L‐4‐thiazolylalanine (Protinol), a novel non‐proteinogenic amino acid, demonstrates epidermal and dermal efficacy with clinically observable benefits

Objective Facial skin undergoes major structural and functional changes as a result of intrinsic and extrinsic factors. The goal of the current work is to demonstrate L‐4‐thiazolylalaine (L4, Protinol), a non‐proteinogenic amino acid shown to stimulate the production of dermal proteins by fibroblasts, is an alternative efficacious topical ingredient for visible signs of ageing. Methods In vitro studies using 3D human skin tissue models were performed to show changes in protein and gene expression of key dermal markers in samples treated with 0.3% L4 compared to vehicle control. In vivo evaluation of skin turnover was measured in volunteers after treatment with L4 compared to retinol. Skin biopsies (n = 30) were taken to investigate epidermal and dermal changes in cases treated with L4 and compared to retinol. Finally, a clinical evaluation (n = 28) was conducted to assess the efficacy of L4 over a base formulation using various ageing parameters within a population of women 46–66 years old with mild‐to‐moderate wrinkles. Results In vitro studies on 3D tissues displayed significant changes in the dermal matrix via an increase in HA and pro‐collagen I production and a decrease in the expression of inflammatory genes. In vivo biopsy studies demonstrated that L4 and retinol independently increased epidermal thickness and collagen remodelling significantly more compared with the base formula. Clinical evaluation showed firmer and smoother skin at day 28 post‐treatment with L4 over the vehicle control without causing side effects such as redness or irritation. Conclusion L4 is a novel, multi‐functional ingredient which offers a superior alternative to currently available technologies for improving epidermal and dermal parameters that change during ageing and photodamage. Résumé Objectif La peau du visage est sujet à des changements majeurs structuraux et fonctionnels dus à des facteurs intrinsèques et extrinsèques. Dans cette étude, nous montrons que l'acide aminé non‐protéinogène L‐4‐thiazolylalanine (L4, Protinol) est une alternative intéressante pour une application topique. Méthodes Des modèles 3D de peaux ont été utilisés pour mesurer les changements d'expressions géniques et protéiques de marqueurs clés du derme à partir d'échantillons traités avec L4 comparés à une condition contrôle. In vivo, après un traitement L4, le renouvellement cutané a été mesuré chez les volontaires et comparé à un traitement au rétinol. Des biopsies de peaux (n = 30) traitées so