FLT3 mutations are the most frequently identified genetic alterations in acute myeloid leukemia (AML) and are associated with poor prognosis. Multiple FLT3 inhibitors are in various stages of clinical evaluation. However, resistance to FLT3 inhibitors resulting from acquired point mutations in tyrosine kinase domain (TKD) have limited the sustained efficacy of treatments, and a “gatekeeper” mutation (F691L) is resistant to most available FLT3 inhibitors. Thus, new FLT3 inhibitors against both FLT3 internal tandem duplication (FLT3-ITD) and FLT3-TKD mutations (including F691L) are urgently sought. Herein, we identified KX2-391 as a dual FLT3 and tubulin inhibitor and investigated its efficacy and mechanisms in overcoming drug-resistant FLT3-ITD-TKD mutations in AML. KX2-391 exhibited potent growth inhibitory and apoptosis promoting effects on diverse AML cell lines harboring FLT3-ITD mutations and AC220-resistant mutations at the D835 and F691 residues in TKD and inhibited FLT3 phosphorylation and its downstream signaling targets. Orally administered KX2-391 significantly prolonged the survival of a murine leukemia model induced by FLT3-ITD-F691L. KX2-391 also significantly inhibited the growth of 4 primary AML cells expressing FLT3-ITD and 2 primary AML cells expressing FLT3-ITD-D835Y. Our preclinical data highlight KX2-391 as a promising FLT3 inhibitor for the treatment of AML patients harboring FLT3 mutations, especially refractory/relapsed patients with F691L and other FLT3-TKD mutations.

中文翻译：

---

一种双重抑制剂克服耐药性 FLT3-ITD 急性髓系白血病

FLT3 突变是急性髓系白血病 (AML) 中最常见的基因改变，并且与不良预后相关。多种 FLT3 抑制剂正处于临床评估的不同阶段。然而，酪氨酸激酶结构域 (TKD) 获得性点突变导致对 FLT3 抑制剂的耐药性限制了治疗的持续疗效，“看门人”突变 (F691L) 对大多数可用的 FLT3 抑制剂具有耐药性。因此，迫切需要针对 FLT3 内部串联重复（FLT3-ITD）和 FLT3-TKD 突变（包括 F691L）的新 FLT3 抑制剂。在此，我们将 KX2-391 鉴定为 FLT3 和微管蛋白双重抑制剂，并研究其在克服 AML 中耐药性 FLT3-ITD-TKD 突变方面的功效和机制。KX2-391 对携带 FLT3-ITD 突变和 AC220 抗性突变的 TKD 中 D835 和 F691 残基的多种 AML 细胞系表现出有效的生长抑制和细胞凋亡促进作用，并抑制 FLT3 磷酸化及其下游信号靶标。口服 KX2-391 显着延长了由 FLT3-ITD-F691L 诱导的小鼠白血病模型的存活。KX2-391 还显着抑制了 4 个表达 FLT3-ITD 的原代 AML 细胞和 2 个表达 FLT3-ITD-D835Y 的原代 AML 细胞的生长。我们的临床前数据突出显示 KX2-391 是一种很有前景的 FLT3 抑制剂，可用于治疗携带 FLT3 突变的 AML 患者，尤其是具有 F691L 和其他 FLT3-TKD 突变的难治性/复发患者。