SS-31 Peptide: How It Works, Evidence, and Safety

SS-31 is a small synthetic peptide — also known as elamipretide, bendavia, or MTP-131 — that targets the inner mitochondrial membrane. It binds a lipid called cardiolipin, which helps mitochondria produce energy (ATP) more efficiently and release fewer damaging reactive oxygen species. Researchers are studying it for mitochondrial diseases, heart failure, age-related decline, and dry eye conditions, but it is not yet FDA-approved [1][2].

What is SS-31 peptide?

SS-31 is a four-amino-acid synthetic peptide in the family known as Szeto-Schiller peptides, named after the two researchers, Hazel Szeto and Peter Schiller, who developed them [1]. You may also see it called elamipretide (the generic drug name), bendavia, or MTP-131 — these are all the same molecule, just different names used across research papers and clinical trials.

What makes SS-31 unusual is where it goes. Most drugs work on receptors on the outside of cells. SS-31 crosses the cell membrane and concentrates inside mitochondria, the tiny organelles that produce nearly all of your body's energy [2]. That targeting is why it has drawn so much interest in conditions where mitochondrial function is impaired.

How does SS-31 work in the body?

Binding cardiolipin in mitochondria

Cardiolipin is a unique lipid found almost exclusively on the inner mitochondrial membrane. It helps hold together the protein complexes that make ATP. When cardiolipin is damaged — by aging, disease, or oxidative stress — energy production drops. SS-31 binds selectively to cardiolipin and helps stabilize these protein complexes [2][7].

Reducing reactive oxygen species

Damaged mitochondria leak reactive oxygen species (ROS) — unstable molecules that injure cells over time. By stabilizing the inner membrane, SS-31 reduces ROS production at its source rather than just mopping it up afterward like a typical antioxidant [2].

Restoring ATP production

When the inner membrane is healthier, the electron transport chain works more efficiently and ATP synthesis improves. In animal studies of aged muscle and kidney tissue, SS-31 restored ATP levels and improved cellular function within hours to days [3][8].

What is SS-31 being studied for?

Primary mitochondrial myopathy

Primary mitochondrial myopathy (PMM) is a group of rare genetic disorders that weaken muscles because mitochondria cannot produce enough energy. Elamipretide has been studied in several PMM trials, including the MMPOWER series. Results have been mixed: some endpoints improved, others did not reach statistical significance [4][9].

Heart failure and ischemia-reperfusion

Mitochondrial dysfunction is common in heart failure with preserved ejection fraction (HFpEF) and after heart attacks. The PROGRESS-HF and EMBRACE-STEMI trials tested elamipretide in heart failure and ischemia-reperfusion injury. Some short-term measures improved, but primary clinical endpoints were not met [5][10].

Age-related muscle and kidney decline

Aging mitochondria are a leading explanation for why older adults lose muscle strength and kidney function. Early human studies have shown short-term improvements in skeletal muscle energetics in older adults after SS-31 treatment [3].

Dry age-related macular degeneration and Barth syndrome

Elamipretide is also being studied for dry age-related macular degeneration (the ReNEW and ReGAIN trials) and Barth syndrome, an ultra-rare cardiolipin-related disorder in boys [11]. In 2024, the FDA declined to approve elamipretide for Barth syndrome, requesting more data; the developer is continuing studies [6].

Is SS-31 the same as elamipretide?

Yes. SS-31, elamipretide, bendavia, and MTP-131 are four names for the same peptide. SS-31 is the research code (from Szeto-Schiller, peptide 31). Elamipretide is the generic name used in regulatory filings. Bendavia was an earlier development name, and MTP-131 was used by Stealth BioTherapeutics in some trials [1][6]. If you see any of these terms, they refer to the same molecule.

What does the clinical evidence show?

The honest summary: the biology is compelling, the clinical results so far are mixed. Mechanism studies and animal data strongly support that SS-31 improves mitochondrial function [2][7][8]. Human trials have shown some positive signals — such as improved skeletal muscle ATP production in older adults [3] — but several large phase 2 and phase 3 trials missed their primary endpoints [5][9].

This is common for early-stage drugs that target complex, multi-organ biology. It does not mean SS-31 does not work — it means we do not yet have clear answers about which patients benefit most, at what dose, and for how long.

What are the known side effects and safety concerns?

Across clinical trials, elamipretide has generally been well tolerated, but it is not side-effect free [4][5][9]:

• Injection-site reactions — redness, itching, or swelling where the subcutaneous dose is given. This is the most common side effect.
• Headache.
• Nausea or gastrointestinal upset.
• Dizziness.
• Rarely, allergic-type reactions.

Long-term safety data in healthy adults is limited because most trials have been in patients with serious disease over weeks to months. SS-31 should not be used in pregnancy, while breastfeeding, or in anyone with an active allergy to the peptide. Anyone considering it should be evaluated by a licensed clinician who can review their full medical history and other medications.

How is SS-31 administered and dosed?

In clinical trials, elamipretide has most often been given as a once-daily subcutaneous injection. Topical eye-drop formulations have been used in macular degeneration trials [11]. We are deliberately not listing specific milligram amounts here: dosing in trials varies by condition and is set by the protocol, and any use outside a trial should be individualized by a clinician based on the latest evidence and the patient's situation.

Is SS-31 FDA-approved or legal to use?

SS-31 / elamipretide is not FDA-approved for any indication as of late 2025. In 2024, the FDA issued a Complete Response Letter to Stealth BioTherapeutics for elamipretide in Barth syndrome, declining approval and requesting additional data [6]. Other trials in heart failure, mitochondrial myopathy, and macular degeneration are ongoing or have completed without approval.

Because there is no FDA-approved version, patients in the United States typically access SS-31 in one of two ways: (1) by enrolling in a clinical trial, or (2) through a licensed 503A compounding pharmacy that prepares the peptide for an individual patient on a physician's prescription. 503A pharmacies are state-licensed pharmacies that prepare customized medications for specific patients — they are regulated, but compounded products are not FDA-approved as finished drugs.

How do patients access SS-31 peptide today?

Realistically, there are three paths:

1. 1Clinical trials. Search ClinicalTrials.gov for active elamipretide studies. This is the most rigorous path and the only one where the drug itself is free.
2. 2A physician-supervised prescription through a licensed telehealth provider that works with a 503A compounding pharmacy. This is how most patients currently access investigational peptides in the U.S. Chia Health is one such telehealth provider — clinicians review your history, decide whether SS-31 is appropriate, and if so, coordinate with a licensed compounding pharmacy.
3. 3Unregulated 'research chemical' sellers online — this path is unsafe. These products are not tested for sterility, purity, or correct identity, and they are not legal for human use.

Cost varies widely. Compounded peptides are typically paid out of pocket, since insurance does not cover non-FDA-approved drugs. Monthly costs from licensed compounding pharmacies generally range from a couple hundred to several hundred dollars depending on dose and formulation.

SS-31 vs other longevity peptides

SS-31 is distinguished by how directly it targets mitochondrial energy production, rather than working through hormones or growth signals.

Frequently asked questions

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