Science 362, 14161422
In Vivo Activity Duration and Dosing Implications The preclinical dosing regimen provides indirect evidence about the peptide's functional duration in vivo, though formal pharmacokinetic parameters remain unmeasured
-Syn knockout mice were provided by Professor Yang Hui of Capital Medical University
Examples include semaglutide (Ozempic, Wegovy) and tirzepatide (Zepbound, Mounjaro)
The copper content of GHK-Cu formulations has been a theoretical safety consideration, given that excessive copper can be toxic - however, the amounts used in cosmetic and research applications are extremely small, the copper is tightly chelated by the peptide (reducing free copper availability), and topical absorption of copper from these products appears minimal and well below levels that would cause systemic copper accumulation or toxicity

Interestingly, this serums key ingredient list is the longest of our top picks, and it includes: Copper tripeptide-1 (GHK-Cu) Lactococcus ferment lysate Matrixyl 3000 (branded complex of palmitoyl tripeptide-1 and palmitoyl tetrapeptide-7) Matrixyl synthe'6 (branded complex containing palmitoyl tripeptide-38) Argirelox (branded complex of acetyl hexapeptide-8 and pentapeptide-18) Syn-Ake (branded dipeptide diaminobutyroyl benzylamide diacetate) Acetylarginyltryptophyl diphenylglycine Sodium hyaluronate Below, we break down the research behind some of these ingredients