An Open-Label Extension Study to Evaluate the Long-Term Safety and Efficacy of Once Daily Mexiletine PR in Patients with Myotonic Dystrophy Type 1 and Type 2 who have completed the MEX-DM-302 Study (ATLAS Study)

Overview

Sponsor-declared trial summary

Key facts

Sponsor

Lupin Atlantis Holdings SA

Participant type

Pediatric, Patients

Age range

0-17 years, 18-64 years, 65+ years

Gender

Male and Female

Therapeutic area

Phenomena and Processes [G] - Musculoskeletal and Neural Physiological Phenomena [G11]

Trial duration

12 Sep 2025 → ongoing

Decision date (initial)

2024-10-11

Transition trial

No

Low-intervention

No

Rare-disease indication

Yes

Vulnerable population

Yes

Funding sources

LUPIN ATLANTIS HOLDINGS SA

Trial design

CTIS Part I — objectives, methods, condition coding

Main objective

Scope: Safety, Pharmacokinetic, Efficacy

To assess the continuous long-term safety and efficacy of mexiletine PR for the symptomatic treatment of myotonia in patients with myotonic dystrophy type 1 and type 2 who have completed MEX-DM-302 study.

Secondary objectives 3

1. To assess the long-term efficacy of mexiletine PR on patient-reported outcomes
2. To assess the long-term efficacy of mexiletine PR on functional capacity outcome measures
3. To assess the long-term cardiac safety of mexiletine PR

Conditions and MedDRA coding

Myotonic Dystrophy type 1 and type 2 (DM1/DM2)

Regulatory references

Scientific advice from competent authorities

European Medicines Agency

Plan to share IPD

No

IPD plan description

NA

Eligibility criteria

Principal inclusion / exclusion criteria as submitted by sponsor

Inclusion criteria 9

1. DM1 or DM2 diagnosis confirmed genetically;
2. Ability to comprehend and willingness to sign an informed consent (ICF) or ICF of the parent(s)/legal guardian and written assent from the patient (if patient < 18 years of age);
3. Ability to understand the study requirements including intention to stay in the study until the end-of-study visit at 26 weeks of treatment;
4. Male or non-pregnant female ≥16 years of age;
5. Body Mass Index (BMI) of 18.5 kg/m2 to 30 kg/m2, and weight ≥45 kg;
6. Female patients of childbearing potential must be using a highly effective form of birth control for the duration of the study and for at least 7 days after last dose of study drug;
7. No significant cardiac abnormalities as determined by a cardiologist’s assessment;
8. Have sufficient finger flexor strength to grasp the handle of the dynamometer used to measure myotonia;
9. DM1 patients only - Muscular impairment rating scale (MIRS) score of 2, 3 or 4.

Exclusion criteria 15

1. Are pregnant or lactating;
2. Have any one of the following medical conditions: uncontrolled diabetes mellitus, cancer other than skin cancer less than five years previously (e.g., basal-cell carcinoma (BCC) and squamous-cell carcinoma (SCC) of skin allowed), multiple sclerosis, seizure disorders, or other serious medical illness;
3. Severe renal impairment (glomerular filtration rate (GFR) < 30 mL/min);
4. Medical conditions which could interfere with muscle function such as infections, trauma, fractures, or planned surgery;
5. Medical conditions that could affect hand functioning including but not limited to rheumatoid arthritis, Dupuytren’s contracture, hand deformity, etc.;
6. Severe arthritis or medical condition (other thanDM1/DM2) that would significantly impact ambulation;
7. High incidence of falls or fall-associated fractures (>5 falls during the past 12 months);
8. Preexisting elevated liver function tests > 3 times the upper limit of normal (ULN) on Day 1 (alanine transaminase (ALT)/aspartate transaminase (AST), gamma-glutamyl transferase (GGT)) and/or any abnormal chemistry, hematology or urine lab considered clinically significant by investigator;
9. Serum potassium values < 3.5 mmol/L or > 5.0 mmol/L or serum magnesium values < 1.7 mg/dL. Electrolytic imbalance such as hypokalaemia, hyperkalaemia or hypomagnesaemia may increase the proarrhythmic effects of mexiletine. Electrolyte imbalances need to be corrected before administering mexiletine and will be monitored throughout treatment.
10. Intake of any anti-myotonic treatment within 4 weeks prior to baseline (Day 1) or 5 half-lives, whichever is longer such as metformin, such as propafenone, flecainide, lamotrigine, carbamazepine or any other channel-blocker/ anticonvulsive drugs;
11. Use of any concomitant medications that could increase the cardiac risk;
12. Known allergy to mexiletine or any local anesthetics;
13. Participation in another interventional clinical study during the last 3 months or 5 half-lives of the investigational medicinal product, whichever is longer (with the exception of participation in the previous MEX-DM-302 study);
14. Wheelchair-bound or bed-ridden;
15. Any cardiac safety associated condition including any of the following criteria detected by cardiac evaluations including 24-hr Holter monitor, echocardiogram and clinical evaluations: • PR interval ≥240 ms or QRS duration ≥120 ms on resting ECG • Personal history of 3rd degree or 2nd degree type 2 atrioventricular block or sinus node dysfunction with pauses ≥3 seconds, complete bundle branch block, bifascicular and trifascicular block or any heart block susceptible to evolve to complete heart block • Personal history of sustained atrial fibrillation, flutter or tachycardia (duration >30 seconds) • Personal history of non-sustained (ventricular triplets or more) or sustained ventricular tachycardia • Myocardial infarction (acute or past) or coronary artery stenosis >50%, presence of abnormal Q waves • New York Heart Association (NYHA) Class II to IV heart failure • Left ventricular systolic dysfunction with ejection fraction <50% • Sinus node dysfunction (including ECG sinus rate <50 beats per minute (BPM)) • Co-administration of 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) • Co-administration of other classes of antiarrhythmics (class Ib: lidocaine, phenytoin, tocainide; class II: propranolol, esmolol, timolol, metoprolol, atenolol, carvedilol, bisoprolol, nebivolol; class IV: verapamil, diltiazem) • Patients with implantable cardioverter defibrillators (ICDs) and pacemakers are excluded • Presence of symptomatic coronary artery disease

Endpoints

Primary and secondary outcome measures (English text)

Primary endpoints 4

1. Incidence of Treatment Emergent Adverse Events (TEAEs), treatment-related TEAEs, serious AEs, and patient discontinuation rate.
2. Standard clinical laboratory evaluations, physical examinations, and vital signs
3. Mean change from baseline in PR, QRS, and QTc Intervals, and average minimum heart rate by 12-lead in ECG.
4. Clinically relevant arrhythmic events in the Holter monitor results

Secondary endpoints 6

1. Handgrip Dynamometer
2. Individualized Neuromuscular Quality of Life Questionnaire (INQoL) locking domain
3. Myotonia Behavior Scale (MBS)
4. Visual Analog Scale (VAS) for myotonia
5. 10 meter Walk Test (10mWT)
6. DM1-Active-c

Investigational products

Investigational medicinal products (IMPs), comparators, placebo, auxiliary

Test 3

Sponsors and contacts

Sponsor organisations, regulatory contacts, third parties

Lupin Atlantis Holdings SA

Sponsor organisation

Lupin Atlantis Holdings SA

Address

Landis + Gyr-Strasse 1

City

Zug

Postcode

6300

Country

Switzerland

Scientific contact point

Organisation

Lupin Atlantis Holdings SA

Contact name

Alla Zozulya Weidenfeller

Public contact point

Organisation

Lupin Atlantis Holdings SA

Contact name

Alla Zozulya Weidenfeller

Third parties 5

Locations

5 EU/EEA countries · 13 investigational sites

By country

Investigational sites

Country notifications

Trial-start, recruitment-start, end and early-termination notifications submitted per Member State

Results and documents

Annex IV summary of results, Annex V layperson summary, and all documents registered in CTIS for this trial

Documents 95 files

Public protocol annexes, IB summaries, regulatory submissions and post-authorisation documents registered in CTIS.

Application history

6 submissions — initial application plus substantial / non-substantial modifications