Study to Evaluate Pharmacokinetics, Safety, and Tolerability of Subcutaneous Injections of Elamipretide in Pediatric Subjects With Barth Syndrome (SPIBA-101)

Inclusion Criteria:

1. Willing and able to provide signed informed consent form (ICF) prior to participation in any trial-related procedures. If applicable, informed consent in writing from parent(s) or legally-acceptable representative(s) and, informed assent from subject (if age appropriate according to local requirements) should be provided.
2. Agrees to adhere to the trial requirements for the length of the trial.
3. Must have genetically confirmed Barth Syndrome (pathogenic variant in the TAZ gene)
4. Male aged ≥ 1 year and weighing between 7 and 30 kg at time of the Baseline Visit
5. For subjects with a medical history of cardiomyopathy, must be on a stable regimen (unchanged and constant) of background heart failure medications for at least 3 months prior to the Screening Visit.
6. Able to administer IMP or have an appropriate designee who can administer the IMP (i.e., a capable family member or a caregiver).

Exclusion Criteria:

1. History of solid organ transplant, except successful cardiac transplantation >12 months prior to Screening, if, in the opinion of the Investigator, there is no evidence of organ rejection and post-transplant pharmacotherapy, the subject is stable, and participation in the trial does not pose additional safety risk.
2. Current placement on the waiting list for heart transplantation.
3. Hospitalization for heart failure within 6 months prior to the Screening/Baseline Visit
4. Any disease or medical condition that in the opinion of the Investigator would prevent the subject from successfully participating in the trial and reliably completing the assessments or might confound trial results.
5. eGFR of < 30 mL/min at the Screening Visit (for purposes of Screening, eGFR can be confirmed locally at the clinical site. Historical values within 3 months prior to Screening can be accepted).
6. Active malignancy or any other cancer from which the subject has been cancer-free for < 2 years. Localized squamous or non-invasive basal cell skin carcinomas are allowed, if appropriately treated prior to Screening/Baseline.
7. Participation in other investigational drug or device clinical trials within 30 days or 5 half-lives (whichever is longer) of Screening/Baseline; or is currently enrolled in a non-interventional clinical trial that, in the opinion of the Investigator, may be potentially confounding to the results of the current trial. NOTE: Subjects currently treated with elamipretide through an EAP are eligible to participate in the SPIBA-101 study.
8. History of allergic reaction to the IMP or any of its components.