ghk-cu angiogenesis GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration Figure 6 from GHK –

There were 81 participants that began the study, but 6 withdrew prior to completion

& Driscoll, P

Examples of heteroaryl groups include thienyl, imadizolyl, oxadiazolyl, isoxazolyl, triazolyl, pyridyl, pyrimidinyl, pyridazinyl, furyl, pyranyl, thianthrenyl, pyrazolyl, pyrazinyl, indolizinyl, isoindolyl, isobenzofuranyl, benzoxazolyl, xanthenyl, 2H-pyrrolyl, pyrrolyl, 3H-indolyl, indolyl, indazolyl, purinyl, 4H-quinolizinyl, isoquinolyl, quinolyl, phthalazinyl, naphthyridinyl, quinazolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, isothiazolyl, phenothiazinyl, isoxazolyl, furazanyl, and phenoxazinyl groups

You also need to look at the purity of the ingredients and the presence of "co-factors" that help the glutathione do its job