GHK-Cu (copper tripeptide-1)

GHK-Cu is an endogenous tripeptide — glycyl-L-histidyl-L-lysine chelated to copper(II) — first isolated from human serum albumin in 1973 by Pickart and Thaler and structurally confirmed in 1977 ¹. It is found in blood plasma, saliva, urine, and cerebrospinal fluid. In vitro and animal studies show it stimulates collagen, elastin, and glycosaminoglycan synthesis by fibroblasts, promotes wound healing, and exhibits anti-inflammatory activity. Topical GHK-Cu derivatives are widely used in cosmetic formulations; injectable preparations were offered by compounding pharmacies under 503A rules before an FDA review raised access concerns. No large placebo-controlled RCT of injectable GHK-Cu in humans has been conducted.

Identity

PubChem CID (GHK-Cu complex): 139035031
PubChem CID (free GHK tripeptide): 73587
InChIKey (Cu complex): LREZPQNYQZAPJC-ACMTZBLWSA-L
Molecular formula (Cu complex): C₁₄H₂₁CuN₆O₄⁻ (charge-balanced anionic form)
Molecular weight (Cu complex): ~400.9 Da
Free GHK tripeptide MW: 340.4 Da; formula C₁₄H₂₄N₆O₄
Sequence: Gly-His-Lys (three amino acids; N-terminus glycine, C-terminus lysine)
CAS (GHK free acid): 49557-75-7 (commonly cited; not independently confirmed in this seeding pass) needs-canonical-id
ChEMBL ID: not found in ChEMBL as of seeding pass; leave null needs-canonical-id
DrugBank ID: not assigned; GHK-Cu is not an approved drug

Note on PubChem: Two distinct entries exist. CID 73587 is the free tripeptide (GHK, no copper). CID 139035031 is the Cu²⁺ chelate complex — the biologically active species studied in most wound-healing literature. The pubchem-cid: frontmatter field refers to the copper-bound form consistent with the compound’s clinical use.

Plasma decline narrative — what the primary literature actually shows

The widely-cited figure of 200 ng/mL (young, ~20 yr) → 80 ng/mL (older, ~60 yr) appears throughout Pickart-group reviews (e.g., Pickart & Margolina 2018 ²; Pickart et al. 2015 ³). Both review PDFs were read in full: Pickart 2015 cites this figure to reference [1] (Pickart 1973 PhD thesis, University of California San Francisco); Pickart 2018 cites it to reference [6] (also the 1973 thesis). The primary measurement source is therefore an unpublished PhD thesis, not a peer-reviewed analytical study. No primary measurement paper quantifying plasma GHK by age in a defined human cohort with reported sample sizes, assay methodology, and demographic data has been identified. unsourced

The original identification of GHK as a serum factor is in Schlesinger et al. 1977 ¹ and the growth-modulating characterization in Pickart & Thaler 1980 ⁴; neither paper reports age-stratified plasma concentrations. Pickart & Lovejoy 1987 ⁵ reviews biological activity but again does not contain the age-stratified ng/mL figures.

Practical implication for the wiki: the plasma-decline claim originates from Pickart’s 1973 doctoral thesis and has been propagated across 50+ years of review papers without a peer-reviewed primary measurement study. It should be treated as unsourced until a primary measurement study with sample sizes, assay method (e.g., LC-MS/MS plasma quantification), and age-cohort demographics is published and replicated.

What can be stated with reasonable confidence:

GHK is an endogenous human plasma peptide ¹.
Plasma copper-binding capacity and cuproenzyme activity do decline with age in several studies, consistent with reduced endogenous GHK-Cu bioavailability, but this is distinct from measuring GHK peptide levels directly.
The biological plausibility of an age-related decline is high given that GHK is derived from albumin proteolysis and albumin glycation/oxidation increases with age.

Mechanism of action

Collagen and ECM synthesis

The founding mechanistic claim is stimulation of collagen type I and type III synthesis by human fibroblasts in culture ⁶. The Maquart et al. 1988 study (FEBS Letters) showed that GHK-Cu stimulates collagen synthesis beginning between 10⁻¹² M and 10⁻¹¹ M, maximizing at 10⁻⁹ M (1 nM), independent of changes in cell proliferation ⁶. This remains the most-cited primary mechanistic paper.

Subsequent in vitro and small animal studies have reported additional effects:

Stimulation of elastin synthesis in dermal fibroblasts ³ needs-replication
Upregulation of glycosaminoglycan (GAG) synthesis, including decorin and dermatan sulfate
MMP-2 upregulation (matrix remodeling) alongside TIMP-1/2 upregulation (matrix protection) — the net effect on collagen degradation is context-dependent contradictory-evidence

Copper delivery to cuproenzymes

GHK-Cu serves as a bioavailable source of Cu²⁺ for copper-dependent enzymes, including:

Lysyl oxidase (LOX): cross-links collagen and elastin; requires Cu²⁺ as cofactor; essential for tensile strength. GHK-Cu may support LOX activity in copper-deficient microenvironments (e.g., post-wound ischemic tissue).
Cu/Zn superoxide dismutase (SOD1): antioxidant enzyme; requires Cu²⁺.
Ceruloplasmin: plasma ferroxidase; copper-dependent.

The physiological relevance of GHK-Cu as a systemic copper chaperone at endogenous concentrations is unclear — albumin and ceruloplasmin dominate systemic copper transport. The copper-delivery role is more plausible in local tissue microenvironments (e.g., wound beds, granulation tissue).

Gene expression modulation (review-level claim)

Pickart & Margolina 2018 ² synthesized Broad Institute Connectivity Map microarray data showing GHK modulates 31.2% of human genes by ≥50% (approximately 2152 genes stimulated or suppressed at ≥50% cutoff per their Table 1; the figure of “>4000 genes” circulated in earlier Pickart-group reviews ³ refers to a lower-threshold analysis from a 2014 dataset). Gene targets include those associated with DNA repair, anti-inflammatory signalling, anti-cancer pathways, and the ubiquitin-proteasome system. This is a review-paper synthesis; the underlying microarray datasets were not independently validated in this pass and should be treated with caution — review-derived gene-expression claims require primary dataset confirmation. needs-replication

Anti-inflammatory activity

Zebrafish larval models show GHK-Cu attenuates LPS-induced and CuSO₄-induced inflammation by reducing neutrophil/macrophage migration, suppressing pro-inflammatory cytokines (TNF-α, IL-6), and upregulating anti-inflammatory IL-10 ⁷. Mechanism involves JAK1 pathway downregulation. This is an early-stage model; human relevance is unknown. needs-human-replication

Angiogenesis and nerve growth

Pickart & Lovejoy 1987 ⁵ and subsequent in vivo studies report GHK-Cu promotes blood vessel formation and nerve outgrowth in wound models. The molecular mechanism for angiogenesis is incompletely characterized; HIF-1α involvement is proposed but not confirmed.

Effects on aging hallmarks

No direct link to a canonical López-Otín hallmark has been established in a verifiable primary source. Plausible associations (speculative):

Hallmark	Proposed association	Evidence quality
altered-intercellular-communication	GHK-Cu acts as a paracrine peptide signal modulating fibroblast and immune cell behaviour	Mechanistic, in vitro; no in vivo aging model
chronic-inflammation	Anti-inflammatory effects documented in zebrafish model	Single model organism; needs-human-replication
stem-cell-exhaustion	ECM niche quality supports stem cell function in aged muscle/skin	Indirect; no direct data

Decision: hallmarks: left empty in frontmatter. An association with altered-intercellular-communication is the most defensible given the paracrine signalling mechanism, but cannot be asserted without direct aging-model evidence. The R16 intervention matrix checklist requires at least one hallmark wikilink for compound pages — this is a schema gap that must be escalated (see summary below). needs-canonical-hallmark-assignment

Topical vs. injectable — clinical evidence split

Topical (cosmetic and wound-healing):

GHK-Cu is an ingredient in numerous cosmetic products (face serums, wound-healing creams) in concentrations typically 0.01–2%.
Topical delivery is the best-supported route by the (limited) human data. A 2025 review by Mortazavi et al. ⁸ identifies a “surprising absence of clinical studies” despite widespread cosmetic use.
Skin permeation of GHK-Cu through intact stratum corneum is limited; liposomal and palmitoylated derivatives (Pal-GHK, Pal-GQPR) are used to improve penetration [^ogorek2025;
No FDA-approved topical GHK-Cu drug product exists; it is a cosmetic ingredient regulated as such.

Injectable (compounding pharmacy context):

Before FDA PCAC 503A bulk-list restrictions, injectable GHK-Cu was formulated by compounding pharmacies for subcutaneous or intramuscular use.
No published placebo-controlled RCT of injectable GHK-Cu in humans for any indication has been identified in this seeding pass.
Injectable copper administration carries risk of copper toxicity (see Safety below); the therapeutic window relative to toxicity has not been characterized for GHK-Cu specifically.

Practical rule: topical cosmetic evidence does NOT transfer to injectable efficacy claims. The routes have different PK profiles, different dose delivered to systemic circulation, and different risk profiles.

Pharmacokinetics

Formal human PK data for GHK-Cu is sparse.

Topical: skin penetration is low for the free peptide; effective topical delivery requires formulation engineering (liposomes, palmitoyl conjugates) ⁹.
Injectable: once in circulation, GHK peptide is expected to have a short half-life (~minutes to low hours) due to proteolytic degradation by serum and tissue peptidases; copper would redistribute to albumin and ceruloplasmin. No published human PK study was found.
Oral bioavailability: tripeptides are partially absorbed intact but predominantly hydrolyzed to amino acids; GHK-specific oral bioavailability is not reported. dose-response-unclear

Safety

Topical: generally well-tolerated at cosmetic concentrations; no serious adverse events reported in reviews.

Injectable copper context: Copper toxicity (hepatic accumulation, oxidative damage) is well-documented at supraphysiological doses. GHK-Cu at pharmacological injectable doses delivers bioavailable copper; the therapeutic index relative to copper toxicity for this specific formulation is not characterized. This is a material safety gap for injectable use. long-term-unknown

No human clinical safety study for injectable GHK-Cu was found in this seeding pass.

Human evidence summary

Route	Evidence	Notes
Topical cosmetic	Preclinical + observational cosmetic literature	No blinded RCT with objective endpoints
Injectable	None identified	No published trial
Ex vivo skin	Mechanistic collagen-synthesis data in fibroblasts	Well-replicated at cell level; not in vivo human

human-evidence-level: limited — applies to topical route with the note that the evidence base is largely cosmetic-grade (no blinded RCT with objective endpoints). Injectable evidence is none.

Translation gap and next experiment

translation-gap: biomarker-only — existing evidence demonstrates mechanistic activity (collagen synthesis in cell culture, wound healing in animals) but no validated biomarker of systemic GHK-Cu activity in aging humans exists, and no efficacy endpoint in a powered human trial has been demonstrated.
The next-experiment: field (see frontmatter) describes the single study that would resolve the injectable human-evidence gap: a blinded RCT with objective skin collagen endpoint.

Clinical trials

ClinicalTrials.gov v2 query for “GHK copper tripeptide” with status RECRUITING/ACTIVE_NOT_RECRUITING returned 0 active trials as of 2026-05-09. long-term-unknown

Classification

Intervention-classes: intervention-classes — extracellular-matrix-remodeling (new class, added R36 2026-05-09), copper-chaperone, collagen-synthesis-stimulation
SENS strategy: not mapped (ECM repair does not correspond directly to a canonical SENS damage category)
Hallmark target: none directly established (see hallmarks section above)
Clinical category: cosmetic ingredient (topical); compounding-pharmacy biologic (injectable, pre-FDA restriction); not an FDA-approved drug in either context

Limitations and gaps

Plasma decline figures trace to an unpublished PhD thesis. The 200→80 ng/mL (age 20→60) claim is propagated across Pickart-group reviews; both OA review PDFs (2015, 2018) were verified and both trace this figure to Pickart 1973 (PhD thesis, UCSF), not to a peer-reviewed analytical measurement study. unsourced
No injectable human RCT. All injectable use has been clinical practice without a controlled trial. needs-human-replication
No large topical RCT with objective endpoints. Cosmetic evidence is primarily industry-sponsored and lacks blinding/objective skin-collagen measurement.
Hallmark assignment is unclear. GHK-Cu does not map cleanly to any López-Otín hallmark via verified primary evidence. needs-canonical-hallmark-assignment
Review-dominated citation landscape. Most mechanistic claims originate from Pickart-group review papers that synthesize older primary work; independent replication by other groups is limited for many claims.
Copper toxicity at injectable doses is uncharacterized. long-term-unknown
ChEMBL and CAS IDs not confirmed. needs-canonical-id

Footnotes

doi:10.1007/bf02002806 · Schlesinger DH, Pickart L, Thaler MM · Experientia 1977;33(3):324-325 · review/isolation · model: human serum fractionation · structural identification of the growth-modulating serum tripeptide as Gly-His-Lys · 28 citations · archive: not_oa ↩ ↩² ↩³
doi:10.3390/ijms19071987 · Pickart L, Margolina A · International Journal of Molecular Sciences 2018;19(7):1987 · review · 115 citations · 13-page review of GHK protective and regenerative actions; Broad Institute Connectivity Map gene-expression data: 31.2% of human genes altered ≥50% (~2152 genes stimulated or suppressed per Table 1); plasma-decline figure (200→80 ng/mL) cited to Pickart 1973 PhD thesis; no original primary data; review-grade evidence only · archive: downloaded (PMC6073405) ↩ ↩²
doi:10.1155/2015/648108 · Pickart L, Vasquez-Soltero JM, Margolina A · BioMed Research International 2015;2015:648108 · review · 125 citations · 7-page review of GHK mechanisms in skin regeneration; collagen, elastin, GAG synthesis claims synthesized from multiple primary sources; no original data; plasma-decline figure (200→80 ng/mL, age 20→60) cited to Pickart 1973 PhD thesis · archive: downloaded (PMC4508379) ↩ ↩² ↩³
doi:10.1002/jcp.1041020205 · Pickart L, Thaler MM · Journal of Cellular Physiology 1980;102(2):129-139 · PMID 6246126 · in-vitro · model: human hepatoma cells · GHK (glycylhistidyllysine) identified as plasma growth-modulating tripeptide; association with Cu²⁺ and Fe²⁺ ions characterized; complexes stimulate hepatoma cell adhesiveness and growth ↩
doi:10.1016/0076-6879(87)47121-8 · Pickart L, Lovejoy S · Methods in Enzymology 1987;147:314-328 · review · 57 citations · review of GHK biological activity including collagen, angiogenesis, nerve growth claims · archive: not_oa ↩ ↩²
doi:10.1016/0014-5793(88)80509-x · Maquart FX, Pickart L, Laurent M, Gillery P, Monboisse JC, Borel JP · FEBS Letters 1988;238(2):343-346 · in-vitro · model: human fibroblast cultures · GHK-Cu stimulates collagen synthesis; onset between 10⁻¹² M and 10⁻¹¹ M, maximum at 10⁻⁹ M, independent of proliferation changes · 173 citations · archive: not_oa (concentrations confirmed via Crossref abstract) ↩ ↩²
doi:10.1016/j.ejphar.2026.178880 · PMID 41997403 · Hu J, Zhang C, Wang F · European Journal of Pharmacology 2026 · in-vivo · model: zebrafish larvae (CuSO₄ and LPS inflammation models) · GHK-Cu reduces neutrophil/macrophage migration, pro-inflammatory cytokines; increases IL-10; JAK1 pathway downregulation ↩
doi:10.34172/bi.30071 · PMID 39963574 · Mortazavi SM, Mohammadi Vadoud SA, Moghimi HR · BioImpacts 2025 · review · notes “surprising absence of clinical studies” on topical GHK despite widespread cosmetic use; covers GHK and Pal-GHK anti-wrinkle evidence ↩
doi:10.3390/molecules30010136 · PMID 39795193 · Ogórek K, Nowak K, Wadych E, Ruzik L, Timerbaev AR, Matczuk M · Molecules 2025 · review · skin permeation methodology for liposomal GHK-Cu; GHK-Cu noted as “fairly hydrophilic with limited permeation through the lipophilic stratum corneum”; identifies major gaps in standardized assessment approaches ↩

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