Safety and Biomarker Response to (+)-Epicatechin in Becker Muscular Dystrophy

The safety and tolerability of three escalating doses of (+)-epicatechin will be assessed and early effectiveness measured by changes in plasma biomarkers, tissue biomarkers from muscle biopsies, cardiac imaging, and on clinical function assessments of participants' muscle strength. All patients will receive oral (+)-epicatechin for a total duration of approximately 52 weeks. Three doses of (+)-epicatechin will be tested in sequential 2 month periods with total daily doses of 75, 150, and 225 mg/day (+)-epicatechin. Doses will be escalated every 2 months, if tolerated, for the first 6 months of the study. Participants will then continue to receive the highest does they tolerated for an additional 6 months.