CI-1044 is an orally active PDE4 inhibitor with IC50s of 0.29, 0.08, 0.56, 0.09 μM for PDE4A5, PDE4B2, PDE4C2 and PDE4D3, respectively. CI-1044 selectively inhibits PDE4 crude extract from U937 cells with an IC50 value of 0.27±0.02 μM being threefold more potent than rolipram (IC50=0.91±0.14) and tenfold less potent than cilomilast (IC50=0.026±0.007) in the same assay. In the presence of PDE4 inhibitors, the production of TNF-α is dose dependently decreased with mean IC50 values from three separate experiments of 0.31±0.05, 0.26±0.05 and 0.11±0.01 μM, for CI-1044, cilomilast and rolipram, respectively.