SS-31, also known as elamipretide, is a tetrapeptide that targets the inner mitochondrial membrane to stabilize cardiolipin, reduce reactive oxygen species, and support electron transport chain efficiency. Researchers studying mitochondrial dysfunction, heart failure, and metabolic disease have increasingly focused on this compound for its selective mechanism and documented clinical trial activity.
SS-31 (elamipretide) belongs to the Szeto-Schiller family of mitochondria-targeted peptides, developed by Hazel Szeto and Peter Schiller at Weill Cornell Medicine. The peptide sequence D-Arg-2',6'-dimethyltyrosine-Lys-Phe-NH2 allows it to cross cell membranes and concentrate at the inner mitochondrial membrane without requiring a mitochondrial membrane potential gradient.
Unlike other mitochondrial antioxidants that rely on membrane potential for uptake, SS-31 uses electrostatic and hydrophobic interactions to anchor near cardiolipin-rich regions of the inner mitochondrial membrane. This positioning is central to its proposed mechanism action in preserving mitochondrial health. Researchers sourcing peptides for mechanistic work can review SS-31 at VivePeptides alongside the broader catalog.
Cardiolipin is a phospholipid almost exclusively found in the inner mitochondrial membrane. It plays a structural role in organizing the electron transport chain complexes I through IV and ATP synthase into supercomplexes that optimize energy transfer. When cardiolipin becomes oxidized, supercomplex integrity declines, electron transport efficiency drops, and reactive oxygen species production increases.
SS-31 binds directly to cardiolipin through its aromatic residues and cationic charges. Szeto (2014, Biochimie) documented that this binding protects cardiolipin from peroxidation, preserves cristae architecture, and restores electron transport complex activity in models of mitochondrial stress. The outcome is reduced reactive oxygen species generation at the source, improved ATP synthesis, and a dampening of the feedback loop between oxidative stress and mitochondrial dysfunction.
This upstream intervention distinguishes elamipretide from conventional antioxidants, which scavenge oxygen species after they are produced rather than limiting their generation at the membrane.
Reactive oxygen species are a byproduct of normal electron transport. Under healthy conditions, antioxidant enzymes including superoxide dismutase and glutathione peroxidase neutralize excess oxygen species. In disease states, energy deficit, or aging, electron leak increases and overwhelms these defenses.
Sustained oxidative stress damages mitochondrial DNA, proteins, and lipids, producing progressive mitochondrial dysfunction: declining ATP output, impaired calcium buffering, and activation of pro-apoptotic pathways. This cascade is implicated in heart failure, neurodegenerative conditions, ischemia-reperfusion injury, and rare inherited diseases including Barth syndrome.
Sabbah et al. (2016, JACC: Basic to Translational Science) demonstrated that SS-31 treatment improved mitochondrial function and left ventricular performance in a canine model of heart failure, establishing early mechanistic evidence linking cardiolipin stabilization to cardiac outcomes.
The most advanced clinical trial data for elamipretide comes from trials conducted in the United States. PROGRESS-HF examined SS-31 in patients with heart failure with preserved ejection fraction. Redfield et al. (2021, JAMA Cardiology) reported that while the primary endpoint of six-minute walk distance did not reach statistical significance, secondary measures of cardiac remodeling and quality of life showed directional improvement, supporting continued investigation into elamipretide for heart failure.
Barth syndrome is a rare X-linked mitochondrial disease caused by mutations in the tafazzin gene, which directly disrupts cardiolipin remodeling. Patients develop cardiomyopathy, skeletal muscle weakness, and neutropenia, with mitochondrial dysfunction driving the clinical phenotype. Because elamipretide acts directly on cardiolipin, Barth syndrome represented a mechanistically matched target population.
The TAZPOWER clinical trial evaluated elamipretide in pediatric and adult patients with Barth syndrome in the United States. Thompson et al. (2021, JAMA Cardiology) found statistically significant improvements in the six-minute walk test and fatigue scores, with elamipretide demonstrating a favorable safety profile in this genetically defined population. These results establish SS-31 as one of the few peptides with prospective clinical trial evidence specifically targeting mitochondrial function in a defined cardiac disease.
In published clinical trial data, elamipretide has been administered via daily subcutaneous injection. The most commonly reported adverse events are injection site reactions, including mild erythema, pruritus, and localized discomfort at the injection site. These injection site reactions were generally transient and did not result in high discontinuation rates in either TAZPOWER or PROGRESS-HF.
Systemic adverse events were comparable to placebo in available trial data. No serious hepatotoxic or nephrotoxic signals have been reported at clinically studied doses. The manageable injection site reaction profile and absence of notable systemic adverse events have positioned elamipretide as a tractable compound for continued investigation across diverse mitochondrial dysfunction models.
Because mitochondrial dysfunction is a convergent pathway in multiple pathologies, SS-31 has been studied across disease areas beyond heart failure.
Siegel et al. (2013, Aging Cell) reported that SS-31 improved mitochondrial function and reduced contractile fatigue in skeletal muscle from aged mice, suggesting potential relevance to sarcopenia and age-related metabolic decline research.
Multiple preclinical studies have documented SS-31's capacity to reduce infarct size and preserve mitochondrial morphology following ischemia-reperfusion in cardiac and renal models, driven by its ability to maintain electron transport chain integrity during oxidative stress.
Oxidative stress and mitochondrial dysfunction are mechanistically central to models of Parkinson's and Alzheimer's disease. Early preclinical work has evaluated SS-31 in these contexts, though no clinical trial data in neurodegeneration has been published as of this writing.
Researchers investigating complementary mitochondria-targeted compounds may also find MOTS-c a relevant parallel, as it targets mitochondrial function through a distinct pathway encoded within the mitochondrial genome.
What does SS-31 stand for?
SS-31 refers to the Szeto-Schiller peptide series, designation 31. Its generic name is elamipretide, developed by Hazel Szeto and Peter Schiller at Weill Cornell Medicine. The compound is characterized by a tetrapeptide sequence that selectively binds cardiolipin on the inner mitochondrial membrane, distinguishing it from membrane-potential-dependent mitochondrial antioxidants.
How does SS-31 reduce reactive oxygen species?
SS-31 binds cardiolipin on the inner mitochondrial membrane, protecting it from peroxidation. This preserves the structural organization of electron transport chain supercomplexes. Efficient electron transport reduces electron leak, which is the primary source of reactive oxygen species under pathological conditions. The peptide acts upstream of ROS generation rather than scavenging oxygen species after production.
What is the connection between SS-31 and Barth syndrome?
Barth syndrome involves a genetic defect in cardiolipin remodeling that disrupts inner mitochondrial membrane organization. SS-31 compensates by stabilizing cardiolipin directly. The TAZPOWER clinical trial in the United States tested elamipretide in Barth syndrome patients and found improvements in exercise capacity and fatigue, making it one of the few compounds with clinical trial evidence for this rare mitochondrial disease.
What are the most common side effects reported in clinical trials?
Injection site reactions are the most frequently reported adverse events in clinical trial data for elamipretide. These typically include mild redness, itching, or localized discomfort and are generally transient. Systemic adverse events were comparable to placebo in the TAZPOWER and PROGRESS-HF trials, supporting a manageable safety profile at studied doses.
Is SS-31 approved for human therapeutic use?
As of this writing, SS-31 (elamipretide) does not hold FDA approval. It has received Orphan Drug Designation in the United States for Barth syndrome. The compound is available for research purposes only and is not approved for human therapeutic use.
SS-31 (elamipretide) is available for research purposes at VivePeptides. Browse the full selection of research-grade peptides at the VivePeptides shop.
