Safety, Tolerability, and Efficacy of MTP-131 for the Treatment of Mitochondrial Myopathy

Inclusion Criteria: * Diagnosis of mitochondrial disease believed to impair the mitochondrial respiratory chain. * Eligibility requires prior genetic confirmation of mitochondrial disease. * Diagnosis of mitochondrial myopathy judged by the Investigators to be due to existing mitochondrial disease. * Must be able to complete a Screening Visit 6MWT. * Body mass index (BMI) score \>15.0 and \<35.0 kg/m2 at Screening Visit. * Women of childbearing potential must agree to use birth control as specified in the protocol from the date they sign the ICF until two months after the last dose of study drug. Exclusion Criteria: * Any prior or current medical condition that, in the judgment of the Investigator, would prevent the subject from safely participating in and/or completing all study requirements. * Had any exclusionary Newcastle Mitochondrial Disease Adult Scale (NMDAS) scores at Screening Visit. * Hospitalized (admitted as in-patient) within 1 month prior to the Baseline Visit. * A history of type 1 diabetes mellitus (T1DM). * Uncontrolled Type 1 (T1DM) or Type 2 diabetes mellitus (T2DM), in the opinion of the investigator. * A creatinine clearance \<45 mL/min as calculated by the Cockcroft Gault equation. * Requires pacemaker, defibrillator, or has undergone cardiac surgery within 2 years of Screening Visit. * QTc elongation defined as a QTc \>450 msec in male subjects and \>480 msec in female subjects. * Uncontrolled hypertension (\>160 mmHg systolic or \>100 mmHg diastoli…