These studies relate to individual ingredients, not to GHK-Cu Essential Serum as a finished product. Each study used its own concentration and test formula.
GHK-Cu
Pickart, Vasquez-Soltero & Margolina (2015), GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration, BioMed Research International. A review showing that GHK declines with age. In lab work it affects collagen and other skin-structure molecules, and in cosmetic products it was reported to improve the look of firmness, elasticity and fine lines.
Pickart & Margolina (2018), Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data, International Journal of Molecular Sciences. A review noting that GHK in the blood falls from about 200 ng/mL at age 20 to about 80 ng/mL by age 60, and discussing its use in skin and hair products.
Dou et al. (2020), The potential of GHK as an anti-aging peptide, Aging Pathobiology and Therapeutics. A review of research into GHK-Cu's anti-inflammatory and tissue remodelling activity.
Palmitoyl Pentapeptide-4
Robinson et al. (2005), Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin, International Journal of Cosmetic Science. A 12-week, double-blind, placebo-controlled split-face study in 93 women aged 35 to 55, which showed significant improvement in wrinkles and fine lines compared with placebo.
Matrixyl® 3000
Sederma (supplier), Matrixyl® 3000 technical data sheet. The supplier's 2-month test versus placebo showed reductions in the area of deep wrinkles and in wrinkle density. This is manufacturer data, not an independent study.
Ectoin
Kauth & Trusova (2022), Topical Ectoine Application in Children and Adults to Treat Inflammatory Diseases Associated with an Impaired Skin Barrier: A Systematic Review, Dermatology and Therapy. A review of six clinical studies, which found Ectoine formulas were safe and effective for impaired-barrier skin over up to 6 months.