Elamipretide or SS-31 (D-Arg-2', 6'-dimethyltyrosine-Lys-Phe-NH2) is a mitochondria-targeted antioxidant. Elamipretide, is a peptide compound that readily penetrates cell membranes, and targets the inner mitochondrial membrane where it binds reversibly to cardiolipin. In preclinical or clinical studies, elamipretide increases mitochondrial respiration, improves the electron transport chain function and ATP production and reduces formation of pathogenic ROS levels. This elamipretide-cardiolipin association has been shown to normalize the structure of the inner mitochondrial membrane, thereby improving mitochondrial function. Functional benefit is achieved through improvement of ATP production and interruption and potential reversal of damaging oxidative stress. Stealth BioTherapeutics is investigating elamipretide in late stage clinical studies in three primary mitochondrial diseases—primary mitochondrial myopathy, Barth syndrome and Leber’s hereditary optic neuropathy – as well as an earlier stage clinical study in dry age-related macular degeneration.