AHK-Cu (L-Alanyl-L-Histidyl-L-Lysine copper(II)) is a synthetic copper-binding tripeptide composed of alanine, histidine, and lysine chelated to a copper ion. It is a structural analogue of GHK-Cu, differing only in the first amino acid (alanine in AHK-Cu versus glycine in GHK-Cu). This single amino acid substitution increases copper-binding affinity and produces a more targeted activity profile, particularly in dermal papilla cells and hair follicle biology. AHK-Cu is also known by its INCI name Copper Tripeptide-3 in cosmetic ingredient contexts. It is a research compound and is not approved by the FDA for any medical indication.

How does AHK-Cu differ from GHK-Cu?

AHK-Cu and GHK-Cu are structural analogues differing only in their first amino acid: alanine in AHK-Cu versus glycine in GHK-Cu. This substitution gives AHK-Cu a higher copper-binding affinity. In terms of biological activity, AHK-Cu is more targeted, with its primary research focus on dermal papilla cell proliferation and hair follicle stimulation. GHK-Cu has a broader research profile spanning wound healing, collagen synthesis, antioxidant activity, and gene expression modulation across multiple tissue types. GHK-Cu has significantly more published research overall. The two peptides are often combined in dual-peptide topical formulations for hair and skin applications, where their complementary profiles may offer additive benefit.

Does AHK-Cu stimulate hair growth?

Preclinical research suggests AHK-Cu stimulates key biological processes relevant to hair growth. The foundational 2007 Pyo et al. study from Seoul National University demonstrated that AHK-Cu significantly increased human hair follicle elongation in vitro, promoted dermal papilla cell proliferation (p < 0.001), and reduced markers of apoptosis: caspase-3 activity by 42.7% and PARP cleavage by 77.5% (p < 0.05). The copper peptide hair-stimulating effects have been described as comparable to 2% minoxidil in the 2018 Pickart and Margolina review. However, this evidence is primarily in vitro. Large-scale randomised controlled trials in humans with androgenetic alopecia or other hair loss conditions are lacking, and AHK-Cu is not an approved hair loss treatment.

What concentration of AHK-Cu is used in research?

AHK-Cu exhibits a dose-response inversion that is important to understand: biological effects are observed at extremely low concentrations, typically in the range of 10^-12 to 10^-9 molar in cell and tissue models. At higher concentrations, proliferative effects may diminish or reverse. In topical formulations, research concentrations typically range from 0.001% to 0.01% in serum or solution. This is considerably lower than many other cosmetic actives. The dose-response relationship means that more is not better: formulations using AHK-Cu should be optimised for the active concentration range rather than maximising peptide load.

Is AHK-Cu FDA-approved?

No. AHK-Cu is not approved by the FDA for any medical indication, including hair loss, skin repair, or any other condition. It is classified as a cosmetic ingredient in some jurisdictions under its INCI name Copper Tripeptide-3, which allows it to be used in topical skincare and hair care products subject to cosmetic regulations. It is not on the WADA prohibited list. In injectable or research peptide contexts, AHK-Cu is considered a research compound. Anyone considering AHK-Cu for medical purposes should consult a qualified physician.

AHK-Cu (Copper Tripeptide-3), Research Reference

AHK-Cu (L-Alanyl-L-Histidyl-L-Lysine copper(II) complex), also known as Copper Tripeptide-3, is a synthetic copper-binding tripeptide developed as a structural analogue of GHK-Cu. It differs from GHK-Cu by a single amino acid substitution at the N-terminal position (alanine replacing glycine), which results in higher copper-binding affinity and a more targeted biological activity profile focused on dermal papilla cells and hair follicle biology. AHK-Cu is investigated primarily as a hair growth stimulant and dermal regeneration compound, with the most commonly cited evidence coming from a 2007 Seoul National University study demonstrating significant follicle elongation and anti-apoptotic effects in human hair follicle models.

Quick Reference

Parameter	Reported Value
Full name	L-Alanyl-L-Histidyl-L-Lysine Copper (II)
Also known as	Copper Tripeptide-3, AHK·Cu²⁺
Amino acids	3 (Alanine, Histidine, Lysine)
CAS number	682809-81-0
Type	Synthetic copper-binding tripeptide
Primary research areas	Hair follicle stimulation, dermal papilla cell proliferation, angiogenesis, skin repair
Administration routes	Topical (primary); subcutaneous (investigated)
Half-life	Not established
Common topical concentrations	0.001% to 0.01% in serum or solution
Storage (lyophilised)	Refrigerator preferred; protect from light and moisture

What Is AHK-Cu?

AHK-Cu is a synthetic tripeptide composed of three amino acids, alanine, histidine, and lysine, chelated to a copper(II) ion. The copper ion is integral to its biological activity, serving as a cofactor that enables the peptide-copper complex to interact with cellular receptors and enzyme systems involved in tissue repair, collagen metabolism, and cell proliferation.

Structurally, AHK-Cu is an analogue of GHK-Cu, one of the most extensively researched copper peptides in the scientific literature. The two peptides share identical histidine and lysine residues; the only difference is the N-terminal amino acid: alanine in AHK-Cu versus glycine in GHK-Cu. Despite this single substitution, the change in N-terminal chemistry meaningfully increases the copper-binding affinity of AHK-Cu, which is proposed to underlie its more targeted and potent activity at the dermal papilla and hair follicle level relative to GHK-Cu.

While GHK-Cu has broad tissue effects spanning wound healing, antioxidant gene regulation, and systemic collagen synthesis, AHK-Cu is considered more specialised. Its primary investigated applications are hair follicle stimulation and dermal regeneration, and it is frequently incorporated into topical formulations alongside GHK-Cu in dual-peptide preparations targeting scalp and skin health.

AHK-Cu is not naturally occurring in human physiology; unlike GHK-Cu, which is found endogenously in plasma, saliva, and urine, AHK-Cu is a synthetic compound produced specifically for research and cosmetic applications. It is classified as Copper Tripeptide-3 under INCI nomenclature for cosmetic ingredient labelling.

Mechanism of Action

AHK-Cu operates through several converging mechanisms that are relevant to its investigated roles in hair follicle biology and dermal regeneration.

VEGF Induction and Angiogenesis

AHK-Cu stimulates vascular endothelial growth factor (VEGF) expression in dermal cells. VEGF is the primary driver of angiogenesis, the formation of new blood vessels, which is critical for follicle viability. Hair follicles are metabolically demanding structures that require sustained perifollicular vascularisation during the anagen (growth) phase. By upregulating VEGF, AHK-Cu may support scalp microcirculation and improve oxygen and nutrient delivery to active follicles.

Dermal Papilla Cell Proliferation

Dermal papilla cells are specialised mesenchymal cells located at the base of each hair follicle that orchestrate the hair growth cycle. They signal follicle keratinocytes to enter anagen and regulate cycle length. Research has demonstrated that AHK-Cu directly stimulates dermal papilla cell proliferation in vitro, with the Pyo et al. 2007 study reporting statistically significant increases (p < 0.001). This direct action on the cells that control the hair cycle is the mechanistic basis for AHK-Cu's hair growth research focus.

Anti-apoptotic Effects

AHK-Cu reduces markers of programmed cell death in follicle-related cell populations. The 2007 Pyo et al. study reported reductions in caspase-3 activity of 42.7% and PARP (poly(ADP-ribose) polymerase) cleavage of 77.5% compared to controls, both at p < 0.05. Caspase-3 is a key effector in the apoptotic cascade; its suppression extends the survival of dermal papilla cells and potentially prolongs the anagen phase by delaying the catagen (regression) transition.

Bcl-2/Bax Modulation

At the upstream level of apoptosis regulation, AHK-Cu has been shown to shift the balance between pro-survival and pro-apoptotic proteins. Specifically, it increases expression of Bcl-2 (an anti-apoptotic protein) while reducing Bax (a pro-apoptotic protein), resulting in a cellular environment that favours cell survival. This Bcl-2/Bax ratio is a well-established determinant of cellular fate in stress conditions including those experienced by follicle cells under androgenetic or environmental stress.

Extracellular Matrix Remodelling

Like GHK-Cu, AHK-Cu promotes fibroblast activation and extracellular matrix (ECM) synthesis. This includes stimulation of collagen (particularly types I, III, and IV) and elastin production, as well as glycosaminoglycan synthesis. In the follicular context, ECM remodelling supports the structural integrity of the follicle basement membrane and the dermal sheath, contributing to follicle anchoring and maintaining the follicle microenvironment during cycling.

Anti-inflammatory Activity

AHK-Cu modulates local immune responses in the scalp microenvironment. Perifollicular inflammation and fibrosis, driven by mast cell infiltration and pro-inflammatory cytokines including TNF-alpha and IL-1beta, are increasingly recognised as independent contributors to androgenetic alopecia progression beyond DHT-mediated miniaturisation. AHK-Cu's copper-mediated modulation of inflammatory signalling pathways may reduce this inflammatory load and slow follicle deterioration.

Dose-Response Relationship

A critical characteristic of AHK-Cu is its inverse dose-response relationship. Research effects are observed at extremely low concentrations, typically in the range of 10^-12 to 10^-9 molar in vitro. At higher concentrations, the proliferative and survival-promoting effects may diminish or reverse, with potential inhibitory effects on cell growth at supraphysiological concentrations. This bell-shaped dose-response curve is a recognised feature of copper peptide biology and has direct implications for formulation: higher concentrations of AHK-Cu in topical preparations do not produce proportionally greater effects and may reduce efficacy.

Research Evidence

Pyo et al. 2007 (Seoul National University)

The foundational study on AHK-Cu in hair follicle biology was published by Pyo et al. in 2007 at Seoul National University. The study investigated AHK-Cu using an ex vivo human hair follicle elongation model and in vitro dermal papilla cell cultures. Key findings included:

Hair follicle elongation: AHK-Cu significantly increased the elongation rate of human hair follicles compared to untreated controls in ex vivo culture.
Dermal papilla cell proliferation: AHK-Cu significantly boosted the proliferation of dermal papilla cells (p < 0.001), the cells that control the hair growth cycle.
Apoptosis reduction: AHK-Cu reduced caspase-3 activity by 42.7% and PARP cleavage by 77.5% compared to controls (p < 0.05), indicating meaningful anti-apoptotic effects in follicle-associated cells.
Bcl-2/Bax shift: AHK-Cu increased the Bcl-2/Bax ratio, consistent with a pro-survival cellular state.

Comparison to Minoxidil

The Seoul National University research group had previously applied the same ex vivo follicle elongation model to study minoxidil. In their 2018 review of copper peptide research, Pickart and Margolina noted that copper peptide hair-stimulating effects in this model appeared comparable to 2% minoxidil. This comparison should be interpreted cautiously: it is based on in vitro model data, not a head-to-head randomised controlled trial in human subjects with hair loss.

Skin Fibroblast and ECM Research

Beyond follicle-specific studies, AHK-Cu has demonstrated fibroblast-activating properties in skin cell research, supporting collagen and elastin synthesis and ECM remodelling relevant to wound healing and skin repair. These findings are consistent with the broader copper peptide literature, including GHK-Cu's well-characterised effects on fibroblast biology.

Evidence Limitations

The majority of AHK-Cu evidence is in vitro or preclinical. The clinical research base is substantially smaller than that of GHK-Cu, and large-scale randomised controlled trials in human populations with hair loss conditions are not yet available. AHK-Cu is not FDA-approved for hair loss or any other indication, and clinical claims extrapolated from in vitro findings should be interpreted conservatively.

AHK-Cu vs GHK-Cu

Parameter	AHK-Cu	GHK-Cu
Full name	Alanyl-Histidyl-Lysine copper(II)	Glycyl-Histidyl-Lysine copper(II)
N-terminal amino acid	Alanine	Glycine
Origin	Synthetic (no endogenous source identified)	Endogenous (found in plasma, saliva, urine)
Copper binding affinity	Higher	High (Ka ~10¹⁷)
Primary research focus	Hair follicle stimulation, dermal papilla cells	Wound healing, collagen synthesis, gene expression, skin ageing
Hair-specific evidence	More targeted; directly studied in follicle models	Studied in follicle and animal models; broader context
Research volume	Limited; fewer published studies	Extensive; hundreds of published studies
Topical use	Common; often in scalp-focused formulations	Common; skincare, wound care, and scalp formulations
Typical topical concentration	0.001% to 0.01%	0.1% to 1% (topical); broader range in cosmetics
Dose-response inversion	Yes; higher doses may inhibit growth	Yes; same class characteristic
FDA approval	None	None (used as cosmetic ingredient)
Combined use	Frequently combined in dual-peptide topical formulations targeting hair and skin

Reported Protocols

The following information represents commonly reported research approaches drawn from published studies and anecdotal accounts in research contexts. These are not medical recommendations.

Topical Protocol

Topical application is the primary and most widely reported route for AHK-Cu in both research and cosmetic contexts.

Concentration: 0.001% to 0.01% in a serum, solution, or carrier formulation. This is the range supported by in vitro research; concentrations outside this range may produce suboptimal results due to the dose-response inversion.
Frequency: Once or twice daily application to the scalp or target skin area is the most commonly described approach.
Duration: Research protocols typically describe periods of 8 to 24 weeks for hair-related endpoints, consistent with the slow timescales of follicle cycling.
Application method: Applied directly to the scalp and massaged in; no rinsing unless the formulation specifies otherwise.

Subcutaneous Research Use

Subcutaneous administration of AHK-Cu has been described in some research contexts for scalp application, following the pattern established for GHK-Cu. Doses and protocols are not well-established in the published literature for AHK-Cu specifically, and subcutaneous use represents an extrapolation from GHK-Cu protocols. Topical application remains the more supported route for this compound.

Combination Formulations

AHK-Cu is frequently used alongside GHK-Cu in dual-peptide formulations. The rationale is complementary activity: AHK-Cu targets dermal papilla cell proliferation and anti-apoptosis, while GHK-Cu provides broader angiogenic, anti-inflammatory, and ECM remodelling support. Commercial scalp serums targeting hair loss often include both copper peptides. When used in combination, both peptides should still be within their respective optimal concentration ranges.

Reconstitution

AHK-Cu is typically supplied as a lyophilised powder. In research settings, it is reconstituted in sterile water or a suitable carrier solution to the target concentration before application. The resulting solution typically has a pale blue-green colour characteristic of copper complexes.

Diluent: Sterile water or bacteriostatic water; carrier serums in cosmetic formulations.
Storage (lyophilised): Refrigerator preferred; protect from light and moisture.
Storage (reconstituted): Refrigerated; use within 4 to 6 weeks; protect from light.

Dose-Response Considerations

The inverse dose-response profile of AHK-Cu is a critical formulation consideration. Unlike many actives where higher concentration correlates with greater effect, AHK-Cu research demonstrates optimal activity at very low concentrations (10^-12 to 10^-9 M in vitro). Researchers and formulators working with AHK-Cu should treat concentration as a parameter to optimise, not maximise.

Reported Side Effects

The following side effects have been reported in research and anecdotal accounts. No comprehensive human safety trials for AHK-Cu have been published. This list should not be interpreted as a complete safety profile or as predictive of individual outcomes.

Side Effect	Frequency Reported
Skin irritation or redness (topical)	Rarely reported at recommended concentrations
Mild scalp tingling	Occasionally reported; typically transient
Injection site reaction (SubQ)	Common with any subcutaneous injection; not AHK-Cu specific
Copper accumulation	Theoretical concern at very high doses; not reported at research concentrations

Copper considerations: Copper peptides as a class carry theoretical concerns regarding copper accumulation at very high doses or with prolonged use. AHK-Cu at research concentrations (particularly the very low topical concentrations supported by the literature) is generally reported as well tolerated. The chelated tripeptide form of copper has a different pharmacological profile from ionic copper and is not associated with copper toxicity at research doses. No human safety trials for AHK-Cu in injectable contexts have been published.

Regulatory Status

AHK-Cu is not approved by the FDA for any medical indication, including hair loss, androgenetic alopecia, skin repair, or wound healing. It is classified as a research compound in most jurisdictions.

In the cosmetic industry, AHK-Cu is classified as Copper Tripeptide-3 under INCI (International Nomenclature of Cosmetic Ingredients) standards. This classification allows it to be used as an active ingredient in topical skincare and hair care products under cosmetic regulatory frameworks, which apply different standards of evidence than pharmaceutical drug approval. Cosmetic use does not imply medical efficacy claims.

AHK-Cu is not listed on the World Anti-Doping Agency (WADA) prohibited list.

Anyone considering AHK-Cu for therapeutic purposes, including hair loss treatment, should consult a qualified physician or dermatologist. The available evidence does not support AHK-Cu as a validated clinical treatment for any condition.

Related Peptides: GHK-Cu · TB-500 · BPC-157 · Collagen Peptides

Goals: Hair Loss & Regrowth · Skin, Hair & Cosmetic

References & Further Reading

Pyo HK, Yoo HG, Won CH, et al. (2007). The effect of tripeptide-copper complex on human hair growth in vitro. Archives of Pharmacal Research, 30(7), 834-839.
Pickart L, Margolina A. (2018). Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. International Journal of Molecular Sciences, 19(7), 1987. PubMed
Gorouhi F, Maibach HI. (2009). Role of topical peptides in preventing or treating aged skin. International Journal of Cosmetic Science, 31(5), 327-345. PubMed