AHK-Cu

Origin and structure

AHK-Cu is a complex of copper(II) with the tripeptide L-alanyl-L-histidyl-L-lysine (Ala-His-Lys). The peptide on its own has the formula C15H26N6O4 and a molar mass of 354.4 g/mol. It is GHK-Cu with one change: alanine takes the place of glycine at the start of the chain, while the histidine that anchors the copper stays in second position.

The difference in origin is larger than the difference in structure. GHK occurs naturally in the body, and GHK-Cu has decades of research behind it; AHK-Cu is a synthetic analogue. The first hair experiments with it that we could find come from the US company ProCyte, which in a patent filed in 1994 and granted in 1996 described a family of copper peptides for hair growth and tested AHK-Cu in mice and rats. A 2026 review of copper peptides describes AHK-Cu as sharing GHK-Cu's copper-binding motif but resting on a thin, poorly characterised evidence base.

Online, AHK-Cu is often sold as 'copper tripeptide-3'. That is not an official ingredient name: the EU's database of cosmetic ingredients, CosIng, has no entry by that name, and its 'Tripeptide-3' is a different peptide, built from glycine, serine and valine. The sequence Ala-His-Lys is the reliable way to identify AHK-Cu.

How it is thought to work

No receptor or specific target for AHK-Cu has been identified. The one laboratory study of it points to the dermal papilla, the cluster of specialised fibroblasts at the base of the hair follicle that steers hair growth. In culture, AHK-Cu made these cells multiply and shifted the signals that control programmed cell death towards survival: the ratio of the protective protein Bcl-2 to the pro-death protein Bax rose, and the cleaved forms of caspase-3 and PARP, markers of cell death, fell. The authors proposed that this explains why the follicles in their experiment grew longer.

Much of what is said about AHK-Cu online, such as more collagen, more VEGF and more blood vessels in the skin, comes from work on GHK-Cu. The 2007 paper opens by citing such effects of copper tripeptides on skin fibroblasts, but its own experiments, as described in its abstract and in a 2026 review of hair-loss peptides, measured follicle growth, cell division and cell-death markers only. That review notes that AHK-Cu's signalling is less well characterised than GHK-Cu's. We found no study that measured whether AHK-Cu passes through human skin to reach the follicle.

Is AHK-Cu approved?

No. The EMA and the FDA have not authorised any medicine containing AHK-Cu, and we found no regulator elsewhere that has. In the Netherlands it is not a registered medicine and may not be sold or promoted as a medicine for use in people; it is available as research material, which is the basis on which our shop sells it.

Copper peptides are also used in cosmetics, and there the EU Cosmetics Regulation applies. A cosmetic is a product applied to the outer parts of the body, such as skin, hair and nails, or to the teeth and mouth, and the regulation states that anything intended to be injected is not a cosmetic. Most cosmetic ingredients need no approval in advance, but every finished cosmetic must have a safety assessment before it goes on sale.

In the United States AHK-Cu is not an approved drug, and it appears on none of the FDA's lists of substances nominated for pharmacy compounding (May 2026 update). That sets it apart from GHK-Cu: the FDA is evaluating non-injectable GHK-Cu for compounding and intends to consult its advisory committee about it before the end of February 2027.

In sport AHK-Cu is not named on the WADA Prohibited List, but class S0 prohibits at all times any pharmacological substance that no health authority has approved for human therapeutic use, and that describes AHK-Cu. The 2027 list, in force from 1 January 2027, names peptides explicitly as an example of S0. The Dopingautoriteit applies the same list in the Netherlands.

What the research shows

Very little, and none of it in people. There are two sets of data: animal experiments described in ProCyte's 1996 patent, which were never published in a peer-reviewed journal, and one laboratory study from 2007. A 2026 review of short peptides for hair loss lists only the 2007 study for AHK-Cu. All the animal groups were small, and the patent reports no statistical tests.

• ProCyte patent, injection in mice: closely clipped C3H mice whose hair was in the resting phase received AHK-Cu injected into the skin. At the higher of two doses hair grew back around the injection site in 4 of 4 mice, at the lower dose in 1 of 4; in a comparable experiment in the same patent, saline injections gave no hair growth in 5 of 5 mice.
• ProCyte patent, on the skin of mice: a solution of AHK-Cu in propylene glycol and ethanol was applied to clipped skin twice a day on weekdays. With the stronger of two concentrations new hair covered about three quarters of the treated area by day 20 and all of it by day 27; with the weaker one, 90% by day 34. The experiment reports no group treated with the solution alone, so it cannot show how much hair would have regrown anyway.
• ProCyte patent, chemotherapy in young rats: 8-day-old rats received the chemotherapy drug cytarabine, which makes them lose their hair. Where AHK-Cu had been injected into the skin beforehand, more hair stayed: on a scale from 0 (no loss) to 4 (total loss), the injection site scored 1.1 at the highest dose against 4.0 after saline, in groups of 8 or 9 animals. Under the microscope, follicles at the injection site looked normal and those further away were damaged.
• Pyo et al., Seoul National University, 2007: human hair follicles kept alive in culture grew longer when AHK-Cu was added at concentrations between 1 picomolar and 1 nanomolar, and cultured dermal papilla cells multiplied. At 1 nanomolar fewer cells died by apoptosis, but that difference was not statistically significant; the Bcl-2/Bax ratio rose and cleaved caspase-3 and PARP fell. The abstract does not give the number of donors or follicles, and we found no other group that has repeated the work.
• Registered in October 2026 (NCT07888595): a single-group study in Irvine, California, plans to enrol 48 healthy adults aged 50 or over and apply a serum of five peptides, AHK-Cu among them, to defined skin areas, comparing them with untreated areas on the same person. Participants may also receive agents such as metformin by mouth or injection. Its main outcome is 'biological age' estimated from gene activity and blood proteins after four weeks, not hair growth, and the design cannot separate the effect of AHK-Cu from the other ingredients. No results yet.
• Hair loss, skin ageing or wound healing in people: not studied for AHK-Cu.

AHK-Cu versus GHK-Cu

The two differ by one amino acid and are often sold side by side, but the evidence behind them is not comparable. GHK occurs naturally in the body, and GHK-Cu has been studied in cells, animals and people, including a randomised, placebo-controlled multicentre trial in which a GHK-Cu gel improved the closure of diabetic foot ulcers: the median plantar ulcer closed by 98.5%, against 60.8% with the gel base alone (Mulder et al., 1994). Even so, a 2026 review judges the clinical evidence for GHK-Cu sparse. AHK-Cu has one lab study and the animal experiments in ProCyte's patent.

Results for GHK-Cu cannot simply be carried over to a different molecule. ProCyte's own patent shows why: in its mouse experiments, a copper peptide with phenylalanine in place of lysine worked less well on the skin, while the authors report the reverse for injection. Regulators treat the two differently too: the FDA lists non-injectable GHK-Cu among substances under evaluation for compounding, while AHK-Cu appears on none of these lists.

Frequently asked questions

Does AHK-Cu help against hair loss?

That has never been tested in people. In a 1996 patent, the company ProCyte reported that AHK-Cu injected into the skin or applied to it made hair grow in small groups of mice, and that injections limited hair loss from chemotherapy in young rats; these results never appeared in a scientific journal. A 2007 lab study found that human hair follicles kept alive in culture grew longer. Whether any of this applies to a human scalp is unknown.

Is AHK-Cu the same as GHK-Cu?

No. Both carry copper, but they differ by one amino acid: alanine instead of glycine at the start of the chain. GHK occurs naturally in the body, and GHK-Cu has been tested in people, including a placebo-controlled trial in diabetic foot ulcers; AHK-Cu is synthetic and has one lab study and unpublished animal data from a patent. Findings for GHK-Cu cannot be assumed to apply to AHK-Cu.

What is copper tripeptide-3?

It is a name sellers use for AHK-Cu, not an official ingredient name. The EU's cosmetic-ingredient database CosIng has no 'Copper Tripeptide-3', and the 'Tripeptide-3' it does list is a different peptide, made of glycine, serine and valine. To know what a product contains, look for the sequence Ala-His-Lys (alanyl-histidyl-lysine).

Is AHK-Cu legal in the Netherlands?

It is not a registered medicine in the Netherlands or elsewhere in the EU, so it may not be sold, advertised or supplied as a medicine for use in people. In a cosmetic it falls under the EU Cosmetics Regulation, which requires a safety assessment of the finished product, and a product meant for injection is never a cosmetic. Buying and selling it as research material is a different status, which our guide on research-use-only products in the Netherlands explains.

Is AHK-Cu banned in sport?

In effect, yes. It is not named on the WADA Prohibited List, but class S0 prohibits at all times any pharmacological substance that no health authority has approved for human therapeutic use, and AHK-Cu has no such approval; from 1 January 2027 the list names peptides explicitly in S0. The list does not address cosmetics that contain such ingredients; athletes in doubt can ask the Dopingautoriteit, which applies the same list in the Netherlands.

Is AHK-Cu safe?

Nobody knows. We found no published human study, case report or toxicology study of AHK-Cu, so there are no data on side effects in people by any route. Injection into people has never been studied; for injectable GHK-Cu, its closest relative, the FDA has flagged a possible risk of immune reactions from aggregation and peptide impurities.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.

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