A pilot study on the effect of oclacitinib on epicutaneous sensitization and transepidermal water loss in a colony of atopic beagle dogs.

Background: Dogs with atopic dermatitis are prone to sensitization to environmental allergens due to increased skin permeability; the effect of treatments on epicutaneous sensitizations is unknown.

Hypothesis/objectives: To evaluate if oclacitinib (i) prevents new sensitizations and (ii) affects skin barrier function.

Animals: Atopic beagle dogs.

Methods: Aim 1. Ten dogs were randomly assigned to placebo or oclacitinib while exposed epicutaneously to a novel allergen. Sensitization was assessed using serum allergen-specific IgE and clinically by development of skin reactions at the site of allergen application. Time to develop dermatitis and allergen-specific IgE were compared between groups. Aim 2. Eight dogs were randomly assigned to placebo or oclacitinib for four weeks and challenged with an allergen known to trigger flares. After a four week wash-out, dogs were crossed-over and the protocol repeated. Transepidermal water loss (TEWL) was measured on days 0 and 28 of each arm.

Results: Aim 1. Oclacitinib significantly increased (P = 0.006) time to develop skin reactions compared to placebo. Four (of five) dogs receiving oclacitinib failed to develop skin reactions, whereas all placebo dogs developed dermatitis. There were no significant differences in allergen-specific IgE between groups. Aim 2. TEWL results were difficult to interpret. Significantly higher values were detected from the axilla in placebo compared to oclacitinib-treated dogs (P = 0.047). TEWL values were significantly higher from the inguinal area in oclacitinib (P = 0.039) treated dogs but not placebo at the end of the study.

Conclusions And Clinical Importance: Clinically, oclacitinib delayed development of dermatitis at the site of allergen application. TEWL results were difficult to interpret and additional studies are required for clarification.