Summary
SS-31, now the approved drug elamipretide, is a four-residue peptide that binds cardiolipin in the inner mitochondrial membrane. In September 2025 the FDA granted it accelerated approval for Barth syndrome, a rare inherited disease of cardiolipin metabolism, making it the first approved therapy for that condition.
Structure
D-Arg-Dmt-Lys-Phe-NH2, where Dmt is 2′,6′-dimethyltyrosine. Alternating aromatic and basic residues let it cross membranes and concentrate in the inner mitochondrial membrane.
How it works
Cardiolipin anchors the electron transport chain. SS-31 binds it, stabilizing cristae structure, improving electron transport efficiency and reducing reactive oxygen species production. It was developed by Hazel Szeto and Peter Schiller, hence the name.
Research use cases
Areas where SS-31 has been studied. Inclusion here does not mean it works for that purpose.
- Barth syndrome (approved)
- Primary mitochondrial myopathy (phase 3)
- Heart failure and age-related mitochondrial decline (studied)
- Dry age-related macular degeneration (studied)
What the research found
Mechanism review
Szeto describes how SS-31 selectively targets cardiolipin, protects cristae structure and restores mitochondrial bioenergetics across models of ischaemia, heart failure and ageing.1
Barth syndrome trial
A randomized crossover trial did not meet its primary endpoint at 12 weeks, but the open-label extension showed improvements in six-minute walk distance and fatigue over 36 weeks and beyond.2
FDA approval
The FDA granted accelerated approval in 2025 based on improvement in knee extensor muscle strength, with continued approval contingent on confirmatory evidence.3
Safety and open questions
Injection-site reactions are the most common adverse effect. Prescribing information should be consulted for the approved product.
Regulatory status
FDA accelerated approval (Forzinity, September 2025) for Barth syndrome. Prescription only.
Status was accurate when this page was last reviewed on October 26, 2026. Regulations change; check with the relevant authority before relying on it.
SS-31: common questions
Is SS-31 the same as elamipretide?
Yes. SS-31 is the research name; elamipretide is the drug name; Forzinity is the brand name of the approved product.
Is SS-31 approved for human use?
FDA accelerated approval (Forzinity, September 2025) for Barth syndrome. Prescription only.
References
- Szeto HH. (2014). First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. British Journal of Pharmacology.
- Thompson WR, Hornby B, Manuel R, et al. (2021). A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism. Genetics in Medicine.
- U.S. Food and Drug Administration (2025). FDA Grants Accelerated Approval for First Treatment for Barth Syndrome. FDA press announcement.
Links open a PubMed search for the exact title, or the original source where one is given.