SS-31

• Barth syndrome (FDA approved 2025)
• Primary mitochondrial myopathy (trials)
• Heart failure (Phase 3 failed)
• Age-related mitochondrial decline (biohacker use)

Barth syndrome (elamipretide)

FDA-approved in September 2025 for this rare X-linked mitochondrial cardiomyopathy, after trials showed improvements in walking distance, symptoms and cardiac measures. It is one of very few peptides to earn FDA approval and the first for a primary mitochondrial disease.

SS-31 works at the most fundamental level of the cell’s energy system, the mitochondria. It homes specifically to the inner mitochondrial membrane, concentrating there at more than a thousand times the level in the rest of the cell, and binds cardiolipin, a phospholipid found almost only in that membrane and essential for energy production. By stabilizing cardiolipin and the membrane folds (cristae) that house the energy machinery, it improves the flow of electrons, raises ATP output and cuts reactive-oxygen-species damage at its source. Unlike antioxidants that mop up free radicals after the fact, SS-31 prevents the excess from forming in the first place.

SS-31 is a synthetic tetrapeptide with the sequence D-Arg-Dmt-Lys-Phe-NH2, where Dmt is an unusual modified tyrosine that gives it its mitochondrial-targeting ability. It was developed by Hazel Szeto and colleagues at Weill Cornell, the "SS" reflecting the Szeto-Schiller peptide family, and is also known as elamipretide, Bendavia or MTP-131. Its small size and precise membrane targeting make it one of the most distinctive and best-studied peptides in this library.

Type

Mitochondria-targeted tetrapeptide

Sequence

D-Arg-Dmt-Lys-Phe-NH2

Binds

Cardiolipin (inner membrane)

Route

Subcutaneous / IV

FDA-approved

Barth syndrome (2025)

Sponsor

Stealth BioTherapeutics

Barth syndrome presents in childhood, and elamipretide has been studied and used in children with the condition under specialist care, so it has a legitimate pediatric clinical context, unlike most peptides here. That is entirely separate from gray-market SS-31 use for anti-aging or performance in healthy minors, which has no rationale, no oversight and no place. Pediatric use belongs only within the approved rare-disease setting.

Most of the published research on this comes from one place. 56% of it is from USA. Findings that no unrelated group has reproduced are weaker than the study count makes them look.

Research published from: USA, Canada, Europe.

The molecule was designed in the early 2000s by Hazel Szeto and Peter Schiller at Weill Cornell as the 31st compound in their Szeto-Schiller aromatic-cationic peptide series, hence SS-31. Stealth BioTherapeutics licensed and developed it under the code MTP-131 and the brand Bendavia for ischemia-reperfusion, acute kidney injury, and later heart failure, before adopting the generic name elamipretide once those broader cardiac and ophthalmic programs failed. After an August 2021 refuse-to-file, a January 2024 resubmission, a favorable October 2024 advisory committee, and a May 2025 complete response letter, the FDA granted narrow accelerated approval in September 2025 under the brand Forzinity for muscle strength in Barth syndrome only. On the gray research-chemical market it is sold simply as SS-31 for unapproved anti-aging use, a designation carried over from its original series name rather than any approved product.

SS-31 came out of Hazel Szeto’s work at Weill Cornell on peptides that target the mitochondrial membrane, and was developed by Stealth BioTherapeutics across many Phase 2 and Phase 3 trials, making it one of the most clinically tested peptides. The road was rocky: a 2021 regulatory rejection for Barth syndrome, a missed endpoint in mitochondrial myopathy, and mixed heart-failure results. But persistence and long-term Barth data paid off with FDA approval of elamipretide for Barth syndrome in September 2025. In parallel, it spread through the longevity and biohacking world as gray-market SS-31 for anti-aging and recovery.

1. 2000sSzeto and colleagues develop mitochondria-targeting Szeto-Schiller peptides at Weill Cornell.
2. 2010sStealth BioTherapeutics advances SS-31 through multiple Phase 2/3 trials across mitochondrial diseases.
3. 2021A regulatory rejection for Barth syndrome and a missed myopathy endpoint set the program back.
4. 2010s-2020sLongevity and biohacking communities adopt gray-market SS-31 for anti-aging.
5. Sep 2025FDA approves elamipretide for Barth syndrome, a rare milestone for a peptide.

• Whether SS-31 helps the common conditions driving its popularity, heart failure, macular degeneration and aging, where trials have been mixed.
• Whether the anti-aging and longevity use is justified at all by current evidence.
• What its long-term safety is in healthy users.
• Whether the Barth approval opens the door to other mitochondrial-disease indications.

Broader indicationsHeart-failure and macular-degeneration programs continue to test its wider potential.Approval haloWhether the Barth approval leads to additional mitochondrial-disease indications.Longevity questionWhether anti-aging use ever gains real evidential support.Mitochondrial-medicine fieldSS-31 helps validate mitochondria-targeting peptides as a therapeutic class.

SS-31 is FDA-approved as elamipretide for Barth syndrome (September 2025), a narrow rare-disease indication under specialist care. Its broader uses, heart failure, macular degeneration and mitochondrial myopathy, remain investigational, with mixed results. Gray-market SS-31 is sold as a research chemical for longevity and recovery, which is not an approved use. The approved drug and the gray-market peptide are very different things.

Status current as of July 2026. Regulatory positions change, sometimes quickly.

Sequence

D-Arg-Dmt-Lys-Phe-NH₂

Target

Cardiolipin

Mito concentration

1,000-5,000x cytoplasm

Approval

Barth syndrome, Sept 2025

What follows is unfinished work on our side, not a finding about SS-31.

Nothing outstanding on this one.