SS-31Longevity
Mitochondria-targeted peptide studied for cellular energy.
- Status
- Research / not approved
- Developer
- Szeto & Schiller (academic origin); developed as elamipretide by Stealth BioTherapeutics
- Receptors / target
- Mitochondria-targeting tetrapeptide; binds cardiolipin on the inner mitochondrial membrane to stabilize cristae and the electron-transport chain, reducing reactive oxygen species
- FDA-approved?
- NO
- Prescription available?
- NO
- Studied for
- mitochondrial dysfunctionheart failure / cardioprotectionprimary mitochondrial myopathyage-related & ophthalmic disease
Overview
SS-31, known clinically as elamipretide (historically MTP-131 or Bendavia), is a synthetic, cell-permeable, mitochondria-targeting tetrapeptide developed by Stealth BioTherapeutics. On September 19, 2025 the FDA granted it accelerated approval (brand FORZINITY) for the ultra-rare genetic disease Barth syndrome (patients ≥30 kg) — its only approved use, covering roughly 150 US patients. For every other use it is sold for — mitochondrial support, longevity, athletic recovery — it remains investigational and unproven, and is research-use-only. This profile reports what the trials and regulatory record show, not treatment guidance.
Mechanism
Elamipretide accumulates in the inner mitochondrial membrane, where it binds reversibly to cardiolipin, the phospholipid that organizes the electron-transport chain and stabilizes cristae structure. By binding cardiolipin it preserves the cytochrome c-cardiolipin interaction needed for efficient electron transport and reduces electron leak and reactive oxygen species, rather than acting as a conventional antioxidant (Birk et al., JASN 2013, preclinical). The net effect in models is improved ATP production under stress.
Clinical evidence
Elamipretide has an unusually large human-trial record for a peptide, but most pivotal endpoints were negative. The phase 3 MMPOWER-3 trial in primary mitochondrial myopathy did not meet its co-primary endpoints; the phase 2 PROGRESS-HF heart-failure trial did not improve left-ventricular function; and the phase 2 ReCLAIM-2 trial in dry AMD missed its primary visual-acuity and geographic-atrophy endpoints (with a positive secondary signal on ellipsoid-zone preservation). The Barth syndrome program (TAZPOWER) likewise failed its blinded 12-week endpoints, but a long-term open-label extension showed sustained functional improvement — the basis for the 2025 accelerated approval, whose continuation is contingent on confirmatory trials.
Safety profile
Across hundreds of participants in phase 2/3 trials, subcutaneous elamipretide was consistently well tolerated, with injection-site reactions the dominant adverse event and no major systemic safety signal reported. However, no approved use exists outside Barth syndrome; the mitochondrial-myopathy, heart-failure, eye-disease and "longevity/anti-aging" applications all remain investigational and were not validated by the trials run to date. Outside the single narrow prescription indication this is research-use-only material with no established dosing.
- Weeks 4–24
In the phase 2/3 trials (e.g., MMPOWER-3, ~24 weeks), functional endpoints were assessed over weeks — and most primary endpoints were NOT met.
- Long-term (Barth)
The Barth-syndrome open-label extension suggested sustained functional improvement over many months — the basis for its narrow 2025 accelerated approval. Benefit for other uses (e.g., longevity) is unproven.
Reported in published literature and user reports. Not a complete list, and not medical advice.
- Injection-site reactions
- Headache, dizziness
- Nausea / GI upset
- Limited long-term human safety data
If severe or unexpected symptoms occur, contact a qualified medical professional. PEPTIDES·INDEX does not provide medical advice.
- No safety data exist outside the studied trial populations; tolerability in healthy or longevity-seeking users is uncharacterized.
- Avoid in pregnancy and breastfeeding — no reproductive safety data established for these uses.
- Outside the single approved Barth-syndrome indication this is research-use-only with no established dosing; not a substitute for evaluated treatment of heart, eye or mitochondrial disease.
- No documented human drug interactionsInteraction profile uncharacterized outside trial settings (research use only)
Compare
- vs MOTS-c
Another mitochondria-associated peptide marketed for metabolic/longevity benefit; like SS-31's non-Barth uses, MOTS-c remains investigational in humans.
- vs NAD+
A mitochondrial/cellular-energy product often discussed alongside SS-31 for the same longevity framing, also without proven human longevity benefit.
FAQ
What is SS-31 (elamipretide) actually approved for?
Only Barth syndrome. On September 19, 2025 the FDA granted accelerated approval (brand FORZINITY) for the ultra-rare genetic disease Barth syndrome in patients at least 30 kg — covering roughly 150 US patients. That is its sole approved use.
Does SS-31 work for longevity, anti-aging or athletic recovery?
There is no evidence it does. Those uses are investigational and unproven. Most pivotal trials were in fact negative: the phase 3 mitochondrial-myopathy trial, the phase 2 heart-failure trial and the phase 2 dry-AMD trial all missed their primary endpoints.
Why was it approved if trials failed?
The Barth program also failed its blinded 12-week endpoints, but a long-term open-label extension suggested sustained functional improvement — the basis for the narrow accelerated approval, whose continuation depends on confirmatory trials.
How does SS-31 work?
It is a cell-permeable, mitochondria-targeting tetrapeptide that accumulates in the inner mitochondrial membrane and binds reversibly to cardiolipin, the phospholipid that organizes the electron-transport chain and stabilizes cristae. By preserving that structure it reduces electron leak and reactive oxygen species and supports ATP production under stress — a mechanism characterized mainly in preclinical models.
Are SS-31 and elamipretide the same thing?
Yes. SS-31 is the academic research designation; the same molecule was developed clinically as elamipretide (historically MTP-131 or Bendavia) by Stealth BioTherapeutics and is now sold under the brand FORZINITY for its single approved indication. Research-chemical 'SS-31' is not the regulated pharmaceutical product.
Is SS-31 safe?
In trials, subcutaneous elamipretide was consistently well tolerated across hundreds of participants, with injection-site reactions the dominant adverse event and no major systemic safety signal reported. But there are no safety data outside the studied trial populations and dosing — tolerability in healthy or longevity-seeking users is uncharacterized, and outside Barth syndrome it remains research-use-only.
Similar compounds
Starting references for the library summary. These are not dosing instructions or medical advice.
For research-use educational context only. Not medical advice and not a recommendation to use any compound. Consult a qualified healthcare professional before any health decision.