AuthorisedPhase III and phase IV (Integrated)Interventional

4TAZPower: A Phase 3b/4, Randomized, Double-Blind, Parallel-Group, Placebo-Controlled, Trial to Evaluate the Efficacy and Safety of Daily Subcutaneous Injections of Elamipretide in Patients with Genetically Confirmed Barth Syndrome

Barth syndrome is a rare genetic condition that affects males. It often leads to heart problems, muscle weakness, and extreme fatigue. Right now, there are very limited treatment options. The 4TAZPower clinical trial is looking at whether an experimental medicine called elamipretide can help. The trial tests if taking elamipretide once a day through an injection under the skin helps improve muscle power and movement over 72 weeks. Researchers will measure how far participants can walk in six minutes, how quickly they can stand up from a chair, and their overall leg strength. Participants will be placed into two groups at random: one receives elamipretide, and the other receives a dummy treatment called a placebo. Neither the doctors nor the participants will know who is getting which treatment. This study hopes to find out if elamipretide can safely improve daily life for people living with Barth syndrome.

At a glance

Status

Authorised

Phase

Phase III and phase IV (Integrated)

Sponsor

Stealth Biotherapeutics Inc.

Enrolment target

Start

27 Jul 2026

Barth Syndrome

What is this study about?

Barth syndrome is a rare inherited condition that almost exclusively affects boys and men. It alters the way cells produce energy, which can cause an enlarged or weakened heart, muscle weakness, and profound tiredness. Everyday activities, such as climbing stairs or walking short distances, can be exhausting. Because there is currently no cure, finding treatments that boost physical strength and stamina is a top priority for researchers and families alike.

This trial is testing a new drug called elamipretide. Cells rely on tiny power stations inside them to make energy, and in Barth syndrome, these power stations do not work properly. Elamipretide is designed to help these cellular power stations function better. The goal is to see whether improving energy production at the cellular level translates into real-world benefits, like stronger muscles and greater stamina.

Over a period of 72 weeks (about 16 months), doctors will follow participants closely. They will use simple physical tests to track changes. These include checking how far someone can walk in six minutes, timing how fast they can stand up from a chair five times, and testing leg muscle strength using a handheld measuring device.

By comparing the results of participants taking elamipretide with those taking a placebo, researchers can clearly see whether the drug makes a genuine difference. If successful, this trial could provide vital evidence to help bring a new, targeted treatment to people living with Barth syndrome.

Key takeaways

The trial tests elamipretide for adult men with genetically confirmed Barth syndrome.
The treatment involves a daily injection under the skin over 72 weeks.
Half of the participants will receive the active drug, while the other half receive a dummy injection (placebo).
Researchers will track changes in walking distance, chair-rising speed, and leg strength.
Joining the study is completely voluntary, and you can withdraw at any time.

Who may be eligible?

This study is designed specifically for adult men who have a confirmed genetic diagnosis of Barth syndrome. Because Barth syndrome is an X-linked genetic condition that primarily affects males, the trial is open to men aged 18 and older.

To take part, you must be well enough to complete simple physical assessments, such as walking for a few minutes and standing up from a chair. You must also be willing and able to take a daily injection just under the skin, or have a family member or carer who can give it to you.

You may not be able to join if you have certain other severe medical conditions that make taking part unsafe, or if you are currently taking part in another clinical trial for an experimental drug. Your doctor or the study team can review your full medical history to see if the trial is a safe match for you.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a man aged 18 or older.
I have an official genetic test confirming I have Barth syndrome.
I am able and willing to perform simple physical tests like walking and standing from a chair.
I am comfortable giving myself a daily injection under the skin (or have someone to help me).
I can commit to regular hospital visits over an 18-month period.

Answer every question to see your result.

What does participation involve?

Taking part in this study lasts for roughly 72 weeks. You will be asked to give yourself (or have a carer give you) an injection under the skin once every day. You will receive either the study drug or an inactive dummy treatment (placebo). You will need to attend regular clinic visits at a study hospital. During these visits, doctors will check your general health, take blood samples, and test your physical fitness. These fitness checks include a six-minute walking test, a test measuring how quickly you can get up from a chair and walk a short distance, and simple leg-strength measurements. You and your study doctor will also complete questionnaires about your symptoms and how you feel. The study team will support you throughout the entire 72 weeks to monitor your wellbeing.

Potential risks and benefits

Taking part may or may not improve your muscle strength or energy levels, and there is a 50% chance you will receive a placebo rather than the active medicine. However, your participation will provide crucial information that could help others with Barth syndrome in the future. The risks include side effects from the medicine, such as redness, pain, or swelling where the needle enters the skin, as well as possible unexpected side effects that researchers do not yet know about. Taking part is completely your choice. You are free to leave the trial at any time without giving a reason, and doing so will not change your normal NHS care or your relationship with your healthcare team.

Locations (4)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Ireland
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Unverified
Netherlands
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Unverified
France
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Unverified
Italy

Common questions

What is a placebo and why is it used?

A placebo is a harmless dummy treatment that looks identical to the real medicine but contains no active drug. It helps researchers prove whether any improvements are truly caused by elamipretide.

How is the study medicine given?

It is given once a day as a small injection just under the skin (subcutaneous injection), similar to how insulin is given for diabetes. You or a carer will be trained on how to do this safely at home.

Do I have to pay to take part in the trial?

No, the study medicine and all trial-related tests are provided free of charge. Most clinical trials also help cover reasonable travel costs to and from the hospital.

Can I carry on taking my usual heart medications?

In most cases, yes. The study team will carefully review all the medicines you currently take to make sure they are safe to use alongside the study treatment.

What happens if I decide I want to stop?

You can leave the study at any point. Your decision will never affect the standard medical care or treatment you receive from your regular doctors.