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Fms-like tyrosine kinase 3 (FLT3) is an important member of the class III receptor tyrosine kinase (RTK) family, which is involved in the proliferation of hematopoietic cells and lymphocytes. In recent years, increasing evidence have demonstrated that the activation and mutation of FLT3 is closely implicated in the occurrence and development of acute myeloid leukemia (AML). The exploration of small-molecule inhibitors targeting FLT3 has aroused wide interest of pharmaceutical chemists and is expected to bring new hope for AML therapy. In this review, we specifically highlighted FLT3 mediated JAK/STAT, RAS/MAPK, and PI3K/AKT/mTOR signaling. The structural properties and biological activities of representative FLT3 inhibitors reported from 2014 to the present were also summarized. In addition, the major challenges in the current advance of novel FLT3 inhibitors were further analyzed, with the aim to guide future drug discovery.

Despite the fact that five kinds of uranium nitrides, i.e., uranium mononitrides (UN, R3̅m and Fm3̅m), a uranium dinitride (UN 2 , Fm3̅m), and uranium sesquinitrides (α-U 2 N 3 , Ia3̅; β-U 2 N 3 ,P3̅m1), have been confirmed, until now the phase relations are not well understood because of the puzzling nonstoichiometric issue. This work reinvestigated the crystallographic structures of these phases using cluster formula theory. The principal clusters (cuboctahedron with six squares and eight triangles) in these phases were determined. N atoms can occupy either six octahedral sites (square face centers) or eight tetrahedral sites (formed by a center atom and a triangle) in the principal cluster of 13 U atoms, resulting in these diversified phases and the nonstoichiometric issue. Also, phase transformations at certain temperatures and pressures (from CaF 2 -type UN 2 to Mn 2 O 3 -type U 2 N 3 , from Mn 2 O 3 -type U 2 N 3 to NaCl-type UN, and from NaCl-type UN to HgIn-type UN) were deduced by tracking the bond and angle changes of a simplified cluster [U-U 6 N 6 ]. This investigation provides an in-depth understanding of the phase relations in a U-N system.