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Efficacy and Safety of Daily Subcutaneous Elamipretide Trihydrochloride Injections in Patients with Barth Syndrome (Phase 3b/4 Randomized Trial)

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What is this trial about?

A plain-language summary of the goals, design and what participants do

Barth Syndrome is a rare inherited condition that can cause heart problems and weak muscles. The study is testing a medication called Elamipretide, which is given as a daily subcutaneous injection (a small shot placed just under the skin). Some participants will receive the medication while others will receive a placebo, which looks the same but does not contain the active drug.

The purpose of the study is to find out whether daily treatment with Elamipretide can improve heart and muscle function and be safe to use. Participants will be asked to receive the assigned injection each day for a period of about one and a half years, with regular clinic visits to monitor health, record any side effects, and perform simple walking and strength tests.

During the visits, researchers will measure how far a person can walk in six minutes, how quickly they can stand up and sit down several times, and the strength of certain leg muscles using a handheld device. These tests help show any changes in the ability to move around and perform daily activities, as well as overall disease severity as judged by both the participant and the doctor.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and assignment

    After joining the study, you will be randomly placed into one of two groups. you will receive either the active medication elamipretide or a placebo that looks the same but does not contain the drug.

  2. Step 2

    Baseline assessments

    Before starting any treatment, a series of tests will be performed to record your condition. these include:

    6mwt – a six minute walk test that measures how far you can walk in six minutes.

    3tug – a three timed up and go test that measures how quickly you can stand up, walk three meters, turn around, walk back, and sit down.

    5xsst – a five times sit‑to‑stand test that measures how fast you can rise from a chair five times.

    Strength measurements of the knee extensors and hip flexors using a handheld device.

    Questionnaires that ask you and your clinician to rate the severity of your symptoms.

  3. Step 3

    Start of daily injections

    Once baseline testing is finished, you will begin receiving a subcutaneous injection (an injection under the skin) each day.

    The injection contains elamipretide at a dose of 40 mg, or the matching placebo, depending on your assigned group.

  4. Step 4

    Continuous daily treatment

    You will continue the once‑daily injection for a total of 72 weeks (approximately one year and four months).

    The injections are usually given at the same time each day and can be administered by you or a caregiver after proper training.

  5. Step 5

    Regular follow‑up visits

    Throughout the 72‑week period, you will attend scheduled visits to the study site. at each visit the same functional tests (6mwt, 3tug, 5xsst) and strength measurements will be repeated.

    Your safety will be monitored with standard medical checks and any side effects will be recorded.

    The timing of visits follows the study protocol, typically every few months, to track changes over time.

  6. Step 6

    Final evaluation and study completion

    At week 72, a final set of assessments will be performed, identical to the baseline tests.

    The results will be compared to the baseline measurements to determine how the treatment affected your functional abilities and symptom severity.

    After the final visit, the study treatment will end and you will receive any necessary follow‑up care as directed by your physician.

Who can join the trial?

7 criteria

  • You must be willing and able to sign an informed consent form (a paper that shows you understand the study and agree to join). If you are a minor, a parent or legal guardian must also sign, and you may need to give your own agreement if you are old enough.
  • You must agree to follow all study requirements for the entire time the study lasts.
  • You must have Barth syndrome that has been proven by a genetic test showing a disease‑causing change (called a pathogenic variant) in the TAZ gene.
  • You must be a male who is at least 5 years old at the screening visit.
  • Your heart’s pumping ability must be normal enough, measured as a Left Ventricular Ejection Fraction of 50% or higher on an echocardiogram (an ultrasound picture of the heart).
  • You must be able to give yourself the study medication (called the investigational medicinal product or IMP) or have a family member or caregiver who can do it for you.
  • If you have a female partner who could become pregnant, you must agree to use a highly effective method of contraception (such as abstinence or using two methods together) from the day you sign the consent until 28 days after the last dose of the study medication.

Who cannot join the trial?

8 criteria

  • Cannot do the 6‑minute walk test, 3‑time‑up‑and‑go, or 5‑times‑stand‑to‑sit functional tests, and cannot have an echocardiography (an ultrasound picture of the heart).
  • Has any disease or health problem that the doctor believes would stop the person from safely joining the study, finishing the required measurements, or could mix up the study results.
  • Has taken part in another investigational drug or device study within the last 30 days (or for a period equal to five drug half‑lives, whichever is longer) before screening, or is currently enrolled in a non‑interventional trial.
  • Has had a solid organ transplant in the past, except a successful heart transplant performed more than 12 months ago, if there is no sign of organ rejection and the medicines after transplant are stable and safe.
  • Has an implantable cardioverter defibrillator (ICD) and has experienced an ICD discharge (the device delivering a shock) in the three months before screening.
  • Is on the waiting list for a heart transplant.
  • Was hospitalized for heart failure (the heart not pumping blood well enough) within the six months before screening.
  • Has an active malignancy (cancer) or any cancer from which the person has been cancer‑free for less than two years. (Non‑invasive skin cancers are allowed if they have been properly treated.)
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Investigated drugs

Elamipretide is a medication given as a daily injection under the skin. It is being studied to see if it can help people with Barth syndrome, a rare genetic disease that affects the heart and muscles. The drug is designed to support the tiny parts of cells called mitochondria, which produce energy, and may improve the body's ability to use energy properly. In this trial, participants receive the medication in a liquid form that is injected once each day, and researchers will watch for any improvements in health and any side effects.

What is already known about the treatment

Elamipretide - It is supplied as a solution for injection and is given once daily by subcutaneous (under‑the‑skin) injection. The drug is an orphan‑designated medication that is still being evaluated in Phase 3b/4 studies for Barth syndrome, a rare inherited condition. It works by entering the mitochondria, the cell’s power plants, and helping them produce energy more efficiently while protecting them from damage. Elamipretide belongs to the class of mitochondrial‑targeted peptide agents that act as protective energy‑enhancing drugs.

Investigated diseases

Barth syndrome - Barth syndrome is a rare genetic condition that mainly affects boys. It is caused by changes in a gene that helps the tiny power plants inside cells work properly. Children with the disorder often have weak muscles, especially in the heart and legs, leading to reduced stamina and difficulty with everyday activities. As they grow, the muscle weakness may become more noticeable, and heart function can change over time. The condition is present from birth and continues throughout life.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-523837-25-00Protocol codeSPIBA-401Estimated enrolment46 patientsSponsorStealth Biotherapeutics Inc.

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