Design, synthesis and biological evaluation of 1-phenanthryl-tetrahydroisoquinoline derivatives as novel p21-activated kinase 4 (PAK4) inhibitors

Functional versatility and elevated expression in cancers have promoted p21-activated kinase 4 (PAK4) as one of the first-in-class anti-cancer drug targets. In this study, a series of novel 1-phenanthryl-tetrahydroiso-quinoline analogues have been designed and synthesized as a novel class of small-molecule PAK4 inhibitors to fit into the cavity of PAK4. All of the target compounds were evaluated for their in vitro PAK4 inhibitory activities and antiproliferative activities. Lead optimization identified all the derivatives with more potency than the lead compound, especially compound 21a. Moreover, compound 21a significantly induced the cell cycle in the G1/S phase, and inhibited migration and invasion of MCF-7 cells via the regulation of the PAK4-LIMK1-cofilin signaling pathway. A molecular modeling study showed possible novel binding modes between 21a and PAK4 and provided a structural basis for further structure-guided design of PAK4 inhibitors.