Inhibition of PKD by CID755673 analogs in vitro. A-E, inhibition of recombinant human PKD1 in vitro. PKD kinase activity was assayed by a radiometric kinase assay in the presence of increasing concentrations of the CID755673 analogs. A 10-point concentration curve was generated for each compound for IC50 determination. Each IC50 was determined as the mean ± S.E.M. of three independent experiments with triplicate determinations at each concentration in each experiment. Representative graphs are shown.