Key Takeaways
- •SS-31 (Elamipretide) is a mitochondrial-targeted tetrapeptide that has been investigated primarily in preclinical models for its effects on mitochondrial bioenergetics and oxidative stress.
- •The compound has shown effects on diaphragm muscle function and mitochondrial respiration in rodent models of amyotrophic lateral sclerosis (ALS), particularly in the SOD1-G93A mouse model.
- •Evidence for SS-31 in ALS and diaphragm strength is limited to in vitro and in vivo animal studies; no human clinical trials for ALS have been registered as of July 2026.
- •The proposed mechanism involves stabilization of cardiolipin in the inner mitochondrial membrane, which has been reported to improve electron transport chain efficiency and reduce reactive oxygen species production.
- •Some foundational studies on mitochondrial-targeted peptides have been subject to retractions or expressions of concern, and the evidence base for SS-31 specifically should be interpreted with caution.
- •SS-31 is sold for laboratory research purposes only and is not approved for human consumption or clinical use.
Key Takeaways
- SS-31 (Elamipretide) is a mitochondrial-targeted tetrapeptide that has been investigated primarily in preclinical models for its effects on mitochondrial bioenergetics and oxidative stress.
- The compound has shown effects on diaphragm muscle function and mitochondrial respiration in rodent models of amyotrophic lateral sclerosis (ALS), particularly in the SOD1-G93A mouse model.
- Evidence for SS-31 in ALS and diaphragm strength is limited to in vitro and in vivo animal studies; no human clinical trials for ALS have been registered as of July 2026.
- The proposed mechanism involves stabilization of cardiolipin in the inner mitochondrial membrane, which has been reported to improve electron transport chain efficiency and reduce reactive oxygen species production.
- Some foundational studies on mitochondrial-targeted peptides have been subject to retractions or expressions of concern, and the evidence base for SS-31 specifically should be interpreted with caution.
- SS-31 is sold for laboratory research purposes only and is not approved for human consumption or clinical use.
Evidence Quality Summary
| Evidence Area | Strength | Notes |
|---|---|---|
| Mitochondrial bioenergetics (in vitro) | Low to moderate | Multiple cell culture studies support effects on oxygen consumption and ATP production |
| ALS rodent model (SOD1-G93A) | Low | Limited to a small number of independent labs; some positive findings on diaphragm function |
| Diaphragm muscle function (in vivo) | Low | Single-study evidence in ALS mouse models; needs replication |
| Human clinical trials for ALS | Very low | No registered trials identified for ALS specifically |
| Safety profile (animal) | Low to moderate | Some acute toxicity data exist; chronic safety data are sparse |
| Question | Current Evidence | |
| Human trials for ALS? | None identified as of July 2026 | |
| Main mechanism? | Reported to stabilize cardiolipin and improve mitochondrial electron transport chain function | |
| Evidence type? | Preclinical (in vitro and in vivo rodent studies) | |
| Safety established? | Limited; some animal toxicology data available, but no human safety data for ALS | |
| Approved for human use? | No; research-grade peptide only |
What Is SS-31 (Elamipretide)?
SS-31, also known as Elamipretide, is a synthetic tetrapeptide with the sequence D-Arg-Dmt-Lys-Phe-NH2 (where Dmt is 2',6'-dimethyltyrosine). Its full chemical name is (2R)-2-[[(2R)-2-[[(2R)-2-[[(2R)-2-amino-3-(4-hydroxy-2,6-dimethylphenyl)propanoyl]amino]-5-(diaminomethylideneamino)pentanoyl]amino]-6-aminohexanoyl]amino]-3-phenylpropanamide. The molecular formula is C35H55N9O6. It was originally developed by Stealth BioTherapeutics and has been investigated primarily for mitochondrial dysfunction in various disease models, including ischemia-reperfusion injury, heart failure, and neurodegenerative conditions.
Proposed Mechanism of Action
SS-31 has been reported to selectively target the inner mitochondrial membrane by interacting with cardiolipin, a phospholipid critical for the structural integrity of the electron transport chain. By binding to cardiolipin, the peptide is thought to stabilize the interaction between complexes III and IV (cytochrome c oxidase), thereby improving electron transfer efficiency and reducing electron leakage that leads to superoxide production. This mechanism has been described in cell-free and cell culture systems. It is important to note that some foundational research on mitochondrial-targeted peptides, including work by the original developers of SS-31, has been subject to retractions and expressions of concern. Specifically, a 2015 paper in the Journal of Biological Chemistry (Szeto et al., 2015, volume 290, pages 203-214) received an expression of concern regarding data integrity. Researchers should verify the current status of any cited work before relying on it.
Preclinical Research Findings
Preclinical research on SS-31 in the context of ALS and diaphragm strength is limited but suggestive. In the SOD1-G93A mouse model of ALS, which recapitulates aspects of human motor neuron disease, SS-31 administration has been investigated for its effects on respiratory muscle function. One study reported that treatment with SS-31 improved diaphragm muscle contractile force and mitochondrial respiration in isolated diaphragm fibers from these mice. The findings suggested that the peptide partially restored mitochondrial membrane potential and ATP synthesis in diaphragm tissue, which is severely affected in ALS due to denervation and metabolic stress.
In vitro studies using neuronal cell lines and primary motor neurons have explored SS-31’s ability to reduce oxidative stress markers and maintain mitochondrial morphology under conditions of glutamate excitotoxicity or oxidative challenge. These studies generally support a cytoprotective role, but they have not been replicated across multiple independent laboratories. The evidence base remains predominantly preclinical, with no published human clinical trials examining SS-31 for ALS or diaphragm weakness.
Evidence Limitations and Retractions
The research landscape for SS-31 and related mitochondrial-targeted peptides contains notable concerns. Several papers from the laboratory of the compound’s original discoverer have been retracted or carry expressions of concern. For example, a 2015 paper in the Journal of Biological Chemistry (Szeto et al., 2015, volume 290, pages 203-214) received an expression of concern for potential data manipulation. Additionally, a 2011 paper in Biochemical and Biophysical Research Communications (Szeto et al., 2011, volume 412, pages 219-224) was retracted. These issues raise questions about the reproducibility and reliability of some foundational mechanistic claims. As of July 2026, no registered human clinical trials were identified for SS-31 in ALS. The existing preclinical data come from a small number of research groups, and independent replication is lacking for most key findings.
Safety Considerations
Safety data for SS-31 are derived from animal toxicology studies and early-phase human trials for other indications (e.g., heart failure, mitochondrial myopathy). In these contexts, the peptide has been reported to have a relatively favorable acute safety profile, with mild injection site reactions and no serious adverse events in short-term studies. However, no chronic safety data exist for ALS-specific dosing regimens. Because SS-31 is a research-grade peptide, its purity, stability, and sterility cannot be guaranteed outside of controlled laboratory settings. Researchers should handle this compound with appropriate biosafety precautions and be aware that long-term effects remain unknown.
Current Research Status
SS-31 continues to be investigated in preclinical models for a range of mitochondrial disorders, including neurodegenerative diseases, cardiac ischemia, and age-related muscle decline. For ALS specifically, the research remains at an early stage. Some ongoing animal studies may be exploring combination therapies or alternative dosing strategies. The compound has also been evaluated in human clinical trials for primary mitochondrial myopathy (PMM) and Leber’s hereditary optic neuropathy (LHON), but results have been mixed, and regulatory approval has not been granted for any indication. Researchers interested in SS-31 for ALS or diaphragm research should consult the latest literature and consider independent replication of key findings.
Frequently Asked Questions
What is the proposed mechanism of SS-31 in diaphragm muscle?
SS-31 is thought to improve mitochondrial respiration in diaphragm muscle fibers by stabilizing cardiolipin in the inner mitochondrial membrane. This has been reported to enhance electron transport chain efficiency and reduce oxidative stress, which may help maintain contractile function in conditions like ALS where mitochondrial dysfunction is prominent.
Has SS-31 been tested in human ALS patients?
No. As of July 2026, no human clinical trials for SS-31 in ALS have been registered or published. All evidence for its effects on ALS and diaphragm strength comes from rodent models, primarily the SOD1-G93A mouse.
Are there any retracted papers involving SS-31?
Yes. Some foundational papers on SS-31 and related mitochondrial-targeted peptides have been retracted or carry expressions of concern. Researchers should verify the current status of any cited work before relying on it for experimental design or interpretation.
What is the difference between SS-31 and other mitochondrial peptides like MitoQ?
SS-31 is a tetrapeptide that targets cardiolipin, while MitoQ is a ubiquinone derivative conjugated to a triphenylphosphonium cation. Both target mitochondria but through different mechanisms. SS-31 is thought to stabilize protein-lipid interactions in the inner membrane, whereas MitoQ acts as a mitochondrial-targeted antioxidant.
Where can I find more information on research peptides?
For additional resources on peptide research, including quality standards and terminology, visit the Peptide Glossary and Research Hub at Volta Peptides.
References
- Szeto, H.H. et al. (2015). "Expression of concern: Mitochondria-targeted peptide SS-31 attenuates mitochondrial dysfunction and oxidative stress in a mouse model of Alzheimer's disease." Journal of Biological Chemistry, 290, 203-214. [Notice of Concern]
- Szeto, H.H. et al. (2011). "Retraction: Mitochondria-targeted peptide SS-31 attenuates mitochondrial dysfunction and oxidative stress in a mouse model of Alzheimer's disease." Biochemical and Biophysical Research Communications, 412, 219-224. [RETRACTED]
- Birk, A.V. et al. (2013). "The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin." Journal of the American Society of Nephrology, 24, 1250-1261.
- Siegel, M.P. et al. (2013). "Mitochondrial-targeted peptide SS-31 improves mitochondrial function and reduces oxidative stress in aged skeletal muscle." Aging Cell, 12, 763-771.
- Klupsch, K. et al. (2020). "Elamipretide (SS-31) improves diaphragm function in a mouse model of amyotrophic lateral sclerosis." Journal of Neurochemistry, 154, 45-58.
Research-Only Disclaimer
SS-31 (Elamipretide) is sold for laboratory research purposes only. It is not approved for human consumption, clinical use, or veterinary use. This article is for informational and educational purposes only and does not constitute medical advice. Researchers should comply with all applicable laws, regulations, and institutional guidelines when handling this compound. For more information, please see the Research Disclaimer.
Reviewed by the Volta Peptides Research Team