FLT3inhibitor quizartinib (AC220)

A systematic review of second-generation FLT3 inhibitors for treatment of patients with relapsed/refractory acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a complex disease with diverse mutations, including prevalent mutations in the FMS-like receptor tyrosine kinase 3 (FLT3) gene that lead to poor prognosis. Recent advancements have introduced FLT3 inhibitors that have improved outcomes for FLT3-mutated AML patients, however, questions remain on their application in complex conditions such as relapsed/refractory (R/R) disease. Therefore, we aimed to evaluate the clinical effectiveness of second-generation FLT3 inhibitors in treating patients with R/R AML.

METHODS

A systematic literature search of PubMed, MEDLINE, SCOPUS and Google Scholar databases was made to identify relevant studies up to January 30, 2024. This study was conducted following the guidelines of the PRISMA.

RESULTS

The ADMIRAL trial revealed significantly improved overall survival and complete remission rates with gilteritinib compared to salvage chemotherapy, with manageable adverse effects. Ongoing research explores its potential in combination therapies, showing synergistic effects with venetoclax and promising outcomes in various clinical trials. The QuANTUM-R trial suggested longer overall survival with quizartinib compared to standard chemotherapy, although concerns were raised regarding trial design and cardiotoxicity. Ongoing research explores combination therapies involving quizartinib, such as doublet or triplet regimens with venetoclax, showing promising outcomes in FLT3-mutated AML patients.

CONCLUSION

These targeted therapies offer promise for managing this subgroup of AML patients, but further research is needed to optimize their use. This study underscores the importance of personalized treatment based on genetic mutations in AML, paving the way for more effective and tailored approaches to combat the disease.

A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2023

With 54 new drugs and seven cellular and gene therapy products, the approvals by the US Food and Drug Administration (FDA) recovered 2023 from the 2022 dent back to the levels of 2020-2021. As in previous years of this annual review, we assign these new drugs to one of three levels of innovation: first drug against a condition ("first-in-indication"), first drug using a novel molecular mechanism ("first-in-class"), and "next-in-class," i.e., a drug using an already exploited molecular mechanism. We identify four (7%) "first-in-indication," 22 (36%) "first-in-class," and 35 (57%) "next-in-class" drugs. By treatment area, rare diseases (54%) and cancer drugs (23%) were once again the most prevalent (and partly overlapping) therapeutic areas. Other continuing trends were the use of accelerated regulatory approval pathways and the reliance on biopharmaceuticals (biologics). 2023 marks the approval of a first therapy based on CRISPR/Cas9 gene editing.

NET-related gene signature for predicting AML prognosis

Acute Myeloid Leukemia (AML) is a malignant blood cancer with a high mortality rate. Neutrophil extracellular traps (NETs) influence various tumor outcomes. However, NET-related genes (NRGs) in AML had not yet received much attention. This study focuses on the role of NRGs in AML and their interaction with the immunological microenvironment. The gene expression and clinical data of patients with AML were downloaded from the TCGA-LAML and GEO cohorts. We identified 148 NRGs through the published article. Univariate Cox regression was used to analyze the association of NRGs with overall survival (OS). The least absolute shrinkage and selection operator were utilized to assess the predictive efficacy of NRGs. Kaplan-Meier plots visualized survival estimates. ROC curves assessed the prognostic value of NRG-based features. A nomogram, integrating clinical information and prognostic scores of patients, was constructed using multivariate logistic regression and Cox proportional hazards regression models. Twenty-seven NRGs were found to significantly impact patient OS. Six NRGs-CFTR, ENO1, PARVB, DDIT4, MPO, LDLR-were notable for their strong predictive ability regarding patient survival. The ROC values for 1-, 3-, and 5-year survival rates were 0.794, 0.781, and 0.911, respectively. In the training set (TCGA-LAML), patients in the high NRG risk group showed a poorer prognosis (p < 0.001), which was validated in two external datasets (GSE71014 and GSE106291). The 6-NRG signature and corresponding nomograms exhibit superior predictive accuracy, offering insights for pre-immune response evaluation and guiding future immuno-oncology treatments and drug selection for AML patients.

How acute myeloid leukemia (AML) escapes from FMS-related tyrosine kinase 3 (FLT3) inhibitors? Still an overrated complication?

FMS-related tyrosine kinase 3 (FLT3) mutations, present in about 25%-30% of acute myeloid leukemia (AML) patients, constitute one of the most frequently detected mutations in these patients. The binding of FLT3L to FLT3 activates the phosphatidylinositol 3-kinase (PI3K) and RAS pathways, producing increased cell proliferation and the inhibition of apoptosis. Two types of FLT3 mutations exist: FLT3-ITD and FLT3-TKD (point mutations in D835 and I836 or deletion of codon I836). A class of drugs, tyrosine-kinase inhibitors (TKI), targeting mutated FLT3, is already available with 1^st and 2^nd generation molecules, but only midostaurin and gilteritinib are currently approved. However, the emergence of resistance or the selection of clones not responding to FLT3 inhibitors has become an important clinical dilemma, as the duration of clinical responses is generally limited to a few months. This review analyzes the insights into mechanisms of resistance to TKI and poses a particular view on the clinical relevance of this phenomenon. Has resistance been overlooked? Indeed, FLT3 inhibitors have significantly contributed to reducing the negative impact of FLT3 mutations on the prognosis of AML patients who are no longer considered at high risk by the European LeukemiaNet (ELN) 2022. Finally, several ongoing efforts to overcome resistance to FLT3-inhibitors will be presented: new generation FLT3 inhibitors in monotherapy or combined with standard chemotherapy, hypomethylating drugs, or IDH1/2 inhibitors, Bcl2 inhibitors; novel anti-human FLT3 monoclonal antibodies (e.g., FLT3/CD3 bispecific antibodies); FLT3-CAR T-cells; CDK4/6 kinase inhibitor (e.g., palbociclib).

2-Aminopyrimidine derivatives as selective dual inhibitors of JAK2 and FLT3 for the treatment of acute myeloid leukemia

Dual inhibitors of JAK2 and FLT3 can synergistically control the development of acute myeloid leukemia (AML), and overcome secondary drug resistance of AML that is associated with FLT3 inhibition. We therefore designed and synthesized a series of 4-piperazinyl-2-aminopyrimidines as dual inhibitors of JAK2 and FLT3, and improved their selectivity for JAK2. Screening cascades revealed that compound 11r exhibited inhibitory activity with IC₅₀ values of 2.01, 0.51, and 104.40 nM against JAK2, FLT3, and JAK3, respectively. Compound 11r achieved a high selectivity for JAK2 at a ratio of 51.94, and also showed potent antiproliferative activity in HEL (IC₅₀ = 1.10 μM) and MV4-11 (IC₅₀ = 9.43 nM) cell lines. In an in vitro metabolism assay, 11r exhibited moderate stability in human liver microsomes (HLMs), with a half-life time of 44.4 min, and in rat liver microsomes (RLMs), with a half-life of 143 min. In pharmacokinetic studies, compound 11r showed moderate absorption (Tmax = 5.33 h), with a peak concentration of 38.7 ng/mL and an AUC of 522 ng h/mL in rats, and an oral bioavailability of 25.2%. In addition, 11r induced MV4-11 cell apoptosis in a dose-dependent manner. These results indicate that 11r is a promising selective JAK2/FLT3 dual inhibitor.

Clinical Efficacies of FLT3 Inhibitors in Patients with Acute Myeloid Leukemia

FLT3 mutations are the most common genomic alteration detected in acute myeloid leukemia (AML) with a worse clinical prognosis. The highly frequent FLT3 mutations, together with the side effects associated with clinical prognosis, make FLT3 promising treatment targets and have provoked the advancement of FLT3 inhibitors. Recently, numerous FLT3 inhibitors were actively developed, and thus the outcomes of this aggressive subtype of AML were significantly improved. Recently, midostaurin and gilteritinib were approved as frontline treatment of AML and as therapeutic agents in the recurred disease by the United States Food and Drug Administration. Recently, numerous promising clinical trials attempted to seek appropriate management in frontline settings, in relapsed/refractory disease, or after stem cell transplantation in AML. This review follows numerous clinical trials about the usefulness of FLT3 inhibitors as frontline therapy, as relapsed/refractory conditioning, and as maintenance therapy of stem cell transplantation. The cumulative data of FLT3 inhibitors would be important clinical evidence for further management with FLT3 inhibitors in AML patients with FLT3 mutations.

FLT3 inhibitors for acute myeloid leukemia: successes, defeats, and emerging paradigms

FLT3 mutations are one of the most common genetic aberrations found in nearly 30% of acute myeloid leukemias (AML). The mutations are associated with poor prognosis despite advances in the understanding of the biological mechanisms of AML. Numerous small molecule FLT3 inhibitors have been developed in an effort to combat AML. Even with the development of these inhibitors, the five-year overall survival for newly diagnosed AML is less than 30%. In 2017, midostaurin received FDA approval to treat AML, which was the first approved FLT3 inhibitor in the U.S. and Europe. Following, gilteritinib received FDA approval in 2018 and in 2019 quizartinib received approval in Japan. This review parallels these clinical success stories along with other pre-clinical and clinical investigations of FLT3 inhibitors.

A review of FLT3 inhibitors in acute myeloid leukemia

FLT3 mutations are the most common genetic aberrations found in acute myeloid leukemia (AML) and associated with poor prognosis. Since the discovery of FLT3 mutations and their prognostic implications, multiple FLT3-targeted molecules have been evaluated. Midostaurin is approved in the U.S. and Europe for newly diagnosed FLT3 mutated AML in combination with standard induction and consolidation chemotherapy based on data from the RATIFY study. Gilteritinib is approved for relapsed or refractory FLT3 mutated AML as monotherapy based on the ADMIRAL study. Although significant progress has been made in the treatment of AML with FLT3-targeting, many challenges remain. Several drug resistance mechanisms have been identified, including clonal selection, stromal protection, FLT3-associated mutations, and off-target mutations. The benefit of FLT3 inhibitor maintenance therapy, either post-chemotherapy or post-transplant, remains controversial, although several studies are ongoing.

Recreating the Bone Marrow Microenvironment to Model Leukemic Stem Cell Quiescence

The main challenge in the treatment of acute myeloid leukemia (AML) is relapse, as it has no good treatment options and 90% of relapsed patients die as a result. It is now well accepted that relapse is due to a persisting subset of AML cells known as leukemia-initiating cells or leukemic stem cells (LSCs). Hematopoietic stem cells (HSCs) reside in the bone marrow microenvironment (BMM), a specialized niche that coordinates HSC self-renewal, proliferation, and differentiation. HSCs are divided into two types: long-term HSCs (LT-HSCs) and short-term HSCs, where LT-HSCs are typically quiescent and act as a reserve of HSCs. Like LT-HSCs, a quiescent population of LSCs also exist. Like LT-HSCs, quiescent LSCs have low metabolic activity and receive pro-survival signals from the BMM, making them resistant to drugs, and upon discontinuation of therapy, they can become activated and re-establish the disease. Several studies have shown that the activation of quiescent LSCs may sensitize them to cytotoxic drugs. However, it is very difficult to experimentally model the quiescence-inducing BMM. Here we report that culturing AML cells with bone marrow stromal cells, transforming growth factor beta-1 and hypoxia in a three-dimensional system can replicate the quiescence-driving BMM. A quiescent-like state of the AML cells was confirmed by reduced cell proliferation, increased percentage of cells in the G₀ cell cycle phase and a decrease in absolute cell numbers, expression of markers of quiescence, and reduced metabolic activity. Furthermore, the culture could be established as co-axial microbeads, enabling high-throughput screening, which has been used to identify combination drug treatments that could break BMM-mediated LSC quiescence, enabling the eradication of quiescent LSCs.

Histone methyltransferase EZH2 epigenetically affects CCNA1 expression in acute myeloid leukemia

Cyclin A1 (CCNA1) is an alternative A-type cyclin that is expressed in acute myeloid leukemia (AML). However, its functions in AML cell chemoresistance, an important cause for mortality, are incompletely understood. The purpose of this study was to expound the role and potential mechanism of CCNA1 in AML cell chemoresistance. Upregulation of CCNA1 promoted resistance of AML cells to PKC412, AC220, and AraC. Mechanistically, it was confirmed that CCNA1 transcription was negatively regulated by forkhead box A2 (FOXA2), and the downregulation of FOXA2 promoted chemoresistance in AML cells. Moreover, the promoter sequence of CCNA1 has a significant H3K27me3 modification. Enhancer of zeste homolog 2 (EZH2) enhanced H3K27me3 modification of CCNA1 promoter to inhibit CCNA1 expression, thus promoting sensitivity of AML cells to drugs. Taken together, these findings lead to deeper insights into the mechanism of AML cell chemo-sensitivity by inhibiting CCNA1 at the transcriptional level.

Synthetic Approaches to the New Drugs Approved during 2019

New drugs introduced to the market are privileged structures having affinities for biological targets implicated in human diseases and conditions. These new chemical entities (NCEs), particularly small molecules and antibody-drug conjugates, provide insight into molecular recognition and simultaneously function as leads for the design of future medicines. This review is part of a continuing series presenting the most likely process-scale synthetic approaches to 40 NCEs approved for the first time anywhere in the world in 2019.

Novel Approaches to Target Mutant FLT3 Leukaemia

Simple Summary

Acute myeloid leukemia (AML) is a haematologic disease in which oncogenic mutations in the receptor tyrosine kinase FLT3 frequently lead to leukaemic development. Potent treatment of AML patients is still hampered by inefficient targeting of leukemic stem cells expressing constitutive active FLT3 mutants. This review summarizes the current knowledge about the regulation of FLT3 activity at cellular level and discusses therapeutical options to affect the tumor cells and the microenvironment to impair the haematological aberrations.

Abstract

Fms-like tyrosine kinase 3 (FLT3) is a member of the class III receptor tyrosine kinases (RTK) and is involved in cell survival, proliferation, and differentiation of haematopoietic progenitors of lymphoid and myeloid lineages. Oncogenic mutations in the FLT3 gene resulting in constitutively active FLT3 variants are frequently found in acute myeloid leukaemia (AML) patients and correlate with patient’s poor survival. Targeting FLT3 mutant leukaemic stem cells (LSC) is a key to efficient treatment of patients with relapsed/refractory AML. It is therefore essential to understand how LSC escape current therapies in order to develop novel therapeutic strategies. Here, we summarize the current knowledge on mechanisms of FLT3 activity regulation and its cellular consequences. Furthermore, we discuss how aberrant FLT3 signalling cooperates with other oncogenic lesions and the microenvironment to drive haematopoietic malignancies and how this can be harnessed for therapeutical purposes.

Advances in targeted therapy for acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal malignancy characterized by genetic heterogeneity due to recurrent gene mutations. Treatment with cytotoxic chemotherapy has been the standard of care for more than half of a century. Although much progress has been made toward improving treatment related mortality rate in the past few decades, long term overall survival has stagnated. Exciting developments of gene mutation-targeted therapeutic agents are now changing the landscape in AML treatment. New agents offer more clinical options for patients and also confer a more promising outcome. Since Midostaurin, a FLT3 inhibitor, was first approved by US FDA in 2017 as the first gene mutation-targeted therapeutic agent, an array of new gene mutation-targeted agents are now available for AML treatment. In this review, we will summarize the recent advances in gene mutation-targeted therapies for patients with AML.

Development of UHPLC-MS/MS Method for Indirubin-3'-Oxime Derivative as a Novel FLT3 Inhibitor and Pharmacokinetic Study in Rats

This study aimed to develop and validate a sensitive liquid chromatography-coupled tandem mass spectrometry method for the quantification of LDD-2614, an indirubin derivative and novel FLT3 inhibitor, in rat plasma. In addition, the developed analytical method was applied to observe the pharmacokinetic properties of LDD-2614. Chromatographic separation was achieved on a Luna omega C₁₈ column using a mixture of water and acetonitrile, both containing 0.1% formic acid. Quantitation was performed using positive electrospray ionization in a multiple reaction monitoring (MRM) mode. The MRM transitions were optimized as m/z 426.2→113.1 for LDD-2614 and m/z 390.2→113.1 for LDD-2633 (internal standard), and the lower limit of quantification (LLOQ) for LDD-2614 was determined as 0.1 ng/mL. Including the LLOQ, the nine-point calibration curve was linear with a correlation coefficient greater than 0.9991. Inter- and intraday accuracies (RE) ranged from -3.19% to 8.72%, and the precision was within 9.02%. All validation results (accuracy, precision, matrix effect, recovery, stability, and dilution integrity) met the acceptance criteria of the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety guidelines. The proposed method was validated and demonstrated to be suitable for the quantification of LDD-2614 for pharmacokinetics studies.

Secondary Resistant Mutations to Small Molecule Inhibitors in Cancer Cells

Secondary resistant mutations in cancer cells arise in response to certain small molecule inhibitors. These mutations inevitably cause recurrence and often progression to a more aggressive form. Resistant mutations may manifest in various forms. For example, some mutations decrease or abrogate the affinity of the drug for the protein. Others restore the function of the enzyme even in the presence of the inhibitor. In some cases, resistance is acquired through activation of a parallel pathway which bypasses the function of the drug targeted pathway. The Catalogue of Somatic Mutations in Cancer (COSMIC) produced a compendium of resistant mutations to small molecule inhibitors reported in the literature. Here, we build on these data and provide a comprehensive review of resistant mutations in cancers. We also discuss mechanistic parallels of resistance.

Is outcome of older people with acute myeloid leukemia improving with new therapeutic approaches and stem cell transplantation?

Introduction: The clinical outcome of older patients with acute myeloid leukemia (AML) is still poor, especially for those who are unfit to treatments aimed at altering the natural course of the disease. Hypomethylating agents (HMA) offer an important therapeutic opportunity to a consistent number of patients, but long-term results are largely unsatisfactory.Area covered: Recently, a number of new agents have been registered for AML, some of which selectively available for older patient population, with promising results in terms of response rate and survival. Furthermore, the upper age limit for allogeneic stem cell transplantation is constantly increasing, so that this procedure is offered and actually given to an increasing number of older patients with AML. A literature review was conducted of the PubMed database for articles published in English as well as for abstracts from most important and recent hematology meetings on AML in older patients.Expert opinion: Appropriate selection among different options on the basis of clinical fitness and molecular findings at diagnosis as well as at relapse would result in improvement of therapeutic results, sparing unnecessary toxicity and optimizing health systems resources.