Peptide Medicine
SS-31 (Elamipretide): What the Trials Show, Uses, and Safety
Medically reviewed by HealthRX.com Medical Team · Last reviewed
What is SS-31?
SS-31 is a synthetic four-amino-acid peptide, developed under the name elamipretide, that concentrates in mitochondria. The SS stands for Szeto-Schiller, the researchers who created the peptide series. It has also carried the names MTP-131 and Bendavia, and it is now sold as the approved drug Forzinity.
Unlike most peptides sold in wellness settings, SS-31 has a substantial history of formal human clinical trials run under an investigational drug application. [1]
It targets the inner mitochondrial membrane, where energy production happens, rather than acting as a hormone or growth signal. [1]
How does SS-31 work?
SS-31 binds cardiolipin, a phospholipid unique to the inner mitochondrial membrane. By stabilizing that membrane and the protein complexes of the electron transport chain, it is reported to support ATP energy production and reduce the reactive oxygen species that damage cells.
The mechanism is well supported in laboratory and biophysical work. How reliably it produces clinical benefit is a separate question, and the trial record is mixed. [1][2]
What do the human trials on SS-31 show?
The results are mixed and mostly fell short of their main goals. SS-31 earned a narrow FDA approval for Barth syndrome in 2025, based largely on long-term open-label data. Trials in mitochondrial myopathy, dry macular degeneration and heart failure missed their primary endpoints.
- Barth syndrome: the controlled crossover phase missed its endpoints, but a 168-week open-label extension showed strength and walking gains, which supported the 2025 approval. [3]
- Mitochondrial myopathy (MMPOWER-3): missed both co-primary endpoints in a 218-patient trial. [2]
- Dry macular degeneration (ReCLAIM-2): missed both primary endpoints; some secondary signals were positive. [4]
- Heart failure (PROGRESS-HF): missed its primary endpoint. [5]
- Honest framing: outside Barth syndrome, efficacy is not established, and wellness or anti-aging uses are unapproved and unproven.
How is SS-31 used and dosed?
In clinical trials SS-31 was given as a once-daily subcutaneous injection, commonly 40 mg per day. The approved product is also a once-daily subcutaneous injection for patients weighing at least 30 kg. Wellness dosing is not standardized or validated, and any use should follow a prescriber and the approved labeling.
| Setting | Route and dose | Notes |
|---|---|---|
| Clinical trials | 40 mg daily, subcutaneous | Regimen used across chronic-disease studies |
| Approved product (Barth) | Once-daily subcutaneous injection | For patients at least 30 kg; follow the FDA label |
| Wellness or anti-aging | Not standardized | Not FDA approved; unproven; often research-grade material |
Is SS-31 safe, and what are the side effects?
The most common side effects in trials were injection-site reactions such as itching, redness, firmness, bruising and pain. Most were mild to moderate and often resolved on their own, though they sometimes led people to stop treatment. Long-term safety and the safety of research-grade product are less certain.
- Injection-site reactions were the dominant side effect across trials.
- The peptide was generally well tolerated systemically in studies.
- Injection-site reactions were a leading reason for early withdrawal.
- Long-term safety and the safety of non-pharmaceutical research material are not fully characterized.
Is SS-31 legal and FDA approved?
SS-31 is FDA approved, but only as Forzinity for Barth syndrome, a rare mitochondrial disease. That approval is accelerated and depends on a confirmatory trial. For energy, anti-aging, athletic recovery, eye disease or heart failure it is not approved, and material sold online for those uses is unapproved.
The Barth syndrome approval was granted on September 19, 2025, making SS-31 the first therapy for that condition. Continued approval may depend on verifying benefit in a confirmatory trial. [6]
How does SS-31 compare with other peptides?
| SS-31 | MOTS-c | BPC-157 | |
|---|---|---|---|
| Origin | Synthetic designed peptide | Natural mitochondrial peptide | Synthetic sequence |
| Mechanism | Stabilizes mitochondrial membrane | Activates AMPK metabolic signaling | Studied for tissue repair |
| Human evidence | Extensive trials; one approval | Largely preclinical | Preclinical |
| FDA approved | Yes, Barth syndrome only | No | No |
Frequently asked questions
Is SS-31 FDA approved?
Only in a narrow sense. In September 2025 the FDA approved it as Forzinity to improve muscle strength in Barth syndrome, a rare genetic disease. For energy, anti-aging, eye disease or heart failure it is not FDA approved.
Does SS-31 work for anti-aging or mitochondrial health?
There is no human trial proving anti-aging or general energy benefits. The interest comes from laboratory studies and its mechanism. In humans, several rigorous trials in other conditions missed their main goals, so broad claims remain unproven.
What were the results of the big human trials?
Mostly disappointing on their primary goals. Trials in mitochondrial myopathy, dry macular degeneration and heart failure all missed their primary endpoints. In Barth syndrome, long-term open-label data showed gains that supported a narrow approval.
How is SS-31 taken, and what are the side effects?
In trials it was a once-daily subcutaneous injection, typically 40 mg. The most common side effects were injection-site reactions: itching, redness, firmness, bruising and pain. These were usually mild to moderate and often resolved on their own.
Is SS-31 the same as MOTS-c or BPC-157?
No. SS-31 binds cardiolipin to stabilize mitochondria. MOTS-c is a natural mitochondrial peptide that activates metabolic signaling. BPC-157 is studied for tissue repair. They differ in origin, mechanism and evidence, and only SS-31 has an FDA approval.
Citations
- Tung C, et al. Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential. Int J Mol Sci. 2025;26(3):944.
- Karaa A, et al. Efficacy and Safety of Elamipretide in Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology. 2023;101(3).
- Thompson WR, et al. Long-term efficacy and safety of elamipretide in Barth syndrome: 168-week open-label extension of TAZPOWER. Genet Med. 2024;26(7):101138.
- Ehlers JP, et al. ReCLAIM-2: A Randomized Phase 2 Trial of Elamipretide in Age-Related Macular Degeneration and Geographic Atrophy. Ophthalmol Sci. 2024;5(1):100628.
- Butler J, et al. Effects of Elamipretide on Left Ventricular Function in Heart Failure With Reduced Ejection Fraction: PROGRESS-HF. J Card Fail. 2020;26(5):429-437.
- U.S. FDA. FDA Grants Accelerated Approval to First Treatment for Barth Syndrome. September 19, 2025.
This guide is educational and is not a substitute for individualized medical advice. SS-31 is prescription-only and requires evaluation by a licensed provider.