What it is

SS-31 is a four-amino-acid peptide designed by Hazel Szeto and Peter Schiller. Its alternating positive charges and aromatic rings let it pass through cell membranes and concentrate in the inner mitochondrial membrane. It was developed by Stealth BioTherapeutics as elamipretide.

How it works

It binds cardiolipin, a fat unique to the inner mitochondrial membrane that holds the energy-producing machinery in place. Stabilizing cardiolipin improves the efficiency of ATP production and reduces the leak of reactive oxygen species.

What the research shows

Trials in Barth syndrome, a rare inherited disorder of cardiolipin, supported its accelerated approval.
It has also been studied in primary mitochondrial myopathy, heart failure and age-related eye disease, with mixed results.

Regulatory status

FDA granted accelerated approval on September 19, 2025 for Forzinity (elamipretide) to treat Barth syndrome in patients weighing at least 30 kg. Continued approval depends on confirmatory trials. Research-grade SS-31 is not the approved product.

Storage and handling

Lyophilized (freeze-dried) powder is most stable sealed, dry and protected from light. Laboratory practice is to keep unopened vials frozen at about -20 °C for long-term storage, or refrigerated at 2 to 8 °C for shorter periods. After reconstitution, keep the solution refrigerated at 2 to 8 °C, avoid repeated freeze-thaw cycles and use aseptic technique for every draw. Formal stability data in solution has not been published for most research peptides, so follow the supplier's label and certificate of analysis.

Reconstitution math

To work out concentration, volume and U-100 syringe units for any vial size, use the reconstitution calculator with SS-31 selected. Always confirm the vial content against the label and the batch's certificate of analysis.

Key references

FDA press release. FDA grants accelerated approval for first treatment for Barth syndrome. September 2025.
Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol. 2014.
Search PubMed for SS-31 studies
Official drug labeling on DailyMed

Educational content only

Peptide Knowledge is an educational reference. Nothing on this site is medical advice, a treatment recommendation or dosing guidance. Many compounds described here are not approved for human use and are sold for laboratory research only. Talk to a licensed clinician before starting, stopping or changing any medication or supplement.

SS-31