment is conducted. This includes reviewing all collected data to evaluate the overall safety and effectiveness of VX-670 in treating myotonic dystrophy type 1.

Who can join the trial?

7 criteria

  • The patient must have a body mass index (BMI) of less than 35.0 kg/m² and weigh more than 40 kg. BMI is a measure that uses height and weight to estimate body fat.
  • The patient should be between 18 and 64 years old. Both men and women can participate, including women who can have children, as long as local rules allow it.
  • The patient must have a confirmed diagnosis of myotonic dystrophy type 1 (DM1), with symptoms starting after the age of 1, and a positive genetic test showing a specific change in their DNA called a CTG repeat of at least 100.
  • For Part B of the study, the patient must be able to walk 10 meters without help, although they can use a brace or similar device if needed.
  • For Part B, the patient must show signs of myotonia, which means their muscles take longer than normal to relax after contracting. This is measured by a test called HOT, which should be 2 seconds or more.
  • For Part B, the patient must show signs of muscle weakness, measured by how strong their hand grip is compared to what is expected. This should be between 20% and 80% of the expected strength.
  • The patient must have a left ventricular ejection fraction (LVEF) greater than 55% within the last 3 months. LVEF is a measure of how well the heart pumps blood with each beat.

Who cannot join the trial?

4 criteria

  • Individuals who do not have Myotonic Dystrophy type 1 (DM1) cannot participate. This is a genetic condition that affects muscles and other body systems.
  • Participants must be within a specific age range, which is not specified here, but typically means they must be adults.
  • Both males and females are eligible, so gender is not a reason for exclusion.
  • Individuals who are considered part of a vulnerable population, such as those unable to give informed consent, are not included.
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Investigated drugs

VX 670 is an investigational medication being studied for its potential to treat myotonic dystrophy type 1 (DM1). The trial aims to assess how safe and tolerable this medication is when given in single and multiple doses to adults with DM1. The study also looks at how the body processes VX 670 and its effects on the body.

What is already known about the treatment

VX 670 – This medication is administered orally and is currently being studied in clinical trials for its potential use in treating Myotonic Dystrophy Type 1. It is in the early stages of research, specifically in Phase 1/2 trials, where its safety, tolerability, and effects on the body are being evaluated. The main therapeutic indication for VX 670 is to address symptoms associated with Myotonic Dystrophy. At the molecular level, VX 670 is believed to work by modulating specific pathways that are disrupted in this condition, although the exact mechanism is still under investigation. It is classified pharmacologically as an investigational drug, as it is not yet approved for general medical use.

Investigated diseases

Myotonic Dystrophy – Myotonic dystrophy is a genetic disorder characterized by progressive muscle wasting and weakness. It primarily affects the muscles, but it can also impact other systems in the body, such as the heart, eyes, and endocrine system. The condition is marked by prolonged muscle contractions (myotonia) and an inability to relax muscles after use. Symptoms often begin in adulthood and can vary widely in severity among individuals. Over time, muscle weakness and myotonia can lead to difficulties with movement and daily activities. The progression of the disease can be slow, with symptoms worsening gradually over many years.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2023-506028-10-00Protocol codeVX23-670-001Estimated enrolment52 patientsSponsorVertex Pharmaceuticals Inc.

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