total glutathione low Liposomal outperforms plain glutathione in uptake, cell regeneration and systemic availability: evidence from cellular and human models | British Journal of Nutrition Glutathione Metabolism Oxidative stress in hemodialysis :

GHK-Cu has more extensive human clinical research, particularly in dermatological applications

AOD9604 did not result in any of the adverse effects associated with full-length hGH treatment. And to make the safety profile of AOD9604 even more convincing: Recently, AOD9604 was determined by an appropriately qualified GRAS panel of experts who are qualified by scientific training and experience to be Generally Recognized As Safe (GRAS) under conditions of intended uses of AOD9604 in foods. The only reported side effects I could find were headache, chest tightness, palpitations and euphoric feelings (Source)

This induced the development and progression of fatty liver disease to NASH

However, they may be less generally used compared to glutathione and nutrition C