This is a multicenter, randomized, double-blind, parallel-group, placebo-controlled study intended to evaluate the safety and efficacy of mexiletine in patients with myotonic dystrophy type 1 and type 2 (DM1 and DM2). The study will consist of a 4-week screening period and a 26-week treatment phase with patient visits as screening, baseline, weeks 1, 2, 6, 14, 18, and 26. Eligible patients will be randomized to mexiletine or placebo in a 1:1 ratio. Approximately 158 DM1 patients (79 active: 79 placebo) are planned to be enrolled across 10-15 experienced investigational centers in Europe. In addition, up to 16 DM2 patients are planned to be enrolled (sub-group - 8 active: 8 placebo).~Study drug (mexiletine 167 mg or placebo) will be started as a once a day (QD) treatment regimen. The dose will be titrated up at the Week 1 and Week 2 visits to a maximum of 1 capsule three times a day. Depending on tolerability, the dose can also be either maintained or - if required - reduced by one dose step at any time during the study to a minimum dose of 167 mg QD.
A Randomized, Double-blind, Placebo-controlled, Multi-center Study to Investigate the Efficacy and Safety of Mexiletine During 26 Weeks of Treatment in Patients with Myotonic Dystrophy Type 1 and Type 2 [The MIND Study]