Did its clinical trials succeed?

The record is mixed and includes notable failures. The phase 3 MMPOWER-3 mitochondrial myopathy trial and the phase 2 PROGRESS-HF heart-failure trial both missed their primary endpoints, and the ReCLAIM-2 geographic-atrophy trial did not meet its co-primary endpoints.

Is there any positive human evidence?

The most encouraging data come from small, mostly open-label work in Barth syndrome (the TAZPOWER extension), which suggested gradual improvements in muscle and cardiac function. Because that data is unblinded and involves very few patients, it is preliminary, not definitive.

It targets mitochondria by binding cardiolipin in the inner mitochondrial membrane, aiming to stabilize the structures that generate ATP and to reduce excess reactive oxygen species, which is why it has been studied in energy-demanding tissues like heart, muscle, and retina.

In trials the most common issue has been injection-site reactions, and tolerability was generally described as acceptable, but because it is unapproved and has no successful pivotal program, its long-term safety is not established and it should be treated as a research-only compound.

EMA-approved

SS-31 (Elamipretide) — Complete Research Guide (2026)

Last updated 2026-06-30

TL;DR

SS-31 (Elamipretide) is a peptide catalogued under Longevity & Anti-Aging. Neutral reference entry; EU status: EU-approved prescription medicine.

What is SS-31 (Elamipretide)?

SS-31, also known as elamipretide (development code MTP-131), is a synthetic mitochondria-targeting tetrapeptide (D-Arg-dimethylTyr-Lys-Phe-NH2) designed to concentrate in the inner mitochondrial membrane and bind cardiolipin.

It is an investigational drug that is NOT approved by the FDA or EMA; it has been evaluated in multiple real phase 1-3 clinical trials for primary mitochondrial myopathy, heart failure, Barth syndrome, and dry age-related macular degeneration / geographic atrophy.

Its clinical record is honestly mixed and includes several high-profile trials that MISSED their primary endpoints, so despite strong mechanistic rationale, it has not yet demonstrated definitive clinical efficacy.

How does SS-31 (Elamipretide) work?

SS-31 binds cardiolipin in the inner mitochondrial membrane, helping stabilize cristae structure and the electron-transport-chain supercomplexes, which is proposed to improve ATP production and reduce excess reactive oxygen species.

By protecting mitochondrial architecture rather than acting as a simple antioxidant, it aims to restore bioenergetic efficiency in cells with high energy demand such as muscle, heart, and retina. [INFOGRAPHIC: SS-31 cardiolipin binding in mitochondria]

What does the research say about SS-31 (Elamipretide)?

In primary mitochondrial myopathy, the phase 3 MMPOWER-3 randomized controlled trial did NOT meet its primary endpoints (change in 6-minute walk test distance or the mitochondrial-myopathy symptom fatigue score), meaning it failed to show the expected clinical benefit despite earlier promising signals. ^[1]
In heart failure with reduced ejection fraction, the phase 2 PROGRESS-HF trial found that elamipretide did NOT significantly improve the primary endpoint of left-ventricular end-systolic volume versus placebo, another honest negative result for a cardiac indication. ^[2]
In Barth syndrome, the open-label extension of the TAZPOWER trial reported gradual improvements in muscle strength and cardiac measures over 168 weeks, but this was a very small, open-label (unblinded) dataset, so it should be viewed as encouraging preliminary evidence rather than proof. ^[4]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

[1] Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial — Karaa A et al., Neurology 2023. (RCT (phase 3))
[2] Effects of Elamipretide on Left Ventricular Function in Patients With Heart Failure With Reduced Ejection Fraction: The PROGRESS-HF Phase 2 Trial — Butler J et al., J Card Fail 2020. (RCT (phase 2))
[3] Novel Mitochondria-Targeting Peptide in Heart Failure Treatment: A Randomized, Placebo-Controlled Trial of Elamipretide — Daubert MA et al., Circ Heart Fail 2017. (RCT (early-phase, single infusion))
[4] Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER — Thompson WR et al., Genet Med 2024. (open-label extension (small n))
[5] ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration with Geographic Atrophy — Ehlers JP et al., Ophthalmol Sci 2025. (RCT (phase 2))
[6] Targeting mitochondrial dysfunction with elamipretide — Obi C et al., Heart Fail Rev 2022. (review)

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

In clinical trials elamipretide was typically given as a 40 mg once-daily subcutaneous injection (myopathy/Barth) or by intravenous infusion in some cardiac and ophthalmology studies, and intravitreal/topical routes were explored for retinal disease.

These regimens describe trial protocols for context only and are not a recommendation, since the drug is unapproved and its optimal use is undefined.

Side effects & safety profile

Across trials elamipretide has most commonly caused injection-site reactions with subcutaneous dosing, and it has generally been described as having an acceptable tolerability profile in the studied populations.

Because it remains investigational and has not completed a successful pivotal program, its long-term safety is not fully characterized and it is not an approved medicine.

It should be regarded strictly as a research compound used within clinical-trial or laboratory settings.

Stacking & combinations

It has been studied as a standalone investigational agent rather than in defined combination stacks, layered on top of standard care for the relevant disease.

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Frequently asked questions

No. It is an investigational mitochondria-targeting peptide that has been tested in real phase 1-3 clinical trials, but it is not approved by the FDA, EMA, or other major regulators for any indication.

References

[1] Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial — Karaa A et al., Neurology 2023. PMID: 37268435. View sourceStudy: RCT (phase 3)Elamipretide did not meet its co-primary endpoints (6-minute walk distance and symptom fatigue score) versus placebo in primary mitochondrial myopathy.
[2] Effects of Elamipretide on Left Ventricular Function in Patients With Heart Failure With Reduced Ejection Fraction: The PROGRESS-HF Phase 2 Trial — Butler J et al., J Card Fail 2020. PMID: 32068002. View sourceStudy: RCT (phase 2)Elamipretide did not significantly improve left-ventricular end-systolic volume (the primary endpoint) compared with placebo.
[3] Novel Mitochondria-Targeting Peptide in Heart Failure Treatment: A Randomized, Placebo-Controlled Trial of Elamipretide — Daubert MA et al., Circ Heart Fail 2017. PMID: 29217757. View sourceStudy: RCT (early-phase, single infusion)A single infusion showed some favorable changes in left-ventricular volumes at higher doses, providing early signal that later larger trials did not confirm.
[4] Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER — Thompson WR et al., Genet Med 2024. PMID: 38602181. View sourceStudy: open-label extension (small n)Sustained improvements in muscle strength and cardiac parameters were reported over 168 weeks, but the open-label small-sample design limits certainty.
[5] ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration with Geographic Atrophy — Ehlers JP et al., Ophthalmol Sci 2025. PMID: 39605874. View sourceStudy: RCT (phase 2)Elamipretide did not meet the prespecified co-primary endpoints in geographic atrophy, though some secondary structural signals were explored.
[6] Targeting mitochondrial dysfunction with elamipretide — Obi C et al., Heart Fail Rev 2022. PMID: 35037146. View sourceStudy: reviewReviews the cardiolipin-binding mechanism and the mixed clinical trial results across cardiac and mitochondrial indications.

This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.