What is SS-31?
SS-31 — also known as Elamipretide or MTP-131 — is a synthetic tetrapeptide developed as part of a class of "Szeto-Schiller" peptides studied for their unusual ability to concentrate inside the mitochondria, the energy-producing structures of the cell. Where most research peptides act on receptors at the cell surface, SS-31 is studied for activity deep within the cell's energy machinery.
Its sequence is D-Arg-Dmt-Lys-Phe-NH₂, with a molecular weight of approximately 639.8 g/mol. That small, charged structure is what allows it to accumulate selectively in the inner mitochondrial membrane.
How SS-31 Works — The Cardiolipin Connection
The defining feature of SS-31 in the research literature is how it interacts with cardiolipin, a unique lipid found almost exclusively on the inner mitochondrial membrane. Cardiolipin is essential to the structure of the membrane folds (cristae) that house the electron transport chain — the system that generates cellular energy.
Research associates SS-31's binding to cardiolipin with three areas of interest:
- Stabilisation of the cristae structure of the inner membrane
- Support of electron-transport-chain efficiency
- Modulation of reactive oxygen species (the by-products of energy production)
Because cardiolipin damage is a feature of many forms of mitochondrial dysfunction, this mechanism is why SS-31 has been investigated across such a wide range of research models.
Unlike antioxidants that act broadly throughout the cell, SS-31 is studied specifically because it concentrates in the mitochondria — reaching the inner membrane where cardiolipin sits, rather than being diluted across the whole cell.
Key Research Areas
Primary Mitochondrial Myopathy
SS-31's most prominent clinical research has been in primary mitochondrial myopathy — inherited disorders of mitochondrial function — through the MMPOWER trial programme. The research aimed to investigate effects on muscle function and exercise capacity. Results across the programme were mixed: some signals were reported in subgroups, but the larger Phase 3 study did not meet its primary endpoint.
Cardiac and Ischemia-Reperfusion Research
SS-31 has been studied in models of heart failure and ischemia-reperfusion injury — the cellular damage that can occur when blood flow is restored to tissue after a period of restriction. Pre-clinical research examined whether protecting mitochondrial membranes could reduce that injury.
Skeletal Muscle and Cellular Ageing
Because mitochondrial efficiency tends to decline with age, SS-31 has been investigated in research on skeletal-muscle bioenergetics and age-related mitochondrial dysfunction, with studies measuring markers of muscle energy production in model systems.
Ophthalmic and Rare-Disease Research
SS-31 has also been studied in eye conditions with a mitochondrial component, including dry age-related macular degeneration (geographic atrophy) and Leber's hereditary optic neuropathy, as well as Barth syndrome — a genetic disorder directly involving cardiolipin.
Research Status
It's worth being clear-eyed about where SS-31 stands. The mechanism is well characterised and genuinely novel, which is why it attracts ongoing research interest. However, clinical results to date have been mixed, and SS-31 is not an approved medicine in any market. It remains an investigational compound studied in research settings — not a proven treatment.
LA LAB SS-31
LA LAB supplies SS-31 (Elamipretide) as a lyophilized vial, third-party tested by Janoshik Analytical for purity and identity. You can view the compound on our SS-31 product page. For more on how we test and verify every compound, see our peptide research guide.