SS-31

What It Is

SS-31, now marketed as FORZINITY (elamipretide HCl), is a mitochondria-targeted tetrapeptide (D-Arg-DMT-Lys-Phe-NH2) that selectively binds to cardiolipin in the inner mitochondrial membrane, stabilizing cristae structure, reducing oxidative stress, and enhancing ATP production. On September 19, 2025, it became the first FDA-approved mitochondria-targeted therapeutic, receiving accelerated approval for Barth syndrome — a rare, life-limiting genetic disorder affecting approximately 150 individuals in the United States. The approval was supported by the TAZPOWER clinical trial, which demonstrated improved knee extensor muscle strength in Barth syndrome patients. A comprehensive review published in the International Journal of Molecular Sciences (January 2026) detailed SS-31's broad therapeutic potential across cardiovascular, ophthalmic, renal, and neurodegenerative applications. Notably, SS-31 selectively improves aged mitochondria without affecting young healthy mitochondria — increasing ATP production, reducing H2O2 output, and reversing energetic deficits in aged mouse skeletal muscle. A 2024 study in Scientific Reports demonstrated that SS-31 treatment ameliorated cardiac mitochondrial morphology and defective mitophagy in a murine model of Barth syndrome. The Phase 2/3 clinical trial program and precise cardiolipin-binding mechanism make SS-31 arguably the most clinically validated peptide in the mitochondrial medicine space. Active clinical development continues for heart failure with preserved ejection fraction (HFpEF), primary mitochondrial myopathy, and age-related macular degeneration (dry AMD). In 2026, SS-31 is the only mitochondrial peptide with Phase III trial data, and older adults receiving SS-31 in clinical studies showed improved mitochondrial respiration and reduced oxidative stress — their muscle mitochondria moved measurably toward younger adult profiles. As of May 2026, SS-31 remains the most clinically validated compound in the emerging field of mitochondrial medicine, with growing research interest driven by longevity and anti-aging science communities. The most common adverse reactions are injection site reactions.

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Citations

1. [1] FDA Approves FORZINITY (elamipretide) for Barth Syndrome — Stealth BioTherapeutics, September 2025 PubMed
2. [2] UMDF — FDA Approves First Mitochondrial Disease Therapy PubMed
3. [3] Johns Hopkins Hub — FDA approves drug for Barth syndrome, September 2025 PubMed
4. [4] Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential — IJMS. 2026 PubMed
5. [5] SS-31 treatment ameliorates cardiac mitochondrial morphology in Barth syndrome model — Scientific Reports. 2024 PubMed

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