Suppression of the Th2 Pathway by Suplatast Tosilate in Patients with Perennial Nasal Allergies

Background Suplatast tosilate (IPD-1151T), a selective Th2 cytokine inhibitor that suppresses the production of interleukin (IL)-4 and IL-5 in vitro or in animal models has been proved clinically effective for allergic rhinitis (AR). The aim of this study was to investigate changes in the Th2 pathway in human nasal mucosa after medication with IPD-1151T. Twelve patients were treated with IPD-1151T. Methods Twelve healthy volunteers served as normal controls. The following parameters were evaluated: (i) subjective nasal clinical symptoms, (ii) percentages of inflammatory cells (EG2, CD4, and CD8) by immunocytological staining, and (iii) levels of cytokines (IL-4, IL-5, IL-13, regulated on activation, normal T-cell expressed, and secreted [RANTES], and interferon [IFN] γ) by enzyme-linked immunosorbent assay. Results Nasal symptom scores significantly decreased after treatment. With respect to cell infiltration, a significant decrease was observed in the percentage of inflammatory cells (EG2 and CD4) and CD4/CD8 ratio. The levels of cytokines (IL-4, IL-5, IL-13, and IFN-γ) and the IL-5/IFN-γ ratio were significantly decreased, and the IL-4/IFN-γ ratio became not significantly different from that in normal subjects. In contrast, RANTES did not change significantly. The percentage of reduction in IL-5 correlated with that in eosinophil infiltration, whereas that in RANTES did not. Conclusion These results suggest that IPD-1151T can reduce the Th2 pathway.