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.

Status

Recruiting

Phases

Phase 3

Study type

Interventional

Source

EU CTIS

Registry ID

CTIS2024-511178-66-00

Acronym

MEX-DM-303

Enrollment

146

Registered

2024-10-07

Start date

2025-09-12

Completion date

Unknown

Last updated

2026-01-22

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

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

Brief summary

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

Detailed description

Handgrip Dynamometer, Individualized Neuromuscular Quality of Life Questionnaire (INQoL) locking domain, Myotonia Behavior Scale (MBS), Visual Analog Scale (VAS) for myotonia, 10 meter Walk Test (10mWT), DM1-Active-c

Interventions

DRUGMexiletine granules for prolonged-release oral suspension 333 mg

DRUGMexiletine granules for prolonged-release oral suspension 167 mg

DRUGMexiletine granules for prolonged-release oral suspension 500 mg

Eligibility

Sex/Gender

All

Age

0 Years to No maximum

Design outcomes

Primary

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

Secondary

Measure	Time frame
Handgrip Dynamometer, Individualized Neuromuscular Quality of Life Questionnaire (INQoL) locking domain, Myotonia Behavior Scale (MBS), Visual Analog Scale (VAS) for myotonia, 10 meter Walk Test (10mWT), DM1-Active-c	—

Countries

Belgium, Denmark, Germany, Italy, Spain

Outcome results

None listed

Source: EU CTIS · Data processed: Feb 4, 2026