Recent progress in AML with recurrent genetic abnormalities.

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by various molecular abnormalities that significantly impact its pathogenesis and prognosis. Currently, the prognosis of AML patients is stratified on the basis of co-existing chromosomal and genetic abnormalities. AML patients with NPM1 or CEBPA mutations, which are frequently identified in cytogenetically normal AML, are classified in the favorable-risk group, although approximately 40% of patients relapse. Similarly, a clinical high-risk group has been identified among patients with acute promyelocytic leukemia, but the underlying molecular abnormalities remain unclear. FLT3 mutations frequently overlap in these favorable-risk AMLs, including core binding factor AML, and their prognostic impact is still controversial. As such, further risk stratification and treatment optimization based on various molecular abnormalities are warranted to improve the prognosis of favorable-risk AMLs. These molecular abnormalities are also considered therapeutic targets, and targeted therapies have been developed over the years. In recent years, several targeted agents have been approved and demonstrated to improve the prognosis of AML. However, resistance to targeted therapies is also a challenge. This Progress in Hematology features current trends and challenges in favorable-risk AML and FLT3 mutations that are frequently identified in these patients.

[Pathogenesis and treatment of acute myeloid leukemia with FLT3 mutations].

FLT3 mutations are the most frequently identified genetic abnormalities in adult acute myeloid leukemia (AML) patients, accounting for approximately 30%. FLT3-ITD mutation specifically is considered as a poor prognostic factor in AML, and allogeneic hematopoietic cell transplantation in first remission is recommended for younger patients. The recent clinical introduction of FLT3 inhibitors has been reported to improve the prognosis of patients with FLT3 mutation-positive AML. In Japan, alongside monotherapy with gilteritinib or quizartinib for relapsed/refractory patients, combination of quizartinib with intensive chemotherapy was approved in 2023 for untreated FLT3-ITD mutation-positive AML. Studies to date have demonstrated the utility of measurable/minimal residual disease evaluation targeting FLT3 mutations and the efficacy of maintenance therapy after allogeneic transplantation. However, emergence of additional genetic mutations associated with treatment resistance has been observed. Thus, FLT3 mutations are utilized not only as a prognostic factor in AML but also as a target for treatment and for response assessment. Furthermore, the development of new treatment strategies involving FLT3 inhibitors is highly anticipated to improve clinical outcomes for patients with FLT3 mutation-positive AML.

A simplified and robust risk stratification model for stem cell transplantation in pediatric acute myeloid leukemia.

The efficacy of stem cell transplantation (SCT) in pediatric acute myeloid leukemia (pAML) remains unsatisfactory due to the limitations of existing prognostic models in predicting efficacy and selecting suitable candidates. This study aims to develop a cytomolecular risk stratification-independent prognostic model for SCT in pAML patients at CR1 stage. The pAML SCT model, based on age, KMT2A rearrangement (KMT2A-r), and minimal residual disease at end of course 1 (MRD1), effectively classifies patients into low-, intermediate-, and high-risk groups. We validate the effectiveness in an internal validation cohort and in four external validation cohorts, consisting of different graft sources and donors. Moreover, by incorporating the FMS-like tyrosine kinase 3/internal tandem duplication (FLT3/ITD) allelic ratio, the pAML SCT model is refined, enhancing its ability to effectively select suitable candidates. We develop a simple and robust risk stratification model for pAML patients undergoing SCT, to aid in risk stratification and inform pretransplant decision-making at CR1 stage.

Safety considerations for drugs newly approved for treating acute myeloid leukemia.

INTRODUCTION: Acute myeloid leukemia (AML) is typically characterized by a poor prognosis, mainly due to the median age at diagnosis. Until recently, treatment options were limited to intensive chemotherapy (IC) for young patients or hypomethylating agents for those ineligible for IC. Since 2017, nine molecules were registered for newly-diagnosed AML: midostaurin, gilteritinib, quizartinib, enasidenib, ivosidenib, gemtuzumab ozogamicin, CPX-351, glasdegib, and venetoclax. AREAS COVERED: The review examines the safety profile of these drugs and their interactions with other agents used in supportive care. The PubMed and Google Scholar databases were searched for articles in English concerning new agents in AML from 2017 until 2023. Further relevant publications were obtained by reviewing the prescribing information and Food and Drug Administration (FDA) data. EXPERT OPINION: The therapeutic spectrum in AML has broadened over several years and can also improve outcomes in older patients. However, in addition to their well-known cytotoxic activity, new molecules cause several unique, off-target toxicities. Also, potential drug-drug interactions (DDI) should be taken into consideration when choosing optimal first-line therapy; this remains a challenge in clinical practice.

A disproportionality analysis for assessing the safety of FLT3 inhibitors using the FDA Adverse Event Reporting System (FAERS).

Objectives: This pharmacovigilance analysis was conducted to assess the safety signals of FMS-related tyrosine kinase 3 (FLT3) inhibitors in a real-world setting using the United States Food and Drug Administration Adverse Event Reporting System (FAERS). Design: We analyzed adverse event (AE) reports related to FLT3 inhibitors submitted to the FAERS database from the first quarter of 2015 to the fourth quarter of 2022. Disproportionality analysis was used to identify AEs of FLT3 inhibitors in the FAERS database. Results: A total of 55,393 AE reports were identified, of which 5938, 44,013, and 5442 were attributed to midostaurin, sorafenib, and gilteritinib, respectively, as primary suspects. Compared to the full database, significant safety signals at the system organ class level were observed for midostaurin (blood and lymphatic system disorders and hepatobiliary disorders), sorafenib (skin and subcutaneous tissue disorders and hepatobiliary disorders), and gilteritinib (investigations, blood and lymphatic system disorders, infections and infestations, and hepatobiliary disorders). All the drugs studied were associated with hepatobiliary disorders. The most prominent AEs associated with midostaurin, sorafenib, and gilteritinib were cytopenia, palmar-plantar erythrodysesthesia syndrome, and increased blast cell count, respectively. Compared with chemotherapy, midostaurin and gilteritinib showed a higher risk of electrocardiogram QT prolongation, gastrointestinal hemorrhage, cerebral hemorrhage, and increased white blood cell count. Gilteritinib had the highest overall death percentage (30.28%), whereas sorafenib had the lowest (23.06%). Conclusion: Mining AE signals using the FAERS database provides a method for analyzing the safety of FLT3 inhibitors in post-marketing. We found several significant AE signals that corresponded to previous studies; however, some AE signals were not mentioned in the drug instructions. Our study could provide a direction for follow-up real-world studies to verify the results further.

Introduction: The United States Food and Drug Administration Adverse Event Reporting System (FAERS) is an essential tool for the United States Food and Drug Administration (FDA) to detect adverse events (AE). This study explored the safety signals of FMS-related tyrosine kinase 3 (FLT3) inhibitors (midostaurin, sorafenib, and gilteritinib) using the FAERS database. Research design and methods: We used reporting odds ratios, proportional reporting ratios, and Bayesian confidence propagation neural network to analyze the safety signals of FLT3 inhibitors by comparing them with the full database and chemotherapy agents from 2015 to 2022. Results: A total of 5,938, 44,013, and 5,442 reports were attributed to midostaurin, sorafenib, and gilteritinib, respectively. Based on the analysis results, we observed the following:• Regarding the analysis of system organ class level compared with the full database, "hepatobiliary disorders" appeared as an important signal in all three drugs. In addition, "blood and lymphatic system disorders" of midostaurin, "skin and subcutaneous tissue disorders" of sorafenib, and "investigations," "blood and lymphatic system disorders," and "infections and infestations" of gilteritinib were significant.• Cytopenia was the most prominent AE associated with midostaurin in comparisons of midostaurin versus the full database, and electrocardiogram QT prolonged was the strongest signal in comparisons of midostaurin versus chemotherapy.• In both comparisons of FLT3 inhibitors versus the full database and chemotherapy, the strongest safety signals of sorafenib and gilteritinib were palmar-plantar erythrodysesthesia syndrome and increased blast cell count, respectively.• Gilteritinib exhibited the highest overall mortality rate, whereas sorafenib had the lowest. Conclusion: We identified several significant AE signals that corresponded to previous studies. However, some AE signals were not mentioned in the drug instructions. The AE signals should be evaluated further based on real-world data in the future.

A study on the adverse effects of FLT3 inhibitors.

Autophagy and inflammasome activation are associated with poor response to FLT3 inhibitors in patients with FLT3-ITD acute myeloid leukemia.

Beyond its clinical diversity and severity, acute myeloid leukemia (AML) is known for its complex molecular background and for rewiring biological processes to aid disease onset and maintenance. FLT3 mutations are among the most recurring molecular entities that cooperatively drive AML, and their inhibition is a critical molecularly oriented therapeutic strategy. Despite being a promising avenue, it still faces challenges such as intrinsic and acquired drug resistance, which led us to investigate whether and how autophagy and inflammasome interact and whether this interaction could be leveraged to enhance FLT3 inhibition as a therapeutic strategy. We observed a strong and positive correlation between the expression of key genes associated with autophagy and the inflammasome. Gene set enrichment analysis of the FLT3-ITD samples and their ex vivo response to five different FLT3 inhibitors revealed a common molecular signature compatible with autophagy and inflammasome activation across all poor responders. Inflammasome activation was also shown to strongly increase the likelihood of a poor ex vivo response to the FLT3 inhibitors quizartinib and sorafenib. These findings reveal a distinct molecular pattern within FLT3-ITD AML samples that underscores the necessity for further exploration into how approaching these supportive parallel yet altered pathways could improve therapeutic strategies.

Targeting rapid TKI-induced AXL upregulation overcomes adaptive ERK reactivation and exerts antileukemic effects in FLT3/ITD acute myeloid leukemia.

Acute myeloid leukemia (AML) patients with the FMS-related receptor tyrosine kinase 3 internal tandem duplication (FLT3/ITD) mutation have a poorer prognosis, and treatment with FLT3 tyrosine kinase inhibitors (TKIs) has been hindered by resistance mechanisms. One such mechanism is known as adaptive resistance, in which downstream signaling pathways are reactivated after initial inhibition. Past work has shown that FLT3/ITD cells undergo adaptive resistance through the reactivation of extracellular signal-regulated kinase (ERK) signaling within 24 h of sustained FLT3 inhibition. We investigated the mechanism(s) responsible for this ERK reactivation and hypothesized that targeting tyrosine-protein kinase receptor UFO (AXL), another receptor tyrosine kinase that has been implicated in cancer resistance, may overcome the adaptive ERK reactivation. Experiments revealed that AXL is upregulated and activated in FLT3/ITD cell lines mere hours after commencing TKI treatment. AXL inhibition combined with FLT3 inhibition to decrease the ERK signal rebound and to exert greater anti-leukemia effects than with either treatment alone. Finally, we observed that TKI-induced AXL upregulation occurs in patient samples, and combined inhibition of both AXL and FLT3 increased efficacy in our in vivo models. Taken together, these data suggest that AXL plays a role in adaptive resistance in FLT3/ITD AML and that combined AXL and FLT3 inhibition might improve FLT3/ITD AML patient outcomes.

Clinical features and long-term outcomes of pediatric patients with de novo acute myeloid leukemia in China with or without specific gene abnormalities: a cohort study of patients treated with BCH-AML 2005.

Acute myeloid leukemia (AML), which has distinct genetic abnormalities, has unique clinical and biological features. In this study, the incidence, clinical characteristics, induction treatment response, and outcomes of a large cohort of Chinese AML pediatric patients treated according to the BCH-AML 2005 protocol were analyzed. RUNX1-RUNX1T1 was the most common fusion transcript, followed by the CBFß-MHY11 and KMT2A rearrangements. FLT3-ITD and KIT mutations are associated with unfavorable clinical features and induction responses, along with KMT2A rearrangements, DEK-NUP214, and CBF-AML. The 5-year event-free survival (EFS) and overall survival (OS) rates of our cohort were 53.9 ± 3.7% and 58.5 ± 3.6%, with the best survival found among patients with CBFß-MYH11 and the worst survival among those with DEK-NUP214. In addition, we found that patients with FLT3-ITD mutation had adverse outcomes and that KIT mutation had a negative impact on OS in RUNX1-RUNX1T1+ patients. Furthermore, the risk classification and response to treatment after each induction block also influenced the prognosis, and HSCT after first remission could improve OS in high-risk patients. Not achieving complete remission after induction 2 was found to be an independent prognostic factor for OS and EFS. These findings indicate that genetic abnormalities could be considered stratification factors, predict patient outcomes, and imply the application of targeted therapy.

Distinct FLT3 Pathways Gene Expression Profiles in Pediatric De Novo Acute Lymphoblastic and Myeloid Leukemia with FLT3 Mutations: Implications for Targeted Therapy.

Activating FLT3 mutations plays a crucial role in leukemogenesis, but identifying the optimal candidates for FLT3 inhibitor therapy remains controversial. This study aims to explore the impacts of FLT3 mutations in pediatric acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) and to compare the mutation profiles between the two types to inspire the targeted application of FLT3 inhibitors. We retrospectively analyzed 243 ALL and 62 AML cases, grouping them into FLT3-mutant and wild-type categories, respectively. We then assessed the associations between FLT3 mutations and the clinical manifestations, genetic characteristics, and prognosis in ALL and AML. Additionally, we compared the distinct features of FLT3 mutations between ALL and AML. In ALL patients, those with FLT3 mutations predominantly exhibited hyperdiploidy (48.6% vs. 14.9%, p < 0.001) and higher FLT3 expression (108.02 [85.11, 142.06] FPKM vs. 23.11 [9.16, 59.14] FPKM, p < 0.001), but lower expression of signaling pathway-related genes such as HRAS, PIK3R3, BAD, MAP2K2, MAPK3, and STAT5A compared to FLT3 wild-type patients. There was no significant difference in prognosis between the two groups. In contrast, AML patients with FLT3 mutations were primarily associated with leucocytosis (82.90 [47.05, 189.76] G/L vs. 20.36 [8.90, 55.39] G/L, p = 0.001), NUP98 rearrangements (30% vs. 4.8%, p = 0.018), elevated FLT3 expression (74.77 [54.31, 109.46] FPKM vs. 34.56 [20.98, 48.28] FPKM, p < 0.001), and upregulated signaling pathway genes including PIK3CB, AKT1, MTOR, BRAF, and MAPK1 relative to FLT3 wild-type, correlating with poor prognosis. Notably, internal tandem duplications were the predominant type of FLT3 mutation in AML (66.7%) with higher inserted base counts, whereas they were almost absent in ALL (6.3%, p < 0.001). In summary, our study demonstrated that the forms and impacts of FLT3 mutations in ALL differed significantly from those in AML. The gene expression profiles of FLT3-related pathways may provide a rationale for using FLT3 inhibitors in AML rather than ALL when FLT3 mutations are present.

Quizartinib: a new hope in acute myeloid leukemia, an applied comprehensive review.

Acute myeloid leukemia (AML) is caused by a defective precursor leading to malignant clonal expansion, often with FMS-like tyrosine kinase-3 receptor (FLT3) mutations, particularly internal tandem duplication (ITD), which has a poor prognosis. Quizartinib, a second-generation FLT3 inhibitor, has FDA approval for relapsed/refractory AML with FLT3/ITD mutation. It has shown promise in clinical studies since 2013 due to its excellent oral absorption and potent activity on FLT3. This review explores Quizartinib's mechanism of action, efficacy in monotherapy or combination with chemotherapy, drug interactions, adverse events, resistance mechanisms and future research directions.

Discover Quizartinib's journey in AML treatment: from its targeted FLT3 inhibition mechanism to overcoming resistance. Clinical trials show promise, but the battle against side effects continues. #Quizartinib #AML #FLT3resistance #ClinicalTrials.

Only FLT3-ITD co-mutation did not have a deleterious effect on acute myeloid leukemia patients with NPM1 mutation, but concomitant with DNMT3A co-mutation or a < 3log reduction of MRD2 predicted poor survival.

Co-occurring mutations are frequently observed in acute myeloid leukemia (AML) with NPM1 mutation, and NPM1 measurable residual disease (MRD) is an effective prognostic biomarker. This retrospective study investigated the impact of gene co-mutations and NPM1 MRD on outcomes in these patients. Among 234 patients, 11.5% carried the rare type NPM1 mutation (NPM1RT). The median age was 49 years (IQR 36-58), with a median follow-up of 30.4 months (IQR 12.1-55.7). Nine genes were mutated in > 10%, with DNMT3A (53.8%) and FLT3-ITD (44.4%) being most prevalent. Univariable analysis in 137 patients showed FLT3-ITD, DNMT3A co-mutations, and MRD2 < 3 log reduction predicted poorer survival. FLT3-ITD and DNMT3A co-mutations correlated with the lowest event-free (EFS) and overall survival (OS) (3-year EFS 30.0%; 3-year OS 34.4%; both p < 0.001). FLT3-ITD alone did not worsen survival compared to patients without FLT3-ITD. Multivariable analysis identified DNMT3A co-mutation [EFS, HR = 1.9, p = 0.021; OS, HR = 2.2, p = 0.023] and MRD2 ≥ 3 log reduction (EFS, HR = 0.2; OS, HR = 0.1, both p < 0.001) as independent survival predictors. Patients with FLT3-ITD and DNMT3A co-mutations or a MRD2 < 3 log reduction were identified as high risk, but allogeneic hematopoietic stem cell transplantation (allo-HSCT) improved survival significantly compared to chemotherapy only (3-year EFS, 57.9% vs. 30.0%, p = 0.012; 3-year OS, 72.9% vs. 34.4%, p = 0.001). In AML patients with NPM1 mutation, the detrimental impact of FLT3-ITD mutation was exacerbated by DNMT3A co-mutation. Poor-risk younger patients identified by FLT3-ITD and DNMT3A co-mutations or MRD2 < 3 log reduction benefit from allo-HSCT.

Tracking Response and Resistance in Acute Myeloid Leukemia through Single-Cell DNA Sequencing Helps Uncover New Therapeutic Targets.

Acute myeloid leukemia (AML) is an aggressive hematologic neoplasia with a complex polyclonal architecture. Among driver lesions, those involving the FLT3 gene represent the most frequent mutations identified at diagnosis. The development of tyrosine kinase inhibitors (TKIs) has improved the clinical outcomes of FLT3-mutated patients (Pt). However, overcoming resistance to these drugs remains a challenge. To unravel the molecular mechanisms underlying therapy resistance and clonal selection, we conducted a longitudinal analysis using a single-cell DNA sequencing approach (MissionBioTapestri® platform, San Francisco, CA, USA) in two patients with FLT3-mutated AML. To this end, samples were collected at the time of diagnosis, during TKI therapy, and at relapse or complete remission. For Pt #1, disease resistance was associated with clonal expansion of minor clones, and 2nd line TKI therapy with gilteritinib provided a proliferative advantage to the clones carrying NRAS and KIT mutations, thereby responsible for relapse. In Pt #2, clonal architecture was less complex, and 1st line TKI therapy with midostaurin was able to eradicate the leukemic clones. Our results corroborate previous findings about clonal selection driven by TKIs, highlighting the importance of a deeper characterization of individual clonal architectures for choosing the best treatment plan for personalized approaches aimed at optimizing outcomes.

α- Triazolylboronic acids: a novel scaffold to target FLT3 in AML.

The treatment of acute myeloid leukemia (AML) presents a challenge to current therapies because of the development of drug resistance. Genetic mutation of FMS-like tyrosine kinase-3 (FLT3) is a target of interest for AML treatment, but the use of FLT3-targeting agents on AML patients has so far resulted in poor overall clinical outcomes.1 The incorporation of the boronic group in a drug scaffold could enhance the bioavailability and pharmacokinetic profile of conventional anticancer chemotypes. Boronic acids represent an intriguing and unexplored class of compounds in the context of AML, and they are only scantly reported as inhibitors of protein kinases. We identified a-triazolylboronic acids as a novel chemotype for targeting FLT3 by screening a library of structurally heterogeneous in-house boronic acids. Selected compounds show low micromolar activities on enzymatic and cellular assays, selectivity against control cell lines and a recurring binding mode in in-silico studies. Furthermore, control analogues synthesized ad hoc and lacking the boronic acid are inactive, confirming that this group is essential for the activity of the series. All together, these results suggest α-triazolylboronic acids could be a promising novel chemotype for FLT3 inhibition, laying the ground for the design of further compounds.

Simultaneous inhibition of FLT3 and HDAC by novel 6-ethylpyrazine-2-Carboxamide derivatives provides therapeutic advantages in acute myelocytic leukemia.

Synergetic inhibition of FMS-like tyrosine kinase 3 (FLT3) and histone deacetylase (HDAC) by small molecule chimera presents a promising therapeutic approach for acute myeloid leukemia (AML) with FLT3 mutations. In this study, we first observed that the combined use of FLT3 inhibitor gilteritinib and HDAC inhibitor vorinostat increased the survival rate of leukemia xenograft mouse model. Then, we employed a pharmacophore fusion strategy to develop a novel series of FLT3/HDAC dual inhibitors. Among them, compound 25h demonstrated superior inhibitory activity against both FLT3 and HDAC. In particular, compound 25h exhibited enhanced anti-proliferation activity against MOLM-13 cells in comparison to gilteritinib, vorinostat, and their combination, while maintaining reduced cytotoxicity towards normal cells. Mechanistically, the heightened anti-tumor effect of compound 25h was attributed to its more potent regulation of intracellular pathways, notably phosphorylation of ERK, compared to single drug and combination treatments. Furthermore, compound 25h demonstrated superior anti-tumor efficacy in the MOLM-13 xenograft model compared to combination therapy, along with reduced in vivo toxicity. To conclude, we have identified a novel FLT3/HDAC dual inhibitor that could serve as a potential candidate for the treatment of AML.

Cytotoxicity of Doxorubicin-Curcumin Nanoparticles Conjugated with Two Different Peptides (CKR and EVQ) against FLT3 Protein in Leukemic Stem Cells.

A targeted micellar formation of doxorubicin (Dox) and curcumin (Cur) was evaluated to enhance the efficacy and reduce the toxicity of these drugs in KG1a leukemic stem cells (LSCs) compared to EoL-1 leukemic cells. Dox-Cur-micelle (DCM) was developed to improve the cell uptake of both compounds in LSCs. Cur-micelle (CM) was produced to compare with DCM. DCM and CM were conjugated with two FLT3 (FMS-like tyrosine kinase)-specific peptides (CKR; C and EVQ; E) to increase drug delivery to KG1a via the FLT3 receptor (AML marker). They were formulated using a film-hydration technique together with a pH-induced self-assembly method. The optimal drug-to-polymer weight ratios for the DCM and CM formulations were 1:40. The weight ratio of Dox and Cur in DCM was 1:9. DCM and CM exhibited a particle size of 20-25 nm with neutral charge and a high %EE. Each micelle exhibited colloidal stability and prolonged drug release. Poloxamer 407 (P407) was modified with terminal azides and conjugated to FLT3-targeting peptides with terminal alkynes. DCM and CM coupled with peptides C, E, and C + E exhibited a higher particle size. Moreover, DCM-C + E and CM-C + E showed the highest toxicity in KG-1a and EoL-1 cells. Using two peptides likely improves the probability of micelles binding to the FLT3 receptor and induces cytotoxicity in leukemic stem cells.

Long-term remissions with Gilteritinib in early relapse after allogeneic stem cell transplantation of FLT3/NPM1 mutated acute myeloid leukemia.

Early post-allogeneic hematopoietic stem cell transplantation (allo-HSCT) relapse in patients with acute myeloid leukemia (AML) has an almost invariably dismal prognosis. Recent studies have demonstrated that FLT3 inhibition enhances the graft-versus-leukemia effect in vitro and in vivo. Thus, FLT-3 inhibitors may be viable treatment options in this setting. Here, we report three patients with FLT3 and NPM1 mutated AML who relapsed early after allo-HSCT and were treated with gilteritinib (associated with donor lymphocyte Infusion in two patients) to achieve long-term remission without a second transplantation.

[Concentration of gilteritinib in the cerebrospinal fluid of a patient with relapsed FLT3-ITD positive acute myeloid leukemia with optic nerve involvement].

A 72-year-old woman with relapsed FLT3-ITD-positive acute myeloid leukemia was treated with gilteritinib and achieved complete remission with incomplete hematological recovery. However, two months later, she developed optic nerve infiltration and lost vision in her right eye while maintaining hematological remission on gilteritinib. Intrathecal injection of cytotoxic drugs reduced the number of blasts in the cerebrospinal fluid (CSF), but her vision did not recover. At the onset of optic nerve infiltration, at a dose of 80 mg/day gilteritinib, the plasma trough and CSF levels of gilteritinib were 151.9 ng/ml and 1.9 ng/ml, respectively, with a central nervous system (CNS) penetration rate of 1.3%. Hematologic progressive disease (PD) was detected after 40 days, and the patient died one month later. Target sequencing at the time of hematologic PD revealed the FLT3 F691L mutation, which is known to confer resistance to gilteritinib. In this patient, pharmacokinetic (low CNS penetration of gilteritinib) and pharmacodynamic (acquisition of a drug resistance mutation) mechanisms were thought to be responsible for the CNS relapse and hematologic PD, respectively. We believe this is a valuable case to report considering the scarcity of data on CNS penetration of FLT3 inhibitors and their effects on CNS disease in the literature.

Flt3 ligand augments immune responses to soluble PD1-based DNA vaccine via expansion of type 1 conventional DCs.

DNA vaccines are prospective for their efficient manufacturing process, but their immunogenicity is limited as they cannot efficiently induce CD8+ T cell responses. A promising approach is to induce cross-presentation by targeting antigens to DCs. Flt3L can expand the number of type 1 conventional DCs and thereby improve cross-presentation. In this study, we first constructed a DNA vaccine expressing soluble PD1 and found that the therapeutic effect of targeting DCs with only the sPD1 vaccine was limited. When combined the vaccine with Flt3L, the anti-tumor effect was significantly enhanced. Considering the complexity of tumors and that a single method may not be able to activate a large number of effective CD8+ T cells, we combined different drugs and the vaccine with Flt3L based on the characteristics of different tumors. In 4T1 model, we reduced Tregs through cyclophosphamide. In Panc02 model, we increased activated DCs by using aCD40. Both strategies triggered strong CD8+ T cell responses and significantly improved the therapeutic effect. Our study provides important support for the clinical exploration of DC-targeted DNA vaccines in combination with Flt3L.

Real-Life Management of FLT3-Mutated AML: Single-Centre Experience over 24 Years.

We analyzed 140 patients with a median age of 51 years; 21% had WBC ≥ 100 × 109/L, and 52% had an NPM1 co-mutation. Until 2018, 101 patients received chemotherapy; thereafter, 39 received 3+7+midostaurin. The overall CR rate was 64%, higher in NPM1 mutant patients (73%). Univariate analysis showed that NPM1 mutation (p = 0.032) and WBC < 100 × 109/L (p = 0.013) positively influenced the response, with a trend for FLT3i administration (p = 0.052). Multivariate analysis confirmed WBC count as an independent prognostic factor (p = 0.017). In CR1, 41/90 patients underwent allogeneic and 18 autologous transplantation. The median EFS was 1.1 vs. 1.6 years in autografted and allografted patients, respectively (p = 0.9). The one-year non-relapse mortality was 0.00% for autologous and 28% for allogeneic transplants (p = 0.007); CIR at 1 and 3 years was higher in autologous transplants (39% vs. 15% and 57% vs. 21%, p = 0.004). The median survival was not reached in the FLT3i group. Overall, 69 patients received stem cell transplantation (18 autologous, 51 allogeneic). Post-transplant FLT3i was resumed in eight patients, all alive after a median of 65 months. Allogeneic transplantation is crucial in FLT3-mutated AML, but the next challenge will be to identify which patients can benefit from transplants in CR1 and in which to intensify post-transplant therapy.