Safety, Tolerability, Efficacy of MTP-131 for Treatment of Mitochondrial Disease in Subjects From the MMPOWER Study

Inclusion Criteria: * Subject completed participation in the SPIMM-201 study without a significant protocol deviation that would suggest the subject may not be able to complete all study requirements in the opinion of the Sponsor * Subject must reside in North America for the duration of the study * Subject has not received study drug in the SPIMM-201 study within 3 weeks prior to Screening * Women of childbearing potential must agree to use 1 of the methods of birth control specified in the protocol from the date they sign the informed consent form (ICF) until two months after the last dose of study drug * Subject has been on stable (unchanged and constant) medications (including over-the counter treatments, vitamins, or supplements) for at least 1 month prior to the Baseline Visit Exclusion Criteria: * Subject has 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 (i.e. unstable angina or recent myocardial infarction) * Subject has received any investigational compound and/or has participated in another interventional clinical study within 30 days prior to the Baseline Visit or is concurrently enrolled in any non-interventional research of any type judged to be scientifically or medically incompatible with the study as deemed by the Investigator in consultation with the Sponsor * Subject experienced an adverse reaction to study drug in the SPIMM-…