Conclusion
The effectiveness of this maintenance regimen was objectively demonstrated at the clinical, biochemical and microbiological level. Correlations between clinical signs and biomarkers could provide clues to explain the resolution of SD and confirm the interest of biomarkers for SD treatment assessment.
Methods
A new shampoo containing beta-glycyrrhetinic acid (18βGA) in addition to cyclopiroxolamine (CPO) and zinc pyrithione (ZP) was tested in 67 subjects suffering from SD with moderate to severe erythema and itching in a biphasic study. After a first common intensive treatment phase (investigational product thrice a week × 2 weeks), subjects randomly received the investigational product once a week × 8 weeks (maintenance) or a neutral shampoo (discontinuation) in a comparative, parallel group maintenance phase. Efficacy was assessed clinically (overall clinical dandruff score, erythema, overall efficacy, self-evaluation), biochemically and microbiologically by quantitative polymerase chain reaction (qPCR), high performance liquid chromatography (HPLC) or enzyme-linked immunoabsorbent assay (ELISA) analysis of scale samples (Malassezia species (restricta and globosa), cohesion proteins (plakoglobins), inflammation (Interleukin (IL)-8, IL-1RA/IL-1α) and pruritus (histamine, cathepsin S) markers).
Results
During the intensive treatment phase, SD improved significantly (p < 0.0001) with a decrease in clinical signs as well as Malassezia species, cohesion proteins, inflammation and pruritus markers. During the maintenance phase, the improvement persisted in the 'maintenance' group only, with a significant intergroup difference. A consistently positive relationship was found between dandruff, itching, erythema and Malassezia populations, histamine levels and IL-1RA/IL-1α ratio.