Tandutinib

The FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutation is a key target for acute myeloid leukemia (AML) treatment. The second-generation inhibitors such as Gilteritinib still present off-target effects and associated side effects. Therefore, identifying novel FLT3-ITD inhibitors has become a promising strategy for AML treatment. In this study, a 4D-QSAR model was developed based on Gilteritinib and its analogues, and it was found that introducing hydrophobic bulky groups at the piperazine or piperidine of Gilteritinib would enhance the binding affinity to FLT3-ITD. So, three series of targeted compounds (A1-A5, B1-B5 and C1-C5) were designed and synthesized. The antiproliferative activity against MOLM-13 cells was evaluated in vitro. Compound A1 (IC₅₀ = 25.65 nM), with a cubane group at the piperazine position; Compounds B2 (IC₅₀ = 63.38 nM) and C2 (IC₅₀ = 54.96 nM), with a norbornene group at the piperidine position, showed the strongest inhibition in their series. Their IC₅₀ values were comparable to that of the positive control Gilteritinib (IC₅₀ = 22.37 nM). FLT3-ITD was confirmed as the degradation target through a kinase inhibition assay, where the IC₅₀ values were 2.12 nM (Compound A1), 1.29 nM (Compound B2), and 3.06 nM (Compound C2), which were comparable to that of Gilteritinib (IC₅₀ = 0.43 nM). Additionally, molecular docking and molecular dynamics (MD) simulations showed that Compounds A1, B2, and C2 had similar binding modes to that of Gilteritinib with more stable affinities. Overall, these results demonstrated that Compounds A1, B2, and C2 were promising inhibitors for targeting AML with FLT3-ITD mutation.

The bacterium Bacillus coagulans has attracted interest because of its ability to produce spores and advantageous probiotic traits, such as facilitating food digestion in the intestine, managing some disorders, and controlling the symbiotic microbiota. Spore-forming probiotic bacteria are especially important in the probiotic industry compared to non-spore-forming bacteria due to their stability during production and high resistance to adverse factors such as stomach acid. When spore-forming bacteria are exposed to environmental stresses, they enter the sporulation pathway to survive. This pathway is activated by the final phosphorylation of the master regulator of spore response, Spo0A, and upon achieving the phosphorylation threshold. Spo0A is indirectly inhibited by some enzymes of the aspartate response regulator phosphatase (Rap) family, such as RapJ. RapJ is one of the most important Rap enzymes in the sporogenesis pathway, which is naturally inhibited by the pentapeptides.

This study used structure-based virtual screening and molecular dynamics (MD) simulation studies to find potential RapJ hits that could induce the sporulation pathway. The crystal structures of RapJ complexed with pentapeptide clearly elucidated their interactions with the enzyme active site.

Based on the binding compartment, through molecular docking, MD simulation, hydrogen bonds, and binding-free energy calculations, a series of novel hits against RapJ named tandutinib, infigratinib, sitravatinib, linifanib, epertinib, surufatinib, and acarbose were identified. Among these compounds, acarbose obtained the highest score, especially in terms of the number of hydrogen bonds, which plays a major role in stabilizing RapJ-ligand complexes, and also according to the occupancy percentages of hydrogen bonds, its hydrogen bonds were more stable during the simulation time. Consequently, acarbose is probably the most suitable hit for RapJ enzyme. Notably, experimental validation is crucial to confirm the effectiveness of the selected ligands.