Acetyl Tetrapeptide-3

What Acetyl Tetrapeptide-3 is

A synthetic tetrapeptide: four residues, acetylated at the N-terminus and amidated at the C-terminus, sequence Ac-Lys-Gly-His-Lys-NH₂. The formal chemical name in the public record is N²-acetyl-L-lysylglycyl-L-histidyl-L-lysinamide, which spells out the same thing.

The middle three residues — Gly-His-Lys — are the GHK motif, the tripeptide at the heart of the copper-peptide literature. That resemblance is why this peptide is often introduced alongside GHK-Cu, and it is worth being precise about what the resemblance is and is not. Structurally: same three residues, plus a lysine at the front and an acetyl cap. Chemically: no copper. GHK-Cu is a copper(II) complex whose whole character comes from the coordination chemistry of that metal centre; this molecule is an uncomplexed acetylated peptide. It is a related molecule, not a variant of the same active, and reading the copper-peptide literature onto it would be a mistake.

The peptide is sold under several trade names, including Folixyl and Kollaren, and is the peptide component of the hair-care blend Capixyl, where it is combined with a biochanin-A-rich red clover extract.

A naming hazard

The public record for CAS 827306-88-7 carries “Acetyl tetrapeptide-1” in its synonym list alongside Acetyl Tetrapeptide-3. Acetyl Tetrapeptide-1 is a distinct INCI name in ordinary use. If a supplier document treats the two as interchangeable, verify against the CAS number and the sequence, not against the name on the label.

Reference data

Verified against the public chemical record; the deposited structure was inspected and matches the stated sequence.

Use concentration — what is documented

The only citable numbers describe the blend, not the peptide. A 2025 review in the International Journal of Trichology tabulates Capixyl — the trade complex containing this peptide plus red clover extract — at 5% for intensive treatment and 0.5–2.5% for preventive care, attributing the ingredient to Lucas Meyer Cosmetics. Those are percentages of a diluted trade blend in a carrier, and the peptide content within that blend is a supplier figure we cannot independently source.

For the isolated peptide as raw powder, no independently published use concentration exists that we could find, and we located no Cosmetic Ingredient Review safety assessment for it. A formulator working from powder is therefore setting a use level without an independently reviewed reference point — which is a legitimate thing to do, but should be done knowingly, and documented in the product’s own safety assessment.

The evidence, and whose it is

The trial that exists

Lueangarun and Panchaprateep (2020, J Clin Aesthet Dermatol) ran a 24-week, prospective, randomised, triple-blind controlled trial in 32 subjects with mild-to-moderate androgenetic alopecia, comparing twice-daily application of a combination of biochanin A, acetyl tetrapeptide-3 and ginseng extracts against 3% minoxidil solution. Terminal hair counts rose in both arms (8.3%, p = 0.009 for the combination; 8.7%, p = 0.002 for minoxidil) with no statistically significant difference between them. The authors declared no funding and no conflicts of interest, and themselves recommended larger and longer studies.

The design is genuinely better than most of what surrounds this ingredient class — triple-blind, randomised, an active comparator rather than a vehicle, 24 weeks. Two caveats belong with it. First, “comparable to minoxidil” is being inferred from the absence of a significant difference in a 32-person trial, and a study that size has limited power to detect a real difference; absence of evidence of a difference is not evidence of equivalence. Second, the tested article is a three-component combination, so nothing in the result is attributable to the peptide alone.

What is quoted but is not a paper

The other figure that circulates — 30 men with androgenetic alopecia, 15 on 5% Capixyl lotion and 15 on placebo for four months, with a reported 46% increase in the anagen-to-telogen ratio against a 33% reduction on placebo — comes from the Lucas Meyer Cosmetics technical file for Capixyl, dated 2013. The 2025 review cites it as such. It is a supplier document, not a peer-reviewed publication, and it should be read as a manufacturer’s account of its own testing.

That same review, surveying this whole class of hair actives, notes that most of the underlying studies have limited sample sizes, lack comparison with standard therapies, show non-uniformity between study groups, do not disclose the type of alopecia treated, and carry conflicts of interest. That is a fair summary of the position here.

Formulation, stability and storage

• Water phase, and strongly basic. Two lysine residues and a histidine give the molecule a high net positive charge at cosmetic pH. Cationic actives can interact with anionic polymers and anionic surfactants, which is a practical compatibility question in a shampoo or a carbomer-thickened serum. This follows from the structure; it is not a measurement on this ingredient.
• Histidine and metals. The imidazole side chain of histidine is the residue that binds transition metals in the GHK system. This peptide is supplied uncomplexed, but the same coordinating group is present, so combining it with copper or zinc salts in the same phase is a real interaction to consider rather than a neutral one.
• Capped at both ends. N-acetylation and C-amidation remove the free termini that exopeptidases attack, which is the usual reason for those modifications. No published dermal-stability figure for this peptide was found; the method paper in this area used pal-KTTKS as its reference substrate.
• No published pH-stability window. None found in the indexed literature.

As powder, store dry, cold and dark, and avoid repeated warming and re-chilling. See how to store peptides.

Verifying identity and purity

Mass spectrometry confirms the material is Ac-Lys-Gly-His-Lys-NH₂ by comparing the measured mass against approximately 510 Da. HPLC reports how much of the material is that peptide. Because this molecule is frequently sold under trade names and has a genuine synonym collision in the public record, an identity check against the expected mass is worth more here than usual. See how to read a COA and how to verify peptide purity, and look up any batch we ship on verify.

What is not established

• Any effect of this peptide in isolation. No standalone trial was found.
• Equivalence to minoxidil. The trial that is quoted for it found no significant difference in 32 subjects, which is not the same finding.
• An independently published use concentration for the isolated peptide, or a Cosmetic Ingredient Review safety assessment for it.
• Published stability, pH-compatibility or permeability data specific to this molecule.

Sourcing and related ingredients

Supplied as raw material with a per-batch Certificate of Analysis reporting HPLC purity and mass-spectrometric identity confirmation. Not supplied as a finished cosmetic, and the certificate is not a cosmetic safety assessment.

Related: Capixyl is the trade blend built around this peptide; GHK-Cu and AHK-Cu are the copper tripeptides that share its central motif; Matrixyl 3000 contains a lipidated GHK peptide. The full ingredient list with live availability is on the cosmetic ingredient hub.

Frequently asked questions

Literature cited

1. Lueangarun S, Panchaprateep R. “An Herbal Extract Combination (Biochanin A, Acetyl tetrapeptide-3, and Ginseng Extracts) versus 3% Minoxidil Solution for the Treatment of Androgenetic Alopecia: A 24-week, Prospective, Randomized, Triple-blind, Controlled Trial.” J Clin Aesthet Dermatol. 2020;13(10):32–37. PMID 33584955. pubmed.ncbi.nlm.nih.gov/33584955. (n = 32; no funding declared.)
2. Bikash C. “Topical Alternatives for Hair Loss: Beyond the Conventional.” Int J Trichology. 2025;17(1):13–19. PMID 40654553. pubmed.ncbi.nlm.nih.gov/40654553. (Source of the Capixyl use concentrations and of the identification of the Lucas Meyer technical file as the source of the 30-man data.)
3. Lucas Meyer Cosmetics. “Technical File Capixyl™.” 2013. A supplier document, not a peer-reviewed publication; cited here only because the widely-quoted 30-subject figures originate from it, as identified by Bikash (2025).
4. National Center for Biotechnology Information. “PubChem Compound Summary for CID 11752568, Acetyl Tetrapeptide-3.” pubchem.ncbi.nlm.nih.gov/compound/11752568 (sequence, formula, mass, CAS, synonyms).
5. Errante F, Menicatti M, Pallecchi M, et al. “Susceptibility of cosmeceutical peptides to proteases activity: Development of dermal stability test by LC-MS/MS analysis.” J Pharm Biomed Anal. 2021;194:113775. PMID 33281001. pubmed.ncbi.nlm.nih.gov/33281001.
6. Mortazavi SM, Moghimi HR. “Skin permeability, a dismissed necessity for anti-wrinkle peptide performance.” Int J Cosmet Sci. 2022;44(2):232–248. PMID 35302659. pubmed.ncbi.nlm.nih.gov/35302659.