Phase 3 Clinical Trials • Larimar Therapeutics

SS-31: The Cardiolipin-Targeting Peptide

Last updated: March 2026

SS-31 (Elamipretide) is a synthetic tetrapeptide that specifically binds cardiolipin — a phospholipid unique to the mitochondrial inner membrane — stabilizing mitochondrial structure and electron transport chain function. Developed by Stealth BioTherapeutics, it has advanced to Phase 3 clinical trials for three conditions: Barth syndrome, heart failure with preserved ejection fraction, and dry AMD.

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What Is SS-31?

SS-31 (Elamipretide) is a tetrapeptide developed by Stealth BioTherapeutics (now Larimar Therapeutics) that specifically targets cardiolipin — a unique phospholipid in the mitochondrial inner membrane.

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Cardiolipin Target

SS-31 specifically binds to cardiolipin, a unique phospholipid found only in the mitochondrial inner membrane. This targeted delivery is unique among mitochondrial therapeutics.

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Membrane Stabilization

By binding to cardiolipin, SS-31 stabilizes the mitochondrial inner membrane structure, preventing cytochrome c release and protecting against apoptosis.

ATP Production

Improves mitochondrial energy production by optimizing the electron transport chain function, leading to increased ATP synthesis.

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Reduced Oxidative Stress

Decreases mitochondrial reactive oxygen species (ROS) production, protecting cells from oxidative damage associated with aging and disease.

What the Research Shows

SS-31 has advanced further than most mitochondrial peptides, with Phase 3 trials completed.

📋 Clinical Status Phase 3 Orphan Drug

SS-31 (Elamipretide) has completed Phase 3 trials for Barth syndrome and is in trials for heart failure and AMD. It is not yet FDA approved but has received Orphan Drug designation.

Barth Syndrome (Phase 3)
Improvement in left ventricular stroke volume
Positive
Heart Failure (Phase 2/3)
Improvement in exercise capacity
Positive
Age-related Macular Degeneration
Phase 2 trials for geographic atrophy
Ongoing
Mitochondrial Myopathy
Improvement in mitochondrial function biomarkers
Positive

Study Citations

Study 1 — Cardiolipin Binding
SS-31 binds to cardiolipin and protects mitochondrial structure and function
Szeto HH et al. JACC, 2014
PMID: 24731664
Study 2 — Barth Syndrome
Elamipretide in patients with Barth syndrome: Phase 3 trial results
Chatfield KC et al. Nat Med, 2019

Key Takeaways

✅ What We Know
  • Tetrapeptide targeting cardiolipin specifically
  • Developed by Larimar Therapeutics (formerly Stealth BioTherapeutics)
  • Phase 3 trials completed for Barth syndrome
  • Received FDA Orphan Drug designation
  • Improves mitochondrial ATP production
  • Reduces oxidative stress
⚠️ What We Don't Know
  • FDA approval timeline
  • Pricing if approved
  • Accessibility after approval
  • Long-term safety in broader populations

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🔗 Related Resources

🧬 Humanin Research ⚡ MOTS-c Guide 📖 Peptide Encyclopedia 🧮 Dosing Calculator
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⚠️ Important Disclaimer

This page is for educational and informational purposes only. SS-31 (Elamipretide) is not yet FDA approved but has completed Phase 3 trials. It is available only through clinical trials or compassionate use programs. Always consult a qualified healthcare provider.