SS-31 (Elamipretide)
SS-31 (elamipretide) is a mitochondria-targeted tetrapeptide that binds cardiolipin in the inner mitochondrial membrane; its lead indication, Barth syndrome, received FDA accelerated approval under the brand name Forzinity on September 19, 2025 — following an earlier Complete Response Letter — making it the first approved use of this compound, while a separate Phase 3 trial in primary mitochondrial myopathy did not meet its primary endpoint and that indication remains unapproved.
This page is a research-orientation summary, not a dosing guide. For anything beyond general background, read the primary literature or talk to a qualified clinician — specifics like amount, frequency, or administration aren't something we publish here.
What it does & how it works
SS-31 is a small, cell-permeable, alternating aromatic-cationic tetrapeptide (D-Arg-Dmt-Lys-Phe) that concentrates in the inner mitochondrial membrane through electrostatic and hydrophobic interactions with cardiolipin, a phospholipid enriched at contact sites between the inner and outer mitochondrial membranes. By binding cardiolipin, it is proposed to prevent cardiolipin peroxidation, stabilize cristae architecture, and preserve the efficiency of electron transport chain complexes and ATP synthase supercomplexes, particularly under oxidative stress. This membrane-stabilizing mechanism is distinct from peptides that act via cell-surface receptors or transcriptional regulation.
Typical results seen in research
In genetic and acquired mitochondrial disease models — including Barth syndrome, which involves a primary cardiolipin-remodeling defect — SS-31/elamipretide improves mitochondrial respiratory efficiency, and in the TAZPOWER clinical program it produced sustained improvements in knee extensor muscle strength over long-term (168-week) follow-up, the basis for its 2025 accelerated approval. In a separate Phase 3 trial (MMPOWER-3) in primary mitochondrial myopathy, elamipretide did not meet its primary endpoint, showing that the benefit seen in Barth syndrome has not generalized to all mitochondrial disease populations studied.
How it’s commonly used
Elamipretide/SS-31 is administered by subcutaneous injection; in its approved Barth syndrome indication it is a prescription drug used under ongoing physician supervision as part of a chronic treatment regimen, while in other contexts it remains an investigational or research-use compound. It is not given orally, since peptides of this type are degraded in the gastrointestinal tract.
- British Journal of Pharmacology · 2014 Targeting mitochondrial cardiolipin and the cytochrome c/cardiolipin complex to promote electron transport and optimize mitochondrial ATP synthesis
- Neurology · 2023 Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial
- Genetics in Medicine · 2024 Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER
- Oxidative Medicine and Cellular Longevity · 2022 SS-31, a Mitochondria-Targeting Peptide, Ameliorates Kidney Disease
Curated from published literature for research orientation. Not an exhaustive review, and not a substitute for reading primary sources.