Challenges and considerations for antifungal prophylaxis in children with acute myeloid leukemia.

INTRODUCTION: Children receiving treatment for acute myeloid leukemia (AML) are at high risk of invasive fungal disease (IFD). Evidence from pediatric studies support the efficacy of antifungal prophylaxis in reducing the burden of IFD in children receiving therapy for AML, yet existing antifungal agents have specific limitations and comparative data to inform the optimal prophylactic approach are lacking. AREAS COVERED: This review summarizes the epidemiology of invasive fungal disease (IFD) and current antifungal prophylaxis recommendations for children with acute myeloid leukemia (AML). Challenges with currently available antifungal agents and considerations related to the changing landscape of AML therapy are reviewed. A keyword search was conducted to identify pediatric studies regarding IFD and antifungal prophylaxis in children with AML up to December 2023. EXPERT OPINION: Children undergoing treatment for AML are recommended to receive antifungal prophylaxis to reduce risk of IFD, with tolerability, pharmacokinetics, feasibility of administration, and drug interactions all factors that require consideration in this context. With increased use of novel targeted agents for AML therapy, together with the development of new antifungal agents, data from well-designed clinical studies to optimize prophylactic approaches will be essential to limit the burden of IFD in this vulnerable cohort.

Efficacy and Safety of Gilteritinib versus Sorafenib as Post-Transplant Maintenance in Patients With FLT3-ITD Acute Myeloid Leukemia.

BACKGROUND: FLT3-ITD AML is associated with an increased risk of relapse, leading many patients to receive an allogeneic hematopoietic stem cell transplantation (alloHCT) after induction. Unfortunately, relapse rate after alloHCT remains high and strategies are needed to improve outcomes. MATERIALS AND METHODS: We performed a retrospective analysis of adult patients with FLT3-ITD AML who received alloHCT from 6/1/2016 to 12/31/2020 and received gilteritinib (GILT) or sorafenib (SORA)as post-transplant maintenance, outside of a clinical trial. RESULTS: A total of 55 patients were treated with either GILT (n = 27) or SORA (n = 29) for post-HCT maintenance. One patient was treated with SORA after first alloHCT and GILT after second alloHCT. Patient characteristics were comparable between groups. FLT3 inhibitors were utilized in pre-alloHCT therapy in all but 1 patient. The median duration of time that patients remained on GILT was 385 days (range, 10-804) and on SORA 315 days (range, 3-1777). 1-year PFS and relapse incidence were similar between GILT and SORA; PFS was 66% versus 76% (P = .4) and relapse incidence was 19% versus 24% (P = .6), respectively.Both groups had high incidence of Grade 3-4 hematological toxicity, including neutropenia (45% GILT and 34% SORA) and thrombocytopenia (30% GILT and 52% SORA). Only 44% and 14% patients who received GILT and SORA did not discontinue maintenance, respectively. CONCLUSION: Our results revealed comparable PFS and a similar toxicity profile when SORA and GILT are used as post- HCT maintenance therapy.

Concurrent versus sequential or no triazole anti-fungal therapy in patients undergoing 7 + 3 plus midostaurin induction for FLT-3 acute myelogenous leukemia.

INTRODUCTION: Midostaurin is a multikinase inhibitor approved for the treatment of adult patients with newly diagnosed FMS-like tyrosine kinase 3 mutated (FLT3m) acute myeloid leukemia (AML). Azole antifungal medications are commonly used in AML and are known to interact with anti-cancer drugs such as midostaurin through the CYP3A pathway. However, there are no midostaurin related dose modifications recommended with strong CYP3A inhibitors. METHODS: We retrospectively reviewed 40 patients between 2017-2022 and compared efficacy and safety outcomes in patients who received azole antifungals concurrently to those who did not receive an azole or received it sequentially to midostaurin for treatment of FLT3m AML. RESULTS: Median age of both groups was approximately 55 years and 70% of patients harbored FLT-3 internal tandem duplication mutations. Most patients in the concurrent arm were on either posaconazole (33%) or isavuconazole (50%) for antifungal prophylaxis and micafungin (72%) for the sequential/no azole arm. Overall CR/CRi rate with concurrent versus sequential/no azole were 72% and 77%, and non-hematologic grade 3 toxicities were 22% and 40% (p = 0.21), respectively. Rates of dose reductions (6% vs. 0%, p = 0.26) and held doses (17% vs. 14%, p = 0.79) were not different between concurrent and sequential/no azole. There were no differences in the rates of new fungal infection during induction between the two groups. CONCLUSION: Azoles given concurrently or sequentially with midostaurin were found to be equally safe and effective in the treatment of newly diagnosed FLT3 AML. Additional confirmatory studies are needed due to our limited sample size.

The impact of different FLT3-inhibitors on overall survival of de novo acute myeloid leukemia: A network meta-analysis.

FLT3 inhibitors combined with chemotherapy are the standard of care for newly diagnosed FLT3-mutated acute myeloid leukemia (AML). However, no head-to-head studies have established the superiority of one FLT3 inhibitor over another. We conducted a network meta-analysis (NMA) to evaluate overall survival (OS) among different FLT3 inhibitors. Three relevant randomized controlled trials (RCTs), involving 1.358 patients treated with midostaurin, quizartinib, and sorafenib, were included in our analysis. The hazard ratios (HRs) revealed no significant differences in OS between midostaurin and quizartinib (HR, 1.00; 95 % CI, 0.73-1.36), midostaurin and sorafenib (HR, 0.97; 95 % CI, 0.52-1.84), or quizartinib and sorafenib (HR, 0.97; 95 % CI, 0.51-1.85). This NMA, the first to explore this issue, found no OS differences among the different FLT3 inhibitors. In the absence of direct comparison trials, our findings provide practical insights for clinical decision-making.

Understanding mechanisms of resistance to FLT3 inhibitors in adult FLT3-mutated acute myeloid leukemia to guide treatment strategy.

The presence of FLT3 mutations, including the most common FLT3-ITD (internal tandem duplications) and FLT3-TKD (tyrosine kinase domain), is associated with an unfavorable prognosis in patients affected by acute myeloid leukemia (AML). In this setting, in recent years, new FLT3 inhibitors have demonstrated efficacy in improving survival and treatment response. Nevertheless, the development of primary and secondary mechanisms of resistance poses a significant obstacle to their efficacy. Understanding these mechanisms is crucial for developing novel therapeutic approaches to overcome resistance and improve the outcomes of patients. In this context, the use of novel FLT3 inhibitors and the combination of different targeted therapies have been studied. This review provides an update on the molecular alterations involved in the resistance to FLT3 inhibitors, and describes how the molecular monitoring may be used to guide treatment strategy in FLT3-mutated AML.

FLT3-Mutated Leukemic Stem Cells: Mechanisms of Resistance and New Therapeutic Targets.

Despite the availability of target drugs in the first and second line, only 30% of FLT3mut AMLs are cured. Among the multiple mechanisms of resistance, those of FLT3mut LSC are the most difficult to eradicate because of their metabolic and genomic characteristics. Reactivation of glycogen synthesis, inhibition of the RAS/MAPK pathway, and degradation of FLT3 may be potential aids to fight the resistance of LSC to FLT3i. LSC is also characterized by the expression of a CD34+/CD25+/CD123+/CD99+ immunophenotype. The receptor and ligand of FLT3, the natural killer group 2 member D ligand (NKGD2L), and CD123 are some of the targets of chimeric antigen receptor T cells (CAR-T), bispecific T-cell engager molecules (BiTEs), CAR-NK and nanoparticles recently designed and reported here. The combination of these new therapeutic options, hopefully in a minimal residual disease (MRD)-driven approach, could provide the future answer to the challenge of treating FLT3mut AML.

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.

Identification of a Selective FLT3 Inhibitor with Low Activity against VEGFR, FGFR, PDGFR, c-KIT, and RET Anti-Targets.

FLT3 is mainly expressed in immune and various cancer cells and is a drug target for acute myeloid leukemia (AML). Recently, FLT3 has also been identified as a potential target for treating chronic pain. Most FLT3 inhibitors (FLT3i) identified to date, including approved drugs such as gilteritinib, midostaurin, ponatinib, quizartinib, and FLT3i in clinical trials, such as quizartinib and crenolanib, also inhibit closely-related kinases that are important for immune (c-KIT), cardiovascular (KDR/VEGFR2, FGFR, PDGFR) or kidney (RET) functions. While the aforementioned FLT3i may increase survival rates in AML, they are neither ideal for AML maintenance therapy nor for non-oncology applications, such as for the treatment of chronic pain, due to their promiscuous inhibition of many kinase anti-targets. Here, we report the identification of new FLT3i compounds that have low activities against kinases that have traditionally been difficult to differentiate from FLT3 inhibition, such as KDR/VEGFR, FGFR, PGFR, c-KIT, and RET. These selective compounds could be valuable chemical probes for studying FLT3 biology in the context of chronic pain and/or may represent good starting points to develop well-tolerated FLT3 therapeutics for non-oncology indications or for maintenance therapy for AML.

Research progress of FLT3 inhibitors and drug resistance mechanisms in acute myeloid leukemia / 中国临床药理学与治疗学

The FMS-like tyrosine kinase 3 (FLT3) gene mutation is the most common genetic mutation in acute myeloid leukemia (AML) and is associated with poor prognosis. Various targeted inhibitors have been developed for FLT3 mutations and have shown promising clinical efficacy. However, the emergence of resistance poses new challenges for targeted therapy in AML. This article provides an overview of the pathological and prognostic role of FLT3 mutations in AML, the current research progress on commonly used FLT3 inhibitors (type I and type II), the mechanisms of FLT3 inhibitor resistance, and strategies for overcoming resistance.

CPX-351 in FLT3-mutated acute myeloid leukemia.

CPX-351, a dual-drug liposomal encapsulation of daunorubicin and cytarabine in a 1:5 molar ratio, is approved for the treatment of newly diagnosed therapy-related acute myeloid leukemia (AML) or AML with myelodysplasia-related changes. In a pivotal phase III trial, CPX-351 significantly improved overall survival compared with standard-of-care 7 + 3 chemotherapy (7 days cytarabine; 3 days daunorubicin) in adults aged 60-75 years with newly diagnosed high-risk or secondary AML (median = 9.56 months vs. 5.95 months; hazard ratio = 0.69; 95% confidence interval = 0.52-0.90; p = 0.003). Approximately 30% of patients with newly diagnosed AML have mutations in the FLT3 gene, which may be associated with poor outcomes. Here, we review the current in vitro, clinical, and real-world evidence on the use of CPX-351 in patients with AML and mutations in FLT3. Additionally, we review preliminary data from clinical trials and patient case reports that suggest the combination of CPX-351 with FLT3 inhibitors may represent another treatment option for patients with FLT3 mutation-positive AML.

FLT3-targeted therapy restores GATA1 pathway function in NPM1/FLT3-ITD mutated acute myeloid leukaemia.

One-third of newly diagnosed adult acute myeloid leukaemia (AML) carry FLT3 mutations, which frequently occur together with nucleophosmin (NPM1) mutations and are associated with worse prognosis. FLT3 inhibitors are widely used in clinics with limitations due to drug resistance. AML cells carrying FLT3 mutations in both mouse models and patients present low expression of GATA1, a gene involved in haematopoietic changes preceding AML. Here, we show that FLT3 inhibition induces cellular responses and restores the GATA1 pathway and functions in NPM1/FLT3-ITD mutated AML, thus providing a new mechanism of action for this drug.

A Review of FLT3 Kinase Inhibitors in AML.

Acute myeloid leukemia (AML) is a highly aggressive illness distinguished by the accumulation of abnormal hematopoietic precursors in both the bone marrow and peripheral blood. The prevalence of FLT3 gene mutations is high and escalates the probability of relapse and mortality. The survival rates for AML patients, particularly those over 65, are low. FLT3 mutation screening at diagnosis is mandatory, and FLT3 inhibitors are crucial in treating AML patients with mutations. There are two categories of FLT3 mutations: FLT3-ITD located in the juxtamembrane domain and FLT3-TKD in the tyrosine kinase domain. FLT3-ITD is the most common type, affecting nearly a quarter of patients, whereas FLT3-TKD only affects 6-8% of patients. FLT3 inhibitors are now crucial in treating AML patients with FLT3 mutations. When dealing with FLT3-mutated AML, the recommended course of treatment typically involves chemotherapy and midostaurin, followed by allogeneic hematopoietic cell transplantation (HCT) to maximize the likelihood of success. Maintenance therapy can lower the risk of relapse, and gilteritinib is a better option than salvage chemotherapy for relapsed or refractory cases. Clinical trials for new or combined therapies are the most effective approach. This review discusses treatment options for patients with FLT3-mutated AML, including induction chemotherapy and options for relapsed or refractory disease. Additional treatment options may become available as more studies are conducted based on the patient's condition and susceptibility.

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.

Indole-based FLT3 inhibitors and related scaffolds as potential therapeutic agents for acute myeloid leukemia.

Fms-like tyrosine kinase 3 (FLT3) mutation mechanisms are among the most common genetic abnormalities detected in about 30% of acute myeloid leukemia (AML) patients. These mutations are accompanied by poor clinical response, although all these progressions in identifying and interpreting biological AML bio-targets. Several small structured FLT3 inhibitors have been ameliorated to struggle against AML. Despite all these developments regarding these inhibitors, the Overall survival rate is about five years or more in less than one-third of diagnosed AML patients. Midostaurin was the first FDA-approved FLT3 inhibitor in 2017 in the United States and Europe for AML remedy. Next, Gilteritinib was an FDA-approved FLT3 inhibitor in 2018 and in the next year, Quizartinib was approved an as FLT3 inhibitor in Japan. Interestingly, indole-based motifs had risen as advantaged scaffolds with unusual multiple kinase inhibitory activity. This review summarises indole-based FLT3 inhibitors and related scaffolds, including FDA-approved drugs, clinical candidates, and other bioactive compounds. Furthermore, their chemotypes, mechanism of action, and interaction mode over both wild and mutated FLT3 target proteins had been judgmentally discussed. Therefore, this review could offer inspiring future perspectives into the finding of new FLT3-related AML therapies.

Bridging to transplant and post-transplant maintenance therapy with FLT3 inhibitors in patients with relapsed or refractory FLT3 mutated acute myeloid leukemia.

OBJECTIVES AND METHODS: This single-center retrospective study was performed to evaluate the safety and efficacy of FMS-like tyrosine kinase 3 (FLT3) inhibitors before and after allogeneic hematopoietic cell transplantation (HCT) in relapsed/refractory patients with FLT3-mutation positive acute myeloid leukemia (AML). RESULTS: Ten patients who met the eligibility criteria were included. Eight of them achieved hematological remission at HCT, within a median span of 79 days (range: 43-197). In post-HCT, patients started maintenance therapy (MT; median time-to-start 79 days, range: 43-197), and the median duration of MT was 390 days (range: 67-815). Grade 3 hematological adverse events (AEs) were found in two patients, and non-hematological AEs were found in five patients. Nine patients underwent either dose reduction, discontinuation of therapy, or a switch to another FLT3 inhibitor due to AEs. Disease relapse occurred in one patient during MT. At the time of the last follow-up, seven patients are alive and disease-free, while three have died due to infection or transplant complications. CONCLUSION: In relapsed/refractory FLT3 mutation-positive AML, the use of FLT3 inhibitors can lead to high response rates and provide a safe bridge from HCT to MT. If sufficient attention is paid to safety, this therapy is expected to prevent disease relapse even with reduced dosages.

Design, synthesis, and biological evaluation of a series of indolone derivatives as novel FLT3 inhibitors for the treatment of acute myeloid leukemia.

FLT3-ITD mutant has been extensively studied as a drug discovery target for acute myeloid leukemia. Based on our previous discovered FLT3 inhibitor (2), a series of urea group based indolone derivatives were designed, synthesized, and biological evaluated as novel FLT3 inhibitors for the treatment of FLT3-ITD positive AML. Among them, compound LC-3 exhibited potent inhibitory effects against FLT3 (IC50 = 8.4 nM) and significantly inhibited the proliferation of FLT3-ITD positive AML cells MV-4-11 (IC50 = 5.3 nM). In the cellular context, LC-3 strongly inhibited FLT3-mediated signaling pathways and induced cellular apoptosis by arresting cell cycle in G1 phase. In the in vivo studies, LC-3 significantly suppressed the tumor growth on MV-4-11 xenograft models (10 mg/kg/day, TGI = 92.16%) without exhibiting obvious toxicity. These results suggested that compound LC-3 might be a potential drug candidate for FLT3-ITD positive AML.

Targeting FLT3 Mutation in Acute Myeloid Leukemia: Current Strategies and Future Directions.

FLT3 mutations are present in 30% of newly diagnosed patients with acute myeloid leukemia. Two broad categories of FLT3 mutations are ITD and TKD, with the former having substantial clinical significance. Patients with FLT3-ITD mutation present with a higher disease burden and have inferior overall survival, due to high relapse rates after achieving remission. The development of targeted therapies with FLT3 inhibitors over the past decade has substantially improved clinical outcomes. Currently, two FLT3 inhibitors are approved for use in patients with acute myeloid leukemia: midostaurin in the frontline setting, in combination with intensive chemotherapy; and gilteritinib as monotherapy in the relapsed refractory setting. The addition of FLT3 inhibitors to hypomethylating agents and venetoclax offers superior responses in several completed and ongoing studies, with encouraging preliminary data. However, responses to FLT3 inhibitors are of limited duration due to the emergence of resistance. A protective environment within the bone marrow makes eradication of FLT3mut leukemic cells difficult, while prior exposure to FLT3 inhibitors leads to the development of alternative FLT3 mutations as well as activating mutations in downstream signaling, promoting resistance to currently available therapies. Multiple novel therapeutic strategies are under investigation, including BCL-2, menin, and MERTK inhibitors, as well as FLT3-directed BiTEs and CAR-T therapy.

Gene Mutations and Targeted Therapies of Myeloid Sarcoma.

OPINION STATEMENT: Myeloid sarcoma, a rare malignant tumor characterized by the invasion of extramedullary tissue by immature myeloid cells, commonly occurs concomitantly with acute myeloid leukemia, myelodysplastic syndromes, or myeloproliferative neoplasms. The rarity of myeloid sarcoma poses challenges for diagnosis and treatment. Currently, treatments for myeloid sarcoma remain controversial and primarily follow protocols for acute myeloid leukemia, such as chemotherapy utilizing multi-agent regimens, in addition to radiation therapy and/or surgery. The advancements in next-generation sequencing technology have led to significant progress in the field of molecular genetics, resulting in the identification of both diagnostic and therapeutic targets. The application of targeted therapeutics, such as FMS-like tyrosine kinase 3(FLT3) inhibitors, isocitrate dehydrogenases(IDH) inhibitors, and the B cell lymphoma 2(BCL2) inhibitors, has facilitated the gradual transformation of traditional chemotherapy into targeted precision therapy for acute myeloid leukemia. However, the field of targeted therapy for myeloid sarcoma is relatively under-investigated and not well-described. In this review, we comprehensively summarize the molecular genetic characteristics of myeloid sarcoma and the current application of targeted therapeutics.

Attenuation of renal injury by depleting cDC1 and by repurposing Flt3 inhibitor in anti-GBM disease.

Previous studies found cDC1s to be protective in early stage anti-GBM disease through Tregs, but pathogenic in late stage Adriamycin nephropathy through CD8+ T cells. Flt3 ligand is a growth factor essential for cDC1 development and Flt3 inhibitors are currently used for cancer treatment. We conducted this study to clarify the role and mechanisms of effects of cDC1s at different time points in anti-GBM disease. In addition, we aimed to utilize drug repurposing of Flt3 inhibitors to target cDC1s as a treatment of anti-GBM disease. We found that in human anti-GBM disease, the number of cDC1s increased significantly, proportionally more than cDC2s. The number of CD8+ T cells also increased significantly and their number correlated with cDC1 number. In XCR1-DTR mice, late (day 12-21) but not early (day 3-12) depletion of cDC1s attenuated kidney injury in mice with anti-GBM disease. cDC1s separated from kidneys of anti-GBM disease mice were found to have a pro-inflammatory phenotype (i.e. express high level of IL-6, IL-12 and IL-23) in late but not early stage. In the late depletion model, the number of CD8+ T cells was also reduced, but not Tregs. CD8+ T cells separated from kidneys of anti-GBM disease mice expressed high levels of cytotoxic molecules (granzyme B and perforin) and inflammatory cytokines (TNF-α and IFN-γ), and their expression reduced significantly after cDC1 depletion with diphtheria toxin. These findings were reproduced using a Flt3 inhibitor in wild type mice. Therefore, cDC1s are pathogenic in anti-GBM disease through activation of CD8+ T cells. Flt3 inhibition successfully attenuated kidney injury through depletion of cDC1s. Repurposing Flt3 inhibitors has potential as a novel therapeutic strategy for anti-GBM disease.