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Mitochondrial
SS-31: The Mitochondrial Peptide That Became an Approved Medicine
The short answer
SS-31, known in clinical development as elamipretide, targets the inner membrane of the mitochondrion. In September 2025 the FDA granted it accelerated approval as Forzinity for Barth syndrome, making it the first mitochondria-targeted drug approved in the United States.
Questions people ask about SS-31
SS-31 at a glance
| Also called | Elamipretide; MTP-131; Bendavia; Forzinity (brand name) |
|---|---|
| What it is | A four-amino-acid peptide that concentrates in the inner mitochondrial membrane |
| Acts on | Cardiolipin, the lipid that organises the electron transport chain |
| Main system | Mitochondrial function: energy output, oxidative stress |
| Evidence level | An approved medicine for one ultra-rare disease; investigational everywhere else |
| FDA status (Oct 2026) | Approved 19 September 2025 as Forzinity, for Barth syndrome, in patients weighing at least 30 kg |
| In sport | Not named on the 2026 WADA prohibited list |
What is SS-31?
SS-31 is four amino acids with an unusual property: it accumulates in the inner mitochondrial membrane at concentrations far above the surrounding cell, without needing a membrane potential to get there. That targeting is the reason it works at all.
It has carried several names through development, which is why the literature looks more scattered than it is: SS-31 in the early research, MTP-131 and Bendavia in trials, elamipretide as the approved generic name, Forzinity as the brand.
Targeted Peptide Systems profiles it at pp. 190–193, The Cognitive Advantage at pp. 206–210, Metabolic Precision at pp. 136–139, and Regenerative Resilience at pp. 150–157.
How does SS-31 work?
Cardiolipin is the target. Cardiolipin is a lipid found almost only in the inner mitochondrial membrane, where it holds the components of the electron transport chain in the right arrangement. When cardiolipin is damaged or mis-shaped, that arrangement degrades: energy output falls and reactive oxygen species rise.
SS-31 binds cardiolipin and restores the structure. A 2014 study in the British Journal of Pharmacology set out the mechanism in detail, including how it affects the cytochrome c and cardiolipin complex and shifts those components back towards efficient electron transport (reference 1).
Why that matters beyond one disease. Cardiolipin remodelling is a feature of ageing tissue, heart failure and several mitochondrial disorders, which is why the compound has been tested well outside the indication it was eventually approved for.
Our article on the cellular battery problem covers why the energy layer usually has to be addressed before other compounds show a result.
What does the research show?
The approval. On 19 September 2025 the FDA granted accelerated approval to elamipretide, as Forzinity, for Barth syndrome in adults and children weighing at least 30 kg, to improve muscle strength. Barth syndrome is an ultra-rare genetic mitochondrial disease affecting roughly 150 people in the United States. Accelerated approval means continued approval depends on a confirmatory trial.
The data behind it. The TAZPOWER programme followed patients on elamipretide out to 168 weeks, with improvements in muscle strength, fatigue and cardiac measures reported in Genetics in Medicine in 2024 (reference 2).
Where it has been tested and not approved. Elamipretide has also been studied in primary mitochondrial myopathy, and that programme did not lead to an approval. A 2024 analysis in Orphanet Journal of Rare Diseases went back through the data to ask whether particular genotypes responded better than others (reference 3). That is the honest shape of the wider evidence: a mechanism that clearly does something, in a field where showing it on a clinical endpoint has been hard.
What this changes for the books. Regenerative Resilience (p. 98) describes SS-31 as having Phase II data. That was accurate when written and is now out of date: the compound has an approval, for one specific population.
Side effects and cautions
Because this is an approved medicine, there is a prescribing framework behind it: a defined population, a label, monitoring, and a manufacturer who answers for the product. Injection-site reactions are the most commonly reported effect in the trials.
What that framework covers is Barth syndrome in patients over 30 kg. It does not extend to using the compound for ageing, athletic performance, general fatigue or cognitive support, which are the reasons it is usually discussed outside clinical settings. Those uses have not been through the same assessment.
Material sold as research-grade SS-31 sits entirely outside that framework, with none of the identity, purity or accountability the approved product carries.
Is SS-31 legal or FDA approved?
Approved, for one condition. Forzinity was granted accelerated approval in September 2025 for Barth syndrome. It is a prescription medicine for that population.
Not approved for anything else. There is no approved use for ageing, performance, general mitochondrial complaints or cognition, and the research compound sold under the SS-31 name is not the approved product.
It was not part of the July 2026 compounding review (references 4, 5).
Sport: SS-31 is not named on the 2026 WADA prohibited list. Athletes should check with their governing body, since lists are updated annually.
SS-31 vs MOTS-c, NAD+ and the other energy compounds
These are the compounds aimed at the same layer, and they are not interchangeable.
- vs MOTS-c: MOTS-c is a signal encoded in mitochondrial DNA that acts like an exercise message, shifting how cells handle fuel. SS-31 repairs the physical machinery. One sends instructions, the other fixes the hardware.
- vs NAD+: NAD+ is the fuel the machinery runs on. Restoring the molecule and restoring the structure that uses it are different problems.
- vs the repair peptides: BPC-157 and TB-500 work on tissue structure, not on energy. The books treat the energy layer as the thing to assess first, because repair is expensive and a cell short of energy cannot pay for it.
Regenerative Resilience (pp. 150–157) and The Longevity Map (p. 61) both place SS-31 in the mitochondrial category rather than among the repair compounds.
Risk, benefit, and the conversation this page is for
How to weigh it. Some research peptides have a quiet toxicology record, or an unfinished efficacy record. SS-31 is a different case: on its mechanism it genuinely moves physiology, in this case mitochondrial structure and energy output, and that is the reason to weigh it with due diligence rather than enthusiasm. Monitoring is paramount here, and the markers that matter are whatever the prescribing clinician is following, because this one has a label.
The regulatory picture is moving, selectively. In July 2026 an FDA advisory committee recommended six peptides, BPC-157, TB-500, KPV, MOTS-c, Epitalon and Semax, for the list of bulk substances compounding pharmacies may use. SS-31 did not need the committee’s recommendation. It was approved in September 2025 as Forzinity, which is the far end of the same spectrum this library covers. Reading those decisions one at a time is more useful than treating every compound outside the approved list as equivalent.
Why the class is taken seriously. This is a mechanism that went the whole distance: bench research, trials, approval. The boundary is that the approval covers Barth syndrome, a condition affecting roughly 150 people in the United States, and not the uses the compound is usually discussed for. The useful question is not whether engaging it does anything. It is whether you have done the due diligence to make an informed decision about engaging it at all: what your baseline looks like, what else you are taking, what you would measure along the way, and what would tell you to stop.
Which is the point of the series. Nothing here is a recommendation to use SS-31. People misuse approved medicines and unapproved compounds alike, and that is neither the purpose nor the intent of this page. The point is a better conversation than the internet usually allows: with a clinician who knows your history, your labs and everything else you take, and who can help build a plan that fits you.
SS-31: frequently asked questions
What is SS-31?
A four-amino-acid peptide that concentrates in the inner mitochondrial membrane and binds cardiolipin, the lipid that organises the electron transport chain. Its approved name is elamipretide.
Is SS-31 FDA approved?
Yes, for one condition. It was granted accelerated approval in September 2025 as Forzinity, for Barth syndrome, in patients weighing at least 30 kg.
What is Forzinity?
The brand name for elamipretide, the approved form of SS-31. It is the first mitochondria-targeted drug approved in the United States.
Is SS-31 approved for anti-aging?
No. The approval covers Barth syndrome only. Use for ageing, performance or general fatigue has not been through the same assessment.
How does SS-31 work?
It binds cardiolipin in the inner mitochondrial membrane and restores the arrangement of the electron transport chain, which improves energy output and reduces reactive oxygen species (reference 1).
SS-31 vs MOTS-c: what is the difference?
MOTS-c signals cells to change how they handle fuel. SS-31 repairs the physical structure that produces energy. Different problems, different tools.
What are SS-31’s side effects?
Injection-site reactions are the most commonly reported in the trials. Because it is an approved medicine for one population, the fuller safety picture lives in its label and prescribing framework.
Is SS-31 banned in sport?
It is not named on the 2026 WADA prohibited list. Check with your sport’s governing body, as lists change each year.
Where SS-31 appears in our books
This page is the plain-language overview. The books go further: mechanism detail, evidence tiers, how SS-31 fits a full protocol, and the cautions that go with it. Page numbers refer to the print editions.
Books marked Look Inside include these exact pages in their free preview.
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See how SS-31 fits a protocol
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Open the Protocol BuilderSee the book seriesReferences
- Birk AV, Chao WM, Bracken C, Warren JD, Szeto HH. Targeting mitochondrial cardiolipin and the cytochrome c/cardiolipin complex to promote electron transport and optimize mitochondrial ATP synthesis. Br J Pharmacol. 2014;171(8):2017–2028. View source
- Thompson WR, Manuel R, Abbruscato A, et al. Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension. Genet Med. 2024;26(7):101138. View source
- Genotype-specific effects of elamipretide in patients with primary mitochondrial myopathy: a post hoc analysis. Orphanet J Rare Dis. 2024;19(1):431. View source
- U.S. Food and Drug Administration. July 23–24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. View source
- National Community Pharmacists Association. FDA advisory committee nominates six peptides for pharmacies to compound. July 31, 2026. View source
- World Anti-Doping Agency. The 2026 Prohibited List. View source
How this page is maintained. Regulatory status and trial results change. We review this page against current sources and update it as new information becomes available; the date at the top shows the last review.
Educational information only, not medical advice. SS-31 is discussed here for education. Nothing on this page is a recommendation to use it or a dosing guide. Talk to a qualified clinician before starting, stopping or combining any compound.