FLT3 inhibitors for relapsed or refractory acute myeloid leukaemia

Design, synthesis and biological evaluation of 2-aminopyrimidine derivatives as potent FLT3 inhibitors

Acute myeloid leukemia (AML) is an aggressive cancer, which is characterized by clonal expansion of myeloid progenitors in the bone marrow and peripheral blood. FMS-like tyrosine kinase 3 (FLT3) mutations are the most frequently identified mutations, present in approximately 25-30 % AML patients, making FLT3 inhibitors a crucial treatment option for AML. In this study, we described the design, synthesis and biological evaluation of a series of 2-aminopyrimidine derivatives as potent FLT3 inhibitors. Notably, compound 15 displayed potent kinase inhibitory activities against FLT3 (FLT3-WT IC50 = 7.42 ± 1.23 nM; FLT3-D835Y IC50 = 9.21 ± 0.04 nM) and robust antiproliferative activities against MV4-11 cells (IC50 = 0.83 ± 0.15 nM) and MOLM-13 cells (IC50 = 10.55 ± 1.70 nM). Compound 15 also possessed potent antiproliferative activities against BaF3 cells carrying various FLT3-TKD and FLT3-ITD-TKD mutations, indicating its potential to overcome on-target resistance caused by FLT3 mutations. In summary, compound 15 showed promising potential for further exploration as a treatment of AML.

The new small tyrosine kinase inhibitor ARQ531 targets acute myeloid leukemia cells by disrupting multiple tumor-addicted programs

Tyrosine kinases have been implicated in promoting tumorigenesis of several human cancers. Exploiting these vulnerabilities has been shown to be an effective anti-tumor strategy as demonstrated for example by the Bruton's tyrosine kinase (BTK) inhibitor, ibrutinib, for treatment of various blood cancers. Here, we characterize a new multiple kinase inhibitor, ARQ531, and evaluate its mechanism of action in preclinical models of acute myeloid leukemia. Treatment with ARQ531, by producing global signaling pathway deregulation, resulted in impaired cell cycle progression and survival in a large panel of leukemia cell lines and patient-derived tumor cells, regardless of the specific genetic background and/or the presence of bone marrow stromal cells. RNA-seq analysis revealed that ARQ531 constrained tumor cell proliferation and survival through Bruton's tyrosine kinase and transcriptional program dysregulation, with proteasome-mediated MYB degradation and depletion of short-lived proteins that are crucial for tumor growth and survival, including ERK, MYC and MCL1. Finally, ARQ531 treatment was effective in a patient-derived leukemia mouse model with significant impairment of tumor progression and survival, at tolerated doses. These data justify the clinical development of ARQ531 as a promising targeted agent for the treatment of patients with acute myeloid leukemia.

Prognosis and outcome of patients with acute myeloid leukemia based on FLT3-ITD mutation with or without additional abnormal cytogenetics

The FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) gene mutation is present in ~20% of patients with de novo acute myeloid leukemia (AML). Patients with an FLT3-ITD mutation have a poor prognosis. However, the prognostic function of FLT3-ITD combined with other cytogenetic abnormalities are not clear. In the present study, a retrospective analysis of 103 newly diagnosed patients with AML was performed. The results revealed that the overall survival (OS) and recurrence-free survival (RFS) times were significantly longer in patients with an FLT3-ITD mutation combined with other favorable risk genes, compared with in those patients with a single FLT3-ITD mutation (P=0.0361 and P=0.0426). Sorafenib combined with chemotherapy significantly improved the overall response rate (ORR) when compared with mono-chemotherapy (P=0.039), but no significant differences were observed in the OS and RFS. In conclusion, favorable-risk cytogenetics may improve the clinical outcomes of patients with FLT3-ITD-mutated AML, but adverse-risk cytogenetics may not further worsen the prognosis. Sorafenib combined with chemotherapy may increase the ORR but would not result in a longer OS and RFS.

Self-nanoemulsifying system improves oral absorption and enhances anti-acute myeloid leukemia activity of berberine

BACKGROUND

Recently, we found that berberine (BBR) exerts anti-acute myeloid leukemia activity, particularly toward high-risk and relapsed/refractory acute myeloid leukemia MV4-11 cells in vitro. However, the poor water solubility and low bioavailability observed with oral BBR administration has limited its clinical use. Therefore, we design and develop a novel oil-in-water self-nanoemulsifying system for BBR (BBR SNE) to improve oral bioavailability and enhance BBR efficacy against acute myeloid leukemia by greatly improving its solubility.

RESULTS

This system (size 23.50 ± 1.67 nm, zeta potential - 3.35 ± 0.03 mV) was prepared with RH40 (surfactant), 1,2-propanediol (co-surfactant), squalene (oil) and BBR using low-energy emulsification methods. The system loaded BBR successfully according to thermal gravimetric, differential scanning calorimetry, and Fourier transform infrared spectroscopy analyses. The release profile results showed that BBR SNE released BBR more slowly than BBR solution. The relative oral bioavailability of this novel system in rabbits was significantly enhanced by 3.41-fold over that of BBR. Furthermore, Caco-2 cell monolayer transport studies showed that this system could help enhance permeation and prevent efflux of BBR. Importantly, mice with BBR SNE treatment had significantly longer survival time than BBR-treated mice (P < 0.001) in an MV4-11 engrafted leukemia murine model.

CONCLUSIONS

These studies confirmed that BBR SNE is a promising therapy for acute myeloid leukemia.