SS-31 (elamipretide)

SS-31 (Elamipretide): What The Studies Actually Say

The pharmaceutical version really is FDA-approved: for one ultra-rare disease, on one muscle test, over the objections of the FDA's own reviewers. The anti-aging story comes from mice.

Updated 22 September 2026

Before you read this

This page explains what published studies found. That is all it is. It is not medical advice, and it is not instructions for using anything. Nothing here is meant to find, treat, cure or stop any illness. The compounds discussed on this site, retatrutide included, are not approved by the FDA for use in people. Research compounds are sold for laboratory use only — not for use in humans or animals. A study tells you what happened to the people in it. It does not tell you what would happen to you. What you do with what you read here is your responsibility, so talk to a doctor first. This page is published by Ascend Vials, which sells research compounds.

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Most of what you have heard about SS-31 comes from studies in mice. The studies in people tell a different story.

Here is what the actual research found. Every claim has a link. Read them yourself.

The 30-second version

SS-31 is a real drug called elamipretide. The FDA approved it in September 2025 — but only for Barth syndrome, a rare inherited disease with about 150 patients in the US.
The approval rests on one muscle test: knee strength. In the only placebo-controlled Barth trial, walking did not improve at all.
The FDA's own reviewers recommended saying no. The head of their office approved it anyway. The approval can be pulled if a follow-up trial fails.
Trials in muscle disease, heart failure, heart attacks and eye disease all missed their main goals.
The anti-aging claims come from mice. In older people, one drip gave a brief rise in muscle energy that was gone within a week.
Every Barth patient on the drug in the placebo trial got skin reactions at the shot. Some people have had serious allergic reactions.
It is not approved outside the US, or for anything but Barth syndrome. Nothing sold online has been shown to match what the trials used. No study has checked.

The numbers, from the real study

Barth syndrome is passed down on the X chromosome. It damages the heart and the muscles. The FDA puts it at about 150 patients in the whole US. FDA announcement · FDA review

The only randomized trial in Barth syndrome had 12 patients, aged 12 to 35. Each spent 12 weeks on the drug and 12 weeks on a fake shot, and nobody knew which was which. The results:

Six-minute walk: 0.8 meters worse than on the fake shot. That is no difference at all.
Tiredness: no change.
Knee strength: 6.7 newtons higher, a gap small enough to be chance.

Genetics in Medicine, 2021

Then everyone switched to the drug, and everyone knew it. That is when the numbers moved.

Knee strength gain from the start, in newtons (middle patient). Everyone on the drug. No placebo group.

Week 12+34 N

Week 24+68 N

Week 36+57 N

Week 48+41 N

Week 72+35 N

Week 168+63 N

The middle patient started at 124 newtons. Ten people were measured at week 12, and only 8 from week 36 on. The label also says plainly that the drug did not beat placebo on walking or tiredness, the trial's main goals. FDA label Walking went up in this part too: 96 meters more by week 168. Genetics in Medicine, 2024

So why not believe those? Both tests depend on effort, and effort can rise when you know you are on the drug. That was the FDA reviewers' main worry. They would not credit the drug with the walking and tiredness gains from this part. A comparison with 19 untreated patients from an older study did not fix that problem either, the FDA said. FDA review · Orphanet, 2022

How it got approved anyway

The company applied in January 2024. An FDA advisory panel voted 10 to 6 that it works. In May 2025 the FDA said no. The company applied again, and on 19 September 2025 the FDA said yes.

Here is the part almost nobody mentions. In that final round, the FDA's own doctors, its statisticians and their team leader all recommended saying no again. The director of the FDA office in charge approved it anyway, accepting "more uncertainty than we would accept for more common diseases." FDA review

It was a special kind of approval, called accelerated approval. It covers only Barth patients who weigh at least 30 kg, and it is based on knee strength alone. The FDA treats strength as a step toward real benefit. It has not concluded that the benefit is there. FDA announcement · Approval letter

So the company must run a new placebo-controlled trial of about 48 patients for 72 weeks. It started in July 2026. The final report is due by March 2030. If it fails, the FDA can pull the approval. Trial record · Approval letter

How it did everywhere else

Here is what happened when it was tested against a placebo in other diseases.

Tested in	People	How long	Main result
Mitochondrial muscle disease	218	24 weeks	Missed. Walked 3.2 m less than placebo
Mitochondrial muscle disease	30	4 weeks each way	Missed
Heart failure	71	4 weeks	Missed
Heart attack	300	One drip	Missed
Dry macular degeneration (eyes)	176	48 weeks	Missed both goals
Inherited optic nerve disease (eye drops)	12	52 weeks	Missed
Healthy older adults	39	One drip	Brief rise, gone by day 7

Sources: MMPOWER-3, Neurology 2023 · MMPOWER-2, 2020 · PROGRESS-HF, 2020 · EMBRACE STEMI, 2016 · ReCLAIM-2, 2025 · LHON, 2024 · Older adults, 2021

You will see hopeful signals quoted. Each is smaller, shorter or weaker than the table:

In heart failure, one 4-hour drip shrank the heart's main pumping chamber by the end of the drip. Circulation: Heart Failure, 2017 The 4-week trial above then found nothing.
In the big muscle trial, people with certain gene changes seemed to walk farther. That was spotted after the trial failed. Orphanet, 2024 A trial built to check it finished in December 2024 and has posted no results. Trial record
In the eye trial, some extra measures looked better after the main goals were missed. A 313-person trial is running. Its main phase is set to finish around August 2027. Trial record
In a pilot of 14 people having a kidney artery stented, kidney blood flow improved. Circulation: Cardiovascular Interventions, 2017

The compounds used in this study can be found here: →ascendvials.com

What it is

Elamipretide is a tiny lab-made peptide, just four amino acids long. It comes from Stealth BioTherapeutics, now owned by Mighty Therapeutics. In the US it is sold as Forzinity, a prescription shot given under the skin once a day. FDA label · Company release

It targets mitochondria, the power plants inside your cells. The label says it sticks to cardiolipin, a fat in their inner wall, and improves their shape and how they work. FDA label In rats, it protected mitochondria when blood flow to the kidney was cut off. JASN, 2013

Half of it is gone in about 3 to 4 hours, and nearly all of it comes out in urine within two days. FDA review Swallowed, it is not absorbed. Source

Nobody is sure exactly how it works. Labs have pointed to cardiolipin, to the electric charge on the membrane, and to a different protein called PLSCR3. J Biol Chem, 2020 · JASN, 2024 FDA reviewers wrote that it does not meaningfully fix the cardiolipin imbalance behind Barth syndrome. It did not fix it in Barth-model mice either. FDA review · Scientific Reports, 2022

The anti-aging part was only shown in mice

This is the story you have probably heard: SS-31 makes old muscles young again.

In old mice, one shot brought muscle energy production back to young-mouse levels within an hour. Aging Cell, 2013 Eight weeks of it made old mice run longer. Free Radic Biol Med, 2019 It also helped old hearts and old kidneys in mice. eLife, 2020 · Kidney International, 2017

In people, it has been tested for this once. 39 healthy adults aged 60 to 85 got a single two-hour drip. Right after, peak energy output in one hand muscle rose 27%. On the placebo drip it rose 12%. By day 7 there was no difference, and there was no clear effect on how fast the muscle tired. PLoS One, 2021

Animals do not always predict people. In dogs with failing hearts, three months of SS-31 made the heart pump harder. Circulation: Heart Failure, 2016 In people with failing hearts, the 4-week trial found no effect. PROGRESS-HF, 2020

What to expect

Skin reactions at the shot are the main story. Here is the Barth placebo trial:

	Placebo	Elamipretide
Any reaction at the shot	67%	100%
Redness	25%	100%
Pain	42%	75%
Hardening	17%	67%
Itching	17%	67%
Hives	0%	25%

That was 12 people over 12 weeks. FDA label Later, 2 of 10 stopped because of skin reactions. Genetics in Medicine, 2021

Allergic reactions are the serious risk. The label warns of serious allergic reactions that needed emergency treatment, anywhere from minutes to months after starting. FDA label In one case a 20-year-old woman got a cough and a rash 15 minutes after a shot. Paramedics gave her adrenaline, and she never took it again. FDA review

Also flagged:

A type of white blood cell rose in 9 of 12 Barth patients. It faded and caused no symptoms. FDA review
The kidneys clear it. In severe kidney disease, blood levels more than doubled. FDA label
It may change how the body handles metformin, a common diabetes drug. No cancer studies in animals were done before approval. Both are now required, with the last due in 2030. FDA label · Approval letter
There were no deaths in the Barth trial. Deaths in other studies were not judged to be caused by the drug. FDA review

The compounds used in this study can be found here: →ascendvials.com

What is still unknown

Elamipretide is approved in one country, the US, for one disease. Europe has only given it orphan status, which the regulator says does not mean it is approved. EMA We found no approval anywhere else. Company pipeline

These gaps are still open:

Whether stronger knees mean patients walk better, feel less tired or live longer. The answer is due by 2030. Trial record
Whether it works or is safe in Barth patients under 30 kg, including babies. FDA review
Safety past about four years. Only 8 Barth patients reached 168 weeks. FDA label
Whether it does anything for healthy aging in people. One drip in 39 people is the whole record. PLoS One, 2021
Pregnancy, breastfeeding and dialysis. The label has no data. FDA label

What is in the bottle is not what was studied

One more thing.

Every human result on this page came from the company's own drug. Made in a pharmaceutical plant. Given under a doctor's care. Reviewed by the FDA — which, when it said no in May 2025, listed problems at the manufacturing plant. FDA review

No study has ever shown that a product sold online as "SS-31" is the same thing. Not the same purity. Not the same strength. Not even proof it is the same molecule.

There is one legal way to get the real thing. In the US, Forzinity is a prescription medicine for Barth syndrome, and a doctor prescribes it. For anything else, it is not approved. FDA announcement

So take every number on this page for what it is. It describes the pharmaceutical drug. It describes nothing else.

The compounds used in this study can be found here: →ascendvials.com

How to check a number yourself

You are going to see more claims about SS-31. In a reel. In a comment. On somebody's store page.

Here is how to tell a real one from a marketing one. Five questions. About ten seconds each.

1. Is there a link to a study, and was it done in people?

A real number comes from a paper you can open. No link means it is a claim, not a result. Search the drug name on pubmed.gov yourself.

Then check who was in it. Most of the exciting SS-31 links go to mouse studies. A mouse getting younger is a reason to test people. It is not a result in people.

2. How big was it, and how long did it run?

Small studies swing. The only randomized Barth trial had 12 people. The only human aging study was one drip, checked for a week.

3. Was there a group that got a fake shot?

This is the whole story of this drug. Same Barth trial, same walking test. With a placebo group: 0.8 meters worse. Without one, after 36 weeks on the drug: 96 meters better. Genetics in Medicine, 2021 Nobody can tell how much of that second number was the drug.

4. How did it feel to take?

Headlines lead with the good number. Look further down for how the drug felt. Here it is 12 out of 12 with reactions at the shot, against 8 out of 12 on placebo.

5. Who paid for it?

The Barth trials were paid for by the company that makes the drug, and some authors worked there. That is normal. It matters more when the good numbers come only from the part with no placebo group.

Now run those five on this page

Every number above links to the paper it came from. The study sizes are in the tables. The chart says in its title that it has no placebo group. The side-effect table is there. And you were told which results came from mice.

For this drug, add one more question: approved for what? Elamipretide is FDA-approved. For one ultra-rare disease, on one muscle test, with a trial still due to confirm it. "FDA-approved" on a store page does not tell you that.

That is the whole difference: a number you can check, and a number you are asked to believe.

This page has a date on it, near the top. When the follow-up trial and the eye trial report, this page changes.

Ascend Vials publishes this guide and sells research compounds. Now you know how to check us: →ascendvials.com

Read the studies yourself

Everything above describes what clinical trials gave to enrolled patients under a doctor's care, or what was done to animals in a lab. This is not advice, a plan, or instructions. Elamipretide is approved only in the US, only as the prescription medicine Forzinity, and only for Barth syndrome. Research compounds are not for human or animal use.