SS-31 Peptide (Elamipretide): What It Is, How It Works, and What the Research Shows

SS-31 — also known as elamipretide, MTP-131, or Bendavia — is a synthetic four-amino-acid peptide that targets the inner membrane of mitochondria, the energy-producing structures inside your cells. It works by binding a lipid called cardiolipin, which helps mitochondria make ATP more efficiently and produce fewer harmful reactive oxygen species [1][2]. SS-31 is not FDA approved for any condition. It has been studied in mitochondrial myopathy, heart failure, kidney disease, age-related macular degeneration, and muscle aging, with results that are promising in some trials and disappointing in others [3][4].

What is SS-31 peptide?

SS-31 is a small synthetic peptide made of just four amino acids (D-Arg-2',6'-dimethylTyr-Lys-Phe-NH2). It belongs to a family of molecules called Szeto-Schiller peptides, named after the two researchers — Hazel Szeto and Peter Schiller — who developed them at Weill Cornell Medical College in the early 2000s [2].

Other names for SS-31

If you see any of these names in research papers or clinical trial listings, they all refer to the same molecule: SS-31, elamipretide (the official International Nonproprietary Name), MTP-131, or Bendavia (an older development name). Stealth BioTherapeutics is the company that has held the main clinical development program [3].

Peptide sequence and structure

SS-31 carries a net positive charge at physiological pH. That charge, plus its small size, lets it move across cell membranes and concentrate inside mitochondria at levels roughly 1,000 times higher than in the surrounding cytoplasm [1]. This targeting is what makes SS-31 different from most peptides — it goes straight to where mitochondrial dysfunction happens.

How does SS-31 work in the body?

SS-31 has one main job: protect and stabilize mitochondria. It does this by binding to cardiolipin, a unique lipid found only on the inner mitochondrial membrane [1][2].

Cardiolipin and the inner mitochondrial membrane

Cardiolipin helps organize the proteins of the electron transport chain — the molecular assembly line that makes ATP, the cell's main energy currency. In aging cells and in many diseases, cardiolipin becomes damaged or oxidized. When that happens, the electron transport chain leaks electrons, energy production drops, and the cell makes more reactive oxygen species (ROS) [1][6]. SS-31 binds cardiolipin and helps keep the membrane organized, which appears to reduce that leak.

Effects on ATP production and reactive oxygen species

In laboratory and animal studies, SS-31 has been shown to increase ATP production in injured or aged tissue, lower mitochondrial ROS, and reduce signs of cell death after stresses like ischemia-reperfusion injury [6][7]. In healthy mitochondria, the effect is much smaller — SS-31 mainly seems to help when something is already wrong.

How it differs from receptor-based peptides

Most peptides used in medicine work by binding receptors on the cell surface (GLP-1s like semaglutide are a classic example). SS-31 is different: it does not bind a receptor at all. It physically integrates into the inner mitochondrial membrane. That is why it is sometimes grouped with other mitochondrial-support compounds like MOTS-c and NAD+ precursors rather than with growth-factor or hormone peptides.

What is SS-31 used for in research?

SS-31 has been studied across many conditions that share a common thread: mitochondrial dysfunction. Below is a summary of the main areas. Results are mixed, and none of these uses are FDA approved.

Primary mitochondrial myopathy and Barth syndrome

These are rare genetic diseases in which mitochondria do not work properly, leading to muscle weakness and exercise intolerance. The MMPOWER-3 trial in primary mitochondrial myopathy did not meet its primary endpoint of improved six-minute walk distance, although some secondary measures suggested benefit [3]. In Barth syndrome, smaller studies and an open-label extension reported improvements in muscle strength and exercise tolerance, but the data are limited [8].

Heart failure and ischemia-reperfusion

In heart failure with reduced ejection fraction, the PROGRESS-HF trial did not show a meaningful benefit on the primary endpoint [4]. Earlier animal work and small human studies suggested SS-31 might reduce damage when blood flow returns to the heart after a heart attack, but that has not translated into approved therapy.

Chronic kidney disease

Animal studies have shown SS-31 can protect kidney tubules from ischemia and from contrast-induced injury [7]. Human data are still early.

Age-related macular degeneration

In the ReCLAIM-2 trial in patients with dry age-related macular degeneration (geographic atrophy), elamipretide showed signals of slowing visual function loss in some measures, although it did not meet all primary endpoints [9]. Stealth BioTherapeutics has continued development in this area.

Sarcopenia and exercise tolerance

Small studies in older adults with mobility problems have looked at whether SS-31 can improve mitochondrial function in skeletal muscle. Some have shown modest improvements in fatigue and muscle energetics measured by MRI, while functional benefits have been smaller [10].

Neurodegeneration

Preclinical work in models of Alzheimer's, Parkinson's, and traumatic brain injury suggests SS-31 may reduce neuronal mitochondrial damage [6]. There is no approved use in any neurological disease.

Is SS-31 peptide FDA approved?

No. As of 2026, SS-31 (elamipretide) is not FDA approved for any condition. Stealth BioTherapeutics has pursued approval in primary mitochondrial myopathy, Barth syndrome, and dry AMD, but no application has been cleared to date [3][5].

What 'research use only' means

SS-31 is widely sold online by companies that label their products 'for research purposes only, not for human consumption.' That label is not just paperwork — it means the product has not been manufactured to pharmaceutical standards, has not been tested for sterility or purity at clinical levels, and cannot legally be sold or administered for human use in the United States. Buying these vials does not make them safe.

What does the clinical evidence actually show?

Honest summary: the picture is mixed. SS-31 has strong preclinical evidence — it consistently helps mitochondria in cells and animals. In humans, several large trials have missed their primary endpoints, while smaller studies and some secondary measures have shown promise [3][4][9]. The most likely explanation is that SS-31 helps specific patient subgroups in specific tissues, and we do not yet know how to identify them in advance.

Important limits of the current data: most trials have been short (months, not years), populations have been small, and long-term safety beyond one to two years of dosing is not well characterized.

What are the possible side effects and safety concerns?

In published trials, SS-31 has generally been well tolerated. The most common reported side effects are [3][9]:

• Injection-site reactions: redness, itching, swelling, or pain at the subcutaneous injection site (the most common issue by far)
• Headache
• Nausea and gastrointestinal upset
• Dizziness
• Fatigue

Serious adverse events have been uncommon in trials, but the total number of patients exposed remains small compared to approved drugs. Long-term effects of chronic mitochondrial-membrane modification are unknown.

Who should not take SS-31

Because data are limited, SS-31 should be avoided or used only under careful clinician supervision in: pregnancy and breastfeeding (no human data), children (outside of formal trials for genetic mitochondrial disease), people with active cancer (mitochondrial effects on tumor metabolism are not understood), and anyone with severe kidney or liver disease not already part of a research protocol. People with known allergies to peptide drug components or injection-vehicle ingredients should also avoid use.

How is SS-31 administered and dosed?

In clinical trials, elamipretide has been given by once-daily subcutaneous injection, with typical study doses in the range of 4 to 60 mg per day depending on the indication and patient size [3][9]. This is educational information drawn from published trials — it is not a recommendation. Real dosing for any individual depends on body weight, the condition being addressed, kidney function, and other medications, and must be set by a licensed clinician.

Why dosing must be clinician-directed

Because SS-31 is investigational, there is no FDA-approved label to guide dosing in the general population. Self-dosing from a 'research use only' vial carries real risks: contamination, inaccurate concentration, and no way to verify what is actually in the product. A clinician evaluation is the only path that pairs the medication with appropriate screening and follow-up.

How much does SS-31 cost and how can you get it legally?

SS-31 is expensive for two reasons: synthesis of a four-amino-acid peptide with non-standard modifications is technically demanding, and there is no generic, FDA-approved version producing economies of scale. Reported research-grade vial pricing varies widely, often $200–$600 per 10–60 mg vial, with monthly costs for a research protocol commonly in the high hundreds to low thousands of dollars.

Research chemical vendors vs. licensed prescribers

Online peptide shops that sell SS-31 as a 'research chemical' are not a legal route for human use. They do not require a prescription, do not verify purity to pharmaceutical standards, and explicitly disclaim human use on their labels. By contrast, a licensed prescriber can evaluate whether SS-31 is appropriate for you, arrange sourcing through a licensed compounding pharmacy where available, and monitor safety.

Getting a clinician evaluation

If you want to discuss SS-31 or other mitochondrial-support options with a licensed clinician, telehealth providers such as Chia Health offer evaluations and can refer or prescribe when clinically appropriate — one option among several licensed routes. You can also explore related topics on Chia's blog, including our MOTS-c peptide guide, our NAD+ overview, and our explainer on 503A compounding pharmacies, which covers how legal compounded medications differ from research-only products.

How does SS-31 compare to other longevity peptides?

SS-31 is often grouped with other compounds that support mitochondrial health, but the mechanisms are quite different. Here is a side-by-side comparison.

What peptides stack well with SS-31?

In compounding-pharmacy practice and in published research, SS-31 is sometimes combined with other mitochondria-focused or recovery-focused compounds. These pairings are framed as commonly co-administered in research and clinical practice — not as a Chia protocol — and combined dosing must always come from a clinician.

• SS-31 + MOTS-c: Both target mitochondrial health from different angles — SS-31 stabilizes the inner membrane while MOTS-c activates AMPK signaling. Safety caveat: there are no large combination trials, and overlapping effects on energy metabolism mean clinician oversight is essential.
• SS-31 + NAD+ precursors: SS-31 protects existing mitochondria; NAD+ supports the enzymes mitochondria use. Safety caveat: nausea and headache can overlap, and quality of NAD+ products varies widely.
• SS-31 + BPC-157: Occasionally combined in recovery and injury contexts. Safety caveat: BPC-157 itself is not FDA approved and has very limited human data; stacking with another unapproved peptide compounds the unknowns.

Frequently asked questions

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