Tung C, Varzideh F, Farroni E, et al. (2025). Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential. Int J Mol Sci, 26(3).
What is SS-31?
SS-31 is another name for elamipretide, a small peptide being studied for conditions linked to mitochondrial dysfunction. [1] Peptides are short chains of amino acids, which are the building blocks of proteins. [2] SS-31 is also known as MTP-131 and Bendavia in the research literature. [1]
Mitochondria are tiny “power plants” inside cells that help make adenosine triphosphate, or ATP, the main energy molecule cells use. [1] SS-31 is designed to target mitochondria and bind cardiolipin, a fat-like molecule found in the inner mitochondrial membrane. [1]
Researchers are interested in SS-31 because mitochondrial problems are linked with several diseases, including cardiovascular, neurological, metabolic, eye, and muscle-related conditions. [1, 3, 4, 5] For health and fitness readers, the most relevant idea is simple: if mitochondria help power muscle and movement, then protecting mitochondrial function could someday matter for fatigue, exercise tolerance, or recovery in some medical settings. [1, 6, 7]
How might it work?
SS-31 appears to work by targeting the inner mitochondrial membrane, where it binds cardiolipin. [1, 8] Cardiolipin helps support mitochondrial structure and energy production, and SS-31 is described as helping stabilize mitochondrial cristae, the folded inner-membrane structures where energy production happens. [1]
Reviews describe SS-31 as a mitochondria-targeted tetrapeptide, meaning it is made of four amino acids and is designed to localize to mitochondria. [1, 8] In research models, SS-31 has been linked with improved mitochondrial bioenergetics, a term that means how well mitochondria make and manage energy. [1, 8]
A major theme in the abstracts is oxidative stress, which means excess reactive oxygen species that can damage cells. [1, 3, 4] Reviews report that SS-31 may reduce oxidative stress and support ATP production by stabilizing mitochondrial structures and related protein complexes. [1, 3]
Researchers have also studied SS-31 in inflammation-related pathways. [4, 9] In a spinal cord injury animal study, SS-31 reduced pyroptosis, a highly inflammatory type of cell death, and lowered pro-inflammatory cytokines, which are immune-signaling molecules. [9]
The big idea is that SS-31 is not aimed at one organ only. [1] It is being studied as a mitochondrial therapy across several conditions where cell energy problems may play a role. [1, 3, 4, 5]
What has research found?
Primary mitochondrial myopathy
Primary mitochondrial myopathies are genetic disorders that impair oxidative phosphorylation, the process mitochondria use to make energy. [6] These disorders can affect physical function, exercise capacity, and quality of life. [6]
The largest human study in the provided abstracts is MMPOWER-3, a phase 3 randomized, double-blind, placebo-controlled trial in people with genetically confirmed primary mitochondrial myopathy. [6] “Randomized” means participants were assigned by chance, “double-blind” means neither participants nor researchers knew who received the study drug, and “placebo-controlled” means the drug was compared with an inactive treatment. [6]
In MMPOWER-3, 218 participants were randomized to receive either daily subcutaneous elamipretide or placebo for 24 weeks. [6] Subcutaneous means the treatment was injected under the skin. [6]
The trial tested two main outcomes: distance walked in the 6-minute walk test and fatigue on the Primary Mitochondrial Myopathy Symptom Assessment. [6] The study did not meet these primary endpoints, meaning elamipretide did not significantly improve walking distance or fatigue compared with placebo at 24 weeks in the overall study group. [6]
The safety signal in this trial was more encouraging. [6] The authors reported that subcutaneous elamipretide was well tolerated and that most adverse events were mild to moderate. [6]
A later analysis looked back at MMPOWER-3 by genetic subtype. [10] This matters because primary mitochondrial myopathy can come from different genetic causes, including mitochondrial DNA changes and nuclear DNA changes. [6, 10]
In that post hoc analysis, people with mitochondrial DNA maintenance-related nuclear DNA variants appeared more likely to respond on the 6-minute walk test. [10] “Post hoc” means the analysis was done after the main trial, so it can suggest patterns but cannot prove them as strongly as a trial designed in advance for that question. [10]
The post hoc analysis reported a trend toward improved 6-minute walk distance in a mitochondrial DNA replisome subgroup and a significant improvement in participants with replisome variants who had chronic progressive external ophthalmoplegia, a condition involving progressive eye muscle weakness. [10] The authors said these findings helped shape a follow-up phase 3 trial design focused on likely responders. [10]
Barth syndrome
Barth syndrome is a rare X-linked genetic disorder linked with cardiomyopathy, skeletal muscle weakness, growth delays, and cyclic neutropenia, which means recurring low levels of certain white blood cells. [8] Cardiomyopathy means disease of the heart muscle. [8]
A review describes SS-31 as a mitochondria-targeting tetrapeptide that reaches the inner mitochondrial membrane and associates with cardiolipin. [8] The same review says elamipretide improved mitochondrial bioenergetics and structure in induced pluripotent stem cells from people with Barth syndrome and related pediatric cardiomyopathy disorders. [8] Induced pluripotent stem cells are lab-grown cells made from adult cells and used to model disease. [8]
A drug review reports that elamipretide, under the name Forzinity, received accelerated approval in the United States for improving muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. [11] The same review describes this as the first disease-specific treatment approved for Barth syndrome. [11]
Heart failure and cardiovascular research
Heart failure research is another area where SS-31 has drawn interest because mitochondria are involved in both energy production and cell-death signaling. [3] A review reports that SS-31 has been studied as a way to maintain cellular bioenergetics and reduce damage linked with reactive oxygen species. [3]
In animal models, the review reports that elamipretide increased left ventricular ejection fraction in dogs with heart failure with reduced ejection fraction and helped prevent left ventricular remodeling in rats. [3] Left ventricular ejection fraction is a measure of how much blood the heart’s main pumping chamber pushes out with each beat. [3]
The same review states that early-phase clinical trials did not report severe adverse events and showed promising improvements in cardiac hemodynamics at the highest doses. [3] Hemodynamics means measures of blood flow and heart function. [3] The authors also emphasized that more studies are needed to understand long-term safety and efficacy. [3]
Exercise tolerance and aging models
For fitness-minded readers, one of the most interesting abstracts is an animal study in aged female mice. [7] The study tested whether twice-weekly intermittent injections of elamipretide for 8 months could produce functional benefits similar to longer continuous treatment. [7]
In aged female mice, intermittent elamipretide preserved exercise tolerance and left ventricular mass, with modest protection of diastolic function and skeletal muscle force production. [7] Diastolic function refers to how the heart relaxes and fills between beats. [7]
This is exciting as a biology signal, but it is still mouse research. [7] It does not prove that SS-31 improves endurance, recovery, or performance in healthy people. [2, 7]
Brain, spinal cord, and eye research
A review of neurodegeneration research reports that elamipretide has been linked with mitochondrial respiration, mitochondrial biogenesis, mitochondrial fusion, mitophagy, lower oxidative stress, lower neuroinflammation, and reduced toxic protein accumulation in studies of neurodegeneration. [4] Mitochondrial biogenesis means making new mitochondria, and mitophagy means clearing damaged mitochondria. [4]
In an animal spinal cord injury study, elamipretide improved locomotor functional recovery, reduced neuronal loss, inhibited NLRP3 inflammasome activation, reduced pyroptosis, and eased mitochondrial dysfunction. [9] NLRP3 inflammasome activation is an immune pathway that can drive inflammation. [9]
An age-related macular degeneration review lists SS-31/elamipretide among potential therapeutic candidates for AMD. [5] AMD is an eye disease linked with aging, retinal changes, mitochondrial dysfunction, reactive oxygen species, and retinal pigment epithelium cell senescence. [5]
These areas are scientifically interesting, but the abstracts provided do not show that SS-31 prevents dementia, repairs spinal cord injury, or treats AMD in people. [4, 5, 9]
Sports medicine and performance claims
A sports medicine review notes that peptide use is expanding, partly because patients want faster injury recovery and performance enhancement. [2] The same review includes SS-31 among approved and unapproved peptides discussed in sports medicine settings. [2]
The review warns that many unapproved peptides show favorable tissue repair or metabolic effects in animal models, but rigorous human safety data are scarce. [2] It also states that there is potential for serious harm to patients when peptides are used outside proper regulatory oversight. [2]
For athletes and active people, that is the key boundary. [2] SS-31 has intriguing mitochondrial science, but the provided abstracts do not show that it is a proven muscle-building, fat-loss, recovery, or performance-enhancing peptide for healthy users. [2, 6, 7]
How strong is the evidence?
The strongest evidence in the provided abstracts comes from MMPOWER-3, a large phase 3 randomized clinical trial in primary mitochondrial myopathy. [6] That trial found no significant benefit on walking distance or fatigue in the full study population at 24 weeks. [6]
The post hoc genetic analysis is promising but less definitive than the main trial result. [10] It suggests that people with certain mitochondrial DNA maintenance-related nuclear DNA variants may be more likely to benefit, but this needs confirmation in a trial designed for that subgroup. [10]
The Barth syndrome approval signal is important because it shows SS-31 has moved beyond theory for at least one rare disease context. [11] However, evidence for a rare genetic disease cannot be stretched into a general claim for healthy fitness users. [2, 11]
The animal evidence is broad and encouraging, especially for mitochondrial function, exercise tolerance in aged mice, heart models, and spinal cord injury models. [3, 7, 9] Animal studies are useful for learning biology, but they often do not translate directly into human benefits. [2]
Overall, the evidence is strongest for specific medical research settings and weakest for everyday wellness, athletic performance, or self-directed use. [2, 6, 10]
Safety: what we know
In the MMPOWER-3 trial, subcutaneous elamipretide was reported as well tolerated, and most adverse events were mild to moderate. [6] In heart failure research summarized by a review, early-phase clinical trials did not report severe adverse events, but the authors said more studies are needed to define long-term safety and efficacy. [3]
The route of use matters. [7] One animal-study abstract notes that elamipretide is a short tetrameric peptide that is not orally bioavailable, which limits routes of administration. [7] In MMPOWER-3, elamipretide was given by subcutaneous injection. [6]
The sports medicine review raises a broader safety concern about peptides marketed directly to patients. [2] It describes a “gray market” of unapproved compounds operating largely outside regulatory oversight, with scarce rigorous human safety data and possible serious harm. [2]
The provided abstracts do not give enough information to define SS-31 safety for healthy athletes, long-term wellness use, stacking with other peptides, or use without medical supervision. [2, 3, 6]
Legal status
The FDA has announced accelerated approval of the first treatment for Barth syndrome. [S1] This does not make SS-31 a general fitness, recovery, or performance product. [S1]
Peptide legal status can depend on the product, country, medical use, and source. [2] The safest approach is to use SS-31 only through qualified medical and legal channels. [2]
The bottom line
SS-31, or elamipretide, is a mitochondria-targeted peptide that binds cardiolipin in the inner mitochondrial membrane. [1] Its main scientific promise is that it may help stabilize mitochondrial function, reduce oxidative stress, and support cellular energy biology in certain disease settings. [1, 3]
The human evidence is mixed but interesting. [6, 10] In the main MMPOWER-3 trial for primary mitochondrial myopathy, SS-31 did not improve walking distance or fatigue in the full group, but later genetic subgroup analysis suggested possible benefit in specific mitochondrial DNA maintenance-related disorders. [6, 10]
For health and fitness users, SS-31 is worth watching but not worth overhyping. [2, 7] The strongest current story is rare-disease and mitochondrial-medicine research, not proven athletic enhancement. [2, 6, 11]
The exciting part is that SS-31 gives researchers a focused way to study mitochondria as a treatment target. [1] The cautious part is that healthy-user benefits, long-term safety, and performance claims remain unproven in the abstracts provided. [2, 3]