Discovery of a Potent FLT3 Inhibitor (LT-850-166) with the Capacity of Overcoming a Variety of FLT3 Mutations

Abstract

Secondary mutations of FLT3 have become the main mechanism of FLT3 inhibitor resistance that presents a significant clinical challenge. Herein, a series of pyrazole-3-amine derivatives were synthesized and optimized to overcome the common secondary resistance mutations of FLT3. The structure-activity relationship and molecular dynamics simulation studies illustrated that the ribose region of FLT3 could be occupied to help address the obstacle of secondary mutations. Among those derivatives, compound <b>67</b> exhibited potent and selective inhibitory activities against FLT3-ITD-positive acute myeloid leukemia (AML) cells and possessed equivalent potency against transformed BaF3 cells with a variety of secondary mutations. Besides, cellular mechanism assays demonstrated that <b>67</b> strongly inhibited phosphorylation of FLT3 and its downstream signaling factors, as well as induced cell cycle arrest and apoptosis in MV4-11 cells. In the MV4-11 xenograft models, <b>67</b> exhibited potent antitumor potency without obvious toxicity. Taken together, these results demonstrated that <b>67</b> might be a drug candidate for the treatment of FLT3-ITD-positive AML.