KW-2449 is a multiple-targeted inhibitor, mostly for Flt3 (IC50: 6.6 nM), modestly effective to Bcr-Abl, FGFR1, and Aurora A; little inhibitory on PDGFRβ, IGF-1R, EGFR.

FLT3:6.6 nM

在MOLM-13移植瘤模型中,KW-2449（p.o.,14天）抗癌效果明显,该作用存在剂量依赖性.

在携带FLT3突变和抗Imatinib突变的白血病患者体内,KW-2449具有明显活性,且获得临床研究授权。KW-2449可剂量依赖性地使FLT3和 STAT5的磷酸化程度降低。此外, KW-2449对ABL-T315I有显著抑制效果（IC50：4 nM）。另一方面, KW-2449（1 μM）不影响PDGFRβ, IGF-1R, EGFR, 及多种丝/苏氨酸激酶。作用于表达FLT3/ITD的白血病细胞和FLT3/KDM激活的以及过表达野生型FLT3的白血病细胞时,KW-2449对其生长均有明显抑制作用。作用于MOLM-13细胞时,KW-2449剂量依赖性地抑制FLT3及其下游分子磷酸-STAT5的磷酸化。KW-2449还提高G1期百分数,并降低S期百分数,使得凋亡细胞数增高。KW-2449 可以使组成型活化的WT-FLT3 激酶去磷酸化,而对白血病细胞增殖无影响。 KW-2449会迅速被吸收,并转化为一个主要的代谢产物M1。

FLT3 phosphorylation: Leukemia cells are washed in phosphate-buffered saline (PBS), then lysed by resuspending the cells in lysis buffer (20 mM Tris pH 7.4, 100 mM NaCl, 1% Igepal, 1 mM EDTA, 2 mM NaVO4, plus Complete protease inhibitor KW-2449 for 30 minutes while rocking. The extract is clarified by centrifugation at 1.6 × 104?g and the supernatant is assayed for protein (Bio-Rad). A 50-μg aliquot is removed as a whole-cell lysate for analysis of STAT5, and the remainder is used for immunoprecipitation with anti-FLT3. Anti-FLT3 antibody is added to the extract for overnight incubation, then protein A sepharose is added for 2 additional hours. Separate sodium dodecyl sulfate–polyacrylamide electrophoresis (SDS-PAGE) gels for whole-cell lysate and immunoprecipates are run in parallel. After transfer to Immobilon membranes, immunoblotting is performed with antiphosphotyrosine antibody (4 g10) to detect phosphorylated FLT3 or, for the whole-cell lysate gels, with a rat monoclonal antibody against phosphorylated STAT5 (residue Y694) then stripped and reprobed with anti-FLT3 antibody to measure total FLT3. Proteins are visualized using chemiluminescence, exposed on Kodak BioMax XAR film, developed, and scanned using a Bio-Rad GS800 densitometer. The concentration of KW-2449 for which the phosphorylation of FLT3 or STAT5 is inhibited to 50% of its baseline (IC50) is determined using linear regression analysis of the dose response curves. For direct analysis of FLT3 and STAT5 in circulating blasts, peripheral blood is collected in heparinized tubes and promptly chilled on ice. Samples are centrifuged for 10 minutes at 900 g, at 4 °C. The plasma is removed and stored frozen at ?80 °C. The buffy coat is carefully transferred to ice-cold PBS, layered onto chilled Ficoll-Hypaque, and centrifuged for 5 minutes at 600 g, at 4 °C. All subsequent steps are carried out at 4 °C. Mononuclear cells are collected and washed rapidly once in red blood cell lysis buffer (0.155 M NH4Cl, 0.01 M KHCO3, 0.1 mM EDTA), then washed once in PBS. Cells are then lysed as described for FLT3 and STAT5 analysis.

Cell viability is determined by the sodium 3′-[1-(phenylaminocarbonyl)-3, 4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid hydrate assay after incubation with or without KW-2449 for 72 hours at 37 °C. The number of viable cells is determined using the Cell Proliferation Kit II. For cell-cycle analysis, MOLM-13 and RS4;11 cells are treated with KW-2449. After 24, 48, and 72 hours of incubation at 37 °C, DNA contents are analyzed. Cell cycle distribution of K562, TCC-Y, and TCC/Ysr is analyzed 24 hours after treatment with KW-2449 or imatinib. (Only for Reference)