SS-31 (Elamipretide)

SS-31, also known as elamipretide, is a mitochondria-targeted tetrapeptide with the sequence D-Arg-Dmt-Lys-Phe-NH₂, where Dmt is 2',6'-dimethyltyrosine. Developed by Hazel Szeto and Peter Bhatt at Weill Cornell Medical College, SS-31 belongs to the Szeto-Schiller (SS) family of peptides characterized by an alternating aromatic-cationic motif that enables selective concentration in the inner mitochondrial membrane. The peptide accumulates in mitochondria at concentrations 1,000-5,000 fold higher than extracellular levels, driven by the mitochondrial membrane potential, and selectively binds to cardiolipin — a phospholipid unique to the inner mitochondrial membrane that is essential for electron transport chain function.

The primary mechanism of SS-31 involves stabilization of cardiolipin-cytochrome c interactions on the inner mitochondrial membrane. Cardiolipin normally anchors cytochrome c to the membrane surface, facilitating efficient electron transfer between Complex III and Complex IV of the electron transport chain. Under oxidative stress, cardiolipin peroxidation disrupts this interaction, leading to cytochrome c dissociation, electron leak, increased reactive oxygen species (ROS) generation, and ultimately mitochondrial permeability transition and apoptosis. SS-31 binds to cardiolipin and prevents its peroxidation, preserving cristae structure, optimizing electron transport efficiency, and reducing ROS emission. Research by Birk et al. demonstrated that SS-31 restores mitochondrial cristae architecture in aged cardiomyocytes to a morphology resembling young tissue.

Research development of elamipretide has focused on mitochondrial myopathy and heart failure models. Phase 2 research studies in primary mitochondrial myopathy (Barth syndrome and other genetic mitochondrial disease models) have demonstrated improvements in the 6-minute walk test and research-subject-reported outcomes. In heart failure with reduced ejection fraction models, the PROGRESS-HF research study investigated elamipretide's effects on left ventricular volumes and function. Preclinical research has explored applications in ischemia-reperfusion injury, age-related organ dysfunction, neurodegenerative diseases, and skeletal muscle aging, all conditions associated with mitochondrial dysfunction and cardiolipin remodeling.