Acetyl Hexapeptide-8
Also known as Acetyl Hexapeptide-8, Acetyl Hexapeptide-8 Amide, Acetyl Hexapeptide-3, Acetyl Hexapeptide-24, Argireline, Ac-EEMQRR-NH2
“CIR Expert Panel says: safe within use limit.”
Acetyl Hexapeptide-8 (CAS 616204-22-9, sequence Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2; trade name Argireline; INCI synonyms include Acetyl Hexapeptide-3, Acetyl Hexapeptide-8 Amide, and Acetyl Hexapeptide-24 — four names for the same chemical entity per the 2021 CIR Final Report). The peptide was rationally designed by Lipotec from the N-terminal fragment of SNAP-25 (residues 12-17) to mimic the substrate of botulinum toxin A and inhibit Ca2+-dependent SNARE-mediated neurotransmitter release in vitro (Blanes-Mira et al. 2002, PMID 18498523; the foundational paper also reports a 10-volunteer pilot study showing up to 30% wrinkle-depth reduction from a 10% O/W emulsion over 30 days). The CIR Expert Panel for Cosmetic Ingredient Safety published a Final Report on April 5, 2021 (Panel meeting March 11-12, 2021; subsequently published in Int J Toxicol 44(2_suppl):54S-63S, 2025, PMID 40673537) concluding the ingredient is safe up to 0.005% in cosmetics — the highest concentration reported in the 2019 PCPC use survey for leave-on products — but that available data are insufficient to determine safety at concentrations > 0.005%. The Panel's safety conclusion rested significantly on the peptide's high hydrophilicity (log Kow -7.68 / log P -6.3) and consequent low percutaneous absorption, supported by LC-MS/MS dermal penetration studies (Kraeling et al. 2015, PMID 24754410) showing the peptide remained almost entirely in the stratum corneum (0.54% in hairless guinea pig, 0.22% in human cadaver skin) with no detection in dermis or receptor buffer. The marketing positioning as a 'topical Botox alternative' is built on in vitro SNARE-inhibition data and small uncontrolled human studies; the Kraeling penetration data create a mechanistic tension because demonstrable wrinkle effects at 10% (well above the 0.005% CIR-safe ceiling) likely reflect formulation hydration or surface effects rather than the proposed neuromuscular mechanism. A randomized placebo-controlled trial in Chinese subjects (Wang et al. 2013, PMID 23417317; n unspecified in abstract, 4-week twice-daily application) reported 48.9% subjective anti-wrinkle efficacy in the argireline group vs 0% in placebo, with significant improvement in objective roughness parameters — though the study used an unstated argireline concentration substantially above the 0.005% CIR-safe limit, which is typical of the published efficacy literature and complicates direct application of efficacy claims to commercially compliant formulations. Genotoxicity (Ames negative across 5 S. typhimurium strains) and HRIPT skin sensitization testing (n=50) returned negative results at the 0.05% tradename-mixture concentration tested.
Peptide structure (hexapeptide with charged termini) and very low log Kow (-7.68) make percutaneous absorption minimal — Kraeling et al. 2015 detected no peptide in dermis or receptor buffer of human cadaver skin, supporting low systemic exposure at cosmetic use levels
CIR-assessed safe up to 0.005% in leave-on cosmetic products (Final Report 04/2021); Ames-negative across 5 S. typhimurium strains and non-sensitizing in HRIPT (n=50)
Designed as a SNAP-25 N-terminal mimetic; in vitro work (Gutierrez et al. 1995, FEBS Lett 372(1):39-43; Blanes-Mira et al. 2002, PMID 18498523) demonstrates inhibition of Ca2+-dependent neurotransmitter release in chromaffin cells — the mechanistic basis for the marketing positioning
RCT in Chinese subjects (Wang et al. 2013, PMID 23417317) reported significant reduction in periorbital wrinkle roughness parameters and 48.9% subjective anti-wrinkle efficacy vs 0% placebo over 4 weeks at unstated study concentration
CIR concluded data insufficient to determine safety above 0.005%; products marketed at higher use concentrations exist and were noted by the Panel as potentially being marketed as drugs and thus outside the Panel's purview (Final Report 04/2021)
Marketing claims of 'topical Botox alternative' are based on in vitro SNARE-inhibition data and Lipotec's 2002 pilot study (n=10, no placebo control beyond vehicle); independent dermal penetration evidence (Kraeling et al. 2015, PMID 24754410) shows the peptide does not meaningfully cross the stratum corneum, creating a substantial mechanism-vs-claim gap
Most published efficacy studies use concentrations well above the 0.005% CIR-safe ceiling (the foundational Blanes-Mira 2002 study used 10%); efficacy at compliance-level concentrations is poorly characterized in independent literature
In vitro antiproliferative activity observed at >10 μM in human epidermal fibroblasts and HEK-293/IMR-32 cell lines (CIR FR 04/2021); not flagged by the Panel as a use-concentration concern given low percutaneous absorption, but worth tracking for future re-review
Safety Assessment of Acetyl Hexapeptide-8 Amide as Used in Cosmetics — CIR Final Report (Release Date April 5, 2021; Panel Meeting March …
“The Expert Panel for Cosmetic Ingredient Safety concluded that Acetyl Hexapeptide-8 Amide is safe in cosmetics in the present practices of use and concentration described in this safety assessment when the concentration does not exceed 0.005%, and that the available data are insufficient to make a determination that Acetyl Hexapeptide-8 Amide is safe under the intended conditions of use in cosmetic formulations at concentrations > 0.005%.”— acetyl032021FR.pdf, p. 9