Acetyl tetrapeptide-3 sells hair serums on a comparison to minoxidil. The peer-reviewed literature that supports the comparison is one paper, and reading it changes what the comparison means.
A PubMed search on 2026-09-11, across all fields, for both hyphenations of the name and for the trade name it is sold under, returns a single record.
What it actually is
The structure is on file as PubChem CID 11752568: Ac-Lys-Gly-His-Lys-NH2, formula C22H39N9O5, molecular weight 509.6.
Read the middle of that sequence. Glycine, histidine, lysine — GHK, the tripeptide that the whole copper-peptide category is built on. Acetyl tetrapeptide-3 is that tripeptide with one extra lysine on the front and chemical caps on both ends, and without a metal attached.
The arithmetic confirms it rather than merely suggesting it. Free KGHK is C20H36N8O5. Convert the C-terminal acid to an amide and add an acetyl group to the N-terminus, and the formula becomes C22H39N9O5 — the registered formula, to the atom.
This matters commercially because it means an ingredient list can carry two or three peptides that are variations on one molecule while reading like a stack of different technologies. The copper peptide entry covers what is known about the parent tripeptide, and that literature is both larger and older than anything published under this INCI name.
The one trial, read properly
Lueangarun and Panchaprateep, Journal of Clinical and Aesthetic Dermatology, October 2020 (PMID 33584955). Thirty-two people, sixteen of them male, mean age 41.3, with mild to moderate androgenetic alopecia. Twenty-four weeks. Randomised, triple-blind. One millilitre twice daily.
Those are real design strengths, and the study should be credited for them. Triple-blinding and a 24-week endpoint are better than most of what this ingredient class produces, and the authors disclose no funding and no conflicts.
Three things about it are decisive anyway.
There is no placebo arm. The comparison is against 3% minoxidil. Terminal hair counts rose 8.3% in the combination group (P=0.009) and 8.7% in the minoxidil group (P=0.002), a difference the paper reports as not statistically significant. In a two-active trial with no inert third group, "no significant difference" is a statement about the gap between two numbers, not a demonstration that either number was caused by the treatment. Hair counts in a marked scalp region move with the season, with the photographic method, and with the fact that a person enrolled in a hair trial is handling their hair differently for six months.
Thirty-two people is a small base for a non-inferiority reading. The paper does not claim non-inferiority; it says the non-significant difference suggests the combination could potentially be an alternative, and it recommends larger groups and longer follow-up. The marketing shorthand — as effective as minoxidil — is a stronger sentence than the one the authors wrote.
The peptide was one of three actives. The tested product was biochanin A, acetyl tetrapeptide-3 and ginseng extract. Biochanin A is a red clover isoflavone. Whatever the combination did, the trial contains no arm that isolates the peptide, so the result belongs to the bottle.
Why the red clover keeps reappearing
The pattern is not an accident of one study. The hair peptide is sold beside a red clover extract in the supplier blend as well, and the site's account of what the anti-DHT claim for men's hair peptides rests on traces that claim to a mechanistic clause in a 2013 paper about the same pairing, in which no androgen was ever measured in a volunteer.
So the two most-cited pieces of evidence for this peptide are both studies of the peptide plus red clover, and red clover isoflavones are the half of the pairing with an independent anti-androgen rationale in the literature. That does not make the peptide inert. It means no published experiment has been designed in a way that could tell.
The comparison, weighed on both sides
The selling point is a comparison with minoxidil. It is worth putting the two literatures beside each other, because the comparison is being made across a very steep gradient.
Searched the same day, on the same database:
| Indexed records | Randomised controlled trials | |
|---|---|---|
| Minoxidil in androgenetic alopecia | 765 | 88 |
| Acetyl tetrapeptide-3 | 1 | 1 |
Minoxidil's 88 randomised controlled trials are what make it possible to say anything confident about how much hair it grows, in whom, and how often it fails. The peptide's single trial is one of those 88 — it is the same study counted twice, because the one paper naming the peptide is itself a minoxidil comparison.
That asymmetry is not an argument that the peptide does nothing. It is the reason a single 32-person study cannot carry the sentence built on it. When a treatment with 88 randomised trials and a treatment with one are compared in a study with no placebo arm, the well-characterised drug is supplying the credibility of the result and the new ingredient is borrowing it.
Products and labels
On finished products the ingredient usually appears twice over: the blend name in the marketing copy and the INCI name in the ingredient list, typically low in the list, after the preservatives in many cases. Neither position discloses a concentration.
The supplier's usage guidance for the blend and the 1 mL twice-daily dose in the trial are the only quantities publicly attached to it, and they are not comparable to each other — one is a formulation percentage and the other is an applied volume. A shopper comparing two scalp serums that both list acetyl tetrapeptide-3 has no published number to compare.
No Cosmetic Ingredient Review safety assessment for this peptide could be located; the panel's published peptide assessments cover protein-derived and plant-derived peptides rather than the numbered synthetic actives.
What the evidence does not show
No trial of acetyl tetrapeptide-3 alone against a vehicle control appears in the indexed literature. No published measurement of scalp or serum androgens in people using it. No dose-response data, and no disclosed concentration in the finished products that carry it — the label names the blend or the peptide, never the percentage.
Products that list it are not making an unusual claim by the standards of this category; they are resting a strong comparison on a single 32-person study that was not designed to support it. The same shape recurs across the class, and the SNAP-8 entry documents it from the supplier-study side.
Sources and dates
Opened 2026-09-11: PubMed E-utilities, all-field and title/abstract searches for both hyphenations of acetyl tetrapeptide-3 and for Capixyl (one record each); the full abstract and conflict-of-interest statement of Lueangarun and Panchaprateep 2020, PMID 33584955, PMCID PMC7840088; PubChem compound record CID 11752568 for the structure, formula and molecular weight. Molecular-formula arithmetic was carried out for this entry and can be checked against the PubChem record. The comparison table was produced by two further PubMed counts run in the same session: minoxidil with androgenetic alopecia in a title or abstract (765 records), and the same query restricted to the randomised-controlled-trial publication type (88). Both are raw database counts, not a systematic review's yield, and they are cited here as a measure of how much has been published rather than of how well.
A note on what was searched for and not found: no Cosmetic Ingredient Review safety assessment covering this peptide was located. The Expert Panel's published peptide assessments — soy proteins and peptides (2023), skin and connective tissue-derived proteins and peptides (2022), plant-derived proteins and peptides (2022) — address protein-derived material rather than the numbered synthetic actives sold under names like this one, which is itself a fact about how lightly regulated this ingredient class is. Corrections go to the contact page; the review standard is on the testing notes page.