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 MEX-DM-302 Study.
NCT Number: NCT06549400
Status: NOT_YET_RECRUITING
Study Type: INTERVENTIONAL
Phases: PHASE3
Conditions: Myotonic Dystrophy
Interventions: DRUG: Mexiletine granules for prolonged-release oral suspension
Sponsor: Lupin Ltd.
Collaborators: Lupin Atlantis Holdings S.A.
Sex: ALL
Age: CHILD, ADULT, OLDER_ADULT
Enrollment: 176
Study Design: Allocation: NA|Intervention Model: SINGLE_GROUP|Masking: NONE|Primary Purpose: TREATMENT
Start Date: 2025-02-27
Completion Date: 2027-06-22

Summary:
This is an open-label extension study intended to evaluate the long-term safety and efficacy of mexiletine PR in patients with myotonic dystrophy type 1 and type 2 (DM1 and DM2) who have completed the parent study MEX-DM-302.

Primary Outcome Measures: To assess the long-term efficacy of once daily mexiletine PR for the symptomatic treatment of myotonia in patients with myotonic dystrophy type 1 and type 2 (DM1 and DM2) who have completed MEX-DM-302 study., Handgrip relaxation time in DM1 patients by mean change in baseline of handgrip relaxation time (seconds) after maximal voluntary isometric contraction (MVIC), 78 weeks|To assess the long-term safety of once daily mexiletine PR for the symptomatic treatment of myotonia in patients with myotonic dystrophy type 1 and type 2 (DM1 and DM2) who have completed the MEX-DM-302 study, Number and frequency of AEs/SAEs throughout the study while on treatment, 78 weeks
Secondary Outcome Measures: Mean change in VAS, Score for muscle stiffness (myotonia severity) as self-reported by patients on a Visual Analog Scale (VAS), 78 weeks|Mean change in MBS scores, Mean change in Myotonia Behavior Scale (MBS) scores on a scale of 0 (no stiffness) to 5 (incapacitating stiffness), 78 weeks|Mean change in health-related quality of life, Mean change in health-related quality of life (measured by INQoL), 78 weeks|Mean change in DM1-Activ-c scale (DM1 patients only), Mean change in measure of activity and social participation (measured by a Rasch-built scale with a 0-100 interval range), 78 weeks|Mean change in time to perform the 10-meter Walk Test, Mean change in time (seconds) to perform the 10-meter Walk Test (10mWT), 78 weeks|Mean change in handgrip relaxation time, Mean change in maximal voluntary isometric contraction (MVIC) and relaxation time by Video-recording of Hand Opening Time (VHOT) functional evaluation, 78 weeks|Mean change in time to perform Timed-up and go (TUG) test, Mean change in time (seconds) to perform Timed-up and go (TUG) test, 78 weeks|Mean change in health-related quality of life measured by EQ-5D, Mean change in health-related quality of life measured by EQ-5D (5-point scale), 78 weeks|Mean change in Myotonic Dystrophy Health Index (MDHI) score (DM1 patients), Mean change in Myotonic Dystrophy Health Index (MDHI) score (DM1 patients) as measured by patient's perceived health, 78 weeks|Mean change in Myotonic Dystrophy 2 Health Index (MD2HI) score (DM2 patients), Mean change in Myotonic Dystrophy 2 Health Index (MDHI) score (DM2 patients) as measured by patient's perceived health, 78 weeks|Assess the long-term safety of mexiletine PR by changes in ECG, Mean change in ECG (PR, QRS, and QTc intervals in units of milliseconds \[ms\]) from baseline, 78 weeks|Assess the long-term safety of mexiletine PR by changes in ECG (HR), Mean change in ECG (HR in units of beats per minute) from baseline, 78 weeks|Assess the long-term safety of mexiletine PR by AEs, Incidence of treatment emergent adverse events (TEAEs), treatment-related TEAEs, serious AEs, and patient discontinuation rate, 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (hematology measured in units of μL [microliters]) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by hematology parameters in units of μL: white blood cell (WBC) with differential (absolute count), red blood cells (RBC), platelet count, and red blood cell indicies., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (hematology measured in units of % [percentage]) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by hematology parameters in units of %: white blood cell (WBC) and differential (percentage) and hematocrit., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (hematology measured in g/dL [units of grams per deciliter]) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by hematology parameters in units of g/dL: hemoglobin., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (chemistry measured in units of mmol/L) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by chemistry parameters in units of mmol/L: chloride, carbon dioxide, potassium, and sodium, 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (chemistry measured in units of U/L) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by chemistry parameters in units of U/L: alkaline phosphatase, aspartate aminotransferase (AST), aspartate transaminase (ALT), gamma-glutamyl transferase (GGT), and creatine phosphokinase., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (chemistry measured in units of g/dL) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by chemistry parameters in units of g/dL: albumin and total protein., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (chemistry measured in units of mg/dL) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by chemistry parameters in units of mg/dL: blood urea nitrogen (BUN), calcium, creatinine (eGFR), glucose, total bilirubin, and magnesium., 78 weeks|Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations (urinalysis) from change in baseline, Assess the long-term safety of mexiletine PR by standard clinical laboratory evaluations as measured by urinalysis parameters (measured as normal or abnormal): appearance, specific gravity, pH, protein, glucose, ketones, blood, leukocyte esterase, nitrite, bilirubin, urobilinogen, and microscopic examination., 78 weeks|Assess the long-term safety of mexiletine PR by vital signs (pulse), Assess the long-term safety of mexiletine PR by vital signs (pulse in units of bpm \[beats per minute\]) from change in baseline, 78 weeks|Assess the long-term safety of mexiletine PR by vital signs (body temperature), Assess the long-term safety of mexiletine PR by vital signs (body temperature in units of Fahrenheit or Celsius) from change in baseline, 78 weeks|Assess the long-term safety of mexiletine PR by vital signs (blood pressure), Assess the long-term safety of mexiletine PR by vital signs (blood pressure \[diastolic and systolic\] in units of mmHg \[millimeters of mercury\]) from change in baseline, 78 weeks|Assess the long-term safety of mexiletine PR by vital signs (respiration), Assess the long-term safety of mexiletine PR by vital signs (respiration in units of breaths per minute) from change in baseline, 78 weeks|Assess the long-term safety of mexiletine PR by physical examinations, Assess the long-term safety of mexiletine PR by change in baseline from physical examinations (normal or abnormal) in the following regions and systems: general appearance, head and neck, heart, lung, abdomen, chest and back, upper extremities, lower extremities, neurological, and dermatological., 78 weeks