7-Oxo-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridines as Novel Inhibitors of Human Eosinophil Phosphodiesterase

High-throughput file screening against inhibition of human lung PDE4 led to the discovery of 3-ethyl-1-(4-fluorophenyl)-6-phenyl-7-oxo-4,5,6,7-tetrahydro-1H-pyrazolo-1H-[3,4-c]pyridine (11) as a novel PDE4 inhibitor. Subsequent SAR development, using an eosinophil PDE assay, led to analogues up to 50-fold more potent than 11 with IC 50 values of 0.03-1.6 μM. One such compound, CP-220,629 (22) (IC 50 = 0.44 μM), was efficacious in the guinea pig aerosolized antigen induced airway obstruction assay (ED 50 2.0 mg/kg, po) and demonstrated a significant reduction in eosinophil (55%), neutrophil (65%), and IL-1β (82%) responses to antigen challenge in atopic monkeys (10 mg/kg, po).