Apremilast reduces severity of collagen-induced arthritis in DBA/1 mice. Arthritic, male DBA/1 mice were treated from day one of onset to day 10 post onset of arthritis with a daily, intra-peritoneal dose of apremilast or vehicle, after which the mice were sacrificed and paws were removed for histological analysis. Disease severity was evaluated throughout. Change in clinical score is plotted in (a). Each treatment group comprised of 14 mice, with means and standard errors plotted. (b) The statistical significance of the clinical score of apremilast-treated compared with vehicle-treated mice was calculated from area under the curve (AUC) for each mouse over the 10 day treatment period (* P < 0.05). Representative images of H&E-stained sections through the proximal interphalangeal joint of an apremilast-treated mouse and a vehicle-treated mouse are shown (c). Scale bars are 500 μm. (d) All sections were scored for the extent of inflammation and damage, and graded accordingly. (* P < 0.05).