SS-31 (Elamipretide): Mitochondria-Targeted Peptide Research

Published: May 2026

SS-31, also known as elamipretide (development codes MTP-131 and Bendavia), is an aromatic-cationic, cell-permeable tetrapeptide developed by Hazel Szeto and Peter Schiller in the early 2000s as part of a series of mitochondria-targeting peptides (the Szeto-Schiller, or SS, peptides). The compound has the sequence D-Arg-2′,6′-dimethyl-L-Tyr-L-Lys-L-Phe-NH₂ (D-Arg-Dmt-Lys-Phe-NH₂), carries CAS number 736992-21-5, molecular formula C₃₂H₄₉N₉O₅, and a molecular weight of approximately 639.8 g/mol. Its alternating aromatic-cationic motif allows the peptide to cross cell membranes without a transporter and to concentrate several hundredfold within the inner mitochondrial membrane, where research has centered on its association with cardiolipin. SS-31 has been investigated across a broad preclinical literature spanning oxidative cell death, ischemia-reperfusion injury, aged-muscle bioenergetics, and animal models of heart failure, and it has also entered clinical investigation for genetically defined mitochondrial disorders.

Molecular Profile

Discovery and Mitochondrial Targeting

The SS peptides emerged from work by Szeto and Schiller on dermorphin-derived analogs, where a subset of small peptides built on an alternating aromatic-cationic scaffold was found to enter cells independent of membrane potential and accumulate within mitochondria. Zhao et al. (2004), publishing in the Journal of Biological Chemistry, characterized this first generation of cell-permeable peptide antioxidants and reported that they inhibited mitochondrial swelling, reduced oxidative cell death in cultured cells, and limited reperfusion injury in isolated tissue preparations. That study established the structural logic of the series: a 3+ net charge at physiological pH paired with aromatic residues that together drive uptake into the inner mitochondrial membrane.

A defining property identified in this early work is the degree of mitochondrial concentration. SS-31 partitions into the inner membrane at concentrations far above those in the surrounding cytosol, a behavior attributed to electrostatic attraction to the anionic phospholipid cardiolipin combined with hydrophobic insertion of its aromatic residues. This targeting behavior set SS-31 apart from earlier antioxidant compounds that distributed broadly through the cell, and it framed the subsequent decade of research around the peptide’s interaction with a single membrane lipid. The proposed activity centered on that lipid interaction at the inner membrane, distinct from generalized free-radical scavenging in bulk solution.

Cardiolipin Interaction and Cristae Stabilization

Cardiolipin is a four-tailed phospholipid largely confined to the inner mitochondrial membrane, where it organizes cristae curvature and scaffolds the assembly of electron-transport-chain complexes into supercomplexes. Birk et al. (2013), in the Journal of the American Society of Nephrology, reported that SS-31 binds cardiolipin through electrostatic and hydrophobic interactions and, in ischemic kidney mitochondria, restored membrane potential and oxygen consumption. The authors described SS-31 as re-energizing ischemic mitochondria through preservation of cardiolipin-dependent organization, a mechanism distinct from conventional radical scavenging.

A companion mechanistic account by Birk et al. (2014), published in the British Journal of Pharmacology, examined the cytochrome c/cardiolipin complex specifically. The work reported that cardiolipin binding by cytochrome c can convert the protein into a peroxidase that consumes electrons and generates reactive species, and that SS-31 association with cardiolipin reduces this peroxidase activity while preserving the electron-carrying function of cytochrome c. In this model the peptide promotes electron transport and helps maintain mitochondrial ATP synthesis under conditions of cristae disruption, providing a molecular rationale for the bioenergetic effects observed in tissue studies.

Ischemia-Reperfusion Injury Models

Reperfusion of previously ischemic tissue triggers a burst of mitochondrial reactive oxygen species and opening of the permeability transition pore, events linked to cell death during reflow. Because SS-31 concentrates at the inner membrane, several groups examined whether it alters injury in reperfusion paradigms. Kloner et al. (2012), reporting in the Journal of the American Heart Association, evaluated Bendavia (MTP-131) across multiple cardiac ischemia-reperfusion models and observed reductions in infarct size and in the extent of coronary no-reflow when the peptide was administered around the time of reperfusion in animal preparations.

These cardiac findings paralleled the renal ischemia work and reinforced the proposed mechanism in which preserving cardiolipin organization during the early minutes of reflow limits the surge in mitochondrial oxidant production. The reperfusion literature treated SS-31 as a probe for testing whether a mitochondria-directed intervention changes the trajectory of ischemic tissue in controlled animal models, and the results contributed to the compound’s later progression into clinical investigation under the Bendavia designation.

Aged Skeletal Muscle Bioenergetics

Mitochondrial function in skeletal muscle declines with age, with reduced ATP-generating capacity and elevated oxidant production reported across species. Siegel et al. (2013), publishing in Aging Cell, administered the mitochondria-targeted peptide to aged mice and measured mitochondrial energetics together with in situ muscle performance. The study reported a rapid improvement in mitochondrial ATP-generating capacity and a reduction in oxidant emission in aged muscle, alongside measured gains in fatigue resistance during stimulated contractions.

The timing reported in that work drew attention because the energetic changes appeared within hours of exposure. That speed pointed toward an acute effect on existing membrane organization, a timescale too short for biogenesis of new mitochondria to account for the gains. This rapid-onset bioenergetic signature in aged tissue became a recurring observation in the SS-31 literature and connected the muscle findings to the cardiolipin-based mechanism described in the cell-free and cardiac studies.

Heart Failure Animal Models

Pressure overload and chronic ischemic injury both produce mitochondrial dysfunction in the failing heart, and SS-31 has been examined in animal models of each. Dai et al. (2013), in Circulation: Heart Failure, applied global proteomics and pathway analysis to a mouse model of pressure-overload-induced heart failure and reported that treatment with a mitochondria-targeted peptide attenuated the disease-associated proteomic remodeling, with effects concentrated in pathways governing mitochondrial energy metabolism.

Sabbah et al. (2016), reporting in the same journal, studied dogs with advanced microembolization-induced heart failure that received chronic subcutaneous elamipretide over 3 months. The investigators measured left ventricular systolic function and isolated cardiomyocyte mitochondrial parameters, reporting improvements in ejection fraction and normalization of mitochondrial respiration and ATP synthesis in treated animals relative to controls. These large-animal data extended the SS-31 mechanism from acute ischemia into a chronic structural heart-disease setting and informed the design of subsequent clinical studies.

Clinical Investigation Context

Beyond the preclinical record, elamipretide has been evaluated in human clinical trials for genetically defined mitochondrial conditions, including primary mitochondrial myopathy, Barth syndrome, and the MELAS phenotype, as well as in cardiology cohorts. These investigations are documented in the peer-reviewed literature and in trial registries, and they describe measured endpoints such as exercise capacity, biomarker levels, and cardiac function in defined patient populations under investigational protocols.

Within a research-supply context this clinical activity is relevant only as scientific background. The findings reported in those trials pertain to controlled investigational settings and do not establish any approved use. Elamipretide remains an investigational agent under continued study. The preclinical mechanism papers cited here, centered on cardiolipin binding and mitochondrial bioenergetics, remain the primary reference points for laboratory researchers characterizing the compound.

Key Published References

1. Zhao K, Zhao GM, Wu D, Soong Y, Birk AV, Schiller PW, Szeto HH. Cell-permeable peptide antioxidants targeted to inner mitochondrial membrane inhibit mitochondrial swelling, oxidative cell death, and reperfusion injury. J Biol Chem. 2004;279(33):34682–34690. PMID: 15178689
2. Birk AV, Liu S, Soong Y, Mills W, Singh P, Warren JD, Seshan SV, Pardee JD, Szeto HH. 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
3. Birk AV, Chao WM, Bracken C, Warren JD, Szeto HH. Targeting mitochondrial cardiolipin and the cytochrome c/cardiolipin complex to promote electron transport and optimize mitochondrial ATP synthesis. Br J Pharmacol. 2014;171(8):2017–2028. PMID: 24134698
4. Siegel MP, Kruse SE, Percival JM, Goh J, White CC, Hopkins HC, Kavanagh TJ, Szeto HH, Rabinovitch PS, Marcinek DJ. Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice. Aging Cell. 2013;12(5):763–771. PMID: 23692570
5. Dai DF, Hsieh EJ, Chen T, Menendez LG, Basisty NB, Tsai L, Beyer RP, Crispin DA, Shulman NJ, Szeto HH, Tian R, MacCoss MJ, Rabinovitch PS. Global proteomics and pathway analysis of pressure-overload-induced heart failure and its attenuation by mitochondrial-targeted peptides. Circ Heart Fail. 2013;6(5):1067–1076. PMID: 23935006
6. Kloner RA, Hale SL, Dai W, Gorman RC, Shuto T, Koomalsingh KJ, Gorman JH 3rd, Sloan RC, Frasier CR, Watson CA, Bostian PA, Kypson AP, Brown DA. Reduction of ischemia/reperfusion injury with bendavia, a mitochondria-targeting cytoprotective peptide. J Am Heart Assoc. 2012;1(3):e001644. PMID: 23130143
7. Sabbah HN, Gupta RC, Kohli S, Wang M, Hachem S, Zhang K. Chronic therapy with elamipretide (MTP-131), a novel mitochondria-targeting peptide, improves left ventricular and mitochondrial function in dogs with advanced heart failure. Circ Heart Fail. 2016;9(2):e002206. PMID: 26839394
8. 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

Product Availability

SS-31 is available for qualified research applications through White Market Peptides: SS-31 10 mg: Research Grade.