Apremilast reduces severity of mAb-induced arthritis in BALB/c mice. (a) Arthritic mice were treated orally with apremilast, dexamethasone or vehicle and disease severity was evaluated and assigned a clinical score. (b) Area under the curve for each mouse was calculated and statistical significance relative to vehicle control group was analysed (*** P < 0.001). (c) Paw thickness was measured throughout with microcalipers and statistical significance was calculated by two-way analysis of variance with Bonferroni post test analysis. Means and standard error of the mean are plotted, eight mice per group (*** P < 0.001). H&E staining of a longitudinal section through the tibio-tarsal joint from a vehicle-treated mouse and one treated with 25 mg/kg apremilast is shown in (d). Asterisk shows inflammation of the synovial membrane, small arrow, erosion of articular cartilage, and bold arrow, fibrin deposits and inflammatory cell infiltrate within the articular cavity. Images were acquired at 100 × magnification.