AHK-Cu is a very short peptide — three amino acids (alanine, histidine, lysine) bound to a copper ion. It is a close relative of the far more famous GHK-Cu, differing by a single amino acid at the first position. In cosmetics it goes by the name Copper Tripeptide-3 and is sold on the promise of lengthening the growth phase of the hair. Remarkably little stands behind that promise: PubMed holds exactly one paper devoted to AHK-Cu, published in 2007 by a team from Seoul, and it is a study in cultured cells and in human hair follicles kept alive outside the body. There is no clinical trial at all. Below we set out what that single paper actually showed, and which popular claims about AHK-Cu come from the literature on its relative.
What AHK-Cu is
Copper peptides are short amino-acid chains able to grip a copper ion tightly. The body needs copper — it takes part in collagen maturation and in the work of many enzymes — but free, unbound copper is toxic, because it drives oxidation reactions. The peptide therefore acts as a handle: it carries the ion in bound form and lets it reach the place where it is meant to act.
The best-known member of the group is GHK-Cu, found in human plasma and studied since the 1970s in the context of wound healing and skin regeneration. AHK-Cu came about as a variant of it, with glycine replaced by alanine. The change looks cosmetic, but in peptide chemistry a single residue can alter both the way copper is held and which cells the compound acts on most strongly.
How it is meant to work — the dermal papilla and the hair cycle
Two things are needed to understand the promise. First: at the base of every hair follicle sits a cluster of cells called the dermal papilla. Those cells conduct the whole follicle — whether the hair grows, and how thick it is, depends on them. Second: hair does not grow continuously but cycles through phases — growth (anagen), transition (catagen) and rest (telogen). In pattern hair loss the growth phase shortens and hairs become ever finer.
The hypothesis for AHK-Cu is straightforward: if the compound prompts papilla cells to divide and shields them from dying, the follicle should stay longer in its growth phase. That is a different point of attack from the two established hair-loss medicines — finasteride blocks the formation of dihydrotestosterone, and minoxidil acts on potassium channels in blood vessels. A different mechanism is not by itself proof of efficacy, though, only a hypothesis to be tested.
What was studied — cells and the follicle outside the body
The 2007 paper tested two things at once. The first was a culture of human dermal papilla cells: AHK-Cu, at concentrations from trillionths to billionths of a mole, prompted them to multiply. The second model was the more telling one — human hair follicles dissected out of the skin and kept alive in culture. Under those conditions the compound made the hair elongate, and that is the strongest argument in existence for its action.
The authors also checked whether AHK-Cu shields papilla cells from dying. Here the result is equivocal and worth quoting precisely: the number of apoptotic cells fell, but the difference was not statistically significant. Protein markers of cell death did shift, however — the ratio of Bcl-2 to Bax rose, and the levels of cleaved caspase-3 and of the PARP protein fell. Put plainly: the signals inside the cell pointed to apoptosis being held back, yet counting the dying cells did not confirm it.
Outside the skin, the AHK peptide appears in the literature once more, in an entirely different context. A derivative of it joined to vitamin C increased the differentiation of mouse muscle cells towards bone cells driven by the BMP-2 protein. That is a dish experiment, with a different molecule and no copper involved — we cite it only to show how narrow the entire literature on this tripeptide is.
No human studies — what that means
Searching PubMed under “AHK-Cu”, “alanyl-histidyl-lysine” and “Ala-His-Lys” returns no study involving people. The ClinicalTrials.gov registry knows of no trial of AHK-Cu, of Copper Tripeptide-3, or of alanyl-histidyl-lysine. A 2026 review of peptides in hair loss classes AHK-Cu unambiguously: ex vivo evidence, experimental level — as against GHK-Cu, for which the same review lists clinical data.
Here lies a trap worth watching for when reading sales material. Human studies of “a copper peptide” do exist, but they concern GHK-Cu, a different molecule. The one most often invoked is a 2016 trial in which 45 men with male pattern hair loss used, for six months, a preparation combining the GHK peptide with 5-aminolevulinic acid. Hair count rose significantly in both groups receiving the preparation and hardly at all under placebo, although hair length and thickness did not differ between the groups. A good result — but for a different peptide, and in a mixture with a second active ingredient.
What was not shown — TGF-beta and blood supply
Two claims repeated about AHK-Cu need correcting, because they come from the GHK-Cu literature rather than from research on AHK-Cu itself.
The first: “it lowers TGF-beta1, the factor that flips the hair into its shedding phase”. The statement about lowered TGF-beta1 secretion by skin fibroblasts comes from earlier work on the tripeptide-copper complex and has not been demonstrated for AHK-Cu in the hair follicle. More importantly, the premise itself is inaccurate: in a 2002 study of human follicles the transition phase was driven by TGF-beta2, found in the matrix cells next to the papilla and in the regressing epithelial strands, while TGF-beta1 and TGF-beta3 were essentially absent from those places. Blocking TGF-beta2 made follicles elongate in culture. Reducing hair regression to TGF-beta1 is therefore an oversimplification.
The second: “it improves the follicle's blood supply through VEGF”. Increased VEGF production by skin fibroblasts was described for GHK-Cu; the single AHK-Cu paper measured neither VEGF nor follicular blood supply. That is a hypothesis borrowed from the relative, not a finding.
Safety and the limits of the evidence
Nothing is known about the safety of AHK-Cu in people, because no study capable of testing it has been done. The single paper assessed cell viability in culture — a standard cytotoxicity test, not a human safety assessment. The 2026 review points out a wider problem across this whole group: most papers do not even explain where their tested concentrations came from.
Then there is the copper itself. Copper peptides deliver a metal ion, and the body has a limited capacity to handle an excess of it. People with Wilson's disease, an inherited failure to excrete copper, should avoid anything that supplies it. Combining several copper preparations at once adds up that load, and no study has examined how much copper is absorbed under such combinations.
It is also worth being honest about what a dissected follicle in culture cannot tell us. Such a follicle survives in the dish for days to a couple of weeks and is cut off from the bloodstream, the immune system and hormones. Elongation under those conditions says that the cells respond to the compound, but says nothing about whether the substance reaches the papilla through the scalp at all, or whether it changes anything in a hair cycle that in a human being runs for years. We deliberately give no methods of use and no doses.
The wider context — copper peptides
AHK-Cu is best understood by comparison with its relative. GHK-Cu has half a century of research behind it, analyses of its effect on gene expression, work on wound healing and several human studies. AHK-Cu has one paper from 2007. The pitch “it is like GHK-Cu, only for hair” is therefore a story built on another molecule's record — with a single genuine foothold, the elongation of follicles in culture.
Summary
AHK-Cu is a copper tripeptide differing from GHK-Cu by one amino acid, marketed with the hair follicle in mind. The only study devoted to it showed that it prompts dermal papilla cells to multiply and makes human follicles elongate in culture, while the fall in the number of dying cells did not reach statistical significance. The popular claims about lowered TGF-beta1 and improved blood supply via VEGF come from the GHK-Cu literature and have not been demonstrated for AHK-Cu; moreover, the human hair's shift into its shedding phase is driven rather by TGF-beta2. No study of AHK-Cu in people exists, and no clinical trial of it is registered. The evidence should be described as preliminary, confined to a single paper in cultured cells and dissected follicles.
Sources
- Pyo HK, Yoo HG, Won CH, et al. The effect of tripeptide-copper complex on human hair growth in vitro. Archives of Pharmacal Research. 2007;30(7):834–839. PMID: 17703734. DOI: 10.1007/BF02978833. pubmed.ncbi.nlm.nih.gov/17703734
- Lee WJ, Sim HB, Jang YH, et al. Efficacy of a Complex of 5-Aminolevulinic Acid and Glycyl-Histidyl-Lysine Peptide on Hair Growth. Annals of Dermatology. 2016;28(4):438–443. PMID: 27489425. DOI: 10.5021/ad.2016.28.4.438. pubmed.ncbi.nlm.nih.gov/27489425
- Soma T, Tsuji Y, Hibino T Involvement of transforming growth factor-beta2 in catagen induction during the human hair cycle. The Journal of Investigative Dermatology. 2002;118(6):993–997. PMID: 12060393. DOI: 10.1046/j.1523-1747.2002.01746.x. pubmed.ncbi.nlm.nih.gov/12060393
- Fan C, Chen Y, Huang Q, et al. Overview of Short Peptides for Hair Loss. Biomedicines. 2026;14(4):864. PMID: 42072405. DOI: 10.3390/biomedicines14040864. pubmed.ncbi.nlm.nih.gov/42072405
- Pickart L, Margolina A Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. International Journal of Molecular Sciences. 2018;19(7):1987. PMID: 29986520. DOI: 10.3390/ijms19071987. pubmed.ncbi.nlm.nih.gov/29986520
- Jung JI, Park KY, Lee Y, Park M, Kim J Vitamin C-linker-conjugated tripeptide AHK stimulates BMP-2-induced osteogenic differentiation of mouse myoblast C2C12 cells. Differentiation. 2018;101:1–7. PMID: 29567599. DOI: 10.1016/j.diff.2018.03.001. pubmed.ncbi.nlm.nih.gov/29567599
For in-vitro laboratory research only. It is not a human medicine and is not for treatment.