SS-31
SS-31 (elamipretide) is a mitochondria-targeted peptide. In September 2025 the FDA approved it as FORZINITY for the ultra-rare genetic disease Barth syndrome — the first approved mitochondrial-targeted peptide — but it failed its larger trials in mitochondrial myopathy and dry age-related macular degeneration, so its widely discussed 'anti-aging' uses remain unproven.
Key facts
- Category
- Energy & metabolism
- Legal / FDA status
- FDA-approved as FORZINITY (elamipretide) for Barth syndrome (accelerated approval, Sept 2025); investigational/unproven for all other uses
- Half-life
- Reported as roughly 4 hours after subcutaneous dosing (consistent with once-daily dosing); this figure comes from secondary sources and is not firmly pinned to a primary label, so treat the exact value as approximate
- Typical form
- FORZINITY: 80 mg/mL single-use vials for once-daily subcutaneous injection (prescription)
- Also known as
- elamipretide, MTP-131, Bendavia, FORZINITY
SS-31 — generic name elamipretide — is a mitochondria-targeted peptide. It reached a milestone in September 2025 when the FDA approved it as FORZINITY for the ultra-rare genetic disease Barth syndrome, making it the first approved mitochondrial-targeted peptide. But its larger trials in other conditions failed, so the broader "mitochondrial health" and anti-aging interest in it is not backed by positive human outcomes. This page is educational and is not medical advice; WikiPeps sells nothing.
What is SS-31 / elamipretide?#
SS-31 is a small, water-soluble, cell-penetrating tetrapeptide that concentrates inside mitochondria. It binds cardiolipin, a signature lipid of the inner mitochondrial membrane, which helps stabilize the membrane's folded structure (cristae) and protect the electron-transport chain that generates ATP. The idea is to make struggling mitochondria work better rather than to replace any hormone.
What is it approved for — and what failed?#
- Approved (Barth syndrome): FORZINITY received FDA accelerated approval in September 2025 to improve muscle strength in Barth syndrome, with continued approval contingent on a confirmatory trial. This is the only approved use.
- Failed (mitochondrial myopathy): the pivotal MMPOWER-3 Phase 3 trial (2023) did not meet its primary endpoints.
- Failed (dry AMD / geographic atrophy): the ReCLAIM-2 Phase 2 trial (2024) missed its primary endpoints (with some signal on a secondary measure).
- Heart failure / acute MI: earlier Phase 2 work did not show clear clinical benefit.
So outside Barth syndrome, efficacy is unproven, and the longevity/performance interest rests on mechanism and preclinical data, not positive human results.
Is there a dose?#
For its approved use, the FORZINITY label dose is 40 mg subcutaneously once daily (for patients ≥30 kg, reduced in severe kidney impairment). The same 40 mg/day was used across the major trials. This is a prescription dose for a specific disease, set by a clinician — not a recommendation for off-label or research-chemical use, for which there is no validated dose. WikiPeps does not provide dosing or sourcing guidance for prescription drugs.
Safety#
The dominant adverse effect across trials is injection-site reactions (redness, itching, firmness, pain, bruising), which were very common on drug in the Barth trial and occasionally led to discontinuation; they are managed with antihistamines or topical steroids. The approved product contains benzyl alcohol and is contraindicated in neonates, and in serious hypersensitivity to the ingredients. Long-term and off-label safety outside the studied populations is not established.
The bottom line#
SS-31 (elamipretide / FORZINITY) is a genuine scientific milestone — the first FDA-approved mitochondrial-targeted peptide — but its approval is narrow (Barth syndrome) and its big trials in mitochondrial myopathy and eye disease failed. It is a real prescription medicine for a rare disease, not a proven anti-aging tool, and any use belongs with a licensed clinician.
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Frequently asked questions
What is SS-31 / elamipretide?
- SS-31 (elamipretide) is a small, cell-penetrating peptide that concentrates in mitochondria and binds a lipid called cardiolipin on the inner mitochondrial membrane. By stabilizing mitochondrial structure, it is meant to improve the cell's energy production. It is the active ingredient in the prescription drug FORZINITY.
Is SS-31 FDA-approved?
- Yes, but narrowly. In September 2025 the FDA granted accelerated approval to FORZINITY (elamipretide) to improve muscle strength in patients with Barth syndrome, an ultra-rare genetic disease — it is the first approved mitochondrial-targeted peptide. Continued approval depends on a confirmatory trial. It is not approved for any other condition, and not for general anti-aging or performance use.
Does SS-31 work for aging, mitochondrial myopathy, or eye disease?
- The honest answer is that its largest trials outside Barth syndrome failed. The pivotal primary-mitochondrial-myopathy trial (MMPOWER-3, 2023) and the dry-AMD/geographic-atrophy trial (ReCLAIM-2, 2024) both missed their primary endpoints. So beyond Barth syndrome, efficacy is unproven, and the 'longevity' interest is based on mechanism and preclinical work, not positive human outcomes.
Is there an established dose of SS-31?
- For its approved use, the FORZINITY label dose is 40 mg injected under the skin once daily (for patients weighing at least 30 kg, with a reduction in severe kidney impairment). This is a prescription dose set by a clinician for Barth syndrome — it is not a recommendation for off-label or research use, for which no validated dose exists.
What are the side effects of SS-31?
- The most common issue across trials is injection-site reactions (redness, itching, firmness, pain, bruising) — in the Barth trial these were very common on the drug. The approved product contains benzyl alcohol and is contraindicated in neonates, and in anyone with serious hypersensitivity to the ingredients. A prescribing clinician reviews these for each patient.
References
- 1.FORZINITY (elamipretide) — FDA approval / Prescribing Information (Drugs@FDA app. 215244; DailyMed) — Stealth BioTherapeutics / U.S. Food and Drug Administration · 2025
- 2.Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential — International Journal of Molecular Sciences — PMID 39940712 · 2025
- 3.Phase 2/3 randomized trial + open-label extension of elamipretide in Barth syndrome (TAZPOWER) — Genetics in Medicine — Thompson et al., PMID 33077895 · 2020
- 4.Elamipretide in Primary Mitochondrial Myopathy: the MMPOWER-3 trial (did NOT meet primary endpoints) — Neurology — DOI 10.1212/WNL.0000000000207402 · 2023
- 5.ReCLAIM-2: elamipretide in dry AMD / geographic atrophy (missed primary endpoints) — Ophthalmology Science — PMID 39605874 · 2024
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