Pal-AHK

What is Pal-AHK?

Pal-AHK is a synthetic lipopeptide consisting of the tripeptide alanine-histidine-lysine (AHK) conjugated to palmitic acid. Its molecular formula is C31H56N6O5 with a molecular weight of approximately 592.8 Da. The palmitoyl modification enhances lipophilicity, improving penetration through the skin's lipid-rich stratum corneum compared to the unmodified AHK sequence. While structurally related to Pal-GHK (Palmitoyl Tripeptide-1) — which uses glycine in place of alanine — Pal-AHK has a distinct research profile centered on hair follicle stimulation and dermal papilla cell survival rather than matrikine-driven collagen signaling. The AHK sequence also has affinity for copper ions, forming the AHK-Cu complex, which is the form used in most published in vitro research. Pal-AHK has no established INCI name of its own, and the two names most often attached to it online belong to entirely different molecules. The Cosmetic Ingredient Review's 2012 scientific literature review of palmitoyl oligopeptides defines Palmitoyl Tripeptide-28 as a tripeptide of arginine, lysine and phenylalanine, and lists Palmitoyl Tripeptide-3 as a technical name for Palmitoyl Tripeptide-5 (Pal-Lys-Val-Lys, sold as Syn-Coll). Neither contains alanine or histidine, and no palmitoyl tripeptide anywhere in the CIR inventory is alanine-histidine-lysine. The copper form fares slightly better: it appears in European ingredient listings as Alanine/Histidine/Lysine Polypeptide Copper HCl, a polypeptide-style INCI name rather than a numbered tripeptide. The widely used label Copper Tripeptide-3 is not independently verifiable — unlike Copper Tripeptide-1 for GHK-Cu, which CIR's 2014 final report defines explicitly, it returns nothing in CIR, PubChem or the indexed literature.

What Pal-AHK Is Investigated For

Pal-AHK is a palmitoylated cosmeceutical tripeptide marketed primarily for hair growth stimulation (via dermal papilla cell proliferation and anti-apoptotic signaling), collagen synthesis and skin anti-aging, and — with weaker grounding — for skin pigmentation and tone improvement. The strongest signal, such as it is, comes from a single in vitro and ex vivo study (Pyo et al., 2007) using the copper-complexed form AHK-Cu on cultured human hair follicles and dermal papilla cells. It showed follicle elongation, more dermal papilla cell proliferation, a higher Bcl-2/Bax ratio, and less cleaved caspase-3 and PARP. The drop in the number of apoptotic cells was not statistically significant, and the VEGF and TGF-β1 effects often quoted alongside this paper were background findings for tripeptide-copper complexes, not new AHK-Cu results. A 2026 review of short peptides for hair loss (Fan et al., PMID 42072405) still describes AHK-Cu's evidence as in vitro and ex vivo only, with a signaling mechanism less well characterized than GHK-Cu's. No published human trial has tested Pal-AHK or AHK-Cu on its own for any endpoint, no in vivo animal hair-growth studies have been completed, and whether the palmitoylated form retains the biological activity demonstrated for the copper complex is assumed rather than demonstrated. Pigmentation claims have no peer-reviewed mechanistic support. For androgenetic alopecia, FDA-approved minoxidil and finasteride have an incomparably stronger evidence base.

History & Discovery

The AHK tripeptide (Ala-His-Lys) sits within the broader copper-tripeptide family that includes the much better-studied GHK (Gly-His-Lys), the original copper-binding peptide identified by Loren Pickart in human plasma in the 1970s. Researchers exploring copper-tripeptide structure-activity relationships found that AHK retained copper-binding capacity through its histidine-imidazole and lysine-amine groups while showing a distinct biological activity profile centered on hair follicle and dermal papilla cell biology rather than the matrikine-like collagen signaling associated with GHK-Cu. The key foundational study was published by Pyo and colleagues in 2007, demonstrating that AHK-Cu (the copper-complexed form, also designated copper tripeptide-3) stimulated human hair follicle elongation ex vivo and dermal papilla cell proliferation in vitro at picomolar to nanomolar concentrations, with anti-apoptotic molecular signatures (elevated Bcl-2/Bax ratio, reduced cleaved caspase-3 and PARP). This single study has driven most subsequent commercial interest in the peptide for hair-loss formulations. The palmitoylated form (Pal-AHK) was developed for improved transdermal delivery in cosmeceutical formulations, following the same lipidation strategy used for Pal-GHK and the Matrixyl-family matrikines. Independent peer-reviewed replication of the hair-growth findings remains thin, and no published human clinical trials for Pal-AHK or AHK-Cu specifically have been completed.

How It Works

Pal-AHK works primarily by supporting hair follicle cells. In lab studies, the AHK sequence (in its copper-bound form) stimulated dermal papilla cells — the specialized cells at the base of hair follicles that control the growth cycle — to proliferate and survive longer. It appears to do this by tipping the balance of survival proteins: increasing Bcl-2 (a pro-survival signal) relative to Bax (a pro-death signal). The overall drop in dying cells in that study was small and not statistically significant, so the anti-death effect is a signal rather than a proven result. Earlier work on tripeptide-copper complexes reported more VEGF (which supports blood-vessel growth) and less TGF-β1 (a hair-cycle brake) from skin fibroblasts, but those effects were not measured for AHK specifically. The palmitoyl modification helps the peptide penetrate the skin's outer lipid barrier when applied topically.

The AHK tripeptide (L-alanyl-L-histidyl-L-lysine), particularly in its copper-complexed form (AHK-Cu), exerts biological effects through multiple pathways in dermal papilla cells (DPCs) and fibroblasts. In the key study by Pyo et al. (2007), AHK-Cu at concentrations of 10^-12 to 10^-9 M stimulated human hair follicle elongation ex vivo and DPC proliferation in vitro. At the molecular level, 10^-9 M AHK-Cu elevated the Bcl-2/Bax ratio and reduced the cleaved forms of caspase-3 and PARP in DPCs. Annexin V / propidium iodide flow cytometry showed fewer apoptotic DPCs, but the paper reports that this decrease was not statistically significant — so the protein-marker changes point toward an anti-apoptotic effect without demonstrating one at the level of cell counts. The paper's introduction cites earlier findings that tripeptide-copper complexes stimulate dermal fibroblast proliferation, raise VEGF production, and lower TGF-beta1 secretion; TGF-beta1 is a known catagen-inducing factor, so its reduction would in principle favor sustained anagen-phase activity. Those fibroblast effects are background claims for the copper-tripeptide class and were not measured for AHK-Cu in this study. Claims circulating online of a '300% increase in collagen type I' for AHK could not be traced to any indexed paper. The palmitoyl moiety (C16 fatty acid) conjugated to the N-terminus enhances lipophilicity, following the same strategy used in Pal-GHK and other cosmeceutical peptides. The evidence that this actually delivers peptide into skin is real but narrower than usually implied, and it points in two directions. In favour: a head-to-head permeation study of the collagen pentapeptide KTTKS found the free peptide in none of the skin layers while its palmitoylated form was recovered from stratum corneum, epidermis and dermis alike, and was also more proteolytically stable. Against: a 2026 study measuring cosmetic actives directly in living human stratum corneum by OrbiSIMS found that Pal-GHK — the closest structural analogue to Pal-AHK — showed ion intensities dropping immediately on depth profiling, consistent with the peptide sitting on cell surfaces rather than entering them, and concluded that lipophilicity does not by itself determine permeation pathway. Neither study examined Pal-AHK, for which no permeation data of any kind exists. Whether the palmitoylated form is cleaved to release free AHK or acts as an intact molecule also remains uncharacterised — and notably, no published work demonstrates deacylation for any palmitoylated cosmetic peptide, while the finding that palmitoylation increases rather than decreases stability cuts against a simple prodrug model.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Pal-AHK:

• 01Human clinical trials — no published human trial has tested Pal-AHK or AHK-Cu on its own for hair growth, skin pigmentation, anti-aging, or any other endpoint. All biological activity claims rest on preclinical in vitro and ex vivo work.
• 02Ingredient identity on labels — Pal-AHK has no clearly established INCI name, and the two names most often attached to it (palmitoyl tripeptide-28 and palmitoyl tripeptide-3) are defined in CIR nomenclature as different peptides. Buyers generally cannot confirm from an ingredient list that a product contains Pal-AHK at all.
• 03AHK-specific fibroblast data — the VEGF, TGF-beta1, and collagen effects often attributed to AHK are background claims for tripeptide-copper complexes; no indexed paper measures them for AHK or Pal-AHK.
• 04Independent replication of the foundational Pyo et al. 2007 hair-growth study — most current commercial claims trace back to a single research group's findings, and independent peer-reviewed replication is essential before treating the mechanism as established. The reviews that cite it illustrate why: the 2026 short-peptide review restates Pyo's apoptosis result as confirmed, where the primary paper explicitly reports the reduction was not statistically significant, and gives a concentration range of 10^-13 to 10^-7 M against Pyo's own 10^-12 to 10^-9 M.
• 05Whether the palmitoylated form (Pal-AHK) retains the biological activity demonstrated for the copper-complexed form (AHK-Cu) at the cellular level — this is assumed but not directly characterized, and the gap is total rather than partial: there is no PubMed-indexed study of Pal-AHK for any endpoint, and even the 2026 review of short peptides for hair loss that covers AHK-Cu does not mention the palmitoylated form at all.
• 06In vivo animal hair-growth studies — no published rodent or other in vivo hair-growth models have been completed for AHK-family peptides, which is a notable gap given the strength of in vitro and ex vivo claims.
• 07Real-world skin and scalp penetration quantification across commercial formulations — delivery to dermal papilla cells, fibroblasts, or melanocytes from typical topical products is poorly characterized, and no permeation study has ever been run on Pal-AHK itself. What data exist for the nearest analogues disagree: palmitoylated KTTKS reaches dermis where the free peptide reaches nothing, while Pal-GHK measured in living human stratum corneum by OrbiSIMS appears to remain on cell surfaces rather than entering them.
• 08Safety profile under chronic use, particularly for scalp formulations applied long-term — no formal safety surveillance data exists, and the chronic copper-coordination biology of the AHK-Cu form has not been studied for long-term cumulative effects.
• 09Mechanistic basis for marketed pigmentation and skin-tone claims — no peer-reviewed published research directly demonstrates Pal-AHK or AHK-Cu effects on melanogenesis or melanocyte biology; pigmentation marketing claims are commercially driven rather than evidence-based.

Forms & Administration

Pal-AHK is used exclusively as a topical cosmeceutical ingredient. It is typically formulated in serums, creams, and scalp treatments targeting hair growth or skin anti-aging. Concentrations in commercial products are generally not standardized or disclosed. The copper-complexed form (AHK-Cu) is also available as a topical research compound. No injectable formulations have been studied in humans. Topical cosmeceutical use does not require a prescription.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

Pal-AHK is a cosmetic ingredient, not a drug. It is not FDA-approved to treat hair loss, skin aging, or any other medical condition. Cosmetic claims permitted on labels are limited to appearance-related language. For androgenetic alopecia, FDA-approved options (topical minoxidil, oral finasteride) have a far stronger evidence base than any cosmetic peptide.

Timeline of Effects

Common Questions

Who Pal-AHK Is NOT For

Drug & Supplement Interactions

Documented pharmacological drug interactions for topical Pal-AHK are minimal. Systemic absorption from typical topical use is low, and the palmitoylated tripeptide is not expected to reach clinically relevant plasma levels or interact with oral or injected medications. The relevant interaction space is topical layering. Pal-AHK is generally compatible with other cosmetic actives — niacinamide, hyaluronic acid, peptides, and gentle scalp tonics layer readily. Co-formulation with other copper tripeptides (GHK-Cu, Pal-GHK) is common, though there is a theoretical concern that competing copper-binding peptides could interfere with each other's copper coordination — clinical relevance unclear. Pairing with topical minoxidil in scalp routines is common in over-the-counter hair-growth product designs; no specific interaction has been documented but the combination is not formally studied. High-concentration L-ascorbic acid (vitamin C) and strong AHA/BHA exfoliants may destabilize peptide actives if applied in the same layer or immediately after, so spacing to different times of day is sensible. For hair-loss patients on FDA-approved therapies (oral finasteride, oral minoxidil, dutasteride), there is no documented interaction with Pal-AHK at the level of topical cosmetic exposure, but Pal-AHK should not be relied on as a substitute for evidence-based pharmacologic options.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions