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Study on the Effects of Mexiletine for Treating Myotonic Dystrophy Types 1 and 2 in Patients

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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 the effects of a medication called Mexiletine on a condition known as Myotonic Dystrophy, which comes in two types: Type 1 and Type 2. Myotonic Dystrophy is a genetic disorder that affects muscle function, leading to symptoms like muscle stiffness and weakness. The medication being tested, Mexiletine, is provided in the form of granules for a prolonged-release oral suspension, meaning it is taken by mouth and designed to release the active ingredient slowly over time. The study will also include a placebo group for comparison.

The purpose of this study is to evaluate how effective and safe Mexiletine is in treating the symptoms of myotonia, which is the delayed relaxation of muscles after contraction, in patients with Myotonic Dystrophy. Participants in the study will take the medication once daily for a period of 26 weeks. Throughout the study, various assessments will be conducted to monitor changes in muscle function and overall quality of life. These assessments include measuring handgrip relaxation time and using questionnaires to evaluate the impact of the condition on daily life.

Participants will be randomly assigned to receive either the Mexiletine treatment or a placebo, and neither the participants nor the researchers will know which treatment each participant is receiving. This approach is known as a double-blind study and helps ensure that the results are unbiased. The study aims to provide valuable information on whether Mexiletine can be a beneficial treatment option for individuals living with Myotonic Dystrophy.

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

    Joining the study

    Upon joining the study, the patient will begin a 26-week treatment period. The study is designed to assess the effectiveness and safety of a medication called mexiletine for treating symptoms of myotonia in individuals with myotonic dystrophy types 1 and 2.

  2. Step 2

    Medication administration

    The patient will receive mexiletine granules for prolonged-release oral suspension. The available dosages are 167 mg, 333 mg, and 500 mg. The medication is taken once daily by mouth.

    A placebo, which looks like the medication but does not contain the active ingredient, may also be administered to some patients as part of the study's design.

  3. Step 3

    Treatment duration

    The treatment will last for a total of 26 weeks. During this time, the patient will continue to take the medication or placebo daily as instructed.

  4. Step 4

    Monitoring and assessments

    Throughout the study, the patient will undergo various assessments to monitor the effects of the treatment. These include measuring handgrip relaxation time, which involves timing how long it takes for the hand to relax after squeezing a device called a dynamometer.

    Additional assessments may include questionnaires about quality of life, scales to measure myotonia behavior, and tests such as the 10-meter walk test.

  5. Step 5

    End of study

    At the end of the 26-week period, the patient will have a final visit to complete the study assessments. This will help determine the overall effectiveness and safety of the treatment.

Who can join the trial?

11 criteria

  • Have a confirmed genetic diagnosis of **Myotonic Dystrophy type 1 or type 2 (DM1 or DM2)**.
  • Be able to walk independently for 10 meters, using a cane, walker, or braces if needed.
  • For DM1 patients only: Have a **Muscular Impairment Rating Scale (MIRS)** score of 2, 3, or 4. This scale measures muscle weakness.
  • Be able to understand and willing to sign an **Informed Consent Form (ICF)**. If under 18, a parent or guardian must sign, and the patient must agree in writing.
  • Understand the study requirements and plan to stay in the study until the end, which is 26 weeks of treatment.
  • Be male or a non-pregnant female who is at least 16 years old.
  • Have a **Body Mass Index (BMI)** between 18.5 and 30, and weigh at least 45 kg. BMI is a measure of body fat based on height and weight.
  • If female and able to have children, use a highly effective form of birth control during the study and for at least 7 days after the last dose of the study drug.
  • Have no significant heart problems, as determined by a heart specialist.
  • Have enough finger strength to hold the handle of a device used to measure muscle stiffness.
  • Show signs of **handgrip myotonia**, which means a delay of 3 seconds or more in relaxing the grip after squeezing, during the screening test.

Who cannot join the trial?

5 criteria

  • Patients who do not have **Myotonic Dystrophy type 1 or type 2 (DM1/DM2)** cannot participate. This is a genetic disorder that affects muscle function.
  • Patients who are not within the specified age range for the study cannot participate. The study includes certain age groups only.
  • Patients who are not part of the specified clinical trial group cannot participate. This means the study is looking for specific characteristics in participants.
  • Patients who are not male or female cannot participate, as the study includes both genders.
  • Patients who are not considered part of a vulnerable population cannot participate. Vulnerable populations may include groups like children or the elderly.
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Investigated drugs

Mexiletine PR is a medication being studied for its potential to help manage symptoms of myotonia in patients with myotonic dystrophy type 1 and type 2. Myotonia is a condition where muscles have difficulty relaxing after contraction, and this medication aims to improve muscle function and reduce stiffness. The study is designed to evaluate how effective and safe this medication is when taken once daily over a period of 26 weeks.

What is already known about the treatment

Mexiletine PR – This medication is administered orally in a prolonged-release form, designed for once-daily use. It is currently being studied in clinical trials to evaluate its effectiveness and safety for treating myotonia in patients with Myotonic Dystrophy types 1 and 2. Mexiletine PR is primarily indicated for managing symptoms associated with these conditions. At the molecular level, it works by blocking sodium channels in muscle cells, which helps reduce muscle stiffness and spasms. It is classified pharmacologically as a sodium channel blocker.

Investigated diseases

  • Myotonic Dystrophy Type 1

    This is a genetic disorder characterized by progressive muscle wasting and weakness. It often begins in adulthood and can affect various body systems, including the heart, eyes, and endocrine system. Individuals with this condition may experience prolonged muscle contractions, known as myotonia, which can make it difficult to relax muscles after use. Over time, muscle weakness can become more pronounced, affecting mobility and daily activities. Other symptoms may include cataracts, cardiac issues, and hormonal changes. The severity and progression of symptoms can vary widely among individuals.

  • Myotonic Dystrophy Type 2

    This genetic disorder is similar to type 1 but generally has a later onset and milder symptoms. It is characterized by muscle weakness and myotonia, primarily affecting the neck, shoulders, and hips. Unlike type 1, type 2 often presents with less severe muscle wasting and a slower progression of symptoms. Individuals may also experience pain, fatigue, and stiffness in the muscles. Other possible symptoms include cataracts and heart conduction defects. The condition can vary significantly in its impact on different individuals.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-511179-13-00Protocol codeMEX-DM-302Estimated enrolment176 patientsSponsorLupin Atlantis Holdings SA

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