SS-31 (Elamipretide / Bendavia / MTP-131)
Mitochondria-targeted tetrapeptide that binds cardiolipin and stabilizes inner-mitochondrial-membrane structure.
At a glance
What it is: Mitochondria-targeted tetrapeptide that binds cardiolipin and stabilizes inner-mitochondrial-membrane structure..
Primary research applications:
- Mitochondrial myopathy (Barth syndrome)
- Heart failure and cardiomyopathy research
- Mitochondrial dysfunction and aging research
Editorial summary: SS-31 is one of the most clinically advanced mitochondria-targeted peptides ever developed. Its target — cardiolipin in the inner mitochondrial membrane — gives it a precise mechanistic story. Late-stage trials in Barth syndrome, heart failure, and ischemia-reperfusion have been mixed, but the molecule continues to advance and exemplifies the mitokine / mitochondrial-protection therapeutic class.
- Class / structure
- Synthetic tetrapeptide (D-Arg-Dmt-Lys-Phe-NH2)
- Half-life
- ≈ 2 hours
- First described
- Early 2000s (Hazel Szeto, Cornell)
- Regulatory status
- Investigational; orphan-drug designations for Barth syndrome
What is SS-31?
SS-31 is a four-amino-acid synthetic peptide engineered to selectively accumulate at the inner mitochondrial membrane and bind cardiolipin. Its design draws on alternating aromatic/cationic residues that allow uncharged shuttling across membranes followed by membrane retention.
Discovery and development
SS-31 (Szeto-Schiller peptide 31) was developed by Hazel Szeto and Peter Schiller in the early 2000s. It belongs to a series of "mitochondria-targeted antioxidant peptides" engineered to penetrate the inner mitochondrial membrane and bind cardiolipin, a phospholipid critical to mitochondrial cristae structure and electron transport chain function. It has been developed as elamipretide / Bendavia by Stealth BioTherapeutics.
Mechanism of action
By binding cardiolipin in the inner mitochondrial membrane, SS-31 stabilizes cristae geometry, supports electron transport chain organization, and preserves mitochondrial bioenergetics under stress conditions including ischemia-reperfusion. The molecule does not act as a free-radical scavenger directly — its protective effect comes from preserving mitochondrial structure and function.[1]
Pharmacokinetics
SS-31 is administered by subcutaneous or intravenous injection. Its short plasma half-life (~2 hours) is offset by selective accumulation in mitochondria, where its functional effects persist beyond plasma clearance.
What the research shows
The peer-reviewed literature on SS-31 is summarized below across two tiers: human research (the highest standard), and preclinical / emerging research (animal models and early-stage human work).
Claims and the evidence behind them
This table summarizes commonly discussed claims and how the published evidence weighs in. The aim is clarity — supported claims, claims that look promising but need more data, and claims that outrun the science.
| Claim | What the evidence shows | Verdict |
|---|---|---|
| Binds cardiolipin and preserves mitochondrial structure | Mechanistic literature is robust | Supported |
| Improves cardiac function in heart failure trials | Mixed Phase 2 data | Mixed |
| Treats Barth syndrome | Mixed Phase 2/3; orphan-drug pursuit ongoing | Promising |
| Reverses aging | No rigorous human anti-aging data; aspirational claim | Uncertain |
Reported user experiences
How the research describes administration
Trials use subcutaneous (commonly daily) or intravenous administration. Stealth BioTherapeutics has continued to refine dosing and indications across ongoing programs.
Editorial note
Administration details above describe how the peptide is given in published studies. We summarize this for educational completeness — these descriptions are not protocols, dosing recommendations, or instructions for personal use. Decisions about treatment require an appropriately licensed clinician.
Safety considerations and open questions
The takeaway
SS-31 is a credible mitochondria-targeted therapeutic with one of the most precise targeting strategies in the peptide world — cardiolipin at the inner mitochondrial membrane. Its clinical development has been an instructive lesson in the difficulty of translating clean mechanism into broad clinical efficacy. The story is not over; it remains one to watch in cardiomyopathy and mitochondrial disease.
Frequently asked questions
Is elamipretide the same as SS-31?
Yes. Elamipretide is the development name for the SS-31 peptide as advanced by Stealth BioTherapeutics.
Is SS-31 an antioxidant?
It is sometimes described that way, but its mechanism is structural rather than radical-scavenging. It binds cardiolipin and preserves mitochondrial cristae and electron transport function.
References
- Szeto HH. Mitochondria-targeted cytoprotective peptides for ischemia-reperfusion injury. Antioxid Redox Signal. 2008;10(3):601-619. https://pubmed.ncbi.nlm.nih.gov/18063019/
- 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 (TAZPOWER). Genet Med. 2021;23(3):471-478. https://pubmed.ncbi.nlm.nih.gov/33077888/