- What it is: A synthetic four-amino-acid peptide that concentrates in the inner mitochondrial membrane.
- Research areas: rare mitochondrial myopathy, Barth syndrome, and heart failure with reduced pumping strength.
- Evidence level: Real human trials, which is rare here, but a mixed record. The two larger trials (MMPOWER-3 and PROGRESS-HF) did not hit their main goals. The positive readouts came from a short 5-day trial and a very small long-term group.
- The short version: SS-31 has more human trial data than most in this category, but the record is mixed rather than a clean win. Nearly all of it ran in people with rare mitochondrial or heart disease, not healthy adults.
What it is
SS-31 is a synthetic four-amino-acid peptide that binds cardiolipin, a lipid found on the inner membrane of mitochondria. It was developed in the Szeto and Schiller labs, which is where the “SS” comes from. In clinical trials it goes by its generic name, elamipretide.
Specs at a glance. Reference values for the compound named on the label, from PubChem or KEGG. They describe the compound, not a measurement of the vial you receive. Molecular weight is the free base (the peptide alone, without a salt). Synthetic peptides are usually supplied as a salt such as acetate or TFA, and the salt in this vial has not been confirmed.
| Compound | SS-31 (elamipretide) |
|---|---|
| Sequence | D-Arg-Dmt-Lys-Phe-NH2 (Dmt = 2,6-dimethyl-L-tyrosine) |
| Molecular formula | C32H49N9O5 |
| Molecular weight | 639.8 g/mol (average, free base) |
| CAS number | 736992-21-5 |
| Reference record | PubChem CID 11764719 |
| Form | Lyophilized (freeze-dried) powder in one sealed vial |
| Vial size | 10 mg per vial |
| Storage (dry powder) | -20°C or colder, long term. Keep the vial sealed and away from light. |
| Lab report | Janoshik Analytical, November 2025. Ordered by the supplier, not by Etched Research. The report carries no lot number, so it is not matched to the vial you receive. Results on this page ↓ · All lab reports → |
What the evidence is
SS-31 has more human trial data than most compounds in this category. The record is mixed. All the trials below ran in people with a rare mitochondrial or heart condition, not in healthy adults.
| Study | Type | Who | What was given | What it measured | What it found |
|---|---|---|---|---|---|
| Karaa et al., Neurology, 2018 | Human, phase 1/2, placebo-controlled | 36 adults with primary mitochondrial myopathy | Rising doses over 5 days | 6-minute walk distance | Highest-dose group walked about 64.5 m farther, placebo about 20.4 m |
| Butler et al. (PROGRESS-HF), Journal of Cardiac Failure, 2020 | Human, phase 2, placebo-controlled | 71 adults with heart failure with reduced ejection fraction | 4 mg or 40 mg daily, 28 days | Heart volume on MRI | No meaningful difference from placebo |
| Karaa et al. (MMPOWER-3), Neurology, 2023 | Human, phase 3, placebo-controlled | 218 adults with primary mitochondrial myopathy | 40 mg daily, 24 weeks | Walk distance and a fatigue score | Missed both main goals. A later look found a walking signal in one genetic subgroup only |
| Thompson et al. (TAZPOWER extension), Genetics in Medicine, 2024 | Human, open-label, no placebo | 10 people with Barth syndrome (8 finished) | 40 mg daily, 168 weeks | Walk distance, fatigue, heart measures | Improvements recorded. Injection-site reactions were the most common side effect |
Last reviewed 2026-09-23. The trials were sponsored by Stealth BioTherapeutics. The cell and animal work behind them, and what none of it establishes, is on the full research summary →
Lab reference
Janoshik Analytical tested SS-31 10mg from supplier stock on 24 November 2025. Two vials measured 99.811% and 99.861% purity, and 10.69 mg and 10.61 mg of peptide against the 10 mg label. See it on the lab reference page →
What that report does not cover: it is a reference test of the compound from supplier stock, not a test of the vial in your order. It did not test for endotoxin, sterility or heavy metals.
Storage and shipping
Ships as lyophilized powder in a sealed vial. Store the powder frozen at -20°C, away from light. US addresses only. Shipping costs and cutoff times →
Questions about SS-31
Is SS-31 the same thing as elamipretide?
Yes. SS-31 is the lab code, elamipretide is the generic name used in the trials, and MTP-131 and Bendavia are earlier development names.
Is there human data?
Yes, four trials are listed above. Two of them, including the largest (218 people), did not meet their main goals. The positive results came from a 5-day trial and a small long-term group without a placebo arm.
Where can I buy SS-31 for research?
Etched Research sells SS-31 on this page as a 10mg vial of lyophilized powder, for laboratory research use only, shipped to US addresses. Where an independent laboratory report exists for a compound, the measurements are published on the lab reference page, including the compounds we hold no report for.
Does Etched Research sell Forzinity?
No. Forzinity is a prescription drug whose active ingredient is elamipretide hydrochloride. It received FDA accelerated approval in September 2025. Etched Research sells SS-31 as a research compound for laboratory use only. It is not for human use.
Shipping, eligibility and what comes in the box: store FAQ →
For research use only. Not for human consumption.
