Immunomodulatory effect of long-term oclacitinib maleate therapy in dogs with atopic dermatitis.

Background Canine atopic dermatitis (cAD) is a chronic disease characterised by hypersensitivity to environmental allergens. Oclacitinib maleate selectively inhibits pro-inflammatory mediators associated with cAD. However, the impact of chronic oclacitinib use on immunocompetence requires further investigation. Objectives Herein, we examined the potential immunomodulatory effects of prolonged oclacitinib treatment in dogs. Animals Thirteen privately owned dogs with cAD, treated with 0.4-0.6 mg/kg oclacitinib for 12 months. Methods and materials Pruritus level was evaluated using a pruritus Visual Analog Scale (pVAS) and the canine atopic dermatitis extent and severity index, 4th iteration (CADESI IV). Peripheral blood samples were collected for routine laboratory assays and lymphocyte subtypes were analysed using flow cytometry. Antigen-specific intracellular cytokine production from CD4+ and CD8+ T lymphocytes was analysed following in vitro stimulation by Dermatophagoides farinae antigens. Results Oclacitinib treatment significantly reduced pVAS and CADESI-04 scores, by 51% and 86.7%, respectively. Flow cytometric analysis revealed increased CD4+ and CD14+ lymphocyte populations. The cytokine profile at 360 days after treatment initiation was similar to that before treatment and was not associated with clinical relapse. Conclusion Oclacitinib, when administered at the currently labelled dose for one year, is associated with a significant increase in circulating CD4+ T cells, but does not alter cytokine production from antigen-stimulated T cells. The results reported do not support evidence for immunosuppression mediated by the mechanisms evaluated in this study.