SS-31

SS-31 in the research literature

SS-31 comes from the Szeto-Schiller peptide series. Zhao and colleagues, 2004, set out the design, alternating aromatic and basic residues with 2',6'-dimethyltyrosine as the scavenging group, and showed the peptides concentrate about a thousand-fold in the inner mitochondrial membrane. Their assays were tert-butylhydroperoxide and 3-nitropropionic acid toxicity in N2A cells, swelling and calcium-induced cytochrome c release in isolated mitochondria, and an ex vivo heart reperfusion model; analogues lacking dimethyltyrosine were inactive. Birk and colleagues, 2013, used a polarity-sensitive fluorescent analogue to show high-affinity binding to cardiolipin and inhibition of cytochrome c peroxidase activity, with rat renal ischaemia as the in vivo model. Szeto, 2014, reviews the whole programme.

The clinical record is mixed. The Karaa 2023 trial, MMPOWER-3, randomised 218 participants and did not meet either primary endpoint. The US FDA still granted accelerated approval to elamipretide as Forzinity in September 2025, for a different rare indication.

SS-31 vs MOTS-C: which to order

Both sit under mitochondrial research but share nothing chemically. SS-31 is a synthetic tetrapeptide, D-Arg-Dmt-Lys-Phe-NH2, 639.8 Da, built around a non-natural dimethyltyrosine and studied as a cardiolipin binder on the inner membrane. MOTS-c is a 16-residue mitochondria-derived peptide, MRWQEMGYIFYPRKLR, 2,174.6 Da, with no licensed form anywhere. Elamipretide, by contrast, became a US-licensed medicine in 2025, though this research powder is not that product. The label gives the peptide mass; vendors supply SS-31 as an acetate or trifluoroacetate salt, and the lab report, once published on this page, will show the measured mass of the peptide itself. For a first order to buy SS-31 UK, take the 10mg vial; the 50mg suits repeated assay runs, and packs of two, three or five 10mg vials take 10, 20 and 30% off. Same-day dispatch from Manchester, free UK delivery over £40.