Discovery of 1-(4-(4-Amino-3-(4-(2-morpholinoethoxy)phenyl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)phenyl)-3-(5-(tert-butyl)isoxazol-3-yl)urea (CHMFL-FLT3-213) as a Highly Potent Type II FLT3 Kinase Inhibitor Capable of Overcoming a Variety of FLT3 Kinase Mutants in FLT3-ITD Positive AML.

FLT3-ITD mutant has been observed in about 30% of AML patients and extensively studied as a drug discovery target. On the basis of our previous study that ibrutinib (9) exhibited selective and moderate inhibitory activity against FLT3-ITD positive AML cells, through a structure-guided drug design approach, we have discovered a new type II FLT3 kinase inhibitor, compound 14 (CHMFL-FLT3-213), which exhibited highly potent inhibitory effects against FLT3-ITD mutant and associated oncogenic mutations (including FLT3-D835Y/H/V, FLT3-ITD-D835Y/I/N/A/G/Del, and FLT3-ITD-F691L). In the cellular context 14 strongly affected FLT3-ITD mediated signaling pathways and induced apoptosis by arresting cell cycle into G0/G1 phase. In the in vivo studies 14 demonstrated an acceptable bioavailability (F = 19%) and significantly suppressed the tumor growth in MV4-11 cell inoculated xenograft model (15 mg kg day, TGI = 97%) without exhibiting obvious toxicity. Compound 14 might be a potential drug candidate for FLT3-ITD positive AML.