SS-31
Anti-Aging, Metabolic Health, Mitochondrial Health
In short
- Also known as elamipretide or MTP-131. A mitochondria-targeted tetrapeptide that binds cardiolipin on the inner mitochondrial membrane.
- It has been through multiple phase 2 and phase 3 human trials — a genuinely rare level of development for anything in this library.
- Results have been mixed: the phase 3 in primary mitochondrial myopathy missed its primary endpoint.
- In 2025 the FDA approved it (as Forzinity) for Barth syndrome, an ultra-rare mitochondrial disorder.
- The research-market SS-31 is not the approved product and is not manufactured to that standard.
Structure
How it works
SS-31 is a small aromatic-cationic tetrapeptide that concentrates in the inner mitochondrial membrane, where it binds cardiolipin — a phospholipid essential for the structure of the electron transport chain.
Cardiolipin peroxidation disrupts cristae architecture and impairs ATP production. By binding and stabilising cardiolipin, SS-31 is proposed to preserve cristae structure, improve electron transport efficiency, and reduce mitochondrial reactive oxygen species production.
Unusually, it does not act as a conventional antioxidant scavenger — the mechanism is structural stabilisation rather than radical quenching.
What the research shows
Phase 2 in primary mitochondrial myopathy showed improvement in six-minute walk distance.
The phase 3 MMPOWER-3 trial did not meet its primary endpoint, which was a significant setback for the programme.
Trials in Barth syndrome supported the 2025 FDA approval of elamipretide for that indication.
Studies in heart failure, ischaemia-reperfusion, and diabetic macular oedema have produced mixed results.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — phase 3 primary mitochondrial myopathy (MMPOWER-3) | 40 mg daily | subcutaneous | PubMed |
| Human — Barth syndrome, basis for approval | 40 mg daily | subcutaneous | PubMed |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
| Reported by | Amount | Route |
|---|---|---|
| Commonly reported | 5–20 mg daily | subcutaneous |
The trial dose is 40 mg daily, substantially higher than typical community use — which is unusual, since community doses more often exceed studied ones. Community protocols also target general mitochondrial health rather than the rare genetic diseases the trials studied.
Handling and storage
Supplied as a lyophilised powder requiring reconstitution with bacteriostatic water. The powder is comparatively stable; once reconstituted it is refrigerated and used within weeks. Track the date you reconstitute each vial — the Inventory section does this, and it is the difference between knowing a vial is three weeks old and guessing.
Daily subcutaneous injection in the trial protocols. Injection-site reactions were the most common adverse event in trials and are dose-related.
Side effects
Injection-site reactions are the dominant adverse effect across trials — erythema, pruritus, and induration, common enough to affect tolerability at the 40 mg dose.
Otherwise the trials reported a manageable safety profile, and there is a real human safety database from the development programme.
This is one of the few compounds here where "generally well tolerated" is backed by controlled trials rather than by absence of reporting.
Combinations
No formal interaction data. Commonly combined with other mitochondrial-targeted agents (NAD+ precursors, CoQ10) in community use, on overlapping rationale rather than evidence.
Research status
Developed by Stealth BioTherapeutics with an extensive clinical programme: MMPOWER-1 through 3 in mitochondrial myopathy, plus trials in Barth syndrome, heart failure, and ophthalmic conditions.
The mitochondrial and cardiolipin biology is well published and independently studied. FDA approval for Barth syndrome came in 2025.
Legal status
FDA-approved as elamipretide (Forzinity) for Barth syndrome, an ultra-rare disorder — a narrow indication. Not approved for any other use. Research-market SS-31 is unapproved material unrelated to the licensed product.
WADA status
Not specifically named on the Prohibited List. Falls under WADA class S0, which prohibits any pharmacological substance not currently approved by any governmental regulatory health authority for human therapeutic use. Treat it as prohibited in sport.
Conclusion
SS-31 has the most substantial clinical development programme of any research-market peptide here, including a phase 3 that failed and an eventual approval for an ultra-rare disease.
That is a more honest picture than most: it was tested properly, and the answer was "works for a specific rare mitochondrial disorder, did not meet the endpoint for the broader one." Extrapolating from that to general mitochondrial enhancement in healthy people is not supported.
Sources
Track your own SS-31 protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.