SS-31

What Is SS-31?

SS-31 (elamipretide, formerly Bendavia and MTP-131) is a mitochondria-targeted tetrapeptide (D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2) that binds selectively to cardiolipin on the inner mitochondrial membrane. Cardiolipin is the phospholipid that anchors the electron transport chain complexes and shapes the cristae; in ageing, heart failure, ischaemia, and primary mitochondrial disease it oxidises and disorganises, electron leak rises, and ATP output falls.

SS-31 docks onto cardiolipin without disrupting it, stabilises cristae geometry, protects complex IV (cytochrome c oxidase) supercomplexes, reduces electron leak, and lowers reactive oxygen species production at the source rather than scavenging them downstream as a generic antioxidant would. The literature reports preserved ATP synthesis, reduced mitochondrial swelling under stress, protection against ischaemia-reperfusion injury, restored mitochondrial calcium handling, and improved bioenergetics in tissues with the highest mitochondrial density (heart, skeletal muscle, retina, kidney). The peptide crosses cell membranes through its alternating cationic and aromatic structure and accumulates roughly 1,000- to 5,000-fold in mitochondria relative to cytosol. Stealth BioTherapeutics has taken it through programmes in heart failure with preserved ejection fraction, primary mitochondrial myopathy, dry age-related macular degeneration, and Barth syndrome, and it received FDA approval as Forzinity for Barth syndrome in 2025. It is the most extensively studied mitochondria-targeted peptide in clinical development.