Identification of a dual FLT3 and MNK2 inhibitor for acute myeloid leukemia treatment using a structure-based virtual screening approach

Developments of Fms-like Tyrosine Kinase 3 Inhibitors as Anticancer Agents for AML Treatment

BACKGROUND

FMS-like tyrosine kinase 3 (FLT3) is a commonly mutated gene in acute myeloid leukemia. As a receptor tyrosine kinase (RTK), FLT3 plays a role in the proliferation and differentiation of hematopoietic stem cells. As the most frequent molecular alteration in AML, FLT3 has drawn the attention of many researchers, and a lot of small molecule inhibitors targeting FLT3 have been intensively investigated as potential drugs for AML therapy.

METHODS

In this paper, PubMed and SciFinder® were used as a tool; the publications about "FLT3 inhibitor" and "Acute myeloid leukemia" were surveyed from 2014 to the present with an exclusion of those published as patents.

RESULTS

In this study, the structural characterization and biological activities of representative FLT3 inhibitors were summarized. The major challenges and future directions for further research are discussed.

CONCLUSION

Recently, numerous FLT3 inhibitors have been discovered and employed in FLT3-mutated AML treatment. In order to overcome the drug resistance caused by FLT3 mutations, screening multitargets FLT3 inhibitors has become the main research direction. In addition, the emergence of irreversible FLT3 inhibitors also provides new ideas for discovering new FLT3 inhibitors.

In silico identification and biological evaluation of a selective MAP4K4 inhibitor against pancreatic cancer

Inhibiting a specific target in cancer cells and reducing unwanted side effects has become a promising strategy in pancreatic cancer treatment. MAP4K4 is associated with pancreatic cancer development and correlates with poor clinical outcomes. By phosphorylating MKK4, proteins associated with cell apoptosis and survival are translated. Therefore, inhibiting MAP4K4 activity in pancreatic tumours is a new therapeutic strategy. Herein, we performed a structure-based virtual screening to identify MAP4K4 inhibitors and discovered the compound F389-0746 with a potent inhibition (IC₅₀ 120.7 nM). The results of kinase profiling revealed that F389-0746 was highly selective to MAP4K4 and less likely to cause side effects. Results of in vitro experiments showed that F389-0746 significantly suppressed cancer cell growth and viability. Results of in vivo experiments showed that F389-0746 displayed comparable tumour growth inhibition with the group treated with gemcitabine. These findings suggest that F389-0746 has promising potential to be further developed as a novel pancreatic cancer treatment.

Flavone-based dual PARP-Tubulin inhibitor manifesting efficacy against endometrial cancer

Structural tailoring of the flavone framework (position 7) via organopalladium-catalyzed C-C bond formation was attempted in this study. The impact of substituents with varied electronic effects (phenyl ring, position 2 of the benzopyran scaffold) on the antitumor properties was also assessed. Resultantly, the efforts yielded a furyl arm bearing benzopyran possessing a 4-fluoro phenyl ring (position 2) (14) that manifested a magnificent antitumor profile against the Ishikawa cell lines mediated through dual inhibition of PARP and tubulin [(IC50 (PARP1) = 74 nM, IC50 (PARP2) = 109 nM) and tubulin (IC50 = 1.4 µM)]. Further investigations confirmed the ability of 14 to induce apoptosis as well as autophagy and cause cell cycle arrest at the G2/M phase. Overall, the outcome of the study culminated in a tractable dual PARP-tubulin inhibitor endowed with an impressive activity profile against endometrial cancer.

Brain microvascular endothelial cells possess a second cilium that arises from the daughter centriole

Primary cilia from the brain microvascular endothelial cells (ECs) are specialized cell-surface organelles involved in mediating sensory perception, cell signaling, and vascular stability. Immunofluorescence (IF) analysis of human primary brain microvascular ECs reveals two cilia per cell. To confirm the in vitro observation of the two-cilia phenotype in human primary brain ECs, ECs isolated from mouse brain were cultured and stained for cilium. Indeed, brain ECs from a ciliopathic mouse (polycystic kidney disease or Pkd2 -/-) also possess more than one cilium. Primary cilium emerges from the mother centriole. Centriole analysis by IF suggests that in brain ECs, markers for the mother and daughter centrioles stain both cilia, suggesting that the second cilium in brain ECs arises from the daughter centriole. Further quantification of cilia size in brain ECs revealed that cilia arising from the mother centriole are bigger in size compared with cilia from the daughter centriole. Cell cycle analyses using immunoblotting and flow cytometry suggest that the ciliary proteins ARL13B and IFT88 involved in brain EC ciliogenesis are highly expressed only in the G0/G1 and S phases of the cell cycle. The IF analyses of cells arrested at different cell cycle stages indicate that the two-cilia phenotype is highly specific to the G0/G1 phase. Our findings suggest that in addition to the mother centriole, the daughter centriole also plays a role in ciliogenesis in primary cultured ECs.

Dual FLT3/haspin kinase inhibitor based on 3H-pyrazolo[4,3-f]quinoline scaffold with activities against acute myeloid leukemia

The 3H-pyrazolo[4,3-f]quinoline core, a privileged fusion moiety from quinoline and indazole, facilely synthesized in a one flask multi-component Doebner-Povarov reaction, is a newly described kinase hinge binder. Previous works have demonstrated that the 3H-pyrazolo[4,3-f]quinoline moiety can be tuned, via judicious substitution patterns, to selectively inhibit cancer-associated kinases, such as FLT3 and haspin. A first generation 3H-pyrazolo[4,3-f]quinoline-based haspin inhibitor, HSD972, and FLT3 inhibitor, HSD1169, were previously disclosed as inhibitors of various cancer cell lines. Given the recent revelation that haspin is over-expressed and plays critical proliferative roles in many cancers, and compounds with dual activity against FLT3 and other important kinases are now being actively developed by many groups, we became interested in optimizing the 3H-pyrazolo[4,3-f]quinoline-based compounds to improve activity against both FLT3 and haspin. Herein, we report the discovery of new 3H-pyrazolo[4,3-f]quinoline-based dual FLT3/haspin inhibitor, HSK205. HSK205 has remarkable potencies against FLT3-driven AML cell lines, inhibiting proliferation with GI50 values between 2-25 nM. Western blot analyses of treated AML cells confirm that HSK205 inhibit the phosphorylation of both FLT3 and histone H3 (a haspin target) in cells. While multi-component reactions (MCRs) have been used to make many bioactive molecules, there are very few examples of using MCRs to make compounds that target protein kinases, which have emerged as one of the top drug candidates (especially in oncology). This work highlights our recent efforts to make ultrapotent protein kinase inhibitors using multi-component reactions (especially the Doebner-Povarov reaction).

Therapeutic strategies of dual-target small molecules to overcome drug resistance in cancer therapy

Despite some advances in targeted therapeutics of human cancers, curative cancer treatment still remains a tremendous challenge due to the occurrence of drug resistance. A variety of underlying resistance mechanisms to targeted cancer drugs have recently revealed that the dual-target therapeutic strategy would be an attractive avenue. Compared to drug combination strategies, one agent simultaneously modulating two druggable targets generally shows fewer adverse reactions and lower toxicity. As a consequence, the dual-target small molecule has been extensively explored to overcome drug resistance in cancer therapy. Thus, in this review, we focus on summarizing drug resistance mechanisms of cancer cells, such as enhanced drug efflux, deregulated cell death, DNA damage repair, and epigenetic alterations. Based upon the resistance mechanisms, we further discuss the current therapeutic strategies of dual-target small molecules to overcome drug resistance, which will shed new light on exploiting more intricate mechanisms and relevant dual-target drugs for future cancer therapeutics.

MNK Proteins as Therapeutic Targets in Leukemia

In leukemia, resistance to therapy is a major concern for survival. MAPK-interacting kinases (MNKs) have been identified as important activators of oncogenic-related signaling and may be mediators of resistance. Recent studies in leukemia models, especially acute myeloid leukemia (AML), have focused on targeting MNKs together with other inhibitors or treating chemotherapy-resistant cells with MNK inhibitors. The preclinical demonstrations of the efficacy of MNK inhibitors in these combination formats would suggest a promising potential for use in clinical trials. Optimizing MNK inhibitors and testing in leukemia models is actively being pursued and may have important implications for the future. These studies are furthering the understanding of the mechanisms of MNKs in cancer which could translate to clinical studies.

Ibrutinib Prevents Acute Lung Injury via Multi-Targeting BTK, FLT3 and EGFR in Mice

Ibrutinib has potential therapeutic or protective effects against viral- and bacterial-induced acute lung injury (ALI), likely by modulating the Bruton tyrosine kinase (BTK) signaling pathway. However, ibrutinib has multi-target effects. Moreover, immunity and inflammation targets in ALI treatment are poorly defined. We investigated whether the BTK-, FLT3-, and EGFR-related signaling pathways mediated the protective effects of ibrutinib on ALI. The intratracheal administration of poly I:C or LPS after ibrutinib administration in mice was performed by gavage. The pathological conditions of the lungs were assessed by micro-CT and HE staining. The levels of neutrophils, lymphocytes, and related inflammatory factors in the lungs were evaluated by ELISA, flow cytometry, immunohistochemistry, and immunofluorescence. Finally, the expression of proteins associated with the BTK-, FLT3-, and EGFR-related signaling pathways were evaluated by Western blotting. Ibrutinib (10 mg/kg) protected against poly I:C-induced (5 mg/kg) and LPS-induced (5 mg/kg) lung inflammation. The wet/dry weight ratio (W/D) and total proteins in the bronchoalveolar lavage fluid (BALF) were markedly reduced after ibrutinib (10 mg/kg) treatment, relative to the poly I:C- and LPS-treated groups. The levels of ALI indicators (NFκB, IL-1β, IL-6, TNF-α, IFN-γ, neutrophils, and lymphocytes) were significantly reduced after treatment. Accordingly, ibrutinib inhibited the poly I:C- and LPS-induced BTK-, FLT3-, and EGFR-related pathway activations. Ibrutinib inhibited poly I:C- and LPS-induced acute lung injury, and this may be due to its ability to suppress the BTK-, FLT3-, and EGFR-related signaling pathways. Therefore, ibrutinib is a potential protective agent for regulating immunity and inflammation in poly I:C- and LPS-induced ALI.

Discovery of novel natural products as dual MNK/PIM inhibitors for acute myeloid leukemia treatment: Pharmacophore modeling, molecular docking, and molecular dynamics studies

MNK-2 and PIM-2 kinases play an indispensable role in cell proliferation signaling pathways linked to tyrosine kinase inhibitors resistance. In this study, pharmacophore modeling studies have been conducted on the co-crystalized ligands of MNK-2 and PIM-2 enzyme crystal structures to determine the essential features required for the identification of potential dual inhibitors. The obtained pharmacophore features were then screened against a library of 270,540 natural products from the ZINC database. The matched natural molecules were docked into the binding sites of MNK-2 and PIM-2 enzymes. The compounds with high docking scores with the two enzymes were further subjected to MM-GBSA calculations and ADME prediction. This led to the identification of compound 1 (ZINC000085569211), compound 2 (ZINC000085569178), and compound 3 (ZINC000085569190), with better docking scores compared to the reference co-crystallized ligands of MNK-2 and PIM-2. Moreover, compounds 1‒3 displayed better MM-GBSA binding free energies compared to the reference ligands. Finally, molecular dynamics (MD) study was used to assess the interaction stability of the compounds with MNK-2. To this end, compounds 1 and 3 bound strongly to the target during the whole period of MD simulation. The findings of the current study may further help the researchers in the discovery of novel molecules against MNK-2 and PIM-2.