Combining structure- and property-based optimization to identify selective FLT3-ITD inhibitors with good antitumor efficacy in AML cell inoculated mouse xenograft model.

FLT3 mutation is among the most common genetic mutations in acute myeloid leukemia (AML), which is also related with poor overall survival and refractory in AML patients. Recently, FLT3 inhibitors have been approved for AML therapy. Herein, a series of new compounds with pyrazole amine scaffold was discovered, which showed potent inhibitory activity against FLT3-ITD and significant selectivity against both FLT3-ITD and AML cells expressing FLT3-ITD. Compound 46, possessing the most promising cellular activity, blocked the autophosphorylation of FLT3 pathway in MV4-11 cell line. Furthermore, the apoptosis and downregulation of P-STAT5 were also observed in tumor cells extracted from the MV4-11 cell xenografts model upon compound 46 treatment. Compound 46 was also metabolically stable in vitro and suppressed tumor growth significantly in MV4-11 xenografts model in vivo. Compound 46 showed no toxicity to the viscera of mice and caused no decrease in body weight of mice. In conclusion, the results of this study could provide valuable insights into discovery of new FLT3 inhibitors, and compound 46 was worthy of further development as potential drug candidate to treat AML.

Chemical Space of FLT3 Inhibitors as Potential Anti-AML Drugs.

BACKGROUND: FLT3 is a member of receptor tyrosine kinase III family, mainly expressed in hematopoietic cells. The aberrant expression and function of FLT3 are strongly related to leukemia, especially acute myeloid leukemia. Its varieties of amino-acid residues mutations, such as FLT3-ITDs and -TKDs, can induce constant proliferation of hematological tumor cells with poor prognosis. Hence FLT3 serves as a promising target in AML chemotherapy. OBJECTIVE: This review focused on the progress of FLT3 inhibitors study including those that have entered clinical trials or were reported in numerous patents all over the world. Thus, we provided a useful reference for the development of new anti-leukemia drugs. METHOD: Through a comprehensive retrospective study, FLT3 inhibitors in several patent applications were identified and classified into five categories, including quinolone-related, indole-related, ureas, pyrimidines and other compounds. RESULTS: For each category of compounds, the structural feature, SAR, biological activity and current research status were thoroughly reviewed and analyzed. CONCLUSION: Although some of those compounds expressed potent bioactivities and have reached the advanced clinical trials for the treatment of leukemia, there are still several problems need to be faced before they enter the market eventually, especially the drug resistance issue. The improvement of therapeutic potency for FLT3 inhibitors might depend on the useful combination therapy and further refinement of the intrinsic properties of FLT3 inhibitors.