A one compartment model to assess skin lightening rate of cosmetic formulae in UV induced clinical studies

Ultraviolet-induced skin darkening is often used as a clinical model to assess the efficacy of active ingredients aimed at modulating skin pigmentation ; targeting pigmentary skin disorders. Studying Ultraviolet (UV)-induced skin pigmentation therefore presents challenges due to the complex pigmentation kinetics involved. This work aimed to develop a population pharmacokinetic (popPK) model to describe the UV pigmentation kinetics, compare products efficacy with their corresponding vehicle in terms of elimination, i.e., the efficacy to decrease pigmentation, and conduct a meta-analysis on the elimination rate constants (ke) resulting from the model to compare different products. The use of popPK model is limited to the statistical framework (i.e. differential equation modeling) and this paper does not aim to conduct a formal popPK analysis of the pigmentation. A one-compartment model appropriately accounted for the observed kinetics. The model fits were satisfactory, with data symmetrically distributed around the identity line and individual weighted residuals showing no deviation from normality. Overall, the integration of popPK modeling and meta-analysis represents a novel and promising approach to advancing our understanding of pigmentation kinetics following UV exposure and evaluating the comparative efficacy of skin lightening agents against UV-induced pigmentation based on ke values. Further research in cosmetical product development could lead to more applications of popPK models allowing for a greater understanding of the mechanisms at play in cosmetic product efficacy.