Is SS-20 legal in the United States?

The sibling of SS-31, the peptide that became the approved drug elamipretide. SS-20 cannot scavenge free radicals at all, which made it the control that proved a point, and it works anyway in rats and mice. There is no human study and no registered trial.

SS-20 is Phe-D-Arg-Phe-Lys-NH2, one of the Szeto-Schiller peptides developed at Weill Cornell. Its interest comes from what it lacks.

Mechanism: Selective targeting of cardiolipin in the inner mitochondrial membrane, where it preserves the methionine 80 to iron ligation of cytochrome c. Ischaemia disrupts that ligation, producing a globin-like pentacoordinated heme that inhibits electron transport and turns cytochrome c into an oxygenase, which peroxidises cardiolipin and drives OPA1 degradation and cytochrome c release.

Regulatory history: Not approved and never submitted. Its sibling SS-31, elamipretide, received accelerated United States approval in 2025 for Barth syndrome. SS-20 has no regulatory status of any kind.

Approves prescription drugs by indication and polices unapproved products, including peptides sold online. Compounding pharmacies may prepare some compounds under a prescription when the FDA places them on a permitted bulk-substances category.

The classification above is the The Longevity Archive reading of U.S. Food and Drug Administration listings for SS-20 at the reviewed date, not a legal opinion. Rules change, and importing, prescribing and possessing a compound can each be treated differently. Check the regulator directly before acting on anything here.