Clinical Efficacy of the Human Tyrosinase Inhibitor Thiamidol (isobutylamido thiazolyl resorcinol) in Melasma

Clinical Efficacy of the Human Tyrosinase Inhibitor Thiamidol (isobutylamido thiazolyl resorcinol) in Melasma Dennis Roggenkamp1, Adel Sammain1, Manuela Fürstenau2, Martina Kausch2, Thierry Passeron3,4, Ludger Kolbe2 1International Medical Management, Beiersdorf AG, Hamburg, Germany, 2Research & Development, Beiersdorf AG, Hamburg, Germany, 3Centre Méditerranéen de Médecine Moléculaire – C3M, University Côte d’Azur, INSERM U1065, Nice, France, 4Department of Dermatology, University Côte d’Azur, CHU Nice, Nice, France Thiamidol (isobutylamido thiazolyl resorcinol) was the most potent inhibitor of human tyrosinase identified out of 50,000 screened substances. In vivo, it was well tolerated and improved melasma significantly. This was the first 24-week, randomized, double-blind, vehicle-controlled, cosmetic clinical study to assess the efficacy and tolerability of Thiamidol in moderate-to-severe melasma in phototype III-V subjects with subsequent regression phase. Females allocated to the Thiamidol treatment group (n=23), applied daily Thiamidol-based Serum followed either by a Thiamidol cream with SPF 30 in the morning or by Thiamidol cream without SPF in the evening. The vehicle group (25 females) followed the same skin care routine using the corresponding vehicle formulations. Subjects returned for a follow-up visit 13-20 weeks after treatment (regression phase). Assessments included clinical photography, Melasma Area and Severity Index (MASI), skin lightness, quality of life, and tolerability. Baseline demographics and hyperpigmentation were well balanced across all treatment groups. Clinical photography and MASI improved significantly with Thiamidol versus baseline (p < 0.001) and vehicle (p < 0.001- 0.043) at all time points up to treatment end. At follow-up, MASI was still significantly lower than at baseline but similar for treatment and vehicle groups. Skin lightness and quality of life improved significantly versus baseline without significant differences between treatment and vehicle groups. This study demonstrated that Thiamidol is well tolerated and superior in improving melasma compared to baseline and vehicle over a treatment period of 24 weeks.