What Is SS-31? Definition and What Research Reports

Plain definition

SS-31 is the research name for a very short synthetic peptide — four amino acids long — that concentrates inside mitochondria, the compartments in cells that generate most of the body's chemical energy. Instead of acting on a receptor on the cell surface, it binds to a fat-like molecule called cardiolipin that is found almost exclusively in the inner mitochondrial membrane. Researchers have studied it because mitochondrial damage is a common feature of heart failure, kidney injury, neurodegeneration and ageing tissue. In the clinical development world the same molecule is called elamipretide.

This page is for educational purposes only and is not medical advice; consult a licensed physician about any health question. Nothing here describes how any substance should be used.

The term in biochemical language

SS-31 belongs to the "Szeto-Schiller" (SS) series of aromatic-cationic peptides. Its sequence is D-Arg-2',6'-dimethyltyrosine-Lys-Phe-NH₂. Two features are usually emphasised in reviews: the alternating aromatic and basic residues, which give the molecule a net positive charge and allow it to cross membranes without a transporter, and the fact that its uptake into mitochondria does not depend on the membrane potential — so it can still reach mitochondria that are already depolarised and failing. A 2025 structural and mechanistic review described the peptide's composition, its selective association with cardiolipin on the inner membrane, and the downstream consequences reported for cristae architecture and electron transport efficiency (PMID 39940712).

Mechanistic work has moved beyond the cardiolipin-binding description alone. A proteomic study mapped the mitochondrial protein interaction landscape of SS-31 and reported that the peptide associated with multiple proteins involved in oxidative phosphorylation and in the 2-oxoglutarate dehydrogenase complex, suggesting its effects were not limited to a single binding partner (PMID 32554501). Separately, a genome-wide CRISPR screen identified phospholipid scramblase 3 as a biological target of SS-31 in a kidney model, a finding the authors framed as identifying a protein target rather than a purely lipid interaction (PMID 38530359). A 2025 review of contemporary mechanistic insight summarised how these strands — cardiolipin binding, interactions with respiratory-chain components, and effects on oxidative stress — have been reconciled in the current literature (PMID 40294492).

Names and synonyms

Because the same molecule appears under four labels, literature searches for "SS-31" alone return only part of the published record. Reviews of the compound routinely note the equivalence of these names (PMID 39940712).

Regulatory framing

Elamipretide moved from research compound to an approved product: a 2026 review in Drugs documented its first approval, describing it as a mitochondria-targeting peptide developed for a rare mitochondrial disease indication (PMID 41335372). That regulatory status applies to a specific approved product and indication, and does not extend to material sold under the research label "SS-31", which is generally offered as research-use-only chemical and is not an approved medicine in that form. The distinction between an approved drug product and a research-use-only chemical bearing the same molecular name is one of the most common sources of confusion around this term.

How the term is used in peptide research

Cardiac and ischaemia-reperfusion models

A large share of SS-31 literature sits in cardiology. A review in Heart Failure Reviews examined the rationale for targeting mitochondrial dysfunction with elamipretide in cardiac disease and summarised preclinical and clinical findings available at the time (PMID 35037146). In cell work, researchers constructed an SS-31@Fer-1 nanoformulation and reported that mitochondrial targeting alleviated ferroptosis in cardiomyocytes subjected to hypoxia/reoxygenation (PMID 39848110).

Barth syndrome

Barth syndrome — a genetic disorder of cardiolipin remodelling — has been the clearest clinical use of the term. A commentary described elamipretide for Barth syndrome cardiomyopathy as a gradual rebuilding of a failed power grid (PMID 34623544). The TAZPOWER trial's 168-week open-label extension reported long-term efficacy and safety outcomes in patients with Barth syndrome, and is the longest clinical follow-up in the published record for this molecule (PMID 38602181).

Brain and neuroinflammation

A 2019 mouse study reported that elamipretide (SS-31) improved mitochondrial dysfunction and synaptic and memory impairment induced by lipopolysaccharide (PMID 31747905). More recently, researchers reported that SS-31 improved post-cardiac-arrest brain injury in an animal model by inhibiting microglial ferroptosis and altering microglial polarisation (PMID 41136322).

Ageing tissue and bone

In aged bone marrow stromal cells, a 2025 study reported that SS-31 targeted NOS2 and enhanced osteogenic differentiation by restoring mitochondrial function (PMID 40570323). Findings of this kind are cell-level and do not establish anything about intact humans.

Where the term is misused

• Treating "SS-31" and "elamipretide" as different things. They are the same peptide; separating them creates the false impression that laboratory material is distinct from the clinically studied compound.
• Borrowing approval as general validation. The first approval described in 2026 was for a defined product and indication (PMID 41335372), not a blanket endorsement of the molecule for ageing, performance or cognition.
• Calling it an "antioxidant supplement". Reviews describe a lipid- and protein-targeted mechanism within mitochondria rather than generic free-radical scavenging (PMID 40294492).
• Generalising rodent and cell results. Memory findings in lipopolysaccharide-treated mice (PMID 31747905) and osteogenic findings in cultured aged cells (PMID 40570323) are model-specific observations.
• Confusing it with unrelated "SS" abbreviations. The SS prefix here refers to the Szeto-Schiller peptide series, not to a chemical class or a disease abbreviation.

Related terms

• Cardiolipin — the inner-mitochondrial-membrane phospholipid with which SS-31 is described as associating (PMID 39940712).
• Cristae — the folded inner-membrane structures whose architecture is discussed in mechanistic reviews of the peptide (PMID 40294492).
• Ferroptosis — an iron-dependent form of cell death examined in cardiomyocyte and microglial SS-31 studies (PMID 39848110, PMID 41136322).
• Phospholipid scramblase 3 (PLSCR3) — identified in a CRISPR screen as a biological target (PMID 38530359).
• Oxidative phosphorylation — the energy-producing pathway whose components appeared in the peptide's interaction map (PMID 32554501).

Safety Findings: What Studies Report

The most informative safety data in the cited record come from clinical work rather than animal models. The 168-week open-label extension of TAZPOWER reported long-term efficacy and safety outcomes in patients with Barth syndrome receiving elamipretide, making it the longest-duration safety report available in this set (PMID 38602181). The 2026 first-approval review summarised the development programme and the regulatory assessment that accompanied it (PMID 41335372). Reviews in cardiology have discussed both the promise and the limits of translating mitochondrial-targeting results into clinical benefit (PMID 35037146). The cited papers do not establish a safety profile for unsupervised or non-clinical use of research-labelled material.

Summary of the definition

In short: SS-31 is a four-residue, mitochondria-accumulating peptide, identical to elamipretide, that interacts with cardiolipin and with mitochondrial proteins and has been studied across cardiac, renal, neurological and ageing models, with the deepest clinical evidence in Barth syndrome. Anyone reading the term should check whether a given source means the research compound, the clinical drug, or an unapproved product carrying the name.

References

• Elamipretide (SS-31) improves mitochondrial dysfunction, synaptic and memory impairment induced by lipopolysaccharide in mice (Journal of Neuroinflammation, 2019)
• Mitochondrial protein interaction landscape of SS-31 (PNAS, 2020)
• Elamipretide for Barth syndrome cardiomyopathy: gradual rebuilding of a failed power grid (Heart Failure Reviews, 2022)
• Targeting mitochondrial dysfunction with elamipretide (Heart Failure Reviews, 2022)
• Genome-Wide CRISPR Screen Identifies Phospholipid Scramblase 3 as the Biological Target of Mitoprotective Drug SS-31 (JASN, 2024)
• Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER (Genetics in Medicine, 2024)
• SS-31@Fer-1 Alleviates ferroptosis in hypoxia/reoxygenation cardiomyocytes via mitochondrial targeting (Biomedicine & Pharmacotherapy, 2025)
• Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential (International Journal of Molecular Sciences, 2025)
• Contemporary insights into elamipretide's mitochondrial mechanism of action and therapeutic effects (Biomedicine & Pharmacotherapy, 2025)
• SS-31 Targets NOS2 to Enhance Osteogenic Differentiation in Aged BMSCs by Restoring Mitochondrial Function (Organogenesis, 2025)
• SS-31 improves post-cardiac arrest brain injury by inhibiting microglial ferroptosis and polarization (Neurotherapeutics, 2026)
• Elamipretide: First Approval (Drugs, 2026)