Eltrombopag as an Allosteric Inhibitor of the METTL3-14 Complex Affecting the m6A Methylation of RNA in Acute Myeloid Leukemia Cells.

N6A-methyladenosine (m6A) post-transcriptional modification, the most abundant internal RNA modification, is catalyzed by the METTL3-14 methyltransferase complex. Recently, attention has been drawn to the METTL3-14 complex regarding its significant roles in the pathogenesis of acute myeloid leukemia (AML), attracting the potential of novel therapeutic targets for the disease. Herein, we report the identification and characterization of eltrombopag as a selective allosteric inhibitor of the METTL3-14 complex. Eltrombopag exhibited selective inhibitory activity in the most active catalytic form of the METTL3-14 complex by direct binding, and the mechanism of inhibition was confirmed as a noncompetitive inhibition by interacting at a putative allosteric binding site in METTL3, which was predicted by cavity search and molecular docking studies. At a cellular level, eltrombopag displayed anti-proliferative effects in the relevant AML cell line, MOLM-13, in correlation with a reduction in m6A levels. Molecular mechanism studies of eltrombopag using m6A-seq analysis provided further evidence of its cellular function by determining the hypomethylation of leukemogenic genes in eltrombopag-treated MOLM-13 cells and the overlapping of the pattern with those of METTL3-knockdown MOLM-13 cells. In conclusion, eltrombopag was first disclosed as a functional METTL3-14 allosteric inhibitor in AML cells, which could be utilized for the further development of novel anti-AML therapy.

Discovery of indirubin-3'-aminooxy-acetamide derivatives as potent and selective FLT3/D835Y mutant kinase inhibitors for acute myeloid leukemia.

Mutations in Fms-like tyrosine kinase 3 (FLT3) have been implicated in the pathogenesis of acute myeloid leukemia (AML) by affecting the proliferation and differentiation of hematopoietic stem and progenitor cells. Although several FLT3 inhibitors have been developed, the occurrence of secondary TKD mutations of FLT3 such FLT3/D835Y and FLT3/F691L lead to drug resistance and has become a key area of unmet medical needs. To overcome the obstacle of secondary TKD mutations, a new series of indirubin-3'-aminooxy-acetamide derivatives was discovered as potent and selective FLT3 and FLT3/D835Y inhibitors that were predicted to bind at the DFG-in active conformation of FLT3 in molecular docking studies. Through structure-activity relationship studies, the most optimized compound 13a was developed as a potent inhibitor at FLT3 and FLT3/D835Y with IC50 values of 0.26 nM and 0.18 nM, respectively, which also displayed remarkably strong in vitro anticancer activities, with single-digit nanomolar GI50 values for several AML (MV4-11 and MOLM14) and Ba/F3 cell lines expressed with secondary TKD mutated FLT3 kinases as well as FLT3-ITD. The selectivity profiles of compound 13a in the oncology kinase panel and various human cancer cell lines were prominent, demonstrating that its inhibitory activities were mainly focused on a few members of the receptor tyrosine kinase family and AML versus solid tumor cell lines. Furthermore, significant in vivo anticancer efficacy of compound 13a was confirmed in a xenograft animal model implanted with FLT3-ITD/D835Y-expressing MOLM-14 cells related to secondary TKD mutation.

Discovery of substituted indole derivatives as allosteric inhibitors of m6 A-RNA methyltransferase, METTL3-14 complex.

m6 A RNA methyltransferase (METTL3-14) catalyzes the methylation of adenosine in mRNA and plays important roles in mRNA functions, and it has been implicated in the progression of multiple cancers, including acute myeloid leukemia (AML). In this study, we describe the discovery of the first allosteric inhibitor of the METTL3-14 complex based on structure-activity relationship (SAR) and optimization studies of the hit compound, 4-[2-[5-chloro-1-(diphenylmethyl)-2-methyl-1H-indol-3-yl]-ethoxy]benzoic acid (CDIBA). Compound 43n was optimized throughout the modifications of 4 different regions of the structure, and it displayed potent enzyme inhibitory activity of the METTL3-14 complex (IC50  = 2.81 µM) and an antiproliferative effect in the AML cell lines by suppressing the m6 A level of mRNA. The inhibition mechanism and binding mode of 43n were based on the interaction of the reversible and noncompetitive inhibitory profile at the allosteric site along with selectivity for the METTL3-14 complex relative to each subunit enzyme or truncated complex enzyme.

Discovery of orally active indirubin-3'-oxime derivatives as potent type 1 FLT3 inhibitors for acute myeloid leukemia.

FMS-like receptor tyrosine kinase-3 (FLT3) is expressed on acute leukemia cells and is implicated in the survival, proliferation and differentiation of hematopoietic cells in most acute myeloid leukemia (AML) patients. Despite recent achievements in the development of FLT3-targeted small-molecule drugs, there are still unmet medical needs related to kinase selectivity and the progression of some mutant forms of FLT3. Herein, we describe the discovery of novel orally available type 1 FLT3 inhibitors from structure-activity relationship (SAR) studies for the optimization of indirubin derivatives with biological and pharmacokinetic profiles as potential therapeutic agents for AML. The SAR exploration provided important structural insights into the key substituents for potent inhibitory activities of FLT3 and in MV4-11 cells. The profile of the most optimized inhibitor (36) showed IC50 values of 0.87 and 0.32 nM against FLT3 and FLT3/D835Y, respectively, along with potent inhibition against MV4-11 and FLT3/D835Y expressed MOLM14 cells with a GI50 value of 1.0 and 1.87 nM, respectively. With the high oral bioavailability of 42.6%, compound 36 displayed significant in vivo antitumor activity by oral administration of 20 mg/kg once daily dosing schedule for 21 days in a mouse xenograft model. The molecular docking study of 36 in the homology model of the DFG-in conformation of FLT3 resulted in a reasonable binding mode in type 1 kinases similar to the reported type 1 FLT3 inhibitors Crenolanib and Gilteritinib.

Potent Suppressive Effects of 1-Piperidinylimidazole Based Novel P2X7 Receptor Antagonists on Cancer Cell Migration and Invasion.

The P2X7 receptor (P2X7R) has been reported as a key mediator in inflammatory processes and cancer invasion/metastasis. In this study, we report the discovery of novel P2X7R antagonists and their functional activities as potential antimetastatic agents. Modifications of the hydantoin core-skeleton and the side chain substituents of the P2X7R antagonist 7 were performed. The structure-activity relationships (SAR) and optimization demonstrated the importance of the sulfonyl group at the R1 position and the substituted position and overall size of R2 for P2X7R antagonism. The optimized novel analogues displayed potent P2X7 receptor antagonism (IC50 = 0.11-112 nM) along with significant suppressive effects on IL-1ß release (IC50 = 0.32-210 nM). Moreover, representative antagonists (12g, 13k, and 17d) with imidazole and uracil core skeletons significantly inhibited the invasion of MDA-MB-231 triple negative breast cancer cells and cancer cell migration in a zebrafish xenograft model, suggesting the potential therapeutic application of these novel P2X7 antagonists to block metastatic cancer.