What is SS-31 (Elamipretide)?

SS-31 (elamipretide, Szeto-Schiller peptide 31) is a synthetic tetrapeptide developed by Hazel Szeto and Peter Schiller at Cornell University that crosses cell membranes and selectively concentrates in the inner mitochondrial membrane, binding cardiolipin — the phospholipid essential for electron transport chain (ETC) function. It protects cardiolipin from oxidation, stabilizes ETC complex assembly, and reduces mitochondrial reactive oxygen species, improving ATP production efficiency and cardiac function.

What clinical trials has SS-31 completed?

SS-31 (elamipretide) has completed Phase II trials in heart failure with preserved ejection fraction (HFpEF), showing significant improvements in 6-minute walk distance; Phase II in primary mitochondrial myopathy showing improved strength and fatigue; Phase II in kidney ischemia-reperfusion injury; and the Phase III EMBARK trial in Barth syndrome (rare genetic mitochondrial disease) which met its primary endpoint. FDA approval is not yet granted as of mid-2026.

How is SS-31 different from NAD+ or MOTS-c?

The three compounds address mitochondrial health from different angles. SS-31 directly protects the structural integrity of the inner mitochondrial membrane by binding cardiolipin and stabilizing ETC complexes — a structural intervention. MOTS-c signals from mitochondrial DNA to activate AMPK (a metabolic regulatory pathway). NAD+/NMN provides the fuel substrate for sirtuin enzymes and ETC enzyme cofactors. They are mechanistically complementary, not redundant.

Is SS-31 FDA approved?

Not yet as of mid-2026. The Phase III EMBARK trial in Barth syndrome met its primary endpoint, and FDA approval review is underway for that rare disease indication. For heart failure with preserved ejection fraction and other indications, Phase III has not been completed. For biohacker use, SS-31 is a research chemical.

COMPOUND LIBRARY·SS-31

COMPOUND PROFILE · PEPPERLEDGER

SS-31 (Elamipretide)

Hazel Szeto & Peter Schiller · Cornell University · Licensed to Stealth BioTherapeutics

Type

Synthetic tetrapeptide — D-Arg-2′6′-Dmt-Lys-Phe-NH₂ — cell-permeable, mitochondria-targeting peptide

Class

Mitochondria-targeting peptide (MTP) — selectively concentrates in inner mitochondrial membrane; cardiolipin protector

Administration

Subcutaneous injection (clinical trials and biohacker use)

Half-life

~2–3 hours in plasma; concentrates rapidly in mitochondria

Most studied use

Cardiac protection and heart failure · Primary mitochondrial disease · Mitochondrial aging · Energy and physical performance

Regulatory status

Not FDA-approved · Phase III trial (EMBARK) completed for Barth syndrome · Phase II trials for heart failure, macular degeneration, primary mitochondrial myopathy · Research chemical

Human evidence

Strong mechanistically — Phase II/III data in disease populations; limited healthy adult data

Preclinical evidence

Exceptional — one of the most studied mitochondria-targeting peptides; extensive cardiac, kidney, and aging models

EDUCATIONAL TOOL — NOT MEDICAL ADVICE

What is SS-31?

SS-31 (elamipretide) occupies a unique position in the peptide space: it's one of the few compounds in this guide that was purpose-engineered to target mitochondria directly. Where most peptides act through cell-surface receptors, SS-31 crosses cell membranes and concentrates in the inner mitochondrial membrane — specifically binding cardiolipin, a phospholipid essential for the electron transport chain. This targeted mitochondrial action makes SS-31 the most mechanistically specific mitochondrial intervention available, distinct from MOTS-c (which signals from mitochondrial DNA) and NAD+ precursors (which fuel mitochondrial enzymes).

Cardiolipin is the structural and functional foundation of the inner mitochondrial membrane. It stabilizes the electron transport chain complexes, maintains the proton gradient necessary for ATP synthesis, and protects cytochrome c from being released as an apoptosis signal. With aging and cellular stress, cardiolipin oxidizes and its protective function degrades — contributing to mitochondrial dysfunction, reduced ATP production, and increased oxidative stress. SS-31 binds cardiolipin, prevents its oxidation, and restores ETC function.

The clinical evidence is strongest in cardiovascular disease. Phase II trials in heart failure with preserved ejection fraction (HFpEF) showed significant improvements in 6-minute walk distance and exercise capacity. A Phase III trial (EMBARK) in Barth syndrome — a rare genetic mitochondrial disease — met its primary endpoint. This is a compound with genuine clinical trial history, not just preclinical data. For biohackers, the application is mitochondrial optimization: better energy production, improved exercise capacity, and potentially slowed mitochondrial aging — extrapolated from disease-population data to healthy adults.

How it works

Cardiolipin Binding and ETC Protection

SS-31's primary mechanism is binding to cardiolipin in the inner mitochondrial membrane. Cardiolipin serves as an organizational anchor for ETC complexes I, III, IV, and V, maintaining the curvature and integrity of the inner membrane and sequesters cytochrome c. SS-31's binding: protects cardiolipin from peroxidation by reactive oxygen species, maintains the mitochondrial membrane potential, and stabilizes cytochrome c — keeping it in the ETC rather than releasing it as an apoptosis signal.

Electron Transport Chain Enhancement and ROS Reduction

By stabilizing cardiolipin and ETC complex assembly, SS-31 improves electron flow through the ETC, increases ATP production efficiency, and reduces electron leak (which produces superoxide). The net effect: more ATP from the same substrate, less oxidative stress as a byproduct. SS-31's alternating cationic and aromatic amino acids also give it intrinsic free radical scavenging activity — dual mechanism of structural protection AND direct ROS scavenging.

Aging and Mitochondrial Dysfunction

Mitochondrial dysfunction is one of the nine hallmarks of aging. Cardiolipin oxidation and ETC dysfunction accumulate with age in all tissues — heart, brain, skeletal muscle, kidney. Animal models show SS-31 reverses many of these age-related mitochondrial changes: improved ETC function, restored ATP production, reduced mitochondrial ROS, and improved function in aged cardiac and skeletal muscle. These findings are the basis for the longevity and healthy aging applications.

What the research shows

HUMAN AND PRECLINICAL EVIDENCE

STUDYJournal of Cardiac Failure · 2020

Effects of elamipretide on left ventricular function in heart failure with reduced ejection fraction (PROGRESS-HF)

Butler J et al.

PROGRESS-HF, a randomized, double-blind, placebo-controlled Phase 2 trial in 71 adults with heart failure with reduced ejection fraction. Elamipretide (4 or 40 mg daily for 4 weeks) was well tolerated but did NOT significantly improve left-ventricular function (LVESV) versus placebo. An honest counterweight: elamipretide's strong mitochondrial-bioenergetic rationale has not yet produced a positive human cardiac-efficacy result.

View on PubMed →

STUDYNeurology · 2018

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

Karaa A, Haas R, Goldstein A et al.

Randomized, double-blind, placebo-controlled dose-escalation trial (MMPOWER) in 36 adults with primary mitochondrial myopathy. IV elamipretide improved the 6-minute walk distance dose-dependently (highest dose ~51 m gain vs. ~3 m on placebo after adjustment, p=0.03), while other endpoints — including muscle strength and fatigue — did not significantly change. Established safety, tolerability, and the walk-distance signal that led to larger trials.

View on PubMed →

STUDYeLife · 2020

SS-31 Reverses Mitochondrial Dysfunction and Rescues Diastolic Function in Aging

Chiao YA, Zhang H, Sweetwyne M et al.

Aged mice. SS-31 reversed mitochondrial dysfunction in aged cardiac muscle, improved diastolic function, and reduced ROS. Key aging model evidence supporting the anti-aging application extrapolated to biohacker healthy adult use.

View on PubMed →

WHAT THE RESEARCH SHOWS

✓KNOWN

✓Cardiolipin binding and ETC stabilization — well-characterized mechanism
✓Exercise capacity improvement in HFpEF Phase II RCT
✓Safety and tolerability in Phase II/III disease trials
✓Reversal of mitochondrial aging in aged animal models
✓Phase III EMBARK trial completion in Barth syndrome — met primary endpoint

?UNCERTAIN

?Whether benefits in diseased mitochondria translate to healthy aging adults
?Optimal dosing and frequency for healthy adult biohacker use
?Long-term effects beyond Phase II/III trial durations
?Interaction effects with exercise and other mitochondrial interventions
?Whether subjective energy improvements translate to objective performance metrics in healthy adults

What the community reports

—Improved energy and reduced fatigue — the most consistently reported effect; described as cleaner and more sustained; typically noticeable within 1–2 weeks

—Exercise performance improvement — endurance specifically; faster recovery between sessions

—Cognitive clarity — improved mental energy alongside physical energy; consistent with mitochondrial function improvements in brain tissue

—The mitochondrial longevity stack: SS-31 + MOTS-c + NAD+ — three-pronged mitochondrial optimization, each targeting a different mechanism

—Subtle but consistent improvement — effects are more gradual than compounds with acute subjective impact; careful tracking over weeks reveals meaningful changes

—Clean side-effect profile — injection site reactions occasionally; otherwise minimal

Common misconceptions

"SS-31 is just another antioxidant."

REALITY

SS-31 specifically targets and concentrates in the inner mitochondrial membrane — accumulating several hundred-fold compared to cytosolic concentrations. Its cardiolipin-binding, ETC-stabilizing mechanism is categorically different from systemic antioxidants like vitamin C or NAD+. It's a mitochondrial structural protectant, not a general antioxidant.

"If it works in heart failure, it will definitely work in healthy people."

REALITY

Compounds that rescue severely dysfunctional mitochondria don't necessarily produce proportional benefits in healthy mitochondria. The question of whether SS-31 optimizes healthy mitochondria or primarily rescues damaged ones is not resolved. The animal aging models are encouraging; healthy human data is limited.

"SS-31 is nearly FDA-approved."

REALITY

The Phase III EMBARK trial in Barth syndrome was completed, but FDA approval requires a complete application and regulatory review — that process is still underway as of mid-2026. For HFpEF and other indications, Phase III has not been completed. FDA approval is not imminent for any indication.

MITOCHONDRIAL STACK

SS-31 (inner membrane structural protection) pairs with MOTS-c (AMPK activation, metabolic signaling) and NAD+ (sirtuin activation, ETC enzyme fuel). Three different entry points into mitochondrial health — complementary, not redundant.

RECONSTITUTION CALCULATOR

Peptide in vial (mg)BAC water (mL)Desired dose (mcg)

EDUCATIONAL TOOL — NOT MEDICAL ADVICE · VERIFY WITH YOUR CLINICIAN

AI RESEARCHER PREVIEW

I want to add SS-31 to my MOTS-c and NAD+ stack. What dose and timing makes sense for energy optimization?

The SS-31 + MOTS-c + NAD+ stack is the most mechanistically coherent mitochondrial optimization combination available — each compound addresses a different layer of mitochondrial function. Here's how to integrate SS-31 specifically. Mechanism orientation: SS-31 protects the structural integrity of the inner mitochondrial membrane by binding cardiolipin — it prevents the cardiolipin oxidation that degrades ETC complex function with age and stress. MOTS-c activates AMPK and improves metabolic signaling. NAD+/NMN fuels the sirtuin and ETC enzyme systems. These are genuinely different mechanisms at different levels of the same system. Dose: 1–2 mg subcutaneous daily. The Phase II HFpEF trial used weight-based dosing (0.05–0.25 mg/kg), which for most users translates to 3.5–17.5 mg — higher than community biohacker dosing. The community converges on 1–5 mg daily, with 2 mg being the most common midpoint. Start at 1 mg and assess over 2–3 weeks. Timing: morning — energy enhancement aligns with daytime metabolic activity. No strong argument for specific meal timing; inject and proceed with your day. With your existing stack: run simultaneously. No known interactions between SS-31, MOTS-c, and NAD+ precursors — the mechanisms are complementary and additive in theory. Cycle: 4–8 weeks on, 2–4 weeks off. What to track: daily energy rating (consistent scale, same time each morning), exercise performance metric (something objective you can repeat weekly — time trial, grip strength, training volume), and resting heart rate if you track it (an indirect signal for cardiovascular efficiency). SS-31 effects are gradual — you're looking for a trend over weeks, not an acute subjective shift like you'd feel from caffeine or even ipamorelin. The community is consistent on this: the energy improvement is real but builds over time. Don't assess at 1 week. Assess at week 4. What does your current MOTS-c and NAD+ protocol look like — doses and timing?

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Authoritative sources

Registered trials and extra catalog links. These are not Study cards — a registry page is not proof of efficacy.

ClinicalTrials.gov · completed · NCT05168774
Elamipretide (SS-31) in Friedreich ataxia
ClinicalTrials.gov · terminated · NCT03323749
Elamipretide in primary mitochondrial myopathy