SS-31 (Elamipretide)

SS-31 (D-Arg-Dmt-Lys-Phe-NH2, also called elamipretide or Bendavia) is a tetrapeptide with a molecular weight of 639.8 Da. CAS number: 736992-21-5. It was developed by Dr. Hazel Szeto at Weill Cornell Medical College, which is why it's sometimes called a 'Szeto-Schiller peptide' (SS peptide).

What makes SS-31 unique is its targeting mechanism. Most drugs distribute throughout the body and reach mitochondria only at low concentrations. SS-31 has an alternating aromatic-cationic structure that drives it to accumulate on the inner mitochondrial membrane at concentrations 1,000 to 5,000 times higher than in the surrounding cytoplasm. It gets where it needs to go.

Once there, SS-31 binds to cardiolipin, a phospholipid found almost exclusively on the inner mitochondrial membrane. Cardiolipin is the scaffold that holds electron transport chain complexes in the correct position and orientation. In aged cells, cardiolipin becomes oxidized and loses its structure. The electron transport chain complexes drift apart, electron transfer becomes inefficient, electrons leak onto oxygen to form superoxide, and the mitochondrion produces less ATP and more damaging free radicals. SS-31 stabilizes cardiolipin, restoring the whole system.

The speed of this effect is notable. A 2014 study in Aging Cell (PMID: 24888552) showed that a single IV dose of SS-31 reversed age-related diastolic dysfunction in old mice within one hour. A 2018 study in Cell Metabolism (PMID: 30017357) demonstrated that one hour of SS-31 treatment reversed mitochondrial dysfunction in aged mouse skeletal muscle, restoring energy production to near-youthful levels. These aren't gradual improvements over months. They're rapid, measurable changes that happen within an hour.

The clinical data is more modest. A Phase 2 trial published in JACC in 2016 (PMID: 27012404) tested elamipretide in heart failure patients with reduced ejection fraction. The treatment improved left ventricular volumes and function, though the trial was small. Larger Phase 3 trials are ongoing for both heart failure and Barth syndrome (a rare genetic mitochondrial disease).

SS-31 is not yet available as an FDA-approved medication. Some compounding pharmacies offer it, and it's used by practitioners who focus on mitochondrial health and longevity medicine. Typical research doses are 5-20 mg injected subcutaneously daily.

The longevity community is particularly interested in SS-31 because mitochondrial dysfunction is considered one of the primary hallmarks of aging. If a compound can rapidly restore mitochondrial function to near-youthful levels (as shown in mice), the implications for human aging are significant. The catch is that we don't yet know if the marked effects seen in mice translate to equivalent human benefits.

Store lyophilized SS-31 at -20C. Reconstitute with bacteriostatic water. Once reconstituted, store at 2-8C and use within 14-21 days.