Leuphasyl

Leuphasyl, with the INCI (cosmetic ingredient) designation Pentapeptide-18, is a synthetic peptide with the sequence Tyr-D-Ala-Gly-Phe-Leu. Structurally, it is a close analog of Leu-enkephalin, one of the endogenous opioid pentapeptides (Tyr-Gly-Gly-Phe-Leu) first identified in the 1970s as natural ligands for opioid receptors. The key modification distinguishing Leuphasyl from native Leu-enkephalin is a single D-alanine substitution at position 2, replacing the natural glycine — a classic peptide-stabilization strategy (D-amino acid substitution confers resistance to enzymatic degradation) that has been used across decades of opioid peptide research, not a modification unique or proprietary to this specific cosmetic ingredient.

Chemically, Leuphasyl has molecular formula C29H39N5O7, molecular weight approximately 569.7 g/mol (independently cross-checked via manual atomic-mass calculation from the formula, which matched), CAS number 64963-01-5. It is marketed as a topical cosmetic ingredient, informally described in commercial materials as a "Botox-like peptide," positioned within the same general category of neuropeptide-based anti-wrinkle cosmetic ingredients as Argireline, also built on this site.

We were not able to locate a PubChem entry we could confidently confirm corresponds specifically to Leuphasyl with matching chemical data, and we are omitting this identifier rather than listing an unconfirmed one — a data gap that itself reflects the generally thinner independent documentation available for this specific ingredient compared to more extensively characterized compounds elsewhere in this catalog.

At Verified Peptides, we think Leuphasyl's evidence base is even more limited than Argireline's, and we want to describe it directly. The primary published study we located (Dragomirescu, Andoni, Ionescu, and Andrei, "The Efficiency and Safety of Leuphasyl — A Botox-Like Peptide," Cosmetics, 2014, DOI 10.3390/cosmetics1020075) tested three emulsion concentrations (0.5%, 1%, and 2%) applied to the eyebrow and periorbital zones, using a pro-derm Analyser imaging system to assess wrinkle regression. We want to note that we could not locate a PMID for this study — it appears to be indexed in the MDPI Cosmetics journal's own system and academic aggregators, but not with a PubMed identifier, so we are citing it by its DOI rather than fabricating or omitting the reference.

The study reported an average wrinkle-depth reduction of 11.31% across the tested concentrations — a real, measured, but genuinely modest effect, and considerably smaller than the up-to-47% wrinkle-depth reduction figure commonly cited in manufacturer and vendor marketing materials for Leuphasyl. We think this discrepancy between the modest, independently-published academic finding and the much larger manufacturer-cited figure is important for researchers to understand directly, since the larger figure appears to originate from unpublished, non-independently-verified manufacturer testing rather than the peer-reviewed literature.

We are not aware of any large, randomized, placebo-controlled human trial for Leuphasyl specifically, and independent, non-industry-affiliated academic validation remains limited even by the standards of cosmetic peptide research generally — a category where, as we noted in Argireline's own profile, rigorous independent evidence is often thinner than the scale of commercial marketing claims. No FDA, EMA, or other Western regulatory body evaluates Leuphasyl as a drug, since it is regulated as a cosmetic ingredient. At Verified Peptides, we sell research-grade Leuphasyl exclusively for laboratory research, and we encourage researchers to weigh the modest, independently-published 11.31% finding rather than commercial marketing figures when evaluating this compound's likely real-world topical effect size.

Leu-enkephalin, the natural peptide Leuphasyl is derived from, was one of two enkephalins (alongside Met-enkephalin) first identified and characterized in the mid-1970s as the first endogenous opioid peptides discovered, a landmark finding in neuropharmacology that predates and is entirely independent of any cosmetic application developed decades later. This discovery fundamentally shaped understanding of the body's own pain-modulation systems and opioid receptor biology.

The D-alanine-2 substitution used in Leuphasyl is one of the most common and well-understood modifications in synthetic enkephalin analog chemistry, used across numerous research compounds developed for pain and opioid receptor pharmacology research long before any cosmetic application — meaning Leuphasyl's specific structural modification strategy, while effective for improving stability, is not a novel innovation specific to this ingredient.

The gap between Leuphasyl's modest, independently-published 11.31% wrinkle-reduction finding and manufacturer marketing claims of up to 47% illustrates a recurring pattern across the cosmetic peptide industry, also documented for Argireline in this catalog: manufacturer-sponsored or unpublished internal testing frequently reports larger effect sizes than the more limited independent academic literature that does exist, and researchers should weight peer-reviewed, independently-conducted studies more heavily than marketing-cited figures when evaluating any specific cosmetic peptide's likely real-world effect.

Leuphasyl's commercial combination with Argireline (marketed as Argirelox and similar branded blends) reflects a broader cosmetic-industry strategy of combining multiple peptides with different proposed mechanisms into single formulations, on the theory that addressing neurotransmitter release through multiple distinct pathways simultaneously could produce additive cosmetic benefits — a reasonable mechanistic hypothesis that, to our knowledge, has not itself been independently validated through dedicated combination-specific clinical research.

Leuphasyl's development also reflects a broader trend in cosmetic-ingredient design of repurposing well-characterized molecules from other fields of pharmacology — in this case, decades-old opioid receptor research — for topical cosmetic applications, rather than developing entirely novel compounds from scratch. This approach can offer a head start in terms of basic mechanistic plausibility, since the receptor system itself is well studied, even though it does not substitute for dedicated, compound-specific efficacy testing in the actual cosmetic application context.

At Verified Peptides, we require independent third-party HPLC purity testing and mass spectrometry identity confirmation for every batch of research-grade Leuphasyl we offer, with a Certificate of Analysis (COA) available for each lot. As a five-residue peptide including a D-amino acid substitution, Leuphasyl requires appropriate synthesis chemistry to correctly incorporate the D-alanine residue at position 2, and identity confirmation should verify this specific stereochemistry, not just overall amino acid composition.

We source exclusively from manufacturers operating under Good Manufacturing Practice (GMP)-aligned quality systems, and every lot is independently verified rather than accepted solely on a supplier's internal documentation. Researchers should always request and review the specific COA for the lot they receive, confirming purity percentage and molecular identity before use in any experimental protocol.

Lyophilized Leuphasyl is stable when stored at -20°C, protected from light and moisture, and researchers can generally expect the unreconstituted peptide to maintain integrity over an extended period under these conditions. At Verified Peptides, we ship lyophilized peptide with appropriate cold-chain packaging to preserve stability in transit.

Once reconstituted, Leuphasyl solution should be stored refrigerated at 2–8°C and used within the timeframe indicated on the product's documentation. As with other short peptides in this catalog, reconstituted solutions are generally less stable than the lyophilized form and more susceptible to degradation and microbial contamination with repeated freeze-thaw cycling.

Researchers should avoid repeated freeze-thaw cycles of reconstituted material and should follow the specific storage guidance provided with each lot's documentation to preserve sample validity for research use.