SS-31 (Elamipretide)
Granted FDA accelerated approval Sept 19, 2025 as FORZINITY (elamipretide) to improve muscle strength in Barth syndrome patients ≥30 kg — the first FDA-approved mitochondria-targeted therapeutic. Not approved for heart failure or primary mitochondrial myopathy, both of which failed their primary endpoints in Phase 2/3 trials.
SS-31 is a cell-permeable aromatic-cationic tetrapeptide that concentrates in the inner mitochondrial membrane, proposed to bind and stabilize cardiolipin, preserving cristae structure and electron tr...
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SS-31 is a cell-permeable aromatic-cationic tetrapeptide that concentrates in the inner mitochondrial membrane, proposed to bind and stabilize cardiolipin, preserving cristae structure and electron transport chain organization and reducing reactive oxygen species production. Its clinical trial history is a useful, honest case study in mixed results: it improved 6-minute walk distance and fatigue in Barth syndrome (the basis for its 2025 approval), but did not significantly improve left ventricular function in a heart failure trial (PROGRESS-HF) or meet its primary endpoints in a primary mitochondrial myopathy trial (MMPOWER-3) — it was generally well tolerated across all of these, with injection-site reactions as the most frequent adverse event.