Background:

PF-3758309 is an inhbitor of PAK4 with IC50 of 1.3 nM [1].

P21-activated kinases (PAKs) are the family of serine/theronine kinases, which play important role in linking Rho GTPase to cytoskeleton reorganization and nuclear signaling. PAK4 is a member of PAKs family, specifically responsive for interacting with GTP bound form of Cdc42 and JNK family. PAK4 is involved in filopodia formation and may play a role in the reorganization of the actin cytoskeleton.

Biochemical study had identified that PF-3758309 was an ATP-competitive inhibitor of PAK4, which inhibited the kinase activity [1]. When PAK4 was screened with a panel of tumor cell lines, it was found PF-3758309 inhibited the phosphorylation of PAK4 substrate GEF-H1, and also the PAK4-induced anchorage-independent cell growth, with IC50 value of 1.3 nM and 4.7 ±3 nM respectively [1]. When PF-3758309 was screened with a panel of PAKs related kinases, it exhibited good potency and specificity for PAK4 [1]. Cell analysis con?rmed that PF-3758309 modulates PAK4-dependent signaling nodes and identi?es unexpected links to additional p53pathways [1].

In vivo activity of PF-3758309 was examined in a panel of human xenograft model, including HCT116 and A549 model. Twice daily oral administration of PF-3758309 (7.5-30 mg/kg BID) for 9-18 days resulted in significant inhibition of tumor growth in all the models. The tumor growth was shown to be caused by PAK-dependent pathways in HCT116 and A549 model. Additionally, PF-3758309 was shown to regulate PAK-associated cell proliferation and survival in certain models. Therefore, PF-3758309 exhibited inhibitory activity on PAK4 [1].

Reference:
[1] Murray B W et al. , Small-molecule p21-activated kinase inhibitor PF-3758309 is a potent inhibitor of oncogenic signaling and tumor growth. Proc Natl Acad Sci USA. 2010, 107(20): 9446-9451.