Figure 3. Tested compounds exhibit high potency and selectivity towards PDE4.

For the PDE activity assay, all test compounds were diluted in DMSO with final concentrations in each assay of 100, 10, 1, 0.1, 0.01, 0.001, 0.0001 µM. For the PDE4 activity assay, 10 mU of purified PDE4 (Millipore) was used per reaction. Compounds 6, 7, 9 and 13 (blue underline) were further tested in PDE3, 5, 7, 10 activity assays in which 25 mU of purified enzyme was used per reaction. Summary of compound IC₅₀ in lower right corner.