SS-31 / Elamipretide
SS-31 is a synthetic four-amino-acid peptide, also called elamipretide, studied for its interaction with the inner mitochondrial membrane. A prescription product containing it, FORZINITY, received a specific FDA approval for Barth syndrome in 2025. That approval does not establish general anti-aging or weight-loss benefits, or make an online SS-31 research vial equivalent to the medicine.
The evidence has two very different clinical stories. Longer-term findings in a small Barth syndrome program contributed to accelerated approval for muscle strength. In a separate randomized trial of 218 people with primary mitochondrial myopathy, elamipretide did not improve the two primary walking and fatigue endpoints. The population, outcome and study design explain why both statements can be true. FDA approval announcement · MMPOWER-3
What is SS-31, and is it the same as elamipretide?
SS-31, MTP-131 and elamipretide refer to the same active peptide in this research literature; Bendavia is an earlier development name. FORZINITY identifies a finished prescription formulation. Those names connect the research history, but they do not establish that different suppliers, salts or formulations are interchangeable.
Four residues. A specific chemical identity.
- D-Arg1 · D-arginine
- Dmt2 · modified L-tyrosine
- Lys3 · L-lysine
- Phe4 · L-phenylalanine
H–D-Arg–Dmt–Lys–Phe–NH₂. Dmt means 2′,6′-dimethyltyrosine. The terminal –NH₂ denotes amidation; it is not a fifth amino acid.
The neutral peptide reference is C32H49N9O5, about 639.8 g/mol. The drug label describes a trihydrochloride salt, which has a different formula weight. A mass-spectrum ion, a neutral molecular reference and a salt-associated vial mass answer different questions. PubChem identity · Current FORZINITY label
The compound emerged from the Szeto–Schiller peptide program. Early accounts connect its development to mitochondrial membrane interactions and energy handling; they are historical explanations, not new clinical trials. 2014 development review
What does SS-31 do to mitochondria?
Its central research target is cardiolipin, a lipid concentrated in the inner mitochondrial membrane. That folded membrane helps organize the machinery that converts fuel-derived energy into ATP. SS-31 is studied for altering this environment and the behavior of proteins associated with it.
Peptide–lipid interaction
Organization of energy-handling proteins
Conceptual illustration, not a measured membrane image or a guarantee of increased ATP in a person.
In lipid systems and isolated mitochondria, researchers examined cardiolipin binding, cytochrome-c behavior and respiration. Rat kidney experiments also found preservation of mitochondrial folds and faster ATP recovery after an ischemic injury. These are specific experimental systems. Membrane and respiration study · Rat kidney study
A later interaction study mapped proteins associated with the compound, adding detail to the membrane model. A 2025 review summarizes this evolving mechanism. Neither establishes that every symptom attributed to “mitochondrial dysfunction” responds to elamipretide. Protein-interaction study · Mechanism review
What benefits have animal studies suggested?
Aged skeletal muscle
Mouse studies reported improved muscle energetics and exercise tolerance. An eight-week experiment also found better redox balance without an increase in mitochondrial content. Improved function in that model was not evidence that the treatment simply created more mitochondria. 2013 study · 2019 study
Injured or failing organs
The kidney work examined ischemic injury. A small randomized dog model of chronic heart failure examined cardiac function and mitochondrial measures. These results helped motivate clinical research; they do not establish an approved treatment for human kidney disease or heart failure. Heart-failure model
“Reverses aging” is a much larger claim than improving a measured variable in aged mice. These studies did not demonstrate reversal of human biological age, longer human life or a validated weight-loss effect.
What did human SS-31 trials actually find?
Barth syndrome: follow the change in study design
Barth syndrome is a rare genetic condition involving abnormal cardiolipin remodeling. The TAZPOWER program began with a randomized, blinded crossover comparison. It then continued into an extension in which participants knew they were receiving elamipretide. The initial comparison did not meet its walking-distance or fatigue primary endpoint. Later within-person improvements came from a different design. Original trial report · Trial registry
- 12Entered the randomized crossover trial
- 10Entered the open-label extension
- 8Reached the extension’s week 168 visit
The longer follow-up reported sustained functional improvements, including an approximately 96-meter walking-distance increase from the extension baseline at week 168. With eight participants and no concurrent randomized control at that stage, this is not the same estimate as a placebo-controlled treatment difference. 168-week report
A separate analysis compared eight treated participants with 19 untreated natural-history controls and reported favorable functional differences. Matching can improve comparability, but it cannot reproduce random assignment or eliminate every difference between cohorts. These papers analyze related patients; their participant counts should not be added as independent successful trials. Natural-history comparison
Primary mitochondrial myopathy: a larger negative trial
Early MMPOWER research was small and short, with exploratory signals that justified further investigation. The larger MMPOWER-3 trial tested a more demanding question over 24 weeks in 218 people. Early study · MMPOWER-3 registry
MMPOWER-3 · 218 participants · 24 weeks
−3.2 metersThis is the difference in six-minute walking-distance change, elamipretide minus placebo. The 95% confidence interval ran from −18.7 to +12.3 meters; P=.69. It did not demonstrate a walking benefit. The fatigue primary endpoint was also negative. Read the primary report
The publication’s abstract and full results report different uncertainty statistics for the fatigue estimate. Both describe a negative result. We therefore give the consistent walking result above instead of presenting an unexplained fatigue P-value.
The practical lesson is to ask which disease and which endpoint a benefit claim refers to. A membrane mechanism, an uncontrolled extension and a negative randomized trial are different forms of evidence, even when they concern the same active molecule.
Is SS-31 FDA approved?
FORZINITY received accelerated FDA approval on September 19, 2025 to improve muscle strength in adults and children with Barth syndrome weighing at least 30 kg. The decision relied on knee-extensor strength as an intermediate clinical endpoint; continued approval may depend on confirmation of clinical benefit. FDA announcement · Approval letter
This does not mean the randomized portion met its original walking and fatigue goals. The regulatory decision concerns a particular outcome and population. It also does not authorize a general longevity, fat-loss or athletic-performance claim. A later approval overview is useful historical context; the current FDA decision and prescribing information are the sources for the indication. Approval overview
Apex’s SS-31 is a research-use-only reagent. Its listing and analytical records do not establish equivalence to FORZINITY’s finished formulation, clinical manufacturing controls or labeled use. The current label was checked on September 8, 2026. Prescribing information
What side effects and safety limits matter?
Injection-site reactions were common in the small Barth clinical program. The current medicine label also identifies serious hypersensitivity and a benzyl-alcohol warning specific to its formulation. These are clinically meaningful risks, not a generic “well tolerated” endorsement. Rates from a small drug trial cannot predict the risk of a differently prepared research material. Label safety sections · Trial safety findings
The studies reviewed here do not establish safe self-directed cycles, anti-aging schedules or combinations with other peptides. An approved prescription regimen for a defined disease is not an instruction for using a research vial. Patient treatment questions belong with a clinician who can apply the actual prescribing information and clinical context.
SS-31 versus MOTS-c: why they are not interchangeable
SS-31 is a synthetic tetrapeptide studied at the inner mitochondrial membrane. MOTS-c is a 16-residue mitochondrial-derived peptide studied in stress signaling and metabolism. “Mitochondrial peptide” is a broad description, not evidence that the two have the same mechanism, human evidence or regulatory status.
None of the elamipretide trials discussed above establishes that SS-31 should be taken before MOTS-c, or that combining them improves outcomes. To compare them, keep the material, the intervention and the measured endpoint separate.
How to read an SS-31 COA without confusing purity and amount
The Apex-issued record APX-2026-0605-E names the SS-31 50 mg configuration and an issue date of June 5, 2026. It is a specific report example, not a promise about whichever lot ships next.
Chromatographic area
Assigned SS-31 peak share of integrated detector signal. The stated acceptance range is 99.7–100%. This is not the percentage of the vial’s total mass.
Active-content result
A separately calibrated amount on the report’s assigned component basis. The acceptance range is 49–51 mg/vial. Dividing by the nominal 50 mg yields 100.223% label claim.
The record’s identity section explicitly describes acetate-associated material. Its reference molecular mass is therefore not interchangeable with the total salt-associated fill mass. Report issue date also does not establish the date every analysis occurred.
This is an Apex-issued record with reported results and numeric supporting detail, not an independent laboratory endorsement or a set of original instrument exports. Analytical identity and amount cannot establish a biological benefit, sterility for administration or pharmaceutical equivalence. For a deeper explanation, see how to read a peptide COA.
For offered configurations and current availability, use the SS-31 research product page. Related educational topics are in the longevity and bioregulator research hub.
Frequently Asked Questions
What is SS-31 used for?
SS-31, also called elamipretide, is studied for its interaction with cardiolipin in the inner mitochondrial membrane. The prescription product FORZINITY has a specific FDA-approved use in Barth syndrome. The studies here do not establish general anti-aging or weight-loss benefits for a research reagent.
Is SS-31 the same as elamipretide or FORZINITY?
SS-31 and elamipretide name the same active peptide in this literature. FORZINITY is a finished prescription formulation containing elamipretide. A research vial is not shown to be equivalent merely because its listing uses the same peptide name.
Does SS-31 reverse aging or help with weight loss?
Aged-mouse studies reported changes in muscle energetics and exercise tolerance. They did not establish reversal of human aging. The human trials discussed here also do not demonstrate a validated general weight-loss effect.
Did SS-31 work in human clinical trials?
The result depends on the population and endpoint. A small Barth syndrome program produced longer-term findings relevant to a specific accelerated approval. The separate 218-person MMPOWER-3 trial did not meet its walking or fatigue primary endpoint in primary mitochondrial myopathy.
What are the side effects of SS-31?
The elamipretide clinical program reported frequent injection-site reactions, and the current drug label includes serious hypersensitivity. Those observations concern defined clinical material and monitored patients. They do not establish the safety of a differently prepared research product.
Should SS-31 be used before or with MOTS-c?
The elamipretide trials reviewed here do not establish a before-and-after sequence or a combination benefit with MOTS-c. The molecules have different structures and evidence. Calling both mitochondrial peptides does not validate a combined protocol.
Is there an evidence-based SS-31 cycle for anti-aging?
These studies do not establish a self-directed anti-aging cycle for a research reagent. A prescription regimen for a specific disease cannot be transferred to that purpose. Treatment decisions require the actual medicine label and clinical assessment.
Does a high SS-31 HPLC percentage prove clinical quality?
No. Chromatographic area is one analytical measurement. It does not establish the vial’s active amount, an effective treatment, suitability for administration or equivalence to an approved drug. Read the report’s identity, configuration, lot and separate result definitions.
References and source notes
The papers below include experiments, related follow-ups and reviews; they are not 14 independent clinical trials. Current prescribing information, the original approval letter and the two trial registries are linked beside the claims they support.
- Birk AV et al. Targeting mitochondrial cardiolipin and the cytochrome c/cardiolipin complex to promote electron transport and optimize mitochondrial ATP synthesis. British journal of pharmacology. 2014. PMID 24134698.
- Szeto HH et al. Serendipity and the discovery of novel compounds that restore mitochondrial plasticity. Clinical pharmacology and therapeutics. 2014. PMID 25188726.
- Birk AV et al. The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. Journal of the American Society of Nephrology : JASN. 2013. PMID 23813215.
- Chavez JD et al. Mitochondrial protein interaction landscape of SS-31. Proceedings of the National Academy of Sciences of the United States of America. 2020. PMID 32554501.
- Siegel MP et al. Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice. Aging cell. 2013. PMID 23692570.
- Campbell MD et al. Improving mitochondrial function with SS-31 reverses age-related redox stress and improves exercise tolerance in aged mice. Free radical biology & medicine. 2019. PMID 30597195.
- Sabbah HN et al. Chronic Therapy With Elamipretide (MTP-131), a Novel Mitochondria-Targeting Peptide, Improves Left Ventricular and Mitochondrial Function in Dogs With Advanced Heart Failure. Circulation. Heart failure. 2016. PMID 26839394.
- Sabbah HN et al. Contemporary insights into elamipretide's mitochondrial mechanism of action and therapeutic effects. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie. 2025. PMID 40294492.
- Karaa A et al. Randomized dose-escalation trial of elamipretide in adults with primary mitochondrial myopathy. Neurology. 2018. PMID 29500292.
- Karaa A et al. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology. 2023. PMID 37268435.
- Reid Thompson W et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism. Genetics in medicine : official journal of the American College of Medical Genetics. 2021. PMID 33077895.
- Hornby B et al. Natural history comparison study to assess the efficacy of elamipretide in patients with Barth syndrome. Orphanet journal of rare diseases. 2022. PMID 36056411.
- Thompson WR et al. Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER. Genetics in medicine : official journal of the American College of Medical Genetics. 2024. PMID 38602181.
- Zhao C et al. Elamipretide: The first cardiolipin-directed mitochondrial therapeutic for Barth syndrome approved under accelerated approval. Drug discoveries & therapeutics. 2026. PMID 41260682.
