Synthesis and Biological Evaluation of Novel Analogues of the Pan Class I Phosphatidylinositol 3-Kinase (PI3K) Inhibitor 2-(Difluoromethyl)-1-[4,6-di(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole (ZSTK474)

A structure activity relationship (SAR) study of the pan class I PI 3-kinase inhibitor 2-(difluoromethyl)-1-[4,6-di(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole (ZSTK474) identified substitution at the 4 and 6 positions of the benzimidazole ring as having significant effects on the potency of substituted derivatives. The 6-amino-4-methoxy analogue displayed a greater than 1000-fold potency enhancement over the corresponding 6-aza-4-methoxy analogue against all three class Ia PI 3-kinase enzymes (p110 alpha, p110 beta, and p110 delta) and also displayed significant potency against two mutant forms of the p110 alpha isoform (H1047R and E545K). This compound was also evaluated in vivo against a U87MG human glioblastoma tumor xenograft model in Ragl(-/-) mice, and at a dose of 50 mg/kg given by ip injection at a qd x 10 dosing schedule it dramatically reduced cancer growth by 81% compared to untreated controls.