Pancreatic cancer is one of the most aggressive cancers with poor prognosis and a low 5-year survival rate.The family of P21-activated kinases (PAKs) appears to modulate many signaling pathways that contribute to pancreatic carcinogenesis.In this work,we demonstrated that PAK1 is a critical regulator in pancreatic cancer cell growth.PAKl-targeted inhibition is therefore a new potential therapeutic strategy for pancreatic cancer.Our small molecule screening identified a relatively specific PAK1targeted inhibitor,CP734.Pharmacological and biochemical studies indicated that CP734 targets residue V342 of PAK1 to inhibit its ATPase activity.Further in vitro and in vivo studies elucidated that CP734 suppresses pancreatic tumor growth through depleting PAK1 kinase activity and its downstream signaling pathways.Little toxicity of CP734 was observed in murine models.Combined with gemcitabine or 5-fluorouracil,CP734 also showed synergistic effects on the anti-proliferation of pancreatic cancer cells.All these favorable results indicated that CP734 is a new potential therapeutic candidate for pancreatic cancer.