Synthesis and biological evaluation of 4-(4-aminophenyl)-6-methylisoxazolo[3,4-b] pyridin-3-amine covalent inhibitors as potential agents for the treatment of acute myeloid leukemia.

Fms-like tyrosine kinase 3 (FLT3) mutation has been strongly associated with increased risk of relapse, and the irreversible covalent FLT3 inhibitors had the potential to overcome the drug-resistance. In this study, a series of simplified 4-(4-aminophenyl)-6-methylisoxazolo[3,4-b] pyridin-3-amine derivatives containing two types of Michael acceptors (vinyl sulfonamide, acrylamide) were conveniently synthesized to target FLT3 and its internal tandem duplications (ITD) mutants irreversibly. The kinase inhibitory activities showed that compound C14 displayed potent inhibition activities against FLT3 (IC50 = 256 nM) and FLT3-ITD by 73 % and 25.34 % respectively, at the concentration of 1 µM. The antitumor activities indicated that C14 had strong inhibitory activity against the human acute myeloid leukemia (AML) cell lines MOLM-13 (IC50 = 507 nM) harboring FLT3-ITD mutant, as well as MV4-11 (IC50 = 325 nM) bearing FLT3-ITD mutation. The biochemical analyses showed that these effects were related to the ability of C14 to inhibit FLT3 signal pathways, and C14 could induce apoptosis in MV4-11 cell as demonstrated by flow cytometry. Fortunately, C14 showed very weak potency against FLT3-independent human cervical cancer cell line HL-60 (IC50 > 10 µM), indicating that it might have no off-target toxic effects. In light of these data, compound C14 represents a novel covalent FLT3 kinase inhibitor for targeted therapy of AML.

[Quality value transmitting of substance benchmarks of Zhuru Decoction].

A total of 18 batches of Zhuru Decoction samples were prepared. Chromatographic fingerprints were established for Zhuru Decoction and single decoction pieces, the content of which was then determined. The extraction rate ranges, content, and transfer rate ranges of puerarin, liquiritin, and glycyrrhizic acid, together with the common peaks and the similarity range of the fingerprints, were determined to clarify key quality attributes of Zhuru Decoction. The 18 batches of Zhuru Decoction samples had 25 common peaks and the fingerprint similarity higher than 0.95. Puerariae Lobatae Radix, Glycyrrhizae Radix et Rhizoma, and Zingiberis Rhizoma Recens had 21, 3, and 1 characteristic peaks, respectively. The 18 batches of samples showed the extraction rates within the range of 18.45%-25.29%. Puerarin had the content of 2.20%-3.07% and the transfer rate of 38.5%-45.9%; liquiritin had the content of 0.24%-0.85% and the transfer rate of 15.9%-37.5%; glycyrrhizic acid had the content of 0.39%-1.87% and the transfer rate of 16.2%-32.8%. In this paper, the quality value transmitting of substance benchmarks of Zhuru Decoction was analyzed based on chromatographic fingerprints, extraction rate, and the content of index components. A scientific and stable method was preliminarily established, which provided a scientific basis for the quality control and formulation development of Zhuru Decoction.