Key facts
- Compound
- SS-31 (elamipretide)
- Classification
- Synthetic tetrapeptide with modified residues
- Residues
- 4
- Sequence
- D-Arg-Dmt-Lys-Phe-NH2
- Molecular formula
- C32H49N9O5
- Molecular weight
- 639.8 g/mol
- CAS number
- 736992-21-5
- Vinnix status
- Reference only, not sold
What Is SS-31?
The compound is a four-residue synthetic peptide. It comes from a family of small aromatic-cationic peptides described by Hazel Szeto and Peter Schiller, and their initials are where the "SS" prefix comes from. Elamipretide is its nonproprietary name; the research code and the name refer to one and the same molecule [1][2].
The peptide alternates aromatic residues with positively charged ones, and two of its four residues aren't standard L-amino acids. That is why you can't write its sequence in plain one-letter code. If you want the general rules for how residues link and how short peptides are named by length, see peptide bonds and what are peptides.
This peptide isn't currently in the Vinnix catalog. We keep this entry in the Compound Library to describe the molecule, and it makes no claim about the effects of any material.
SS-31 Product Specifications
Because it is not a Vinnix product, the table covers verified chemical identity only. Product-specific fields are marked not applicable.
| Field | Value |
|---|---|
| Compound | SS-31 (elamipretide) |
| Classification | Synthetic tetrapeptide |
| Sequence | D-Arg-Dmt-Lys-Phe-NH2 |
| Molecular formula | C32H49N9O5 (PubChem CID 11764719) |
| Molecular weight | 639.8 g/mol (PubChem) |
| CAS number | 736992-21-5 |
| Product quantity | Not applicable, not sold by Vinnix |
| SKU | Not applicable |
| Batch/Lot | Not applicable |
SS-31 Identity
The research code and elamipretide name a single structure. We checked the registry records below against PubChem and the FDA Global Substance Registration System.
| Identifier | Value | Source |
|---|---|---|
| PubChem CID | 11764719 (Elamipretide) | PubChem |
| CAS Registry Number | 736992-21-5 | PubChem synonyms |
| FDA UNII | 87GWG91S09 | FDA GSRS |
| Names | SS-31; elamipretide; MTP-131 | PubChem synonyms |
Don't assume one SS code means another. SS-02 and SS-20, for instance, belong to the same Szeto-Schiller series but are different peptides with different sequences. A code by itself can't confirm identity; the full modified sequence and the mass can.
SS-31 Peptide Sequence & Molecular Information
Written out, the sequence is D-Arg-Dmt-Lys-Phe-NH2. Dmt stands for 2',6'-dimethyltyrosine, and the phenylalanine at the C-terminus is amidated.
| Position | Residue | Note |
|---|---|---|
| 1 (N-terminus) | D-Arginine | D-configuration, the mirror image of the usual L-form; positively charged |
| 2 | Dmt (2',6'-dimethyltyrosine) | Non-standard aromatic residue with two added methyl groups |
| 3 | Lysine | Positively charged side chain |
| 4 (C-terminus) | Phenylalanine amide | Aromatic; C-terminal amide instead of a free acid |
The molecule has three positively charged groups (the N-terminal amine and the arginine and lysine side chains) and two aromatic rings, so at physiological pH it carries a net positive charge. Because of the D-arginine and the Dmt residue, a one-letter string like RYKF would actually describe a different peptide. Peptide sequences explains how modified residues are written.
Research History of SS-31
Over roughly two decades, the peptide went from laboratory chemistry to animal studies and then to human clinical trials. Each stage asked its own questions (in vitro vs. in vivo research explains the early categories).
In vitro and animal studies (preclinical)
The early papers described cell-permeable Szeto-Schiller peptides that gather at the inner mitochondrial membrane in cell and isolated-organ models [1], and a review pulled that series together [2]. More recent reviews call it a cardiolipin-binding peptide [5].
Human clinical trials
Under the name elamipretide, it went into a phase 2/3 randomized trial in Barth syndrome, a rare inherited disorder of cardiolipin metabolism [3], and a phase 3 randomized trial in primary mitochondrial myopathy [4]. Both were controlled studies of a pharmaceutical product in defined patient groups.
Regulatory status
In September 2025, elamipretide received accelerated approval in the United States for a specific indication in Barth syndrome [6]. The approval covers that drug product alone. Research materials sold under the research code fall outside it.
SS-31 Analytical Documentation
Vinnix has no certificate of analysis for this compound because it doesn't sell the peptide. Still, those modified residues make careful identity checks particularly important for anyone who handles it.
- HPLC separates the target peptide from related substances, including diastereomers that differ in the configuration of just one residue. See HPLC testing.
- Mass spectrometry checks the measured mass against the full modified structure (C32H49N9O5). Swap Dmt for ordinary tyrosine and the peptide would come out 28 Da lighter. See mass spectrometry.
- Stereochemistry is invisible to mass alone, since D- and L-arginine weigh exactly the same. Chiral or comparative chromatography handles that question.
FAQSS-31 FAQ
What is SS-31?
SS-31 is a synthetic tetrapeptide, D-Arg-Dmt-Lys-Phe-NH2, also called elamipretide. It is one of the better known members of the Szeto-Schiller series of small aromatic-cationic peptides. Vinnix doesn't sell it; this page is a Compound Library reference covering its identity, research history and regulatory status.
Is SS-31 a peptide?
Yes, a tetrapeptide: four residues joined by three peptide bonds. It is a modified one, though. It contains D-arginine, the non-standard residue 2',6'-dimethyltyrosine and a C-terminal amide, so it isn't built only from the 20 standard L-amino acids that make up most natural peptides.
What is the SS-31 sequence?
Read from N-terminus to C-terminus, it is D-Arg-Dmt-Lys-Phe-NH2. Dmt means 2',6'-dimethyltyrosine, and -NH2 marks the C-terminal amide. With two non-standard residues, plain one-letter code can't capture it. Write it as RYKF and you've described a different, unmodified peptide, which is an easy slip to make.
What molecular information identifies SS-31?
Its molecular formula is C32H49N9O5, with an average molecular weight of 639.8 g/mol, CAS number 736992-21-5, PubChem CID 11764719 and FDA UNII 87GWG91S09. Search under elamipretide and you'll land on the same identifiers, since they describe the same molecule. PubChem also lists the development code MTP-131 as a synonym.
How is SS-31 studied?
In cell and animal models, and, as elamipretide, in randomized human clinical trials in Barth syndrome and primary mitochondrial myopathy. The preclinical findings describe laboratory systems only. The clinical data are about a regulated drug product, not about research materials sold under the research code.
How can SS-31 be analytically characterized?
HPLC handles purity and related substances, and mass spectrometry confirms the full modified structure, dimethyltyrosine included. What mass can't tell you is whether the arginine is in the D or L form, so analysts use chromatographic comparison to check the stereochemistry.
Where can I find the Vinnix SS-31 COA?
There isn't one, because the peptide isn't part of the Vinnix catalog. For Vinnix products, certificates of analysis go into the Vinnix COA Library by product and batch as they are published, and the guide to reading a COA explains each section of a report.
REFScientific references
-
Zhao K, et al. Cell-permeable peptide antioxidants targeted to inner mitochondrial membrane inhibit mitochondrial swelling, oxidative cell death, and reperfusion injury. J Biol Chem. 2004;279(33):34682-90. PubMed 15178689
in vitro and animal study -
Szeto HH. Cell-permeable, mitochondrial-targeted, peptide antioxidants. AAPS J. 2006;8(2):E277-83. PubMed 16796378
review -
Reid Thompson W, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism. Genet Med. 2021;23(3):471-478. PubMed 33077895
human clinical, phase 2/3 randomized trial -
Karaa A, et al. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology. 2023;101(3):e238-e252. PubMed 37268435
human clinical, phase 3 randomized trial -
Tung C, et al. Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential. Int J Mol Sci. 2025;26(3). PubMed 39940712
review -
Shirley M. Elamipretide: First Approval. Drugs. 2026;86(3):377-383. PubMed 41335372
review, regulatory profile
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