Question 1

Which outcomes did the elamipretide trials actually measure?

Accepted Answer

The useful question about SS-31 (elamipretide) is not whether it works but what was measured, because the answer changes with the disease being studied. The registered programme is unusually explicit about its endpoints, which makes this record easier to read than most on this site. In primary mitochondrial myopathy, primary efficacy endpoints included change from baseline to week 24 on the distance walked on the 6-minute walk test (6MWT) and total fatigue on the Primary Mitochondrial Myopathy Symptom Assessment (PMMSA). In Barth syndrome, the extension's primary endpoints were safety and tolerability, with walking distance and fatigue as secondary. So two walking tests, two fatigue scales, a strength measure and a set of heart and lipid readings. Everything below is one of those, an animal measurement or a cell experiment, and the distinctions matter more here than usual. The amounts behind each figure are set out separately on the dosage page.

Question 2

Did walking distance improve in the trials?

Accepted Answer

Twice, in opposite directions, and the gap between them is the lesson. In the Barth syndrome extension, significant improvements from OLE baseline on 6MWT occurred at all OLE time points, accumulating to 96.1 m of improvement by week 168. Ten patients entered the extension and 8 reached the week 168 visit. In primary mitochondrial myopathy the same test moved nowhere. Among those participants, the difference in the least squares mean from baseline to week 24 on distance walked on the 6MWT was -3.2 metres, with a confidence interval running from -18.7 to 12.3. That trial randomised 218 adults against placebo, and the Barth extension had no placebo arm at all. Measured against each other, these are a demonstration rather than a contradiction. An open-label extension in eight people captures improvement, expectation and the passage of time together, while a randomised comparison isolates the compound.

Question 3

What happened to fatigue scores?

Accepted Answer

Fatigue was a primary endpoint in one trial and a secondary one in the other, and it behaved exactly like the walking test in both. In the myopathy trial the total fatigue score was -0.07, which is a difference of nothing on a scale whose mean score for total fatigue on the PMMSA was 10.6 at baseline. Among the Barth syndrome patients in that extension, mean BTHS-SA Total Fatigue scores were below baseline (improved) at all OLE time points. Those were patients who knew what they were receiving, compared against their own earlier scores rather than against anybody else's. Fatigue is the symptom people in these conditions name first. At screening, the most frequent bothersome PMM symptom on the PMMSA was tiredness during activities, named by 28.9% of participants, and that is the outcome the controlled trial did not shift.

Question 4

Was muscle strength measured, and what did it show?

Accepted Answer

Muscle strength is the outcome the approval names, and in the trial it sat among the secondary measures. In the Barth syndrome extension, muscle strength, physician- and patient-assessed outcomes, echocardiographic parameters, and biomarkers, including cardiolipin (CL) and monolysocardiolipin (MLCL), were assessed. Cardiolipin is a fat in the inner wall of the mitochondria, and Barth syndrome is the inherited disease in which it is built wrong. A secondary measure is one a trial writes down without being built to settle it. The regulator's wording is narrow and worth reading exactly as written: elamipretide is indicated for the improvement of muscle strength in individuals with Barth syndrome. That is one outcome, in one inherited disease, in a population numbering a few hundred people worldwide. In animals the strength signal is thinner. In aged mice, intermittent injections over eight months produced modest protection of diastolic function and skeletal muscle force production. Force production is the push a muscle makes when it is asked to work. The word modest is the authors' own, and it is a smaller claim than the word strength usually carries.

Question 5

What did the heart measurements record?

Accepted Answer

The cardiac readings are the steadiest positive measurements in the human record, and they are still from eight people. Among the Barth syndrome patients in that extension, three-dimensional (3D) left ventricular stroke, end-diastolic, and end-systolic volumes improved, showing significant trends for improvement from baseline to week 168. Those volumes are how full the heart is before and after a beat. The animal work underneath is older and broader. A 2022 review reports that elamipretide has been shown to increase left ventricular ejection fraction in dog models of heart failure with reduced ejection fraction and to prevent left ventricular remodeling in rats. Ejection fraction is the share of blood the heart pushes out on each beat. Read the chain as it is: dogs and rats for the mechanism, eight people for the human echo figures, and no control group for any of the eight. The same review adds that early-phase clinical trials showed promising improvements in cardiac hemodynamics at highest doses, meaning pressures and flow inside the heart rather than how anybody felt.

Question 6

Did a mitochondrial marker change in people?

Accepted Answer

It did, and it is the most mechanism-specific human result available. In the Barth syndrome extension, MLCL/CL values showed improvement, correlating to important clinical outcomes. Those initials stand for monolysocardiolipin and cardiolipin, the damaged and the intact forms of a fat in the inner membrane of the mitochondria. A 2026 review calls that ratio a rare lipid biomarker with direct interpretability for diagnosis, stratification and target engagement. Target engagement means the compound reached what it was aimed at, which is a different claim from the compound helping the person carrying it. So the marker moved in the direction the mechanism predicts, in eight patients whose disease is a defect in that exact lipid. That is strong evidence the compound does what it is designed to do, and weak evidence about anything further downstream.

Question 7

Is there a measured result after a heart attack?

Accepted Answer

One small study looked, and what it measured was a blood marker rather than anything the patients would notice. Peripheral blood was obtained from patients (n=19) with first-time acute anterior STEMI after percutaneous coronary intervention, and 10 of those patients received the mitochondria-targeting peptide elamipretide. A STEMI is a heart attack in which a main artery is blocked, and percutaneous coronary intervention is the wire-and-stent procedure that opens it again. In those patients, elamipretide significantly reduced the HtrA2 median serum level after myocardial infarction. HtrA2 is a protein that leaves the mitochondria when heart muscle cells die, which the authors put forward as a possible marker of that process. A serum level is simply how much of it is floating in the blood. Nineteen people, ten of them treated, and a laboratory value as the endpoint. The authors say as much themselves, writing that this must be validated in a larger clinical trial, and no such validation appears among the research behind this page.

Question 8

What has been measured in the eye?

Accepted Answer

Eye disease is the largest open branch of this work. Almost none of it has reported an outcome yet. Pharmacokinetics, meaning how the body takes a compound up and clears it, is one thing the largest of those trials records. A Phase 3 Study of Efficacy, Safety & Pharmacokinetics of Subcutaneous Injections of Elamipretide in Subjects With Dry Age-Related Macular Degeneration (Dry AMD) is listed as ACTIVE_NOT_RECRUITING with 313 participants. Dry AMD is an age-related loss of central vision. Behind that trial sit smaller finished ones. Their results do not appear among the research behind this page. One is an Open-Label, Phase 1 Clinical Study to Evaluate the Safety and Tolerability of Subcutaneous Elamipretide in Subjects With Intermediate Age-Related Macular Degeneration. It enrolled 40 people. Phase 1 asks whether a compound is tolerated, not whether it works. Another tested a topical ophthalmic solution in Leber's Hereditary Optic Neuropathy, an inherited cause of sudden sight loss, in 12 participants. A completed registration is a fact about a trial rather than a finding from one. Until the Phase 3 reports, the eye evidence is a list of studies and not a list of results.

Question 9

What did the ageing-mouse studies preserve?

Accepted Answer

Two long mouse experiments are where the healthy-ageing claims originate, and both measured function rather than lifespan. In the first, mice were fed regular chow or a diet high in fat and sugar and treated with 3 mg/kg of Elam or saline subcutaneously 5 days per week for 10 months. What that produced was divided by sex. In those mice, Elam lifted physical performance in males but not in females, while in females it improved cognitive performance and better maintained body weight and fat mass. In the same mice it also improved diastolic function in both males and females, but to a greater extent in males. The second experiment asked whether a lighter schedule would reproduce it. Intermittent treatment with elamipretide for 8 months preserved exercise tolerance and left ventricular mass in those mice, but did not affect kidney function as previously reported using continuous treatment. One schedule held the kidney result and the other did not, which makes it a finding about scheduling as much as about ageing.

Question 10

What did the liver-fat experiments in mice find?

Accepted Answer

Body fat is the outcome this question gets asked about most, and the measurements that exist are in mice with a liver condition. Aged female C57BL/6 mice (12-14 months) were fed a high-fat, high-fructose diet for 16 weeks to induce MASLD, a fatty liver disease, and one group then received SS-31 at 3 mg/kg/day. Histological analysis using H&E staining revealed marked reductions in hepatic steatosis, which means less fat stored inside the liver cells of those animals. The same experiment reported that both compounds tested improved insulin sensitivity by increasing p-Akt and GLUT2 expression in the treated mice. Read what that is. It is fat inside one organ, in mice held on a controlled diet, measured against untreated mice on the same diet. A 2024 editorial on mitochondria-targeted antioxidants reports that the results regarding glycemic control have been mixed, and the question of body-fat change in a person has not been asked at all in the research behind this page.

Question 11

What did the lung, spinal cord and skin models measure?

Accepted Answer

Three further experiments measured three unrelated outcomes, which is what a compound aimed at an organelle rather than at a disease tends to produce. An organelle is a working part inside a cell, and the mitochondria are the ones that make its energy. In a 2025 mouse study of lung scarring, SS-31 (intraperitoneal injection, 5mg/Kg) was administered daily, meaning into the abdominal cavity. The animals were assessed 28 days later. In those mice SS-31 could reduce reactive oxygen species and myeloperoxidase, two laboratory measures of oxidative stress and inflammation. A 2023 spinal-cord study reports that a spinal cord contusion injury model as well as the Basso Mouse Scale, footprint assessment, and inclined plane test were employed. Those last three are scoring systems for how well a mouse walks. On them, its authors report that SS-31 promotes functional recovery in those mice. A 2025 skin experiment loaded the peptide into milk-derived exosomes and applied it to cultured human skin cells, where the complex was capable of mitigating Human dermal fibroblast (HDF) damage induced by ultraviolet exposure. Exosomes are tiny bubbles cells use to carry cargo, and a fibroblast is the skin cell that makes collagen. Not one of the three measured an outcome in a living person.

Question 12

What has been measured in a healthy person?

Accepted Answer

Nothing has reported yet. A Study of Healthy Aging and Physical Function With Elamipretide is listed as RECRUITING with 30 participants, and it is the only entry among the research behind this page that enrols people without a diagnosis. A trial that is still open has no result to give yet. Every published human measurement above comes from somebody with a named condition: primary mitochondrial myopathy, Barth syndrome, a recent heart attack or an inherited eye disease. Each of those groups was picked because the cells are known to be damaged, which is the opposite of the reader this question usually comes from. A healthy adult has nothing broken for the compound to put right. A 2026 sports medicine review makes the general point about compounds sold this way, noting that many unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, but rigorous human safety data are scarce. Treating an animal result as a personal expectation is the one step that record does not carry.

Question 13

Why do better mitochondria not always become a better patient?

Accepted Answer

This is the question the whole record turns on, and a 2026 review states it in the opening line. Mitochondrial therapeutics have repeatedly fallen short of disease modification, in part because inner-membrane architecture constrains both molecular access and the reversibility of bioenergetic failure. Disease modification means changing the course of an illness, not moving a number on a chart. Bioenergetic failure means the cell can no longer make enough energy to do its job. The same review draws the distinction that governs every figure above, separating settings in which structural support yields functional benefit from those in which organ-level remodelling limits translation despite improved respiration, and it draws that distinction from the clinical trial evidence. Respiration there means the mitochondria burning fuel for energy. In plainer words, the mitochondria can get better while the organ stays where it was. That is the pattern the human data shows. A lipid ratio moved in eight Barth syndrome patients and their walking distance moved with it; in 218 adults whose disease had other genetic causes, the walking distance did not move. Target engagement and benefit are different questions rather than two names for one.

Question 14

Which outcomes remain unmeasured?

Accepted Answer

Several, and they are the ones most often attached to the name. No study among the research behind this page has measured body composition, strength or endurance in a healthy adult, because the only trial enrolling that population is still recruiting. A trial that is still recruiting has no result to give yet. Nothing in the record follows anybody after the final injection either. The longest published human exposure ends at week 168 in eight people, and each animal experiment ends on the day the animals are assessed. Nor has one mitochondrial compound been set against another in a person. The fatty-liver experiment compared SS-31 with MitoQ in aged mice and concluded that MitoQ enhances antioxidant defense, SS-31 preserves integrity, which is a comparison between two animal results rather than a comparison anybody has run in people. MitoQ is another compound aimed at the same part of the cell.

SS-31: what the research measured