SS-31
Mitochondria-targeted tetrapeptide (D-Arg-2'6'-Dmt-Lys-Phe-NH₂) that selectively binds cardiolipin on the inner mitochondrial membrane
- Class
- Mitochondrial peptide
- Half-life
- ~1-2 hours
- Route
- Subcutaneous (SubQ)
- Cadence
- Daily
- Evidence
- Human clinical trials
Overview
SS-31 (elamipretide) is the first FDA-approved mitochondria-targeted peptide — approved in September 2025 as Forzinity for Barth syndrome, a rare genetic disorder where the mitochondrial membrane lipid cardiolipin breaks down and causes heart and muscle failure. It's a four-amino-acid peptide engineered to slip through cell membranes, embed itself in the inner mitochondrial membrane, and physically stabilize cardiolipin — the phospholipid that holds the entire electron-transport chain together. When cardiolipin degrades (as it does with age, disease, or genetic mutations), ATP production drops, reactive oxygen species spike, and cells slide into dysfunction. SS-31 reverses that process at the membrane level.
The mechanism is one of the most precisely characterized in the peptide field. SS-31 binds cardiolipin through electrostatic and hydrophobic interactions, which stabilizes mitochondrial cristae structure (the folds where ATP is made), reduces electron leak from the respiratory chain (the source of most oxidative damage), and restores Complex I, III, and IV activity. The result is measurable: improved oxygen consumption, higher ATP output, less oxidative stress. In failing human heart tissue treated ex vivo, SS-31 improved mitochondrial respiration by 10-15% within hours.
Outside of Barth syndrome, SS-31 is in Phase 2 and 3 trials for heart failure, primary mitochondrial myopathy, age-related macular degeneration, and Friedreich's ataxia — but those indications are not yet approved. The peptide sold in research markets is unregulated (purity and content vary), and it's expensive compared to oral mitochondrial interventions like NAD+ precursors. Injection-site reactions are common — roughly 80% of clinical-trial participants get redness, itching, or mild pain at the injection site. Otherwise, the safety profile has been clean through Phase 3.
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
- FDA-approved only for Barth syndrome (Forzinity brand). All other uses are off-label or research-market unregulated peptide — purity and actual peptide content vary wildly between sellers.
- Injection-site reactions are the dominant side effect — roughly 80% of trial participants experienced redness, itching, pain, or swelling at the subcutaneous injection site. Most are mild to moderate and resolve within hours. Rotating injection sites helps.
- Headache, nausea, and mild GI discomfort reported in a subset of trial participants — generally transient and low-frequency.
+ 3 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching SS-31.
- Physical endurance markers (6-minute walk distance used in trials)
- Subjective fatigue and recovery — most users notice energy shifts after 4-6 weeks
- Injection-site reactions (track severity and whether rotation helps)
- Cardiac function if you have underlying heart disease (ejection fraction, NT-proBNP)
- Skeletal muscle strength if using for myopathy
- Oxidative stress markers if accessible (8-OHdG, F2-isoprostanes)
Frequently asked questions
What is SS-31?
Mitochondria-targeted tetrapeptide (D-Arg-2'6'-Dmt-Lys-Phe-NH₂) that selectively binds cardiolipin on the inner mitochondrial membrane. SS-31 (elamipretide) is the first FDA-approved mitochondria-targeted peptide — approved in September 2025 as Forzinity for Barth syndrome, a rare genetic disorder where the mitochondrial membrane lipid cardiolipin breaks down and causes heart and muscle failure. It's a four-amino-acid peptide engineered to slip through cell membranes, embed itself in the inner mitochondrial membrane, and physically stabilize cardiolipin — the phospholipid that holds the entire electron-transport chain together. When cardiolipin degrades (as it does with age, disease, or genetic mutations), ATP production drops, reactive oxygen species spike, and cells slide into dysfunction. SS-31 reverses that process at the membrane level.
How is SS-31 administered?
Subcutaneous (SubQ), typically daily.
What is the half-life of SS-31?
~1-2 hours — Short plasma half-life, but accumulates 1,000-5,000× in mitochondria and persists there for hours.
Is SS-31 approved for human use?
SS-31 is investigational — not approved by the FDA, EMA, or MHRA for human use at the time of writing.
What does the evidence show for SS-31?
Evidence tier: Human clinical trials. TAZPOWER trial (Barth syndrome, Phase 2/3, Thompson 2021): 48 weeks of elamipretide 40 mg daily improved 6-minute walk distance and muscle strength vs natural-history controls — the data that led to FDA approval.
What is commonly monitored when researching SS-31?
Commonly tracked markers + signals: Physical endurance markers (6-minute walk distance used in trials), Subjective fatigue and recovery — most users notice energy shifts after 4-6 weeks, Injection-site reactions (track severity and whether rotation helps), Cardiac function if you have underlying heart disease (ejection fraction, NT-proBNP), Skeletal muscle strength if using for myopathy, Oxidative stress markers if accessible (8-OHdG, F2-isoprostanes).
Related compounds
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.