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SS-31
SS-31, now known pharmaceutically as elamipretide, is a synthetic mitochondria-targeting tetrapeptide designed to associate with the inner mitochondrial membrane. Its interaction with the phospholipid cardiolipin has been investigated for effects on mitochondrial membrane organization, cristae architecture, oxidative phosphorylation and cellular bioenergetics.
What is SS-31?
SS-31 is a synthetic mitochondria-targeting tetrapeptide now known by the generic pharmaceutical name elamipretide.
It was developed as part of the Szeto-Schiller peptide family, a group of short aromatic-cationic peptides investigated for their unusual ability to associate with mitochondrial membranes.
Its sequence is D-Arg-Dmt-Lys-Phe-NH2 , where Dmt represents the modified amino-acid 2,6-dimethyltyrosine.
SS-31 does not function like a classical endocrine peptide hormone and does not depend on a conventional cell-surface peptide receptor as its primary mechanism.
Instead, it partitions into the mitochondrial inner-membrane environment and interacts strongly with cardiolipin.
This interaction appears to influence membrane structure, respiratory-chain organization, cristae stability, oxidative phosphorylation and cellular energy production.
After many years of preclinical and clinical investigation, elamipretide received accelerated FDA approval in 2025 as the prescription medicine Forzinity for a specific population with Barth syndrome.
Why is it called SS-31?
The prefix SS originates from the Szeto-Schiller family of mitochondria-targeting peptides.
SS-31 was one of the compounds developed from this peptide platform and became the lead clinical molecule.
During pharmaceutical development it was also referred to as MTP-131 and Bendavia.
The international generic drug name is elamipretide.
Following regulatory approval in the United States, the pharmaceutical product became available under the trade name Forzinity.
Designed to reach mitochondrial membranes
SS peptides emerged from research into short aromatic-cationic peptides capable of entering cells and selectively associating with mitochondrial membrane environments.
From mitochondrial research peptide to approved drug
The Szeto-Schiller peptide programme was developed during research into short peptides with unusual cellular and mitochondrial distribution properties.
SS-31 emerged as one of the most intensively investigated members of this class.
Early interpretations focused heavily on antioxidant effects because SS-31 reduced oxidative injury in numerous experimental systems.
Subsequent biophysical research produced a more detailed model involving direct interaction with the mitochondrial phospholipid cardiolipin.
Elamipretide then entered clinical programmes involving heart failure, primary mitochondrial myopathy, ocular disorders and Barth syndrome.
Development in Barth syndrome ultimately produced the first U.S. regulatory approval for the molecule in September 2025.
A four-residue mitochondrial peptide
SS-31 is unusually small for a biologically active peptide. Its alternating aromatic and cationic characteristics are central to its membrane interactions.
Why does SS-31 accumulate around mitochondria?
SS-31 belongs to an unusual group of short peptides containing alternating aromatic and positively charged residues .
This chemical architecture gives the molecule strong affinity for negatively charged membrane environments.
Cardiolipin carries a negative charge and is highly enriched within the inner mitochondrial membrane.
Experimental studies show that SS-31 partitions into membrane interfacial regions in a manner strongly influenced by membrane surface charge.
This helps explain how a four-residue peptide can exert effects on mitochondrial structure and function without relying on a classical peptide-hormone receptor.
Why is cardiolipin so important?
Cardiolipin is an unusual phospholipid concentrated primarily within the mitochondrial inner membrane.
It contributes to formation of mitochondrial cristae and interacts with multiple protein complexes responsible for oxidative phosphorylation.
Disturbance of cardiolipin composition or organization can therefore impair respiratory-chain function and cellular energy production.
Early mechanistic work showed that SS-31 binds selectively to cardiolipin and can influence cardiolipin interactions with cytochrome c.
More recent studies suggest a broader mechanism involving changes in membrane surface electrostatics, lipid packing and organization of cardiolipin-dependent proteins.
This is why modern descriptions of elamipretide generally characterize it as a mitochondrial cardiolipin-binding peptide rather than simply an antioxidant.
How does elamipretide influence mitochondrial function?
Current evidence suggests a membrane-centered mechanism involving cardiolipin organization, respiratory proteins, mitochondrial architecture and cellular bioenergetics.
Cardiolipin Binding
SS-31 interacts with negatively charged cardiolipin within the inner mitochondrial membrane.
Membrane Electrostatics
Binding can alter membrane surface charge and the local physical environment of mitochondrial proteins.
Oxidative Phosphorylation
Stabilization of cardiolipin-dependent systems may support respiratory-chain efficiency and ATP production.
Oxidative Stress
Improved mitochondrial organization can reduce pathological reactive-oxygen signalling and oxidative membrane injury.
What has SS-31 been investigated for?
Because mitochondrial dysfunction occurs across many disease states, elamipretide has been studied in a broad range of experimental and clinical settings.
Barth Syndrome
Cardiolipin abnormalities are central to Barth syndrome, making the condition a particularly relevant mechanistic target.
Mitochondrial Myopathy
Clinical studies have examined exercise function and skeletal-muscle performance in primary mitochondrial disease.
Cardiac Research
Heart-failure and ischaemia-reperfusion models have been used to investigate mitochondrial energetic effects.
Ocular Research
Mitochondrial involvement in retinal and macular pathology has generated clinical investigation of elamipretide.
Elamipretide is now an FDA-approved drug molecule
FDA granted accelerated approval in September 2025. The indication is narrow and should not be extrapolated to unrelated mitochondrial, cardiovascular, neurological, ageing or performance applications.
Forzinity — elamipretide
The U.S. Food and Drug Administration granted accelerated approval to Forzinity as the first approved treatment for Barth syndrome.
The approved indication is improvement of muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg .
Approval was based on improvement in knee extensor muscle strength, which FDA considered reasonably likely to predict clinical benefit.
Accelerated approval requires continued study after approval. FDA lists a required randomized, double-blind, placebo-controlled confirmatory trial in patients aged five years and older with Barth syndrome.
The confirmatory study is intended to verify and describe the clinical benefit predicted by the muscle-strength endpoint.
Elamipretide has been studied beyond Barth syndrome
The molecule has entered clinical studies across several conditions characterized by mitochondrial dysfunction. Results have been mixed, which is important when evaluating claims that SS-31 is a general-purpose mitochondrial therapy.
Primary Mitochondrial Myopathy
Clinical trials evaluated walking performance and patient-reported fatigue in people with genetically defined primary mitochondrial myopathy.
Large controlled studies did not establish broad clinical efficacy across their key endpoints.
Heart Failure
Elamipretide was studied in patients with heart failure following substantial preclinical evidence of improved myocardial mitochondrial function.
Translation of strong animal findings into clear clinical benefit has been more challenging.
Macular & Ocular Research
Ocular programmes have examined whether targeting mitochondrial dysfunction could influence visual and retinal outcomes in selected age-related conditions.
These programmes remain separate from the approved Barth-syndrome indication.
How strong is the evidence?
SS-31 now has evidence spanning membrane biophysics, extensive animal research, numerous human trials and an FDA-approved indication. Evidence for other proposed uses remains much less certain.
Molecular Mechanism
Cardiolipin association, mitochondrial membrane interactions and bioenergetic effects are supported by substantial experimental research.
Preclinical Evidence
Extensive cell and animal literature exists across cardiac, muscular, neurological, renal and ocular models.
Human Clinical Research
Multiple controlled human programmes have evaluated elamipretide across several mitochondrial disease settings.
Regulatory Evidence
FDA granted accelerated approval for a defined Barth-syndrome indication while requiring confirmatory evidence of clinical benefit.
What should not be assumed?
Factors affecting SS-31 stability
SS-31 is a short modified tetrapeptide. Stability of research material should be established from analytical documentation for the exact chemical form and formulation rather than inferred from the approved pharmaceutical product.
Temperature
Temperature influences peptide chemical stability and degradation kinetics.
Moisture
Humidity can affect dry or lyophilized peptide material and should be controlled according to material specifications.
Solution Conditions
Solvent, buffer, pH and concentration can alter peptide stability once material is in solution.
Material Specification
Identity, salt form, purity and analytical characteristics should be established for the specific research material.
FDA-approved mitochondrial cardiolipin-binding peptide with continuing confirmatory research
SS-31 is the research name for elamipretide, a mitochondria-targeting tetrapeptide that interacts with cardiolipin-rich inner mitochondrial membranes.
On 19 September 2025, FDA granted accelerated approval to Forzinity (elamipretide) to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg.
This made elamipretide the first FDA-approved treatment for Barth syndrome.
Because approval was granted through the accelerated-approval pathway, a confirmatory randomized trial is required to verify clinical benefit.
Other proposed applications involving heart failure, ageing, general mitochondrial enhancement, neurological disease, renal injury, exercise performance or longevity remain separate from the approved indication and should not be described as established uses.
ASA Research Labs provides this information for scientific and educational purposes only. Discussion of the approved pharmaceutical medicine does not establish equivalence between Forzinity and independently supplied SS-31 research material and does not constitute prescribing, administration or dosing guidance.
Selected scientific references
Selected literature and regulatory sources covering SS-31 structure, cardiolipin binding, mitochondrial membrane biology, clinical development and FDA approval.
Scientific and regulatory information
This profile is provided for scientific and educational purposes. Elamipretide is the active molecule in an FDA-approved prescription medicine for a specific Barth-syndrome population. Discussion of cardiolipin, mitochondrial bioenergetics, heart failure, mitochondrial myopathy, ocular disease, ageing or other experimental research should not be interpreted as establishing approved uses outside that indication. Regulatory approval of Forzinity does not establish the identity, purity, sterility, bioavailability or clinical equivalence of independently manufactured SS-31 research material. This page does not provide instructions for administration, dosing or unsupervised human use.