Design, synthesis, structure-activity relationships study and X-ray crystallography of 3-substituted-indolin-2-one-5-carboxamide derivatives as PAK4 inhibitors

We have previously described the identification of indolin-2-one-5-carboxamides as potent PAK4 inhibitors. This study expands the structure-activity relationships on our original series by presenting several modifications in the lead compounds, 2 and 3. A series of novel derivatives was designed, synthesized, and evaluated in biochemical and cellular assay. Most of this series displayed nanomolar biochemical activity and potent antiproliferative activity against A549 and HCT116 cells. The representative compound 10a exhibited excellent enzyme inhibition (PAK4 IC50 = 25 nM) and cellular potency (A549 IC50 = 0.58 μM, HCT116 IC50 = 0.095 μM). An X-ray structure of compound 10a bound to PAK4 was obtained. Crystallographic analysis confirmed predictions from molecular modeling and helped refine SAR results. In addition, Compound 10a displayed focused multi-targeted kinase inhibition, good calculated drug-likeness properties. Further profiling of compound 10a revealed it showed weak inhibitory activity against various isoforms of human cytochrome P450.