Evaluation of Oclacitinib on Skin Barrier Function in Dogs with Allergic Dermatitis

Abstract

Pruritus is one of the main factors in the progression of canine allergic dermatitis. Pruritus-inducing behaviors, such as scratching and rubbing, impair the skin barrier. Consequently, the damaged skin barrier aggravates the severity of allergic dermatitis by enhancing penetration of allergens. Oclacitinib is a janus kinase 1 (JAK-1) inhibitor that blocks the signals of IL-31, a pruritogenic cytokine. Because of the mechanism, oclacitinib has been used to reduce pruritus in dogs with allergic dermatitis. The purpose of the study was to evaluate the effect of oclacitinib on skin barrier function in dogs with allergic dermatitis by measuring transepidermal water loss (TEWL), while assessing its efficacy and safety. Oclacitinib was administered for 84 days

twice a day for the first 2 weeks and then once a day for the remaining period (day 0-28: n=22, day 29-84: n=8). In addition to TEWL, the canine atopic dermatitis extent and severity index-4 (CADESI-4), pruritus visual analog scale (PVAS) and owner satisfaction were measured to evaluate the efficacy of oclacitinib on days 0, 14, 28, 56, and 84. Any abnormal health conditions during the experimental period were recorded and blood samples were collected on days 0, 28, and 84 to evaluate the safety of the medication. The administration of oclacitinib decreased both CADESI-4 and PVAS values significantly from baseline at all assessment points, regardless of the daily dosage (p<0.05). Unlike CADESI-4 and PVAS, TEWL values decreased significantly from baseline only on day 14 for the total TEWL value, including ventral neck and axilla-specific TEWL values (p<0.05). In conclusion, oclacitinib was found to exert a remarkable effect on skin barrier function when the drug was administered twice daily. Although the skin barrier function seemed to be aggravated with the reduction in daily dosage, the changes did not markedly affect visible skin condition or the severity of pruritus. Most owners were content with the oclacitinib treatment for their dogs and the medication was used safely in most patients without causing any significant adverse events. Therefore, this study showed that oclacitinib was effective and safe treatment for the control of canine allergic dermatitis.