SS-31 (Elamipretide): Research, Mechanism & Current Evidence

What is SS-31?

SS-31, known generically as elamipretide, is a synthetic peptide of four amino acids designed to concentrate inside mitochondria. It was developed by Stealth BioTherapeutics.

Unlike most compounds in the longevity category, it has been through multiple registered clinical trials, which makes its results — including the disappointing ones — unusually informative.

Status: Investigational.

What is SS-31 researched for?

Primary mitochondrial myopathy, Barth syndrome and other inherited mitochondrial diseases.

Heart failure, ischaemia-reperfusion injury, and age-related decline in muscle and kidney function.

• Optimizes electron transport chain function for improved cellular energy.
• Prevents cardiolipin peroxidation and reduces mitochondrial oxidative damage.
• Significant improvements in 6-minute walk test and fatigue scores in PMM patients.
• Reduces cardiac injury markers and improves mitochondrial function in surgical patients.
• Reduces ischemia-reperfusion injury and supports cardiac function.
• Enhanced exercise capacity and reduced fatigue.
• Reversed age-related decline in muscle function in animal studies.
• Neuroprotective effects demonstrated in Alzheimer's models.
• Supports overall cellular health through mitochondrial optimization.

How does SS-31 work?

Cardiolipin is a fat unique to the inner mitochondrial membrane, and the machinery that generates cellular energy depends on it being correctly organised. Cardiolipin is also easily damaged by oxidative stress.

SS-31 binds cardiolipin and appears to stabilise it, helping the electron transport chain stay efficient and reducing the leakage of reactive oxygen species.

What does the research show?

Animal and cell studies consistently report improved mitochondrial function. Human trials have been more mixed: some endpoints in mitochondrial myopathy and Barth syndrome improved, while pivotal trials have failed to meet their primary endpoints on more than one occasion.

That pattern — strong preclinical results, inconsistent clinical translation — is itself the most useful thing to know about this compound.

Limitations of the current evidence

Repeated failures to hit primary endpoints in registered trials mean efficacy remains unproven despite a plausible mechanism.

Findings in rare inherited mitochondrial disease do not automatically extend to age-related decline in healthy people.

References

1. Randomized dose-escalation trial of elamipretide in adults with primary mitochondrial myopathy

   Karaa A, Haas R, Goldstein A, et al. · Neurology · 2018

   Phase I/II trial in 36 patients showed dose-dependent improvement in 6-minute walk test (64.5m vs 20.4m placebo at highest dose) after 5 days of treatment with excellent safety profile.

   Controlled clinical trial · PMID 29500292

2. Novel Mitochondria-Targeting Peptide in Heart Failure Treatment (EMBRACE) Daubert, M.A., et al. Circulation: Heart Failure

   2017

   IV infusion in heart failure patients showed significant decrease in left ventricular end-diastolic volume (-18 mL, P=0.009) and end-systolic volume (-14 mL, P=0.005) at the highest dose.

3. Improving mitochondrial function with SS-31 reverses age-related redox stress and improves exercise tolerance in aged mice

   Campbell MD, Duan J, Samuelson AT, et al. · Free radical biology & medicine · 2019

   8 weeks of SS-31 (3 mg/kg/day) in aged mice reversed age-related decline in mitochondrial ATP production, restored redox homeostasis, and significantly increased treadmill endurance.

   Animal study · PMID 30597195

4. TAZPOWER: Phase 2/3 Randomized Clinical Trial of Elamipretide in Barth Syndrome Thompson, W.R., et al. Genetics in

   Medicine · 2021

   40mg daily in Barth syndrome patients. Primary endpoints not met at 12 weeks, but open-label extension showed cumulative 96.1m improvement in 6MWT at 168 weeks (P=0.003) with sustained fatigue improvements.

   Controlled clinical trial

5. Efficacy and Safety of Elamipretide in Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial Karaa, A., et al. JAMA Neurology

   2023

   Phase 3 trial (218 patients) did not meet primary 6MWT endpoint overall, but post-hoc analysis showed improvement in patients with nuclear DNA variants. Well-tolerated with mild-to-moderate adverse events.

   Controlled clinical trial

6. Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential

   Tung C, Varzideh F, Farroni E, et al. · International journal of molecular sciences · 2025

   Comprehensive review covering PROGRESS-HF, TAZPOWER, MMPOWER-3, and ReCLAIM trials. Highlights elamipretide's unique cardiolipin-binding mechanism and broad therapeutic potential across mitochondrial diseases.

   Review or meta-analysis · PMID 39940712

7. Novel Mitochondria-Targeting Peptide in Heart Failure Treatment: A Randomized, Placebo-Controlled Trial of Elamipretide

   Daubert MA, Yow E, Dunn G, et al. · Circulation. Heart failure · 2017

   Controlled clinical trial · PMID 29217757

8. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial

   Karaa A, Bertini E, Carelli V, et al. · Neurology · 2023

   Controlled clinical trial · PMID 37268435

9. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism

   Reid Thompson W, Hornby B, Manuel R, et al. · Genetics in medicine : official journal of the American College of Medical Genetics · 2021

   Controlled clinical trial · PMID 33077895