Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Acetyl tetrapeptide-3 (Ac-KGHK-NH2): what the evidence says

Name: Acetyl tetrapeptide-3 (Ac-KGHK-NH2)
Published: 2026-10-27

At a glance

What it is: a four-amino-acid peptide (acetyl-lysine-glycine-histidine-lysine amide) used in hair products. ^R1 It is usually sold blended with biochanin A, a red-clover compound. ^{R2, R3}

What the evidence says: Human in one 24-week RCT of 32 adults, a blend of acetyl tetrapeptide-3, biochanin A and ginseng extracts increased terminal hair counts about as much as minoxidil solution (8.3% vs 8.7%). ^R4 No study tested the peptide alone.

Biggest risks: no local side effects were reported with the blend in the one trial. ^R4 Long-term data are lacking.

Rating


Human Human evidence	Very limited: one RCT of a blend, n = 32 ^R4
Animal Animal / lab evidence	Not reviewed
Regulatory	Cosmetic ingredient; not FDA-approved ^R5 · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page ^{R6, R7, R8} · not named by WADA ^R9
Established human dose	No

Evidence verdict: Hair loss (androgenetic alopecia): Very limited (one 32-person RCT of a multi-ingredient blend vs minoxidil) · The peptide on its own: No human data

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: one small trial of a three-ingredient product; it was not designed to show what the peptide does by itself, and was too small to prove the blend is as good as minoxidil.

What is it?

Does it work?

Human Blend vs minoxidil (triple-blind RCT, n = 32, 24 weeks): terminal hair counts rose 8.3% with the blend and 8.7% with minoxidil solution, not significantly different. ^R4
Animal Reviews describe the ingredient as targeting the hair follicle's surrounding tissue, mainly from manufacturer lab data. ^{R2, R3} UNVERIFIED against primary data.
Unknown The peptide alone: no human trial found.

Is it safe?

Human No local reactions with the blend in the one RCT (one person on minoxidil developed scalp eczema). ^R4
Patch-test any new scalp product; stop if irritation develops.

Gray-market vials: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.

Is it legal?

US: sold as a cosmetic ingredient. Cosmetics do not need FDA approval before sale; products making drug-type claims can be regulated as drugs. ^R5 No Drugs@FDA application found (openFDA searched Oct 27, 2026).
Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. ^{R6, R7, R8}
Sport: not named on WADA's 2026 Prohibited List. ^R9

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
Lueangarun 2020 (triple-blind RCT)	32 adults with androgenetic alopecia	Topical blend	Per study (vs 3% minoxidil)	24 weeks	Terminal hair +8.3% vs +8.7% (not different)	PMID 33584955

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)

^R1 PubChem CID 11752568, Acetyl tetrapeptide-3 (synonym Ac-Lys-Gly-His-Lys-NH2), checked Oct 27, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/11752568
^R2 Bikash C. Int J Trichology. 2025. PMID 40654553
^R3 Fan C, et al. Biomedicines. 2026. PMID 42072405
^R4 Lueangarun S, et al. J Clin Aesthet Dermatol. 2020. PMID 33584955
^R5 FDA. Is It a Cosmetic, a Drug, or Both? (Or Is It Soap?) Content current as of Sep 11, 2024. https://www.fda.gov/cosmetics/cosmetics-laws-regulations/it-cosmetic-drug-or-both-or-it-soap
^R6 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R7 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R8 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
^R9 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use Acetyl tetrapeptide-3 (Ac-KGHK-NH2). This is a cosmetic ingredient, not an FDA-approved drug. Cosmetic products are not reviewed by FDA for effectiveness before sale. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).