SS-31 — also known as elamipretide or MTP-131 — is a small, synthetic, mitochondria-targeting tetrapeptide that has become one of the most closely studied tools in mitochondrial biology. Developed by Stealth BioTherapeutics and originating from the Szeto-Schiller ("SS") series of cell-permeable peptides, it carries the sequence D-Arg-Dmt-Lys-Phe-NH2. Its alternating aromatic and basic residues give it two features researchers care about: chemical stability with cell permeability, and a strong tendency to concentrate inside the inner mitochondrial membrane.
What keeps SS-31 at the center of the field is where it goes and what it binds. Rather than acting on a classical surface receptor, it targets a single lipid — cardiolipin — that sits at the heart of how mitochondria make energy. This guide summarizes what the peer-reviewed literature reports about that mechanism and the research areas it has been applied to, and — just as importantly — where the human evidence still stands.
Most peptides never reach the mitochondrion in meaningful amounts. SS-31 is unusual because it accumulates there without needing a membrane-potential gradient to pull it in. In laboratory studies it associates with cardiolipin, a signature phospholipid found almost exclusively on the inner mitochondrial membrane. Cardiolipin is essential for organizing the folded membrane structures called cristae and for holding together the protein complexes of the electron transport chain. Because cardiolipin is so central to mitochondrial energy production, a molecule that binds it selectively is, in effect, a molecule aimed at the cell's power supply.
Across in-vitro and preclinical work, the recurring description of SS-31 is that of a mitochondrial-protective peptide. Reviews of its pharmacology report that, by interacting with cardiolipin, SS-31 has been associated with the following activities in model systems — none of which should be read as an established human clinical outcome:
The important nuance — often lost in marketing copy — is that these are mechanistic observations in research models. SS-31 is best understood as a way to protect and stabilize existing mitochondrial function under stress, not as a proven treatment.
Because so many tissues depend on mitochondrial output, SS-31 / elamipretide has been examined across a broad set of research areas. Published work spans:
It is worth stressing that results across these areas have been mixed: strong mechanistic and preclinical signals in some settings, and clinical studies that have not always met their primary endpoints in others. That contrast is exactly why the compound remains an active research subject rather than a settled therapy.
This is the part a responsible sourcing page should state plainly. For most of the uses studied in the literature, elamipretide remains investigational, and the broader human evidence is still developing. Several clinical programs have produced encouraging mechanistic data alongside trials that did not meet their primary endpoints.
There is one narrow exception. In September 2025, a prescription formulation of elamipretide (brand name FORZINITY) received FDA accelerated approval to improve muscle strength in patients with Barth syndrome, an ultra-rare genetic mitochondrial disorder — reported as the first FDA-approved therapy for a mitochondrial disease. Accelerated approval was based on an intermediate endpoint, with continued approval potentially contingent on confirmatory data. Crucially, that regulated medicine is a distinct pharmaceutical product; it is not the same as research-grade SS-31 powder, and its approval does not extend to any other use.
For research applications, identity and purity are what separate a usable reference compound from an unknown. The SS-31 we supply to the research community is a lyophilized powder tested to high purity by HPLC, with a third-party Certificate of Analysis (COA) available for each lot, strictly for in-vitro laboratory use:
New to handling lyophilized peptides? See our Research Center for storage, reconstitution and COA guidance.
SS-31 is a synthetic mitochondria-targeting tetrapeptide (D-Arg-Dmt-Lys-Phe-NH2), also known as elamipretide or MTP-131, developed by Stealth BioTherapeutics. It is one of the most-studied compounds in the Szeto-Schiller (SS) series of cell-permeable peptides that concentrate in the inner mitochondrial membrane.
In laboratory studies SS-31 binds selectively to cardiolipin, a phospholipid of the inner mitochondrial membrane. Research reports that this association helps stabilize cristae architecture, support electron-transport-chain efficiency and ATP production, and reduce the generation of reactive oxygen species. It is described as a mitochondrial-protective peptide rather than a single-receptor drug.
The research-grade SS-31 powder sold for laboratory use is not an approved medicine and is strictly for in-vitro and analytical research. A prescription formulation of elamipretide (FORZINITY) received FDA accelerated approval in September 2025 for the ultra-rare genetic disorder Barth syndrome, but that is a regulated pharmaceutical product, not a research chemical. For most other studied uses the peptide remains investigational and human evidence is still developing.
Published research has examined SS-31 / elamipretide in models and trials relating to mitochondrial dysfunction, heart failure and cardiac ischemia-reperfusion, primary mitochondrial myopathy, skeletal-muscle function, neurodegeneration and age-related conditions. Many of these findings come from cell and animal models or early clinical studies rather than large confirmatory human trials.