445295-04-5

CP 671,305 is a potent inhibitor of phosphodiesterase 4D (PDE4D; IC₅₀ = 3 nM). It is selective for PDE4D over PDE4A, -B, and -C (IC₅₀s = 310, 287, and 3,858 nM, respectively), as well as over PDE1-3 and 5 (IC₅₀s = >5,000 nM for all). CP 671,305 inhibits release of leukotriene E₄ (LTE₄; ) from eosinophils (IC₅₀ = 52 nM) and LTB₄ from neutrophils (IC₅₀ = 106 nM). In vivo, CP 671,305 inhibits antigen-induced pulmonary eosinophil influx in cynomolgus monkeys in a dose-dependent manner.