Efficacy and safety of S-acyl glutathione 2% cream vs. placebo against UVB-induced erythema: a randomized, double-blinded clinical trial

BACKGROUND: Reactive oxygen species have a major role in the UV-induced short- and long-term damage, thus the exogenous supplementation of antioxidant molecules may allow better skin protection. Despite glutathione has pivotal properties in the complex cytoplasmic antioxidant system, its supplementation is hampered by limited transmembrane absorption. Modification of glutathione pharmacokinetic properties via acetylation with long-chain polyunsaturated fatty acid may improve its passage through phospholipidic membranes. METHODS: This was a single center randomized double-blinded clinical trial, versus placebo, cross-sectional pairwise at time 0. The participants were 10 healthy volunteers with skin phototypes II or III and age >= 18 years interested in performing minimal erythema dose (MED) evaluation performed by photoallergology unit of Division of Dermatology at P. Palagi Hospital, in Florence. Each volunteer underwent UVB phototesting, treating four different areas with increasing UVB doses in four different conditions. One arm was treated as standard procedure (naive arm), one applying linolenic-glutathione conjugate (Lin-GSM) cream 2% before irradiation (pre-Lin-GSH arm), one with placebo (placebo arm) and one applying Lin-GSH cream 2% (SoloSale Srl, Florence, Italy) after irradiation (post-Lin-GSH arm). The main endpoint was to evaluate efficacy of Lin-GSH cream 2% before UVB irradiation compared with placebo. A secondary endpoint was the evaluation of the same cream applied after irradiation compared to no treatment. Another secondary' objective is the evaluation of safety in both conditions. Mean MED was evaluated at distinct conditions. Safety was evaluated reporting all grade 3-4 adverse events up to 30 days after treatment. All volunteers were treated in all four experimental conditions. The pre-Lin-GSH and placebo arms were applied in a double-blind condition for each volunteer. Neither the volunteer nor the investigator executing MED evaluation knew which aim was given Lin-GSM and which one placebo. RESULTS: Ten volunteers among 12 recruited for the study were correctly randomized and completed all study evaluations. Recruitment went from April 1st, 2016 to May 18 1st, 2016, up to adequate population number. Mean MED in pre-Lin-GSH arm was superior to mean MED in placebo arm (135 +/- 5.53 mJ/cm(2) vs. 105 +/- 7.64 mJ/cm(2), P=0.0003). No difference was observed among mean MED in post-Lin-GSH and naive arms. No grade 3-4 adverse events were reported. CONCLUSIONS: Lin-GSH 2% cream seems a safe and effective in producing a significant increase in MED compared with placebo thanks to its antioxidant properties.