Discovery of N‑(4-(6-Acetamidopyrimidin-4-yloxy)phenyl)-2-(2-(trifluoromethyl)phenyl)acetamide (CHMFL-FLT3-335) as a Potent FMS-like Tyrosine Kinase 3 Internal Tandem Duplication (FLT3-ITD) Mutant Selective Inhibitor for Acute Myeloid Leukemia

Most of the current FMS-like tyrosine kinase 3 (FLT3) inhibitors lack selectivity between FLT3 kinase and cKIT kinase as well as the FLT3 wt and internal tandem duplication (ITD) mutants. We report a new compound 27, which displays GI50 values of 30–80 nM against different ITD mutants and achieves selectivity over both FLT3 wt (8-fold) and cKIT kinase in the transformed BaF3 cells (>300-fold). 27 potently inhibits the proliferation of the FLT3-ITD-positive acute myeloid leukemia cancer lines through suppression of the phosphorylation of FLT3 kinase and downstream signaling pathways, induction of apoptosis, and arresting the cell cycle into the G0/G1 phase. 27 also displays potent antiproliferative effect against FLT3-ITD-positive patient primary cells, whereas it does not apparently affect FLT3 wt primary cells. In addition, it also exhibits a good therapeutic window to PBMC compared to PKC412. In the in vivo studies, 27 demonstrates favorable PK profiles and suppresses the tumor growth in the MV4-11 cell inoculated mouse xenograft model.当前绝大多数FMS样酪氨酸激酶3（FMS-like tyrosine kinase 3, FLT3）抑制剂在FLT3激酶与cKIT激酶之间，以及FLT3野生型（wild-type, wt）与内部串联重复（internal tandem duplication, ITD）突变体之间均缺乏选择性。本研究报道了一种新型化合物27，其对不同ITD突变体的半数生长抑制浓度（GI50）为30~80 nM，在转化型BaF3细胞中对FLT3野生型展现出8倍选择性，对cKIT激酶的选择性更是超过300倍。化合物27可通过抑制FLT3激酶的磷酸化及下游信号通路、诱导细胞凋亡、将细胞周期阻滞于G0/G1期，强效抑制FLT3-ITD阳性急性髓系白血病细胞系的增殖。此外，该化合物对FLT3-ITD阳性患者原代细胞具有显著的抗增殖活性，却对FLT3野生型原代细胞无明显影响。相较于PKC412，化合物27对外周血单个核细胞（peripheral blood mononuclear cell, PBMC）展现出良好的治疗窗口。在体内研究中，化合物27呈现出优异的药代动力学（pharmacokinetics, PK）特征，并在MV4-11细胞接种的小鼠异种移植模型中显著抑制肿瘤生长。