We are recruiting patients with genetically confirmed primary mitochondrial myopathy who are at least 18 years old for a randomized, double-blind, placebo-controlled study of a new drug to treat this disorder. This study is designed to assess whether experimental drug ASP0367 is safe and effective for patients with mitochondrial myopathy. Participants will take the study drug orally once per day. This is a placebo-controlled study followed by an open-label extension, which means that during the treatment period some patients will receive ASP0367 and some will receive a placebo, which does not contain active study medication. At the end of the treatment period all participants will be offered ASP0367 for a 6-month period.

The study will last roughly 1 year and 8 months and involves at least 11 visits to CHOP, remote interviews, video assessments, and home visits for additional blood draws. If you are interested in learning more about this study, please visit ClinicalTrials.gov or contact the study team for additional information.