Potent and selective PDE4 inhibitor (IC50 values are 0.2 to 4.3 nM for various splice variants of PDE4). Exhibits > 1000-fold selectivity for PDE4 over other PDE family members. Demonstrates effects on functioning of neutrophils, CD4+ and CD8+ T-cells, endothelial, epithelial and smooth muscle cells, as well as fibroblasts, in vitro. Attenuates lung inflammation, mucociliary malfunction, lung fibrosis, oxidative stress, pulmonary vascular remodeling and pulmonary hypertension in animal models of COPD disease mechanisms. Purity 98%. MW (observed): 403.21