Klotho (KP1) vs SS-31
Klotho (KP1) and SS-31 (elamipretide) meet in two places: both have been studied in kidney injury, and both act on mitochondria, by different routes. SS-31 is a four-amino-acid peptide that binds cardiolipin in the inner mitochondrial membrane and has an accelerated FDA approval for one rare disease. KP1 is a 30-amino-acid piece of the Klotho protein, studied only in cells and mice. This page compares them as research compounds.
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| Klotho (KP1) | SS-31 | |
|---|---|---|
| What it is | 30-amino-acid fragment of human alpha-Klotho | Tetrapeptide D-Arg-Dmt-Lys-Phe-NH2 (elamipretide) |
| Main target | TGF-beta receptor 2; mitochondrial protein ATAD3A in kidney injury | Cardiolipin in the inner mitochondrial membrane |
| Kidney research | Mouse fibrosis and acute kidney injury models | Aged-mouse and kidney injury models |
| Human data | None | Clinical trials; FDA accelerated approval for Barth syndrome (September 2025) |
| Status | Research compound | Approved only for Barth syndrome, pending a confirmatory trial |
| Peptx availability | Not stocked, waitlist on this page | UK single vials and Factory Direct kits |
- What it is
- 30-amino-acid fragment of human alpha-KlothoTetrapeptide D-Arg-Dmt-Lys-Phe-NH2 (elamipretide)
- Main target
- TGF-beta receptor 2; mitochondrial protein ATAD3A in kidney injuryCardiolipin in the inner mitochondrial membrane
- Kidney research
- Mouse fibrosis and acute kidney injury modelsAged-mouse and kidney injury models
- Human data
- NoneClinical trials; FDA accelerated approval for Barth syndrome (September 2025)
- Status
- Research compoundApproved only for Barth syndrome, pending a confirmatory trial
- Peptx availability
- Not stocked, waitlist on this pageUK single vials and Factory Direct kits
Two routes into the mitochondria
SS-31 is built to reach mitochondria. It binds cardiolipin, a lipid of the inner mitochondrial membrane, which stabilises the electron transport chain and reduces oxidative damage.
KP1 was found for a different reason: it blocks TGF-beta receptor 2, the receptor behind fibrosis. A 2026 mouse study then reported a second action in acute kidney injury. KP1 entered kidney tubule cells, bound the mitochondrial protein ATAD3A and prevented its breakdown, which limited cytochrome c release and cell death. That result comes from one study by the group that discovered KP1.
Very different evidence levels
SS-31 has years of animal work and human trials behind it. In September 2025 it received FDA accelerated approval for Barth syndrome, a rare inherited disorder of cardiolipin, with continued approval depending on a confirmatory trial. It is not approved for anything else.
KP1 has five published cell and mouse studies since 2022, all from one group, and no human data.
Bottom line for research labs
SS-31 is the established mitochondria-targeted peptide, with human data and one approval. Klotho (KP1) is an early-stage TGF-beta receptor blocker whose mitochondrial action rests on a single mouse study. For mitochondrial research today SS-31 is the documented choice; KP1 is one to watch if other laboratories reproduce its kidney results.