MOTS-c is a mitochondrial-encoded peptide studied in cells, mouse interventions and human measurements of the body’s own peptide. SS-31 is a development name for elamipretide, which acts at mitochondrial membranes and has controlled patient trials. Its large mitochondrial-myopathy trial did not establish better walking or fatigue, while its defined product has accelerated approval for muscle strength in Barth syndrome. These findings cannot rank the compounds for general energy, exercise or aging.
Research reviewed October 15, 2026. Educational information only.
Two different relationships with mitochondria
MOTS-c is a sixteen-residue peptide encoded within mitochondrial DNA, in a short reading frame in the 12S ribosomal-RNA region. The discovery study linked it to cellular metabolism and insulin responses. SS-31 is the development name for elamipretide, a synthetic modified tetrapeptide. The approved Forzinity product contains a defined hydrochloride salt; a development nickname alone does not specify a product’s formulation or quality.
The mitochondrial connection therefore means different things. MOTS-c belongs to a class of small peptides encoded in the organelle’s genome. Elamipretide localizes to the inner mitochondrial membrane and binds cardiolipin, a lipid important to that membrane’s organization. Neither description establishes a general human increase in energy or performance.
The main differences
What does their mitochondrial connection mean?
The compounds differ in origin and studied action. A shared organelle does not make them interchangeable.
MOTS-c
MOTS-c is a sixteen-residue peptide encoded in mitochondrial DNA. Experimental cells showed changes in folate/purine metabolism and signaling through AMPK, an energy-sensing enzyme; separate mice showed improved insulin responses in the tested conditions.
Elamipretide
SS-31 names elamipretide, a synthetic modified tetrapeptide. The defined Forzinity product binds cardiolipin and localizes to the inner mitochondrial membrane. Its molecular action does not itself estimate clinical benefit.
Which human observations involved giving the peptide?
Human-derived cells, endogenous blood measurements and a patient treatment trial represent different kinds of evidence.
MOTS-c
In the ten-man cycling study, investigators measured MOTS-c produced by the body. Muscle and blood measurements rose transiently; participants were not given MOTS-c. The mouse intervention arms were separate experiments.
Elamipretide
MMPOWER-3 assigned 218 people with primary mitochondrial myopathy to elamipretide or placebo for 24 weeks. It directly tested treatment, measuring six-minute walking distance and patient-reported fatigue.
What did the performance and patient-outcome studies find?
Mouse running capacity cannot be compared numerically with walking in patients who have inherited muscle disease.
MOTS-c
Separate mouse experiments in the exercise paper found better rotating-rod and selected treadmill performance. The comparisons did not establish an improvement in grip strength or maze learning. The human cycling component measured the endogenous peptide rather than treatment benefit.
Elamipretide
In MMPOWER-3, walking increased 14.1 meters with elamipretide versus 17.3 with placebo. The adjusted difference was −3.2 meters (95% CI −18.7 to 12.3), leaving the comparison uncertain; fatigue also showed no established benefit.
How much human pharmacokinetic information is available?
A concentration after exercise does not measure exposure after a manufactured peptide is administered.
MOTS-c
FDA’s 2026 briefing identified no clinical pharmacokinetic study of native MOTS-c free base or acetate. Endogenous exercise measurements cannot provide a numerical administered-human elimination half-life.
Elamipretide
The product label documents absorption after injection under the skin, with peak concentrations after 0.5–1 hour and about 92% of the administered amount reaching the blood (absolute bioavailability). Elamipretide breaks down into inactive peptide metabolites. Parent and metabolites are excreted in urine, and kidney impairment increases exposure.
What do approval and adverse-event records establish?
A condition-specific product approval and an unmeasured safety profile cannot be converted into a general safety ranking.
MOTS-c
FDA identified major gaps in administered-human safety and nonclinical toxicity for native MOTS-c, with concerns about immune responses and peptide impurities. Missing reports do not establish a lower risk.
Elamipretide
Forzinity has accelerated approval for muscle strength in Barth syndrome at body weight at least 30 kg, with confirmation of clinical benefit required. The label identifies injection-site reactions and serious hypersensitivity, meaning allergic reactions; in the controlled twelve-person Barth dataset local reactions occurred in twelve on elamipretide and eight on placebo.
Cellular stress signaling and membrane binding are distinct hypotheses
Lee and colleagues found that MOTS-c altered folate and purine metabolism in experimental cells. Purines are building blocks used in nucleic acids and energy-carrying molecules. Accumulation of the intermediate AICAR accompanied activation of AMPK, an enzyme that helps cells respond to energy stress. Related mouse experiments found better insulin responses under the tested aging or high-fat-diet conditions.
The elamipretide label describes cardiolipin binding and localization at the inner mitochondrial membrane, with improved mitochondrial morphology and function in its pharmacological characterization. This membrane action differs from the MOTS-c cell-metabolism findings. A mechanism can help explain why an outcome is plausible; it cannot determine how much farther a patient walks or how much fatigue improves.
Human exercise measurements were separate from mouse treatment
Reynolds and colleagues collected muscle and blood samples from ten sedentary healthy young men around a cycling session. No MOTS-c was administered. Muscle measurements rose about 11.9-fold after exercise, while circulating measurements rose 1.6-fold during and 1.5-fold after exercise before returning toward baseline after four hours. These are changes in endogenous peptide, meaning peptide made by the body. They do not show what a manufactured injection would do.
The same paper contained separate mouse interventions. Treated young mice performed better on a rotating-rod task and selected treadmill tests, while the comparisons did not establish improvement in grip strength or maze learning. Those different outcomes narrow the interpretation: a response in running or coordination does not demonstrate universal strength or cognitive enhancement. Neither the mouse treatment nor the ten-person exercise observation compares MOTS-c with elamipretide in people.
The largest myopathy trial did not establish walking or fatigue benefit
MMPOWER-3 randomly assigned 218 people with genetically confirmed primary mitochondrial myopathy, 109 to elamipretide and 109 to placebo for 24 weeks. Myopathy means muscle disease; this trial concerned inherited mitochondrial disorders with muscle symptoms. Participants and investigators were blinded to assignment. The six-minute walk test measured the distance participants could cover in six minutes, alongside a patient-reported fatigue score.
Walking distance increased by an adjusted 14.1 meters with elamipretide and 17.3 meters with placebo. The between-group difference was −3.2 meters, with a 95% confidence interval from −18.7 to 12.3 meters (P=0.69). The interval includes a modest disadvantage and a modest advantage; the comparison did not establish benefit. Fatigue also improved similarly, without an established treatment difference. Later subgroup hypotheses cannot replace those whole-trial results.
The approved Barth-syndrome indication concerns a different disease and evidence set. In the small twelve-person crossover trial described in the label, elamipretide was not superior to placebo on the primary walking and fatigue outcomes. Increased strength in the muscles that straighten the knee was observed later in the open-label extension, where everyone knew treatment was given and there was no concurrent placebo group. The label bases accelerated approval on that intermediate clinical measurement and requires confirmation of clinical benefit.
Human exposure is documented for the defined elamipretide product
The Forzinity label reports peak elamipretide concentrations 0.5–1 hour after subcutaneous administration and approximately 92% absolute bioavailability. The latter is the estimated fraction reaching the circulation compared with intravenous exposure. Elamipretide is broken down from its terminal end into inactive tripeptide and dipeptide metabolites. Parent and metabolites leave through urine, and impaired kidney function increases exposure.
FDA’s 2026 MOTS-c briefing identified no clinical studies providing pharmacokinetic data for native MOTS-c free base or acetate. Measuring the body’s own peptide before and after exercise does not establish absorption or elimination after administration. No numerical administered-human elimination half-life for native MOTS-c was verified.
Approval and safety remain tied to a defined condition and product
Forzinity has accelerated U.S. approval to improve muscle strength in adults and children with Barth syndrome weighing at least 30 kg. That indication does not cover general fatigue, healthy aging or athletic performance. The label identifies frequent injection-site reactions and hypersensitivity, including serious allergic reactions. In its twelve-person controlled Barth dataset, all twelve had a local administration reaction on elamipretide versus eight during placebo.
In MMPOWER-3, adverse events were recorded in 107 of 109 elamipretide recipients and 83 of 109 placebo recipients; most were mild or moderate. Eight and two participants, respectively, stopped treatment because of adverse events. MOTS-c has no comparable administered-human safety dataset in the FDA briefing, which identifies major safety, impurity and immune-response gaps. That absence cannot be treated as a lower adverse-event rate.
No head-to-head treatment trial was identified. Elamipretide has more direct clinical evidence, including an unsuccessful broad myopathy comparison and a narrowly defined accelerated approval. MOTS-c remains a cell-and-animal intervention hypothesis alongside human endogenous-peptide research. These facts describe what is known; they do not identify a preferred general “mitochondrial peptide.”
Frequently asked questions
Is SS-31 the same name as elamipretide?
SS-31 is a development name used for elamipretide. Forzinity specifies a particular hydrochloride product and formulation; the nickname does not verify the identity or quality of a separately supplied material.
Did the human MOTS-c exercise study administer a peptide?
No. Ten men exercised while investigators collected blood and muscle samples. Those endogenous measurements were separate from the paper’s mouse treatment experiments.
Does Barth-syndrome approval mean the large myopathy trial succeeded?
They concern different populations. MMPOWER-3 did not establish walking or fatigue benefit. The Barth indication received accelerated approval based on later knee-extension strength observations in a small open-label extension and still requires confirmation of clinical benefit.
Can either compound be ranked for healthy aging or energy?
No shared trial in healthy people establishes a relative effect on those outcomes. Mouse performance, endogenous exercise measurements and disease-specific patient trials cannot supply that ranking.
Profiles and related reading
References
- Lee C, Zeng J, Drew BG, Sallam T, Martin-Montalvo A, Wan J, Kim SJ, Mehta H, Hevener AL, de Cabo R, Cohen P. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell metabolism. 2015;21(3):443–454. doi:10.1016/j.cmet.2015.02.009. PMID:25738459.
MOTS-c altered cellular folate/purine metabolism and AMPK-linked signaling. Treated mice were protected against diet- and age-related insulin resistance in the tested models.
- Reynolds JC, Lai RW, Woodhead JST, Joly JH, Mitchell CJ, Cameron-Smith D, Lu R, Cohen P, Graham NA, Benayoun BA, Merry TL, Lee C. MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis. Nature Communications. 2021;12:470. DOI: 10.1038/s41467-020-20790-0.
Ten young men produced more endogenous MOTS-c in muscle and blood around exercise. Separate mouse interventions improved selected physical-performance tests, while the comparisons did not establish improvement in grip strength or maze learning.
- Karaa A, Bertini E, Carelli V, Cohen BH, Enns GM, Falk MJ, Goldstein A, Gorman GS, Haas R, Hirano M, Klopstock T, Koenig MK, Kornblum C, Lamperti C, Lehman A, Longo N, Molnar MJ, Parikh S, Phan H, Pitceathly RDS, Saneto R, Scaglia F, Servidei S, Tarnopolsky M, Toscano A, Van Hove JLK, Vissing J, Vockley J, Finman JS, Brown DA, Shiffer JA, Mancuso M, MMPOWER-3 Trial Investigators. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology. 2023;101(3):e238–e252. doi:10.1212/WNL.0000000000207402. PMID:37268435.
In 218 people with primary mitochondrial myopathy, elamipretide did not establish better walking or fatigue outcomes than placebo after 24 weeks. Injection-site reactions were frequent.
- U.S. Food and Drug Administration. Forzinity (elamipretide) injection: prescribing information. NDA 215244. Revised September 2025. Reference ID 5662523. Accessed October 15, 2026.
The label defines the hydrochloride product, its accelerated Barth-syndrome indication, subcutaneous pharmacokinetics and adverse reactions, including local reactions and hypersensitivity (allergic reactions).
- U.S. Food and Drug Administration. FDA Briefing Document: MOTS-c-Related Bulk Drug Substances (MOTS-c free base and MOTS-c acetate). Pharmacy Compounding Advisory Committee, July 23–24, 2026.
The briefing identifies no clinical administration studies or human pharmacokinetic data for native MOTS-c and describes major gaps in toxicity and immune-response information.