AHK-Cu vs GHK-Cu: differences, evidence and safety
Answer first
AHK-Cu and GHK-Cu are copper complexes of two three-part peptides that differ by one building block. GHK occurs naturally and has decades of cell and animal research; its two controlled human trials missed their objective targets. AHK-Cu is synthetic, with one study on hair follicles in a dish. Neither is an approved medicine. No direct comparison could be found.
At a glance
How they work
No mechanism of either copper peptide has been established in people. Everything below comes from cells, tissue in a dish or animals, so each point is a hypothesis.
GHK-Cu. GHK is the three-part sequence glycine, histidine and lysine, a sequence found in human blood serum [1]. In GHK-Cu it is bound to one copper ion [2]. The same triplet sits inside type I collagen, the main structural protein of skin. That led to the idea that injury releases it from the tissue [3].
- Collagen in skin cells. Fibroblasts are the cells that build connective tissue. In cultured human fibroblasts, collagen production rose from about 10⁻¹² mol/l and peaked at 10⁻⁹ mol/l, with no change in cell number [3].
- Scaffolding sugars. The same cells made more sulphated glycosaminoglycans, sugar chains that fill the space between cells. The response was bell-shaped, peaking at 10⁻⁹ to 10⁻⁸ mol/l [4].
- A carrier for copper. In the test tube GHK competes with albumin, the main blood protein, for copper. At equal concentrations about 42 per cent of the copper sat on the peptide. At concentrations found in blood, only about 6 per cent sat on small molecules [5].
- Copper may not be the key part. Where both were tested in skin cells, copper-free GHK produced the same result as the complex [6].
AHK-Cu. AHK-Cu swaps the glycine at the front of the chain for alanine, which chemically is a single methyl group [7]. All of its mechanistic data come from one study published in 2007 [8].
- Cells from the hair root. The dermal papilla is the small bundle of tissue that feeds a hair. Its cells multiplied more and showed higher viability in a standard growth test [8].
- Cell survival signals. A shift in two proteins that govern cell survival was reported, a higher Bcl-2 to Bax ratio, but without any statistical test [8].
- A longer growth phase. Human hair follicles kept alive in a dish grew longer under treatment [8].
The core difference is where each has been looked at. GHK-Cu research centres on skin cells, wounds and connective tissue; AHK-Cu research consists of one look at the hair follicle.
A 2026 review states that the signalling of AHK-Cu is "less well characterized than GHK-Cu" [9]. The 2007 study also ran no copper-only or copper-free comparison, so whether the peptide, the copper or the complex acts is untested [8].
What the studies show
No study that compares AHK-Cu and GHK-Cu directly could be found in the published record reviewed for this page. The 1996 patent that first describes AHK-Cu calls it more active on mouse skin than related peptides [7]. The claim sits in a patent, not in a peer-reviewed journal, and names no study that tests it against GHK-Cu.
How much evidence each one has
Systematic review A 2026 review of GHK-Cu searched three large literature databases and included 20 studies: 18 preclinical and 2 randomised controlled trials [10]. Its authors call the findings "constrained by methodological variability and a limited number of well-designed clinical studies".
Evidence count For AHK-Cu the whole record is one peer-reviewed paper, a patent and a review that repeats the paper's numbers. Literature searches on 20 September 2026 found no other study that tests the substance [11]. Registry searches on the same day found no trial in people [12].
Registered trials No verified trial of GHK-Cu on its own is registered [13]. One registry entry that names the peptide tests a device with a booster serum in 27 people. Another plans to measure blood levels under a patch in 100 people. Neither gives GHK-Cu as the treatment under test.
Hair: what has actually been tested
Ex vivo organ culture Human hair follicles grew longer when AHK-Cu was added to the surrounding liquid, across 10⁻¹² to 10⁻⁹ M [8]. The 2026 review reports a wider range, 10⁻¹³ to 10⁻⁷ M, and calls 10⁻⁹ M the optimal concentration [9].
Cell culture, not significant At 10⁻⁹ M the count of dying hair-root cells fell, but the paper states that "this decrease was not statistically significant" [8]. The authors wrote that their study "proposed" the effect on cell death. It is the only AHK-Cu result that carries a statistical test.
Animal data, not peer-reviewed After injection into the skin of C3H mice, the patent reports active hair growth between days 14 and 20 [7]. The strongest effect came around day 29, in patches of roughly 0.5 to 5 cm². No journal publication and no repetition of these mouse data could be found [11].
Human RCT, combination product No published human study of GHK-Cu on its own for hair could be found. In 45 men with pattern hair loss, six months of a daily solution raised the hair count by 52.6 and 71.5 in two groups. On placebo the rise was 9.6 [14]. The product was a complex of 5-aminolaevulinic acid and copper-free GHK.
Observational An open study in 1000 patients reported less shedding in 83 per cent. It had no control group, and its formulation combined five growth factors, thymosin beta-4 and Copper Tripeptide-1 [15]. Four further case reports applied a copper peptide alongside topical finasteride [16].
For hair, then, AHK-Cu has substance-specific data only from a dish and from a patent. GHK-Cu has data in people only for mixtures. Neither has a controlled hair trial of the substance alone.
Skin and wounds: a GHK-Cu record only
Human RCT The largest controlled trial compared three creams in 86 patients with venous leg ulcers. A copper tripeptide cream at 0.4 per cent did no better than an inert dummy cream: "There was no difference between the latter two treatments." [17]
Human RCT Thirteen patients completed a trial of a GHK-Cu skin care regime after laser resurfacing, followed for 12 weeks. The authors report that "objective evaluation found no significant improvement in wrinkles or overall skin quality" [18]. Only self-reported satisfaction was higher (p = 0.04).
Animal data In rats with poorly supplied open wounds, the wound area shrank by 64.5 per cent under a copper tripeptide gel by day 13. Under the gel without the peptide it shrank by 45.6 per cent, and without treatment by 28.2 per cent [19]. In rat wound chambers, connective tissue built up in a concentration-dependent way [20].
Animal data In 72 rats after cruciate ligament reconstruction in the knee, the joint was less lax at six weeks in the lower-concentration group. By twelve weeks the difference had gone, and the authors call the effect transient [21].
No data For AHK-Cu no skin, wrinkle or wound study in any species could be found [11]. The collagen and wound results often quoted for it belong to GHK-Cu [9].
Getting through the skin
Ex vivo In donated human skin, "almost no peptide or copper permeated through intact human skin" in a GHK-Cu experiment [22]. Through skin pre-treated with tiny needles, 134 ± 12 nanomoles of peptide and 705 ± 84 nanomoles of copper crossed in nine hours.
No data No measurement of whether AHK-Cu crosses intact skin could be found, in any species [11].
Why the numbers cannot be set side by side
The two substances were tested in different models, with different concentrations, endpoints and durations. Most AHK-Cu figures describe liquid around cells, while the GHK-Cu trials used creams on wounds and skin.
Doses used in the studies
The doses below are simply what the cited studies gave, listed so that the results can be understood. They are not advice on how to use anything.
| Study | Substance | Model | Dose | Route | Duration | Ref |
|---|---|---|---|---|---|---|
| Pyo 2007, follicles and hair-root cells | AHK-Cu | Human hair follicles ex vivo; human dermal papilla cells | 10⁻¹² to 10⁻⁹ M; the cell-death work used 10⁻⁹ M | Added to the culture medium | Length of the culture, not given in the abstract | [8] |
| US patent 5,538,945, mouse work | AHK-Cu | C3H mouse | Peptide-to-copper ratios of 2:1 and 1:1 at 10 mg/ml; 0.5 per cent on the skin | Injected into the skin; applied to the skin | Readings to day 34 | [7] |
| Maquart 1988, collagen | GHK-Cu | Human fibroblasts | 10⁻¹² to 10⁻⁷ mol/l, peak at 10⁻⁹ mol/l | Added to the culture medium | Length of the culture | [3] |
| Canapp 2003, ischaemic wounds | GHK-Cu | Rat | A 2 per cent copper tripeptide gel | Topical | 13 days, once daily | [19] |
| Fu 2015, ligament repair | GHK-Cu | Rat | 0.3 mg/ml or 3 mg/ml | Into the joint | Weekly for 4 weeks | [21] |
| Bishop 1992, leg ulcers | GHK-Cu | Human | Copper tripeptide cream at 0.4 per cent | Topical | Length of the trial | [17] |
| Lee 2016, hair | Complex with copper-free GHK | Human | 100 mg/ml or 50 mg/ml of a complex with 5-aminolaevulinic acid | Topical | 6 months, once daily | [14] |
| Hostynek 2010, skin uptake | GHK-Cu | Donated human skin | 0.68 per cent aqueous copper as the diacetate | Topical, saturating | 48 hours | [23] |
| Cosmetic market survey 2014 | GHK-Cu | Human, market data | Usually under 10 ppm, or 0.001 per cent; survey range 0.0000001 to 0.002 per cent | Topical | Years of use possible | [24] |
Concentrations from a dish describe the liquid around cells, and they cannot be converted into an amount for a person. No published dosing figure for a person could be found for AHK-Cu, and no dose-finding study of injected GHK-Cu in people could be found.
Safety
No controlled safety data for injection could be found for either copper peptide. For creams, only GHK-Cu has been assessed.
GHK-Cu
- One cosmetic assessment. An expert panel concluded in 2014 that the ingredients reviewed "are safe in the present practices of use and concentration in cosmetics" [24]. That verdict is bound to concentrations of 1 to 30 ppm, with under 10 ppm usual. Products sold today often sit well above those levels [24].
- A named risk for injection. The FDA states that injectable GHK-Cu "may pose risk for immunogenicity due to the potential for aggregation and peptide-related impurities" [25]. Immunogenicity means the chance of an immune reaction.
- Two serious spontaneous reports. A query of the FDA adverse event database on 7 September 2026 returned two serious reports. One describes anaphylactic shock, the other an adverse reaction and a lymphatic malignancy [26]. Several peptides had been taken together, and spontaneous reports cannot establish cause.
- Copper on skin is not inert. A study of several copper compounds in skin cells found that their potential to irritate skin "is often overlooked" [27].
- Purity. The 2014 report notes that commercial material is "approximately 95% pure, but often includes small amounts of mildly neurotoxic materials" [24].
- An open warning. In 2013 the panel minuted that "some small peptides are potent stimulators of angiogenesis", the growth of new blood vessels. This "might then be an issue" in people with undiagnosed skin cancer. The final report dropped the point, and no experiment addressing it could be found [28].
AHK-Cu
- No safety study of any kind. No single-dose, repeat-dose, genetic or reproductive testing could be found [11]. The one study measured cell viability, which is not a safety test [8].
- No expert assessment. The American ingredient review covers Tripeptide-1 and related peptides, not AHK [24]. The European consumer safety committee has issued no opinion.
- No adverse-event reports. The American database held none under the name on 20 September 2026, against two for GHK-Cu [29]. For a substance this little studied, a zero means almost nothing.
- Injection is the sharpest gap. AHK-Cu does not appear on the FDA risk list [25]. That list only holds substances nominated for compounding, so the absence records unfamiliarity, not an all-clear.
- Purity cannot be checked. With no pharmacopoeia entry, the purity figures in circulation come from the sellers themselves [30].
Shared questions. By mass, AHK-Cu is about 15.3 per cent copper and GHK-Cu about 15.8 per cent, both calculated from the formula [31], [2]. Europe's food safety authority set 5 mg of copper a day as the limit for adults, a figure that describes swallowing [32].
Injection bypasses the control the gut applies to copper uptake. No measurement of copper balance under repeated use of either peptide could be found [32].
No measurement of how long either lasts in a human body could be found. GHK broke down fast after injection in rats [33]; for AHK-Cu no measurement in any species could be found [11]. This page does not rank the two.
Legal status
Neither substance is approved as a medicine in any of the seven markets checked, on 7 September 2026 for GHK-Cu and 20 September 2026 for AHK-Cu. As a cosmetic ingredient, GHK-Cu is listed as Copper Tripeptide-1 [34]. AHK-Cu is not banned in cosmetics, but its trade name, Copper Tripeptide-3, is missing from the binding EU glossary [34]. The FDA names injectable GHK-Cu among substances that may present significant safety risks, while AHK-Cu does not appear on that list [25]. Neither is named on the 2026 Prohibited List. Injected forms fit class S0; no official clarification for topical cosmetics could be found [35], [36]. More detail is at peptides banned in sport.
Used together?
The blend directory on this site lists no product that combines AHK-Cu and GHK-Cu. GHK-Cu appears in several multi-ingredient blends with other peptides; AHK-Cu appears in none.
No study of the two copper peptides together could be found in the published record reviewed for this page, whether in people, animals or cells. The GHK-Cu hair studies that used mixtures could not isolate any single ingredient either [15].
This page gives no amounts and no schedule for combining the two. AHK-Cu and GHK-Cu each have a full monograph.
Frequently asked questions
Which is better, AHK-Cu or GHK-Cu?
Neither can be called better on the evidence, because no study comparing them directly could be found. GHK-Cu was tested in two controlled human trials, in leg ulcers and after laser treatment, and both missed their objective targets. AHK-Cu has one study, on hair follicles and hair-root cells in a dish. The two bodies of data answer different questions.
Is AHK-Cu or GHK-Cu safer?
That cannot be answered. GHK-Cu has one expert safety assessment, from 2014, which covers creams at the low concentrations then in use, and nothing for injection. For AHK-Cu, no safety study and no expert assessment of any kind could be found. Missing data are not evidence of safety.
What is the difference between AHK-Cu and GHK-Cu?
The two peptides differ by one building block at the front of the chain: alanine in AHK, glycine in GHK. GHK occurs in the human body and is a listed cosmetic ingredient, Copper Tripeptide-1. AHK-Cu is synthetic, came out of a company patent in 1994 and has one peer-reviewed study. No GHK-Cu result counts as evidence for AHK-Cu.
Can AHK-Cu and GHK-Cu be taken together?
This page answers only what the research shows, not how to use anything. No study of the two copper peptides together could be found, in people, animals or cells. The blend directory on this site lists no product that combines them.
Which copper peptide has been studied for hair, AHK-Cu or GHK-Cu?
AHK-Cu is the one studied specifically on hair, but only in a dish: human hair follicles grew longer, and the only mouse experiment found sits in a 1996 patent. For GHK-Cu, the human hair studies all tested mixtures, such as a complex with copper-free GHK in 45 men. Neither has a controlled human hair trial of the substance on its own.
Have AHK-Cu and GHK-Cu been tested in people?
No test of AHK-Cu in a person could be found, and three registry searches on 20 September 2026 returned no trial. GHK-Cu has two controlled trials of a copper tripeptide preparation, with 86 and 13 patients, and both missed their objective targets. No verified trial of GHK-Cu on its own is registered.
Is Copper Tripeptide-3 the same as GHK-Cu?
No. Copper Tripeptide-1 is the listed cosmetic name of GHK-Cu. Copper Tripeptide-3 is the trade name sellers use for AHK-Cu, and the binding EU glossary of ingredient names has no entry of that name. The glossary does list Alanine/Histidine/Lysine Polypeptide Copper HCL, which fits AHK-Cu by description.
Do AHK-Cu and GHK-Cu get through the skin?
For GHK-Cu, almost no peptide and almost no copper crossed intact donated human skin in the laboratory. Measurable amounts appeared only after the skin had been pre-treated with tiny needles. For AHK-Cu, no measurement of skin uptake in any species could be found.
Are AHK-Cu and GHK-Cu banned in sport?
Neither is printed by name on the 2026 Prohibited List. Class S0 covers any drug-like substance that no health authority has approved, and the injected forms of both fit that wording. A cosmetic applied to the skin is a different case, and no clarification from the anti-doping agency could be found.
Sources
- Schlesinger DH, Pickart L, Thaler MM (1977). Growth-modulating serum tripeptide is glycyl-histidyl-lysine. Experientia 33(3):324-325. PMID 858356. DOI 10.1007/BF02002806
- PubChem. Compounds CID 71587328 (Copper Tripeptide-1) and CID 73587 (glycyl-L-histidyl-L-lysine). Retrieved 7 September 2026. The copper share of 15.8 per cent by mass is calculated from the formula mass of 402.92 g/mol and the atomic mass of copper. https://pubchem.ncbi.nlm.nih.gov/compound/71587328
- Maquart FX, Pickart L, Laurent M et al. (1988). Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+. FEBS Letters 238(2):343-346. PMID 3169264. DOI 10.1016/0014-5793(88)80509-x
- Wegrowski Y, Maquart FX, Borel JP (1992). Stimulation of sulfated glycosaminoglycan synthesis by the complex glycyl-L-histidyl-L-lysine-Cu2+. Life Sciences 51(13):1049-1056. PMID 1522753. DOI 10.1016/0024-3205(92)90504-i
- Lau SJ, Sarkar B (1981). The interaction of copper(II) and glycyl-L-histidyl-L-lysine, a growth-modulating tripeptide from plasma. Biochemical Journal 199(3):649-656. PMID 7340824. DOI 10.1042/bj1990649
- Choi HR, Kang YA, Ryoo SJ et al. (2012). Stem cell recovering effect of copper-free GHK in skin. Journal of Peptide Science 18(11):685-690. PMID 23019153. DOI 10.1002/psc.2455
- Pallenberg AJ, Patt LM, Trachy RE / ProCyte Corporation (1996). Stimulation of hair growth by peptide copper complexes. US patent 5,538,945; filed 17 June 1994, granted 23 July 1996. Retrieved 20 September 2026. https://patents.google.com/patent/US5538945A/en
- Pyo HK, Yoo HG, Won CH, Lee SH, Kang YJ, Eun HC, Cho KH, Kim KH (2007). The effect of tripeptide-copper complex on human hair growth in vitro. Archives of Pharmacal Research 30(7):834-839. PMID 17703734. DOI 10.1007/BF02978833. The only peer-reviewed paper in which AHK-Cu is the test substance; abstract retrieved 20 September 2026, full text not freely available.
- Fan C, Chen Y, Huang Q, Ou WY, Zhang C, Sun Y, Wu T, Leung OY, Iu HC, Shi J (2026). Overview of Short Peptides for Hair Loss. Biomedicines 14(4):864. PMID 42072405. DOI 10.3390/biomedicines14040864. Full text retrieved through Europe PMC on 20 September 2026; the six passages naming AHK-Cu were read individually.
- Mokhtar J, Mohamad B, Haddad J et al. (2026). Systematic review of GHK-Cu studies in aesthetic medicine (title paraphrased). Aesthetic Surgery Journal. PMID 42619529. DOI 10.1093/asj/sjag169
- NCBI E-utilities. Seven search strategies run on 20 September 2026: "AHK-Cu" (1 hit), "AHK copper peptide" (1), "AHK-Cu hair" (1), "copper tripeptide-3" (0), "alanyl-histidyl-lysine" (15), "Ala-His-Lys" (29) and "alanine histidine lysine copper" (8). The abstracts of 14 papers were read individually; all but PMID 17703734 proved unrelated or were passing mentions. https://eutils.ncbi.nlm.nih.gov/entrez/eutils/
- ClinicalTrials.gov API v2. Queries for "AHK-Cu", "copper tripeptide-3" and "alanyl-histidyl-lysine", each returning a total count of zero. Retrieved 20 September 2026. https://clinicaltrials.gov/
- ClinicalTrials.gov API v2. Queries for "GHK-Cu", "copper tripeptide", "glycyl-histidyl-lysine", "copper peptide" and "prezatide" on 7 September 2026. No verified trial of GHK-Cu on its own is registered. One entry, NCT07437586, claims a phase 2 study in 60 participants; its sponsor filed further entries whose own summaries call them a mock study, an example record or a fictional study (NCT07481734, NCT07437560, NCT07487363), so it is not counted here. https://clinicaltrials.gov/study/NCT07437586
- Lee WJ, Sim HB, Jang YH et al. (2016). Efficacy of a complex of 5-aminolevulinic acid and glycyl-histidyl-lysine peptide on hair growth. Annals of Dermatology 28(4):438-443. PMID 27489425. DOI 10.5021/ad.2016.28.4.438
- Kapoor R, Shome D (2018). Intradermal injections of a hair growth factor formulation for enhancement of human hair regrowth: a first-in-man pilot clinical study. Journal of Cosmetic and Laser Therapy 20(6):369-379. PMID 29482481. DOI 10.1080/14764172.2018.1439965
- Bertin ACJ, Vilarinho A, Junqueira ALA (2018). Fractional non-ablative laser-assisted drug delivery leads to improvement in male and female pattern hair loss. Journal of Cosmetic and Laser Therapy 20(7-8):391-394. PMID 29452017
- Bishop JB, Phillips LG, Mustoe TA et al. (1992). A prospective randomized evaluator-blinded trial of two potential wound healing agents for the treatment of venous stasis ulcers. Journal of Vascular Surgery 16(2):251-257. PMID 1495150. DOI 10.1067/mva.1992.37086
- Miller TR, Wagner JD, Baack BR, Eisbach KJ (2006). Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin. Archives of Facial Plastic Surgery 8(4):252-259. PMID 16847171. DOI 10.1001/archfaci.8.4.252
- Canapp SO, Farese JP, Schultz GS et al. (2003). The effect of topical tripeptide-copper complex on healing of ischemic open wounds. Veterinary Surgery 32(6):515-523. PMID 14648529. DOI 10.1111/j.1532-950x.2003.00515.x
- Maquart FX, Bellon G, Chaqour B et al. (1993). In vivo stimulation of connective tissue accumulation by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+ in rat experimental wounds. Journal of Clinical Investigation 92(5):2368-2376. PMID 8227353. DOI 10.1172/JCI116842
- Fu SC, Cheuk YC, Chiu WY et al. (2015). GHK-Cu(II) in a rat model of cruciate ligament reconstruction (title paraphrased). Journal of Orthopaedic Research 33(7):1024-1033. PMID 25731775. DOI 10.1002/jor.22831
- Li H, Low YS, Chong HP et al. (2015). Microneedle-mediated delivery of copper peptide through skin. Pharmaceutical Research 32(8):2678-2689. PMID 25690343. DOI 10.1007/s11095-015-1652-z
- Hostynek JJ, Dreher F, Maibach HI (2010/2011). Human skin retention and penetration of a copper tripeptide in vitro as a function of skin layer. Inflammation Research 59(11):983-988. PMID 20703511 and PMID 20721598
- Cosmetic Ingredient Review. Safety Assessment of Tripeptide-1, Hexapeptide-12, their Metal Salts and Fatty Acyl Derivatives, and Palmitoyl Tetrapeptide-7 as Used in Cosmetics. Final report released 30 June 2014; journal version International Journal of Toxicology 2018;37(3_suppl). DOI 10.1177/1091581818807863
- US Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks; page content current as of 22 April 2026, read in full on 20 September 2026. AHK-Cu does not appear. GHK-Cu appears among substances nominated and then withdrawn, for injectable routes. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- openFDA. Drugs@FDA, the drug label database and the adverse event reporting system, queried 7 September 2026. No approved product for prezatide; 390 label entries mentioning copper tripeptide, 20 of them naming it as an active ingredient; two serious adverse event reports for GHK-Cu, both involving several peptides taken together.
- Li H, Toh PZ, Tan JY et al. (2016). Selected biomarkers revealed potential skin toxicity caused by certain copper compounds. Scientific Reports 6:37664. PMID 27892491. DOI 10.1038/srep37664
- Cosmetic Ingredient Review. Draft and tentative reports on the peptide group, February to May 2014, and panel minutes of March 2013 recording the angiogenesis concern and a reported 1 per cent use level that the final report does not contain. https://www.cir-safety.org/
- openFDA, adverse event API (FAERS). Queries for the product names "AHK-CU" and "AHK" on 20 September 2026 returned nothing; the control query for "GHK-CU" returned two reports. https://api.fda.gov/drug/event.json
- Raw-material shops and grey-market listings recorded through web searches on 20 September 2026. They document the market only, not efficacy, safety or legal status: powder and ready-made solutions sold under the name Copper Tripeptide-3 with purity figures the sellers set themselves, together with formulation and handling advice, and separately freeze-dried vials labelled for laboratory use. No trader is named and no figure from these listings is repeated as guidance.
- PubChem. Compound CID 178189140, the AHK-Cu complex without hydrochloride; C15H23CuN6O4 2-, 414.93 g/mol, InChIKey ZVKPVDJSTIFVQR-LBRAPMIBSA-L. Its only synonym is the registry number 767286-83-9. PUG-REST query of 20 September 2026. https://pubchem.ncbi.nlm.nih.gov/compound/178189140
- EFSA Scientific Committee (2023). Re-evaluation of the existing health-based guidance values for copper. EFSA Journal 21(1):7728. DOI 10.2903/j.efsa.2023.7728
- Endo T, Miyagi M, Ujiie A (1997). Simultaneous determination of glycyl-L-histidyl-L-lysine and its metabolite, L-histidyl-L-lysine, in rat plasma by high-performance liquid chromatography. Journal of Chromatography B 692(1):37-42. PMID 9187381. DOI 10.1016/s0378-4347(96)00460-4
- European Commission. Commission Implementing Decision (EU) 2022/677 of 31 March 2022, current version of the glossary of common ingredient names, OJ L 127, 29 April 2022. Full text downloaded and searched on 20 September 2026: entries 7337 to 7341 are COPPER TRIPEPTIDE-1, COPPER TRIPEPTIDE-1 ACETATE, COPPER TRIPEPTIDE-1 PALMITAMIDE, COPPER TRIPEPTIDE-34 and COPPER TRIPEPTIDE-34 HCL; entry 1468 is ALANINE/HISTIDINE/LYSINE POLYPEPTIDE COPPER HCL. Hits for "COPPER TRIPEPTIDE-3" as an exact entry and for "AHK": none. The glossary is a list of names with no sequences, CAS or EC numbers, so it identifies no substance on its own. https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32022D0677
- World Anti-Doping Agency. The 2026 Prohibited List. Full text searched on 20 September 2026 for "AHK", "copper", "tripeptide", "alanyl" and "Ala-His-Lys": no hits, while "peptide" occurs ten times. The wording of class S0 was taken verbatim from the same document.
- World Anti-Doping Agency. The 2026 Prohibited List and the 2026 Monitoring Programme; both searched on 7 September 2026 for "GHK", "copper", "tripeptide" and "Gly-His-Lys" with no match. Class S0 wording quoted as published.