Acetyl Hexapeptide-3

What Is Acetyl Hexapeptide-3?

Acetyl hexapeptide-3 is a synthetic hexapeptide, Ac-EEMQRR-NH2, created through a rational design program to mimic, at much lower potency and without the toxicity, the anti-wrinkle action of botulinum neurotoxins. Its designers showed that it inhibits neurotransmitter release by interfering with the SNARE protein complex required for calcium-dependent exocytosis.^[1]

The same molecule is listed under the INCI name acetyl hexapeptide-8, sometimes abbreviated AH-8. A 2025 review describes it as one of the most widely discussed biomimetic peptides in cosmeceuticals, used in topical products aimed at anti-aging, scar treatment and skin rejuvenation.^[2]

The central research question about acetyl hexapeptide-3 is delivery. It is hydrophilic and relatively large, which limits its passage through the stratum corneum, and reviewers note that its ability to reach neuromuscular junctions after topical application remains uncertain.^[2]

Chemical Structure and Molecular Identity

Acetyl hexapeptide-3 consists of six standard L-amino acids, glutamate, glutamate, methionine, glutamine, arginine and arginine, with an acetylated N-terminus and an amidated C-terminus. PubChem indexes it under CID 71587772, and its CAS number is 616204-22-9.

The sequence combines two acidic glutamate residues near the N-terminus with two basic arginine residues at the C-terminus, giving a highly polar, water-soluble peptide. This hydrophilicity is the main reason for its poor permeation through the lipid-rich outer layer of skin.^[2]

The peptide can be quantified in skin layers and formulation matrices by hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS), using stable isotope-labeled analogues as internal standards.^[3][4] It also binds copper(II) ions, a property that has been used as a starting point for designing new copper-chelating derivatives.^[5]

Names and synonyms

• INCI name: acetyl hexapeptide-8 (also acetyl hexapeptide-8 amide)
• Earlier name: acetyl hexapeptide-3
• Abbreviations: AH-8, Ac-EEMQRR-NH2

Research History and Development

Acetyl hexapeptide-3 was reported in 2002 as the product of a program to design non-toxic molecules that reproduce the anti-wrinkle action of botulinum neurotoxins. The original report described inhibition of neurotransmitter release, a skin topography study in healthy women, and an absence of oral toxicity or primary irritation in safety testing.^[1]

Over the following decade, attention shifted to whether the peptide penetrates skin. Analytical chemists developed HILIC-MS/MS methods to measure it in tape strips, epidermis, dermis and receptor fluid, and these methods were used in diffusion-cell studies on animal and human skin.^[4][3] Formulation scientists compared emulsion types to improve its delivery, noting that it had also been explored as a topical treatment for blepharospasm.^[6]

Later work extended the sequence in new directions. Researchers studying the analgesic peptide DD04107, the palmitoylated version of the same hexapeptide, also tested its acetylated analogue on neuronal exocytosis, and chemists designed copper-binding variants of the sequence.^[7][5] Public interest in the ingredient has also grown: a Google Trends analysis found that searches for it rose sharply in 2022, although they remained well below searches for botulinum neurotoxin. The authors linked the rise to the ingredient’s affordability, over-the-counter availability and ease of self-application.^[8]

Mechanisms Studied in Research

Acetyl hexapeptide-3 is studied as an inhibitor of neuronal exocytosis: it interferes with the SNARE complex, and related work points to synaptotagmin-1 as a possible additional target.

SNARE complex interference

In the original mechanistic work, the hexapeptide inhibited neurotransmitter release with a potency similar to that of botulinum neurotoxin type A but with much lower efficacy. The inhibition was attributed to interference with the formation or stability of the vesicular fusion (SNARE) complex that drives calcium-dependent exocytosis.^[1]

Synaptotagmin-1 binding

In primary sensory neurons, both DD04107 (the palmitoylated hexapeptide) and its acetylated analogue inhibited the exocytotic release of α-calcitonin gene-related peptide (α-CGRP). Side-chain scanning identified the first glutamate, methionine, glutamine and the final arginine as crucial for activity, and isothermal titration calorimetry showed that some peptides in the series bound directly to the C2B domain of synaptotagmin-1 but not synaptotagmin-7.^[7]

Copper binding

The hexapeptide has a measurable affinity for copper(II) ions. Researchers characterized new derivatives by potentiometric titration and calorimetry and compared their cytotoxicity in human skin cells with that of the parent peptide and its copper complexes.^[5]

How these mechanisms operate after topical application is not established. Reviewers describe the biological basis of reported skin effects, and particularly the peptide’s ability to inhibit muscle contraction through intact skin, as incompletely understood.^[2]

Key Findings From Published Studies

Most published data on acetyl hexapeptide-3 concern its mechanism in neurons and its limited penetration into skin; human efficacy data are small-scale. Key results by model:

Skin penetration

• In diffusion cells with hairless guinea pig and human cadaver skin, most of the applied peptide was washed from the surface after 24 hours. What penetrated stayed mainly in the stratum corneum (0.54% of the applied amount in guinea pig and 0.22% in human skin), and about 0.01% reached the epidermis in both.^[3]
• On porcine ear skin, a water-in-oil-in-water multiple emulsion significantly increased penetration compared with simple oil-in-water and water-in-oil emulsions, and water-rich vehicles outperformed the oil-rich one.^[6]

Human studies

• In the 2002 report, skin topography analysis in healthy women showed wrinkle depth reductions of up to 30% after 30 days of use of an emulsion containing the peptide.^[1]
• A 2025 review concluded that preclinical and clinical studies indicate the peptide may reduce wrinkle depth and improve elasticity and hydration, with some studies also reporting effects on scar remodeling and sebum regulation, while emphasizing that low skin penetration limits its bioavailability.^[2]
• A 2014 dermatology review described it as an effective topical anti-wrinkle agent and suggested it could serve as an adjunct to intramuscular botulinum neurotoxin treatment.^[9]

Neuronal and animal studies

• The acetylated hexapeptide inhibited α-CGRP release from primary sensory neurons; a cyclic palmitoylated derivative from the same series showed potent analgesic activity in an inflammatory pain model.^[7]

Because published results hinge on the exact acetylated, amidated hexapeptide, researchers typically confirm identity and purity with HPLC and mass spectrometry certificates of analysis.

Because published results hinge on the exact acetylated, amidated hexapeptide, researchers typically confirm identity and purity with HPLC and mass spectrometry certificates of analysis.

Regulatory and Research Status

Acetyl hexapeptide-3 is a cosmetic ingredient and is not approved by the US Food and Drug Administration as a drug for any indication. It is reported to function in cosmetics as a skin conditioning agent.^[10] The FDA has assigned it a Unique Ingredient Identifier (UNII L4EL31FWIL), which is a substance registration code and does not indicate approval.

The Expert Panel for Cosmetic Ingredient Safety (the Cosmetic Ingredient Review panel) assessed it under the name acetyl hexapeptide-8 amide. The panel concluded that it is safe in cosmetics in present practices of use at the low concentrations currently reported, and that the available data are insufficient to determine safety at higher concentrations.^[10]

As a research compound, acetyl hexapeptide-3 is used to study SNARE-dependent exocytosis, peptide skin penetration and formulation design. Reviewers identify improved delivery systems as the main open problem, since the extent to which the peptide reaches its proposed neuromuscular target through intact skin has not been established.^[2]