Open-Label Extension Trial to Characterize the Long-term Safety and Tolerability of Elamipretide in Subjects With Genetically Confirmed Primary Mitochondrial Myopathy (PMM)

Inclusion Criteria: * Investigator determines the subject can, and subject agrees to, adhere to the trial requirements for the length of the trial including self-administration (by subject or trained caregiver) of the study drug * Subject completed the End-of-Study Visit in SPIMM-202 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 trial requirements * Subject has received any investigational compound (excluding elamipretide) and/or has participated in another interventional clinical trial within 30 days prior to the SPIMM-203 Baseline Visit (excluding SPIMM-202) or is concurrently enrolled in any non-interventional research of any type judged to be scientifically or medically incompatible with the trial as deemed by the Investigator in consultation with the Sponsor * Subject experienced an adverse reaction attributed to study drug resulting in permanent discontinuation of study drug in the SPIMM-202 trial. * Female subjects who are pregnant, planning to become pregnant, or lactating * Subject has undergone an in-patient hospitalization within the 1 month prior to the SPIMM-203 Baseline Visit