SS-31 is sold online as a mitochondria peptide for energy and longevity. Its story is one of the stranger ones in this space. After years of failed or mixed trials, it won FDA approval in September 2025 as Forzinity, for one ultra-rare disease. That approval is real. It is also narrow, conditional, and says nothing about healthy people.
Mostly disappointing in common conditions. Trials in heart attack, heart failure, mitochondrial muscle disease and early macular degeneration missed their main goals. The approval for Barth syndrome rests on a muscle strength measure in a handful of patients, under the FDA’s accelerated pathway, and still needs a confirmatory trial. There is no evidence in healthy people at all.
SS-31 is a tiny peptide of four amino acids, one of a family called Szeto-Schiller peptides after the researchers who created them, Hazel Szeto and Peter Schiller. Its drug name is elamipretide, and it has also gone by MTP-131 and Bendavia. It was developed by Stealth BioTherapeutics, whose parent company renamed itself Mighty Therapeutics in 2026.
Mitochondria are the energy factories of your cells. Their inner membrane is folded into ridges, held together partly by a fat called cardiolipin. SS-31 travels to that inner membrane and binds cardiolipin. The idea is that this stabilizes the membrane’s structure and helps the energy-making machinery run more efficiently, with less wasted energy and fewer damaging byproducts.
Early papers called it an antioxidant. The FDA label now describes it as a “mitochondrial cardiolipin binder,” and lower oxidative stress is seen as a downstream effect. Most of the mechanism work is in cells and animals.
Here is the honest record.
A heart attack trial missed its main goal in 2015. A heart failure trial found no meaningful change in heart function. MMPOWER-3, a Phase 3 trial of 218 people with primary mitochondrial myopathy, missed both main goals, with no difference in walking distance or fatigue. A Phase 2 trial in dry macular degeneration missed its vision goals, though it showed a possible slowing of retinal damage. A Phase 3 macular degeneration trial is ongoing, with no results we could find.
Barth syndrome is a rare genetic disease that affects cardiolipin directly, which is why SS-31 made sense there. The key trial had just 12 patients and missed its blinded main goal. Improvements showed up in the open-label extension. The FDA turned the application down in May 2025, calling the muscle data uninterpretable. The company resubmitted using knee strength, and the FDA granted accelerated approval on September 19, 2025. A confirmatory trial began dosing patients in July 2026.
Online, it is marketed for longevity, mitochondrial “energy,” endurance, eyes and skin. None of those uses has human evidence. Every positive human signal comes from people with disease, and most from secondary analyses.
Injection-site reactions are nearly universal. In the Barth trial, all 12 patients had redness at the injection site, and most had pain, hardening or itching. The label also warns about serious allergic reactions that can appear anywhere from minutes to months after starting, a rise in a type of white blood cell called eosinophils, and benzyl alcohol in the formulation that makes it unsafe for newborns. The dose is cut in half for severe kidney disease.
Long-term safety in healthy people at self-chosen doses is unknown. Gray-market vials add the usual purity and sterility questions.
From the label, not a recommendation. Forzinity is 40 mg injected under the skin once a day, for Barth syndrome patients weighing at least 30 kg. Community sources describe far lower amounts, roughly 1 to 5 mg a day in short cycles, or less a few times a week. Those numbers come from peptide wikis and are not backed by any study. We do not give mixing or injection steps.
SS-31 is an FDA-approved prescription drug for one use: improving muscle strength in people with Barth syndrome who weigh at least 30 kg. Everything else is off-label or experimental. It is not approved in Europe.
Gray-market SS-31 is not that drug. The FDA named it in its August 24, 2026 warning letters to peptide sellers, calling it an unapproved new drug and rejecting the “research use only” label. We explain those letters in our FDA warning letters post. Its status for compounding pharmacies is unclear, so ask any pharmacy for documentation. Athletes should check with their anti-doping agency, since its WADA status is not settled.
Is SS-31 FDA-approved? Yes, as Forzinity, but only for Barth syndrome, under accelerated approval.
Does it work for anti-aging or energy? There is no human evidence. The large trials in common conditions missed their main goals.
Why was it approved if trials failed? Accelerated approval can rest on a surrogate measure, here knee strength, in a rare and serious disease. A confirmatory trial is still running.
What is the most common side effect? Injection-site reactions, which happened in every treated patient in the Barth study.
Is “research” SS-31 the same as Forzinity? No. It is unregulated, and the FDA has warned sellers.
Is it an antioxidant? Not really. It binds cardiolipin in mitochondria, and lower oxidative stress is a downstream effect.
What about macular degeneration? A Phase 3 trial is ongoing. No results yet.
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