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Myotonic DisordersNCT04622553

Open-label Extension Study in Paediatric Patients Who Have Completed the MEX-NM-301 Study.

A study testing Mexiletine in people with Myotonic Disorders, run by Lupin Ltd. at 1 site in France.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

Open-label Extension Study to Evaluate the Long-term Safety and Efficacy of Mexiletine in Paediatric Patients with Myotonic Disorders Who Have Completed the MEX-NM-301 study. Read more about this study

Who is it for?
Ages 6 to 18 years
Conditions the study is for
Myotonic Disorders
What is being tested?
Mexiletine
Could I receive a placebo?
No, everyone receives an active treatment
How many people
12 participants
Where
1 siteFrance
Study dates
5 Nov 2021to 4 Jun 2026
Phase
Interventional
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 6 to 18 years
  • All sexes
  • No healthy volunteers
  • Child, Adult

Who may be able to join

  • Patients previously completed the parent study PIP study 4 (MEX-NM-301) and tolerated the Mexiletine in the study.
  • Able and willing to provide assent to study participation and a parent or legal guardian willing to sign written informed consent prior to study entry.
  • Patients continue to meet inclusion criteria of parent study (MEX-NM-301):
  • No significant cardiac abnormalities as determined by a cardiologist's assessment of the ECG and Echocardiogram
  • No history or evidence of any significant liver disorder Laboratory investigations for haematology, biochemistry, and urinalysis at screening are within normal range, or showing no clinically relevant abnormal values, as judged by the Investigator
  • Female patients of childbearing potential must be using an acceptable form of birth control as determined by the Investigator (e.g., oral contraception, implantable, injectable/transdermal hormonal contraception, intrauterine device (IUD), barrier methods), tubal ligation or have a vasectomized partner or are practicing abstinence

Who cannot join

  • Clinically significant laboratory abnormality, ECG or other clinical findings on physical examination indicative of a clinically significant exclusionary disease as determined by the investigator
  • Any contra-indication to mexiletine (as described in the Namuscla Summary of Product Characteristics [SmPC])
  • Hypersensitivity to the active substance, or to any of the excipients
  • Hypersensitivity to any local anaesthetic
  • Ventricular tachyarrhythmia
  • Complete heart block (i.e., third-degree atrioventricular block) or any heart block susceptible to evolve to complete heart block (first-degree atrioventricular block with markedly prolonged PR interval (≥ 200 ms) and/or wide QRS complex (≥ 120 ms), second-degree atrioventricular block, bundle branch block, bifascicular and trifascicular block),
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  • QT interval > 450ms
  • Myocardial infarction (acute or past), or abnormal Q-waves
  • Symptomatic coronary artery disease
  • Heart failure with ejection fraction <50%
  • Atrial tachyarrhythmia, fibrillation or flutter
  • Sinus node dysfunction (including sinus rate < 50 bpm)
  • Co-administration with medicinal products inducing torsades de pointes (class Ia, Ic, III antiarrhythmics): Co-administration of mexiletine and antiarrhythmics inducing torsades de pointes (class Ia: quinidine, procainamide, disopyramide, ajmaline; class Ic: encainide, flecainide, propafenone, moricizine; class III: amiodarone, sotalol, ibutilide, dofetilide, dronedarone, vernakalant) increases the risk of potentially lethal torsades de pointes.
  • Co-administration with medicinal products with narrow therapeutic index
  • Co- administration with antiarrhythmics
  • Any other neurological or psychiatric condition that might affect the assessment of the study measurements
  • Any concurrent illness, or medications which could affect the muscle function
  • Seizure disorder, diabetes mellitus requiring treatment by insulin
  • Pregnant or breastfeeding
  • Concurrent participation in any other clinical trial.

Trial locations and contacts

1 site in 1 country.

France1 site

  • Hôpital Necker-Enfants-Malades

    Paris

Other trials in France

About this study

Official title: Open-label Extension Study to Evaluate the Long-term Safety and Efficacy of Mexiletine in Paediatric Patients With Myotonic Disorders Who Have Completed the MEX-NM-301 Study.

Open-label Extension Study to Evaluate the Long-term Safety and Efficacy of Mexiletine in Paediatric Patients with Myotonic Disorders Who Have Completed the MEX-NM-301 study.

Read the detailed description

This is an open-label extension study evaluating the long-term efficacy and safety of mexiletine in paediatric patients with myotonic disorders who have completed the initial parent paediatric study with mexiletine (Protocol No. MEX-NM-301 (PIP Study 4) for children and adolescents aged 6 to < 18 years and who continue to meet the eligibility criteria.

Patients who meet the eligibility criteria and provide consent for this study will be enrolled sequentially by decreasing age groups. Patients aged 12 to < 18 years will enter first as this is the first cohort expected to complete the parent study PIP Study 4 based on top down recruiting. Once initial pharmacokinetics (PK), safety and efficacy are confirmed in this population, patients aged 6 to <12 years will be first enrolled in PIP Study 4 and subsequently this study (PIP Study 7).

Enrolled patients will receive mexiletine at a dose determined in the parent study. Dosing is determined according to body weight and tolerability.

The study includes 9 clinic visits - V1 (baseline), and V2 to V9 every 3 months, approximately, thereafter.

The total duration of study will be 24 months per patient. End-of-treatment (EOT) visit will occur at 24 months or in accordance with the availability of product. The overall study duration would be approximately 5 years.

Being tested
Mexiletine
Medical subject headings
Myotonic Disorders

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • MexiletineDrug

    Also called Namuscla ™

    Patients will be enrolled sequentially into 2 cohorts.

    Cohort 1 - (patients aged 12 to < 18 years):

    approximately 8 weeks - 4 weeks of dose titration period + 4 weeks of maintenance period.

    Cohort 2- (patients aged 6 to < 12 years,):

    approximately 8 weeks - 4 weeks of dose titration period + 4 weeks of maintenance period. Enrolment for Cohort 2 will begin after initial pharmacokinetics (PK), safety and efficacy are confirmed in this population, of patients in Cohort 1

Study groups in NCT04622553
Study groupRoleWhat they receive
Cohort 1 and 2Other7 patients aged 12 to < 18 years , inclusive in cohort-1 7 patients aged 6 to < 12 years, inclusive in cohort-2
Receives: Drug: Mexiletine

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Assess the long-term safety and tolerability of mexiletine by AEs

    Assess the long-term safety and tolerability of mexiletine in paediatric patients by number and frequency of AEs/SAEs, throughout the study while on treatment

    Measured: Approximately 24 months

  2. Assess the long-term safety and tolerability of mexiletine by hand relaxation

    Mean time (in seconds) to relaxation of hand muscles and reduction in relaxation time from the first to the fifth contraction

    Measured: Approximately 24 months

  3. Assess the long-term safety and tolerability of mexiletine measurement of AESI

    Assess the long-term safety and tolerability of mexiletine in paediatric patients by Incidence of adverse events of special interest (AESI),

    Measured: Approximately 24 months

  4. Assess the long-term safety and tolerability of mexiletine by changes in ECG

    Assess the long-term safety and tolerability of mexiletine in paediatric patients by changes in ECG assessments from baseline, repeated at each study visit

    Measured: Approximately 24 months

  5. Assess the long-term safety and tolerability of mexiletine by muscle stiffness

    Score for muscle stiffness (myotonia severity) as self-reported by the patients on a Visual Analog Scale (VAS) or Faces scale

    Measured: Approximately 24 months

Secondary outcomes (6)

  1. Mean change in VAS

    Mean change in VAS (8 to < 18 years) or Faces (6 to < 8 years) score for severity of muscle stiffness (if not a primary endpoint) pain, weakness and fatigue (every 3 months).

    Measured: Approximately 24 months

  2. Clinical myotonia assessment

    Mean change in time to open the eyes after forced eye closure as measured on a stopwatch (when eyelid myotonia present)

    Measured: Approximately 24 months

  3. Mean change in health-related quality-of-life

    Mean change in health-related quality-of-life as measured by the Paediatric Quality of Life (PedsQL) score (secondary endpoint for patients aged 6 years to <18 years; every 6 months).

    Measured: Approximately 24 months

  4. Clinical Global Impression (CGI) scores

    Clinical Global Impression (CGI) scores (efficacy and tolerability) evaluated by the patient, a parent or proxy and by the investigator. Measured every 6 months

    Measured: Approximately 24 months

  5. Mean change in Myotonia Behaviour Scale (MBS) scores

    Mean change in Myotonia Behaviour Scale (MBS) scores (for patients aged 6 years to < 18 years; measured every 6 months).

    Measured: Approximately 24 months

  6. Mean change in time to perform Timed-up and go (TUG) test

    Mean change in time to perform Timed-up and go (TUG) test (patients aged 6 to <18 years only)

    Measured: Approximately 24 months

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted10 Nov 2020
  2. Study start5 Nov 2021
  3. Primary completion4 Jun 2026
  4. Study completion4 Jun 2026

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Model description
The aim of this study is to obtain additional information regarding the long-term safety and efficacy of mexiletine for the symptomatic treatment of myotonia in paediatric subjects who have completed the initial paediatric study MEX-NM-301.
Masking
None (open label)
Enrolment
12 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04622553
Sponsor's protocol ID
MEX-NM-303
Status last verified
Sep 2026
First submitted
22 Oct 2020
Last updated
8 Sep 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A study testing Mexiletine in people with Myotonic Disorders, run by Lupin Ltd. at 1 site in France.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 6 inclusion and 20 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 8 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Assess the long-term safety and tolerability of mexiletine by AEs (time frame: Approximately 24 months). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04622553.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Sep 2026.

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