ZSTK-474

A potent inhibitor of class I PI3K isoforms with IC50 of 17 nM, 53 nM, and 6 nM for p110β, p110γ, and p110δ, respectively; shows potent antiproliferative activity against a panel of 39 human cancer cell lines with mean GI50 of 0.32 uM, more effectively than that of LY294002 or wortmannin; induces apoptosis in OVCAR3 cells, and induces complete G1-phase arrest but not apoptosis in A549 cells at 10 uM; completely inhibits the growth of A549, PC-3, and WiDr xenografts in mice at 400mg/kg; and induces the regression of A549 xenograft tumors.Solid Tumors Phase 1 Clinical (In Vitro) :Lineweaver-Burk plot analysis revealed that ZSTK474 inhibits all four PI3K isoforms in an ATP-competitive manner. The Ki values determined for the four PI3K isoforms showed that ZSTK474 inhibited the PI3Kδ isoform most effectively with a Ki of 1.8 nM, whereas the other isoforms are inhibited with 4-10-fold higher Ki values. Therefore, ZSTK474 should be regarded as a pan-PI3K inhibitor. We also determined the IC50 values for inhibiting the four PI3K isoforms with ZSTK474 and LY294002. The IC50 values of ZSTK474 (16, 44, 4.6 and 49 nM for PI3Kα, PI3Kβ, PI3Kδ and PI3Kγ, respectively) are shown to be consistent with the Ki values (6.7, 10.4, 1.8 and 11.7 nM for PI3Kα, PI3Kβ, PI3Kδ and PI3Kγ, respectively), which further supported the idea that ZSTK474 inhibits PI3Kδ most potently. Even at a concentration of 100 μM, ZSTK474 inhibits mTOR activity rather weakly. (In Vivo) :In mice subjected to MCAO, treatment with ZSTK474 is tested at dosages of 50, 100, 200, and 300 mg/kg. Since the 200 mg/kg dose produces significant improvement and no obvious toxic effects (P<0.01), mice are treated with ZSTK474 at a dose of 200 mg/kg/day daily for three post-MCAO days during the remaining experiments of this study. Neurological function is examined in mice suffered from MCAO followed by 24, 48, and 72 h of reperfusion. In the ZSTK474 group, neurological function scores are significantly better than the control group except the corner test.