What is SS-31 (elamipretide)? The cardiolipin-binding peptide in research

Where does SS-31 come from?

SS-31 belongs to the Szeto-Schiller peptides, a series of small synthetic peptides designed by Hazel Szeto and Peter Schiller. The series alternates aromatic residues with basic amino acids, a pattern that lets the peptides cross cell membranes and gather in mitochondria without relying on the membrane potential. SS-31 itself is the tetrapeptide D-Arg-Dmt-Lys-Phe-NH2. Dmt is 2',6'-dimethyltyrosine, an altered tyrosine, and the first residue is the D form of arginine, which makes the peptide more resistant to breakdown by enzymes. The calculated molecular weight is about 640 g/mol.

In clinical development the compound took the name elamipretide, and it has also been called MTP-131 and Bendavia. A 2025 review described it as a tetrapeptide with uptake into many cell types and highly selective targeting of mitochondria.

How is it described at the molecular level?

The central target is cardiolipin, a phospholipid found almost only in the inner mitochondrial membrane. Cardiolipin shapes the cristae, the folds of that membrane, and helps the respiratory complexes assemble into supercomplexes for efficient oxidative phosphorylation. A 2014 review by Szeto described SS-31 binding cardiolipin through electrostatic and hydrophobic interactions.

The same review explained why that binding matters. Cytochrome c normally carries electrons between respiratory complexes. When it interacts with cardiolipin in a certain way it can turn into a peroxidase, which damages cardiolipin itself. SS-31 was reported to block that conversion while keeping the electron carrying function. Later reviews summarised the downstream effects observed in models as stabilised cristae, less oxidative stress and more ATP production.

What has been observed in published research?

• Lung fibrosis (mouse): in a bleomycin model, SS-31 given every other day reduced fibrosis, extracellular matrix deposition and inflammatory cytokines, and lowered IL-1beta and IL-18 by inhibiting the NLRP3 inflammasome in macrophages.
• Inflammation-related memory impairment (mouse): after lipopolysaccharide exposure, mice given elamipretide showed better learning and memory performance, less hippocampal oxidative stress and less loss of dendritic spines.
• Anaesthesia exposure (developing rat): rat pups exposed to isoflurane for six hours on day 7 of life showed less accumulation of reactive oxygen species and mitochondrial damage in the hippocampus, and better later cognitive test results, when given elamipretide beforehand.
• Primary mitochondrial myopathy (human trial): MMPOWER-3 randomised 218 adults to elamipretide or placebo for 24 weeks. It did not meet its primary endpoints, the six minute walk test and total fatigue score, and treatment was reported as well tolerated.
• Barth syndrome (human trial and case reports): in the 168 week open-label extension of TAZPOWER, the six minute walk distance improved by a cumulative 96.1 metres, with reactions at the administration site the most common adverse events. A 2026 case report described a five year old whose left ventricular ejection fraction rose from 20 to 50 percent over six months.
• Regulatory status: a 2026 review of trials in primary mitochondrial diseases listed elamipretide among four therapies with regulatory authorisation, with US accelerated approval for Barth syndrome. Another 2026 review stated that the approval covered muscle strength and that an effect on heart disease remained unconfirmed.

What the evidence does not establish

SS-31 is unusual among research peptides because its human data include a large, negative phase 3 trial. MMPOWER-3 showed that a credible mechanism and positive early studies do not guarantee a measurable effect in a broader patient group. The Barth syndrome findings come from a very rare disease, from small numbers (ten patients entered the extension) and partly from open-label designs, which are more open to bias than blinded comparisons.

Animal studies cover a wide range of organs, but each model is narrow and many come from single laboratories. None of these results describe the effect of research-grade material in any setting outside the laboratory, and the approved medicine is a regulated product, not the research material described on this site.

How does SS-31 compare with related compounds?

SS-31 is frequently mentioned next to MOTS-c, another peptide in mitochondrial research. MOTS-c is a natural 16 residue peptide encoded by mitochondrial DNA and was described as acting through the folate cycle, AMPK and nuclear gene expression in mice. SS-31 is synthetic and binds a lipid in the inner membrane. In evidence terms SS-31 is further along, with several randomised human trials, while MOTS-c has no controlled human trials. The SS-31 vs MOTS-c guide sets the two side by side.

Within its own family, SS-31 is one of several Szeto-Schiller peptides that share alternating aromatic and basic residues. It is the member that moved into clinical development. NAD+ is sometimes discussed in the same context because both relate to mitochondrial energy production, but NAD+ is a coenzyme that cells consume and recycle, not a membrane-binding peptide. No published study has combined SS-31 with MOTS-c or with NAD+.

Which formats does Vitality Peps supply?

Vitality Peps supplies SS-31 (elamipretide) as a 10 mg lyophilised vial for laboratory research, documented by a batch certificate of analysis. Bacteriostatic water is listed separately for reconstitution. MOTS-c, another peptide studied in mitochondrial research, is available as a 40 mg vial.

How is it handled in the laboratory?

Lyophilised SS-31 is stored cold and protected from light. Before use the vial is brought to room temperature and the powder is reconstituted with bacteriostatic water, added slowly down the side of the vial and swirled rather than shaken. The working concentration is calculated from the actual vial mass on the certificate. Reconstituted solution is refrigerated, labelled and dated.

Research use only

SS-31 supplied by Vitality Peps is for in vitro laboratory research only. Not a medicine, not a supplement, not for human or veterinary consumption. Nothing above is instructions for use.