"Klotho" now turns up as a peptide name, but in the research literature it covers a protein, its fragments, a related protein, a gene variant and at least two short peptides. The findings that made Klotho famous do not all belong to the same molecule. This guide sorts out the names. For the KP1 evidence in detail, see our Klotho and KP1 research overview.
The names at a glance
| Name | What it is | Best-known finding |
|---|---|---|
| Alpha-Klotho | 1,012-amino-acid membrane protein, made mainly in the kidney | Co-receptor for the phosphate hormone FGF23 |
| Soluble Klotho | The outer part of alpha-Klotho, shed into the blood | Acts as a circulating hormone in mice |
| Beta-Klotho | A related 1,044-amino-acid protein | Co-receptor for FGF21 and FGF19 |
| KL-VS | A variant of the human Klotho gene | One copy linked to higher Klotho levels and better cognitive scores |
| αKL-F | A larger alpha-Klotho protein fragment | Improved cognition in mice when injected |
| KP1 | 30-amino-acid peptide, residues 57 to 86 of alpha-Klotho | Blocks TGF-beta receptor 2; less fibrosis in mouse kidneys and livers |
| KP6 | A different Klotho-derived peptide | Binds Wnt proteins; studied in diabetic mouse kidneys |
Protein lengths are from UniProt (human alpha-Klotho Q9UEF7, beta-Klotho Q86Z14).
The protein: where the famous results come from
Mice with a defective Klotho gene age early, with a short lifespan, hardened arteries, thin skin, bone loss and emphysema (Kuro-o et al., 1997). Mice engineered to make extra Klotho live longer (Kurosu et al., 2005). A single low dose of the full protein improved memory in aged rhesus monkeys, while a high dose did not (Castner et al., 2023). All three involve the whole protein, made by the animal's own genes or given as a protein.
The cognition story has two more parts. People with one copy of the KL-VS variant had higher Klotho levels and better cognitive scores, and mice overproducing Klotho did better on learning and memory tests (Dubal et al., 2014). A larger fragment, αKL-F, improved cognition in mice when injected, even though it did not cross into the brain (Leon et al., 2017).
The peptides: KP1 and KP6
KP1 was found in 2022 by screening peptides taken from the human Klotho sequence for one property: blocking TGF-beta, the main signal behind fibrosis. It binds TGF-beta receptor 2, and in mouse models it reduced kidney fibrosis, preserved kidney function and restored the kidneys' own Klotho (Yuan et al., 2022). Later mouse studies covered senescence markers in fibrotic kidneys, acute kidney injury and liver fibrosis. KP6, from the same group, binds Wnt proteins instead (Chen et al., 2022).
KP1 has not been tested for lifespan, memory or cognition, and it has never been given to people. Every published KP1 study comes from the group that discovered it.
What "Klotho" on a research peptide listing usually means
A synthetic peptide sold as "Klotho" will almost certainly be a short fragment such as KP1, not the 1,012-amino-acid protein. Full-length Klotho is made as a recombinant protein, a different kind of product. A useful listing names the fragment, gives its sequence and length, and states its molecular weight, so that a lab test can confirm identity. Without that, the label alone does not tell you which molecule is in the vial.
Human studies
As of 30 October 2026, ClinicalTrials.gov lists no trial of KP1. It lists three small studies that try to raise Klotho itself: two open-label gene therapy pilots in healthy adults (NCT07216781, NCT07285629) and a placebo-controlled phase 1b study of Klotho mRNA that has not started recruiting (NCT07544420). None has posted results.
See the Klotho (KP1) profile for the register details, or compare KP1 with Epitalon, SS-31 and FOXO4-DRI. Klotho (KP1) is not yet stocked by Peptx; the profile page has a sign-up for availability notices.
References
- Kuro-o M, et al. "Mutation of the mouse klotho gene leads to a syndrome resembling ageing." Nature. 1997. PubMed 9363890
- Kurosu H, et al. "Suppression of aging in mice by the hormone Klotho." Science. 2005. PubMed 16123266
- Dubal DB, et al. "Life extension factor klotho enhances cognition." Cell Reports. 2014. PubMed 24813892
- Leon J, et al. "Peripheral Elevation of a Klotho Fragment Enhances Brain Function and Resilience in Young, Aging, and α-Synuclein Transgenic Mice." Cell Reports. 2017. PubMed 28793260
- Castner SA, et al. "Longevity factor klotho enhances cognition in aged nonhuman primates." Nature Aging. 2023. PubMed 37400721
- Yuan Q, et al. "A Klotho-derived peptide protects against kidney fibrosis by targeting TGF-β signaling." Nature Communications. 2022. PubMed 35064106
- Chen X, et al. "Klotho-derived peptide 6 ameliorates diabetic kidney disease by targeting Wnt/β-catenin signaling." Kidney International. 2022. PubMed 35644285
- UniProt. Human Klotho (Q9UEF7) and Beta-klotho (Q86Z14). UniProt Q9UEF7