What is SS-31 (Elamipretide) and what is it used for?
SS-31 is a mitochondria-targeted peptide that stabilizes cardiolipin and protects cristae structure. Studied for heart failure, kidney injury, and aging.
Updated May 10, 2026 · 3 min read
SS-31 is a mitochondria-targeted peptide that works by stabilizing cardiolipin — a lipid that holds the inner mitochondrial membrane together. Unlike most peptides in the strength community, SS-31 (also called Elamipretide or MTP-131) has actual human clinical trial data, including FDA Breakthrough Therapy designation for heart failure with preserved ejection fraction (HFpEF). It's one of the most scientifically credible peptides in the mitochondrial category.
What it is and how it works
SS-31 is a tetrapeptide (four amino acids: D-Arg–2′6′-dimethylTyr–Lys–Phe-NH₂). The Szeto-Schiller naming convention (SS-31) comes from its developers, Hazel Szeto and Peter Schiller. The commercial name is Elamipretide (brand: Bendavia).
Its mechanism is unusually specific:
- Accumulates in the inner mitochondrial membrane selectively — the alternating positive/aromatic residues give it a strong affinity for the negatively charged cardiolipin
- Stabilizes cardiolipin — cardiolipin anchors cytochrome c and the respiratory complexes into the cristae structure. When cardiolipin oxidizes (during ischemia, aging, or disease), the cristae unravel and ATP production crashes
- Reduces electron leak — by stabilizing the respiratory chain complexes, SS-31 reduces the production of reactive oxygen species at the source rather than scavenging them afterward
- Does not need a transmembrane potential to enter — unlike other mitochondria-targeting compounds (e.g., MitoQ), SS-31 accumulates in damaged mitochondria without relying on membrane potential
This is what makes it interesting for injury and disease contexts: it works when mitochondria are already failing, not just as a preventive.
What the research shows
SS-31 has more clinical data than almost any other peptide in the mitochondrial or recovery category:
| Study context | Finding |
|---|---|
| Heart failure (HFpEF) | Phase 2 ESPRIT-HF trial showed improved 6-minute walk distance; FDA Breakthrough Therapy designation |
| Ischemia-reperfusion injury | Consistently protective in animal models — heart, kidney, brain |
| Aging skeletal muscle | Restored mitochondrial morphology and improved ex vivo force production in aged mice |
| Barth syndrome (rare cardiolipin disorder) | Phase 2/3 trial data; improved exercise tolerance |
| Acute kidney injury | Phase 2 PROGRESS trial (cardiac surgery patients) — reduced AKI incidence |
The human trial data is primarily in disease populations, not healthy athletes. The strength-community interest is an extrapolation from the aging and exercise physiology data.
How it differs from other mitochondrial peptides
| SS-31 | MOTS-c | Humanin | |
|---|---|---|---|
| Origin | Synthetic, not endogenous | Mitochondrial genome | Mitochondrial genome |
| Primary target | Cardiolipin / inner membrane | AMPK / nuclear | IGF-1R / STAT3 |
| Best evidence | Human clinical trials (disease) | Animal models, human observational | Animal models |
| Main interest | Heart, kidney, aging | Endurance, metabolic | Neuroprotection |
How it's used in the strength and biohacking community
No standard human protocol exists for healthy users — there are no trials in that population. Reported community protocols:
- 2–10 mg subcutaneous, once daily or a few times per week
- Cycles of 4–8 weeks
- Sometimes stacked with MOTS-c for broader mitochondrial coverage
- Also used by older athletes as a recovery-support adjunct alongside GH secretagogues
The rationale for athletes: training imposes transient mitochondrial stress and oxidative damage, and SS-31 theoretically attenuates that stress at the source.
What to watch for
- Supply chain quality — as a tetrapeptide, SS-31 is not trivially synthesized, and research-chemical purity varies dramatically. Identity verification via COA with HPLC and mass spec matters more here than for larger, structurally simpler peptides
- No long-term safety data in healthy humans — clinical trials have been relatively short-duration in sick populations
- Injection site reactions — reported occasionally; not dose-limiting in trials