Small molecule covalent drugs have proved to be desirable therapies especially on drug resistance related to point mutations. Secondary mutations of FLT3 have become the main mechanism of FLT3 inhibitors resistance which further causes the failure of treatment. Herein, a series of 4-(4-aminophenyl)-6-phenylisoxazolo[3,4-b]pyridine-3-amine covalent derivatives were synthesized and optimized to overcome the common secondary resistance mutations of FLT3. Among these derivatives, compound F15 displayed potent inhibition activities against FLT3 (IC₅₀ = 123 nM) and FLT3-internal tandem duplication (ITD) by 80% and 26.06%, respectively, at the concentration of 1 μM. Besides, F15 exhibited potent activity against FLT3-dependent human acute myeloid leukemia (AML) cell lines MOLM-13 (IC₅₀ = 253 nM) and MV4-11 (IC₅₀ = 91 nM), as well as BaF3 cells with variety of secondary mutations. Furthermore, cellular mechanism assays indicated that F15 inhibited phosphorylation of FLT3 and its downstream signaling factors. Notably, F15 could be considered for further development as potential drug candidate to treat AML.

中文翻译：

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发现 4-(4-aminophenyl)-6-phenylisoxazolo[3,4-b]pyridine-3-amine 衍生物作为新型 FLT3 共价抑制剂干预急性髓性白血病

小分子共价药物已被证明是理想的治疗方法，尤其是在与点突变相关的耐药性方面。FLT3的二次突变已成为FLT3抑制剂耐药的主要机制，进一步导致治疗失败。在此，合成并优化了一系列4-(4-氨基苯基)-6-苯基异恶唑并[3,4- b ]吡啶-3-胺共价衍生物，以克服FLT3常见的二级耐药突变。在这些衍生物中，化合物F15 在浓度为 1 μM 时，对 FLT3 (IC ₅₀ = 123 nM) 和 FLT3 内部串联复制 (ITD)的抑制活性分别为 80% 和 26.06%。此外，F15对 FLT3 依赖性人急性髓性白血病 (AML) 细胞系 MOLM-13 (IC ₅₀  = 253 nM) 和 MV4-11 (IC ₅₀  = 91 nM) 以及具有多种二次突变的 BaF3 细胞表现出强大的活性。此外，细胞机制测定表明F15抑制 FLT3 及其下游信号因子的磷酸化。值得注意的是，F15可以考虑作为治疗 AML 的潜在候选药物进行进一步开发。