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Longevity
SS-31 (elamipretide): the mitochondria peptide that won FDA approval
FDA-approved (as Forzinity) Checked against PubMed and official sources Oct 18, 2026
Quick facts
- What it is: a mitochondria-targeting peptide that binds cardiolipin.
- Status: FDA-approved as Forzinity (2025, accelerated approval) for Barth syndrome.
- Evidence: muscle strength gains in a long open-label extension; anti-frailty effects in old mice.
- Most common side effects: injection-site reactions.
- Note: online "SS-31" vials are not Forzinity.
What is SS-31 (elamipretide)?
SS-31, now named elamipretide, is a small peptide that targets mitochondria, your cells' energy factories. The FDA label calls it a "mitochondrial cardiolipin binder" (cardiolipin is a key fat in mitochondrial membranes), which is why it's a favorite in longevity and energy circles (FDA label).
Is SS-31 FDA-approved?
FDA-approved as Forzinity (Sept 19, 2025, Drugs@FDA) under accelerated approval, to improve muscle strength in adults and children with Barth syndrome, a rare mitochondrial disease, who weigh at least 30 kg. Continued approval may depend on a confirmatory trial (FDA label). "SS-31" vials sold online are not Forzinity.
Most common side effects: injection-site reactions; eosinophil increases were also seen (FDA label). Online "SS-31" isn't Forzinity. Choose a tested source.
Forzinity dosing: what the FDA label says
For the approved use only, as prescribed. Online "SS-31" vials have no label and aren't Forzinity.
- Patients weighing at least 30 kg: 40 mg under the skin once daily, at the same time each day.
- Adults with severe kidney impairment (eGFR under 30 mL/min, not on dialysis): 20 mg once daily.
- Missed dose: skip it and take the next one on schedule. Don't double up.
Source: Forzinity FDA label on DailyMed.
What the research shows
- The approval data (FDA label): in a 12-patient crossover trial in Barth syndrome, it didn't beat placebo on walking distance or fatigue. In the open-label extension, knee-extensor muscle strength rose (median +63 newtons at week 168 in the 8 patients still enrolled), which supported accelerated approval.
- Aging, in mice (Aging Cell, 2025): 8 weeks of treatment in old mice slowed frailty and partly reversed declines in heart function and muscle fatigue resistance, without measurable changes in epigenetic "biological age."
- Exercise tolerance, in aged mice (Geroscience, 2023): intermittent treatment preserved exercise tolerance in aged female mice.
- A miss in adults (Neurology, 2023): in MMPOWER-3, 218 adults with primary mitochondrial myopathy, it didn't improve walking or fatigue vs placebo. It was well tolerated.
New to these terms? See the glossary.
SS-31 FAQ
Is SS-31 FDA-approved?
Elamipretide, the drug once called SS-31, is FDA-approved as Forzinity (Sept 2025, accelerated approval) to improve muscle strength in people with Barth syndrome weighing at least 30 kg.
Does SS-31 slow aging?
In old mice, 8 weeks of treatment slowed frailty and partly reversed heart and muscle declines. That hasn't been tested in healthy people.
What are the side effects of elamipretide?
On the FDA label, injection-site reactions (redness, pain, hardening, itching, bruising) are the most common. Increases in eosinophils, a type of white blood cell, were also seen.
What is the Forzinity dose?
The FDA label: 40 mg under the skin once daily for patients weighing at least 30 kg, or 20 mg once daily in adults with eGFR under 30 who aren't on dialysis.
Not medical advice. Education only. Talk to a licensed clinician about your health.
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