SS-31 is a four-residue synthetic peptide that enters cells and collects at the inner mitochondrial membrane, where it binds cardiolipin, the lipid that holds the respiratory chain together. Developed under the names MTP-131 and Bendavia and later as elamipretide, it is one of the few mitochondria-targeted compounds whose story runs from basic membrane biophysics to a regulatory decision.
For researchers, SS-31 is mostly a probe for a single question: what happens to mitochondrial energy production and oxidative stress when cardiolipin is shielded from damage? The sections below cover the peptide’s chemistry and origin, the evidence for its cardiolipin mechanism, the model systems where it has been studied, and the limits of that evidence.
At a glance
- Class: Synthetic aromatic-cationic tetrapeptide; Szeto-Schiller (SS) peptide family
- Origin: Developed from opioid peptide chemistry by Hazel Szeto (Weill Cornell) and Peter Schiller (Clinical Research Institute of Montreal); mitochondrial activity reported in the early 2000s
- Structure: D-Arg-Dmt-Lys-Phe-NH2 (Dmt = 2′,6′-dimethyl-L-tyrosine); C32H49N9O5; MW 639.8 g/mol; CAS 736992-21-5
- Main research areas: cardiolipin and cytochrome c biophysics, ischemia-reperfusion injury, oxidative stress in cell models, mitochondrial aging
- Regulatory status: An elamipretide injection received FDA accelerated approval for Barth syndrome in September 2025; the research reagent sold here is not that product
Structure and origin
The Szeto-Schiller peptides came out of work on short, enzyme-resistant opioid peptides containing the unnatural amino acid Dmt. While studying how these small, positively charged peptides crossed cell membranes, the investigators found that some of them accumulated in mitochondria. Reordering the residues so that D-arginine sits first and Dmt second produced SS-31, which has no meaningful opioid receptor activity but keeps the cell-penetrating, mitochondria-seeking behavior (Szeto, 2014).
The design follows an alternating pattern: basic, aromatic, basic, aromatic. At physiological pH the peptide carries a net charge of +3. The D-arginine and C-terminal amide make it resistant to peptidases, and the Dmt phenol can scavenge some reactive oxygen species, which is why early papers grouped SS-31 with antioxidants. Unlike lipophilic cations such as the triphenylphosphonium compounds, SS-31 does not rely on the mitochondrial membrane potential to accumulate, so it can still reach depolarized mitochondria (Szeto, 2014).
Mechanism: what the research shows
Cardiolipin is a four-chain phospholipid found almost only in the inner mitochondrial membrane. It shapes the cristae, anchors respiratory supercomplexes and binds cytochrome c. Under oxidative stress, cytochrome c bound to cardiolipin can act as a peroxidase that oxidizes cardiolipin itself, an early step toward loss of cristae and release of apoptotic signals.
Birk and colleagues showed that SS-31 binds cardiolipin selectively, interacting through both electrostatic and hydrophobic contacts, and that this binding inhibited the peroxidase activity of the cytochrome c–cardiolipin complex while protecting its electron-carrying function. In isolated mitochondria and a rat model of renal ischemia-reperfusion, the peptide was associated with preserved cristae structure and faster recovery of ATP (Birk et al., 2013). Szeto’s 2014 review pulled these findings into a single model in which SS-31 acts as a cardiolipin-protective agent rather than a simple antioxidant (Szeto, 2014).
Key areas of study
Cardiolipin and cytochrome c biophysics
Liposome binding studies, fluorescence and spectroscopic assays, and measurements of cytochrome c reduction and peroxidase activity form the biophysical core of SS-31 research (Birk et al., 2013). These methods let investigators separate membrane binding from effects on electron transfer.
Ischemia-reperfusion models
Kidney and heart ischemia-reperfusion models were among the first in vivo settings for the peptide. In the rat kidney, SS-31 treatment around reperfusion was associated with preserved mitochondrial cristae, recovery of ATP and reduced tubular injury in the model (Birk et al., 2013).
Oxidative stress in neuronal cells
In neuronal cell lines exposed to tert-butyl hydroperoxide, SS-31 prevented loss of mitochondrial membrane potential and reduced apoptosis (Zhao et al., 2005). Cell studies of this kind established the peptide as a tool for separating mitochondrial from cytosolic sources of oxidative damage.
Mitochondrial aging
In aged mice, an eight-week course of SS-31 was associated with a more reduced glutathione redox state in skeletal muscle, improved mitochondrial energetics and greater treadmill endurance compared with untreated aged controls (Campbell et al., 2019). This study made SS-31 a frequent comparator in research on mitochondrial decline with age.
What the evidence does not show
Most SS-31 data come from isolated mitochondria, cell lines and rodents, and many of the foundational papers originate from the inventor’s laboratory and collaborators. The exact binding mode with cardiolipin is still being refined, and some effects first attributed to antioxidant activity may reflect membrane interactions instead. Results in rodent ischemia and aging models do not establish effects outside those models. The September 2025 FDA action was an accelerated approval tied to a specific rare disease and a specific drug product; it does not extend to research peptides sold under the SS-31 name.
Regulatory status
In September 2025 the FDA granted accelerated approval to an elamipretide injection for Barth syndrome. The SS-31 sold by Rogue Compounds is a research reagent, not that approved drug product, and it is not for human or veterinary use.
Handling and storage in the lab
Lyophilized SS-31 should be kept sealed and refrigerated at 2–8°C (36–46°F), protected from light. Keep the vial closed until use to limit exposure to moisture.
Sourcing and documentation
Rogue Compounds has SS-31 made in small batches. Every vial carries a batch number and a QR code that opens the independent U.S. testing lab’s own report for that batch. The same batch COA is posted on the product page and in the COA Library.
References
- Birk AV, et al. The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. J Am Soc Nephrol. 2013;24(8):1250-1261. PMID 23813215
- Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol. 2014;171(8):2029-2050. PMID 24117165
- Campbell MD, et al. Improving mitochondrial function with SS-31 reverses age-related redox stress and improves exercise tolerance in aged mice. Free Radic Biol Med. 2019;134:268-281. PMID 30597195
- Zhao K, et al. Mitochondria-targeted peptide prevents mitochondrial depolarization and apoptosis induced by tert-butyl hydroperoxide in neuronal cell lines. Biochem Pharmacol. 2005;70(12):1796-1806. PMID 16216225
Research use only. Rogue Compounds products are sold strictly for laboratory research. They are not for human or veterinary use, and nothing in this article is medical advice. The studies cited here describe published research, not this product or any use of it.