01 What is Elamipretide?
In plain English.
Elamipretide is an experimental injectable drug, made of just four [amino acids](/glossary "Amino acid: The building blocks of proteins. A peptide is a short chain of them linked together."), developed by Stealth BioTherapeutics. It is designed to home in on the mitochondria — the tiny structures inside your cells that act as power plants, turning food and oxygen into usable energy. The idea is that in diseases where mitochondria fail, propping up their energy output could help. In the biohacker and longevity world it is often sold (as SS-31) as an "anti-ageing" or "cellular energy" booster, but that framing goes far beyond what the actual trials have shown.
It is investigational, meaning it is not an approved prescription medicine anywhere in the world. The only legitimate way to receive it is enrolment in a registered clinical trial. Vials sold online as "SS-31" are unregulated research chemicals: their contents, purity, sterility and dose cannot be verified, and they are not the clinical-grade drug used in trials.
02 How it works
The simple version, then the science.
Elamipretide targets the cell's power plants — the mitochondria — to help them make energy more efficiently. In cells that are struggling because their mitochondria are damaged or under stress, the peptide is meant to stabilise the machinery that produces energy, so the cell can keep working. That is the theory behind testing it in diseases where failing mitochondria are the core problem, such as inherited mitochondrial myopathies and Barth syndrome.
Go deeper · the proposed mechanism
Elamipretide is a cell-permeable, aromatic-cationic tetrapeptide (D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2) of the Szeto–Schiller (SS) peptide class. It accumulates several-hundred-fold in the inner mitochondrial membrane, where it binds the phospholipid cardiolipin. By associating with cardiolipin it is thought to stabilise cristae architecture and the supercomplexes of the electron transport chain, improve oxidative phosphorylation and reduce reactive-oxygen-species leakage and cytochrome-c peroxidase activity. Unlike antioxidants that scavenge free radicals, its proposed action is structural — preserving the membrane environment in which efficient ATP synthesis occurs.
03 What it's used for
Each use graded by how strong the evidence actually is.
- ModeratePrimary mitochondrial myopathy🔬 The lead clinical indication. The MMPOWER-3 phase 3 trial (Neurology, 2024) tested subcutaneous elamipretide in primary mitochondrial myopathy and missed its co-primary endpoints (six-minute walk distance and a symptom score). Earlier signals from MMPOWER did not translate into a clear phase 3 benefit. Development has continued in narrower sub-populations.
- ModerateBarth syndrome🔬 A rare X-linked cardiolipin disorder. The TAZPOWER crossover trial did not meet its primary endpoints over the blinded period, but an open-label extension reported improvements in muscle and cardiac measures, which became the basis for ongoing FDA interactions in this ultra-rare indication.
- LimitedHeart failure🔬 Originally developed (as Bendavia / MTP-131) for ischaemia-reperfusion injury and heart failure. Early-phase cardiovascular studies, including work in heart failure with reduced ejection fraction, were largely neutral and this line of development was not advanced to approval.
- LimitedDry AMD / geographic atrophy🔬 The ReCLAIM and ReCLAIM-2 studies evaluated elamipretide in dry age-related macular degeneration and geographic atrophy. Results were mixed, with some retinal-function signals but no clear win on the primary endpoint in the controlled phase 2 work.
- AnecdotalGeneral "energy" / "anti-ageing" use💬 Sold by online peptide vendors as SS-31 for fatigue, longevity, fitness recovery and "mitochondrial health" in healthy people. There is no clinical trial evidence supporting these uses; the human programme is in serious rare disease, not anti-ageing, and the consumer framing is not backed by data.
04 What the evidence says
This is an honest "mixed" picture, not a success story dressed up as one. Elamipretide has a genuine, serious clinical programme — that is what separates it from most "longevity" peptides — but its pivotal trials have largely underdelivered. In primary mitochondrial myopathy, the phase 2 MMPOWER signal did not hold up: the phase 3 MMPOWER-3 trial (published in Neurology in 2024) failed to meet its co-primary endpoints. In Barth syndrome, the TAZPOWER crossover did not meet its primary endpoint in the blinded phase, though an open-label extension reported functional gains that have kept the ultra-rare programme alive in FDA discussions. The cardiovascular work (as Bendavia, for ischaemia-reperfusion and heart failure) was broadly neutral and was not advanced. The ReCLAIM eye studies in dry AMD / geographic atrophy were similarly mixed. The fair summary: real human data exist, the mechanism is biologically plausible and the drug is generally well tolerated, but efficacy is unsettled and it is approved nowhere. The popular "reverses ageing / boosts your mitochondria" story is built on cell and animal work and biohacker enthusiasm, not on positive pivotal human trials.
05 Dosing & administration
Reported in the literature, information not advice.
For context only — there is no approved elamipretide product and no validated outpatient protocol. Trials have used once-daily subcutaneous injection (commonly cited around 40 mg/day in the mitochondrial myopathy programme), with dosing administered under clinical supervision. None of this constitutes instructions: self-injecting an unregulated "SS-31" product bought online is outside established medicine, the dose and contents cannot be verified, and a forum protocol cannot make that safe.
06 Side effects & safety
In the clinical trials run to date, elamipretide has generally been reasonably well tolerated, which is part of why development has continued despite efficacy misses. The most commonly reported adverse events are injection-site reactions (redness, itching, swelling at the site of subcutaneous administration). Beyond that, the trial safety profile has not flagged major new concerns, but this is still an investigational drug: there is no long-term, large-population safety data, and effects over years of use are unknown. Anything bought as "SS-31" from a research-chemical vendor carries the separate, larger risk of an unregulated, unverified product — unknown purity, dose, sterility and no clinical oversight. People who are pregnant or breastfeeding, and anyone with significant medical conditions or on other medication, would in any case fall outside the population that has been studied.
07 Can you buy it?
Investigational, not approved or sold as a medicine anywhere.
08 Legal & regulatory status
- UKNot licensed by the MHRA. Available only via clinical trial participation. No legitimate UK supply outside trials.
- USNot FDA-approved. Investigational in rare-disease indications (mitochondrial myopathy, Barth syndrome); no general consumer or compounding pathway.
- EUNot authorised by the EMA. Investigational only.
- SportElamipretide is not named individually on the WADA Prohibited List, but as an unapproved investigational substance it is captured by category S0 ("Non-Approved Substances") and is prohibited at all times in tested sport.
09 Clinical studies & research
Primary sources. Read the science yourself.