myristoyl pentapeptide-17
Myr-KLAKK-NH2, N-myristoyl-L-lysyl-L-leucyl-L-alanyl-L-lysyl-L-lysinamide, myristoyl-Lys-Leu-Ala-Lys-Lys amide
Myristoyl pentapeptide-17 is a synthetic lipopeptide: a cationic five-residue sequence, lysine-leucine-alanine-lysine-lysine, with a 14-carbon myristic acid chain at one end and an amide cap at the other. It appears almost exclusively in eyelash and eyebrow conditioning products, where it is claimed to increase keratin gene expression in follicular cells. Of all the ingredients in this collection it has the thinnest published record: a PubMed phrase search returns no matching record at all.
Mechanism
The proposed mechanism, which comes from supplier documentation rather than published work, is that the peptide upregulates keratin gene expression in hair follicle keratinocytes, producing longer and denser-looking lashes. No receptor, transcription factor or signalling pathway has been identified, and no keratin gene has been named in any peer-reviewed source. What can be said from the structure alone is limited but not nothing: the molecule is strongly cationic, carrying three lysine residues, and amphiphilic, with a C14 myristoyl anchor. Cationic amphiphiles interact readily with the anionic surfaces of cell membranes and of hair, and lipid conjugation is a recognised strategy for improving follicular delivery, since the pilosebaceous unit offers a lipid-rich shunt route that bypasses the stratum corneum. That makes follicular targeting a coherent idea in principle.
It should be said plainly that a coherent idea is all this is. The KLAKK motif is not a fragment of keratin, of a keratin-associated protein, or of any characterised growth factor. It bears a superficial resemblance to the cationic amphipathic KLAKLAK class of membrane-disrupting peptides, but is shorter and not amphipathically helical, so that comparison does not carry over. Consumers should also understand that lash serums frequently contain prostaglandin analogues or their close relatives, and that the visible effect of such products, where real, is usually attributable to those rather than to any peptide.
What the research shows
There is nothing to report from primary literature on this molecule, and saying so clearly is more useful than filling the space. The claims attached to it (increased keratin synthesis, longer lashes, greater lash density, specific percentage improvements over a stated number of weeks) originate in supplier technical brochures and in-house consumer panels. None has appeared in a peer-reviewed journal and none has been replicated by an independent laboratory.
What the surrounding literature can offer is context on the two general questions the ingredient raises. On whether lipid conjugation changes a cosmetic peptide's behaviour, Jones and colleagues showed for a palmitoylated cosmetic peptide that the lipid chain drives self-assembly into nanostructures and alters the interaction with cells, so lipidation is not simply a penetration aid. On whether such peptides can be tracked in real human skin, Ligorio and colleagues demonstrated a label-free analytical approach using orbital trapping secondary ion mass spectrometry and stimulated Raman scattering to follow a different lipopeptide through skin layers, precisely the kind of study that has never been done for this compound. On the safety context of the product category, Nagendran and colleagues reviewed complications and adverse effects of periocular aesthetic treatments, which is the setting in which this ingredient is applied.
Evidence assessment
Preclinical only
This tier is assigned by default, not by evidence. A PubMed phrase search for the compound returns no matching record. The query falls back to the term 'myristoyl' alone, which is how the search engine signals that the exact phrase is absent from the database. There is no cell culture work, no animal work, no human trial, no penetration study and no independent characterisation of any kind. The keratin gene expression claim has never been published. There is no lower tier available on this scale, so 'preclinical' is used, but a reader should understand that it here means 'no published evidence' rather than 'supported by laboratory work'. The citations below are contextual and none of them tests this compound.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Collagen stimulating effect of peptide amphiphile C16-KTTKS on human fibroblasts Preclinical only
A fatty-acid-conjugated cosmetic peptide self-assembles above a critical concentration and this changes its cellular interaction, showing lipidation is not merely a delivery aid.
Noninvasive Monitoring of Palmitoyl Hexapeptide-12 in Human Skin Layers: Mechanical Interaction with Skin Components and Its Potential Skincare Benefits Preclinical only
Established a method for tracking a lipidated cosmetic peptide through stratum corneum and epidermis without labels, the type of penetration evidence entirely absent for myristoyl pentapeptide-17.
Complications and adverse effects of periocular aesthetic treatments Preclinical only
Reviews the ocular and periocular adverse effects associated with cosmetic treatments around the eye, the relevant safety context for lash and brow products.
Safety
No adverse effects have been attributed to the peptide itself, but the absence of reports reflects the absence of study rather than demonstrated safety. The relevant risks in this product category are largely about the eye rather than the molecule. Lash serums are applied to the lash line, where material readily enters the tear film and the conjunctival sac; reported problems with lash-growth products as a class include conjunctival hyperaemia, ocular irritation, periorbital fat atrophy, eyelid skin hyperpigmentation and permanent iris darkening, though those specific effects are associated with prostaglandin analogues rather than with peptides. Anyone using a lash product should read the full ingredient list for prostaglandin analogues and should not assume a product marketed as 'peptide-based' is free of them. There are no sensitisation, ocular tolerance, reproductive or pregnancy data for myristoyl pentapeptide-17. It has not been evaluated for injection or for any periocular procedure.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Permitted as a cosmetic ingredient under the UK Cosmetics Regulation (retained Regulation (EC) No 1223/2009); not listed in any prohibited or restricted annex. Eye-area products require particular attention in the Cosmetic Product Safety Report. The MHRA treats products intended to stimulate hair growth as potentially medicinal by function. No MHRA medicines authorisation. |
| United States | Not an FDA-approved drug and not covered by an OTC drug monograph; marketed as a cosmetic ingredient under the FD&C Act as amended by the Modernization of Cosmetics Regulation Act 2022. The FDA has taken enforcement action against lash products making hair-growth claims or containing prostaglandin analogues, treating them as unapproved drugs; a claim that a product grows lashes is a drug claim. |
| WADA (sport) | Not named on the WADA Prohibited List. Topical cosmetic use raises no anti-doping issue. |
Questions
No. A PubMed phrase search returns no matching record: no cell work, no animal work, no clinical trial, no penetration study. Every claim made for it comes from supplier documentation and in-house consumer panels that have not been peer reviewed.
There is no published evidence that it does. Where lash serums produce a visible effect, it is most often attributable to a prostaglandin analogue in the formulation rather than to a peptide. Reading the full ingredient list matters more than the peptide name on the front of the box.
It makes the otherwise water-soluble cationic peptide amphiphilic. In principle this favours delivery down the lipid-rich follicular shunt route, bypassing the stratum corneum. In practice, no penetration study of this molecule has been published, so the principle remains untested.
The peptide itself has no reported adverse effects, but also no ocular tolerance data. The documented problems in this product category (conjunctival redness, periorbital fat atrophy, eyelid hyperpigmentation, iris darkening) are associated with prostaglandin analogues. Anyone using a lash product should check whether one is present and should discuss ocular symptoms with an optometrist or ophthalmologist.