Genomic landscape of patients with FLT3-mutated acute myeloid leukemia (AML) treated within the CALGB 10603/RATIFY trial

Current knowledge about FLT3 gene mutations, exploring the isoforms, and protein importance in AML

Acute myeloid leukaemia (AML) is a complex haematological malignancy characterised by diverse genetic alterations leading to abnormal proliferation of myeloid precursor cells. One of the most significant genetic alterations in AML involves mutations in the FLT3 gene, which plays a critical role in haematopoiesis and haematopoietic homeostasis. This review explores the current understanding of FLT3 gene mutations and isoforms and the importance of the FLT3 protein in AML. FLT3 mutations, including internal tandem duplications (FLT3-ITD) and point mutations in the tyrosine kinase domain (FLT3-TKD), occur in 25-30% in AML and are associated with poor prognosis. FLT3-ITD mutations lead to constitutive activation of the FLT3 signalling pathway, promoting cell survival and proliferation. FLT3-TKD mutations affect the tyrosine kinase domain and affect AML prognosis in various ways. Furthermore, FLT3 isoforms, including shorter variants, contribute to the complexity of FLT3 biology. Additionally, nonpathological polymorphisms in FLT3 are being explored for their potential impact on AML prognosis and treatment response. This review also discusses the development of molecular treatments targeting FLT3, including first-generation and next-generation tyrosine kinase inhibitors, highlighting the challenges of resistance that often arise during therapy. The final chapter describes FLT3 protein domain rearrangements and their relevance to AML pathogenesis.

Sorafenib plus triplet therapy with venetoclax, azacitidine and homoharringtonine for refractory/relapsed acute myeloid leukemia with FLT3-ITD: A multicenter phase 2 study

BACKGROUND

Patients with relapsed or refractory acute myeloid leukemia (R/R AML) and FLT3-internal tandem duplication (FLT3-ITD) respond infrequently to salvage chemotherapy.

OBJECTIVE

To investigate the efficacy of sorafenib plus triplet therapy with venetoclax, azacitidine, and homoharringtonine (VAH) as a salvage therapy in this population.

METHODS

This multicenter, single-arm, phase 2 study was conducted at 12 hospitals across China. Eligible patients had R/R AML with FLT3-ITD (aged 18-65 years) who were treated with VAH. The primary endpoint was composite complete remission (CRc) after two cycles. Secondary outcomes included the overall response rate (ORR), safety, and survival.

RESULTS

Between July 9, 2020, and March 19, 2022, 58 patients were assessed for eligibility, 51 of whom were enrolled. The median patient age was 47 years (interquartile range [IQR] 31-57). CRc was 76.5% with ORR of 82.4%. At a median follow-up of 17.7 months (IQR, 8.7-24.7), the median duration of CRc was not reached (NR), overall survival was 18.1 months (95% confidence interval [CI], 11.8-NR) and event-free survival was 11.4 months (95% CI, 5.6-NR). Grade 3 or 4 adverse events occurring in ≥10% of patients included neutropenia in 47 (92.2%), thrombocytopenia in 41 (80.4%), anemia in 35 (68.6%), febrile neutropenia in 29 (56.9%), pneumonia in 13 (25.5%), and sepsis in 6 (11.8%) patients. Treatment-related death occurred in two (3.9%) patients.

CONCLUSIONS

The sorafenib plus VAH regimen was well tolerated and highly active against R/R AML with FLT3-ITD. This regimen may be a suitable therapeutic option for this population, but larger population trials are needed to be explored.

TRIAL REGISTRATION

Clinical Trials Registry: NCT04424147.

FLT3 targeting in the modern era: from clonal selection to combination therapies

Fms-like tyrosine kinase 3 (FLT3) is the most frequently mutated gene in acute myeloid leukemia (AML). Modern targeting of FLT3 with inhibitors has improved clinical outcomes and FLT3 inhibitors have been incorporated into the treatment of AML in all phases of the disease, including the upfront, relapsed/refractory and maintenance settings. This review will discuss the current understanding of FLT3 biology, the clinical use of FLT3 inhibitors, resistance mechanisms and emerging combination treatment strategies.

Fms -like tyrosine kinase 3 positive acute myeloid leukemia

PURPOSE OF REVIEW

Fms -like tyrosine kinase 3 (FLT3) mutations are common in newly diagnosed patients with acute myeloid leukemia (AML). They are associated with a high risk of relapse. The identification of FLT3 mutations has important implications for the management of AML. FLT3 inhibitors have shown improved outcomes in FLT3-positive AML when used as a single agent in the salvage setting. However, the combination of inhibitors and chemotherapy in the first-line setting is the real game changer in FLT3mutant AML. The introduction of these drugs has improved the prognosis of FLT3-mutant AML, but the development of resistance is common. There are still many unanswered questions about FLT3-mutant AML.

RECENT FINDINGS

This article will analyze recent advances for FLT3-mutant AML, focusing on front-line therapy and post-transplant maintenance.

SUMMARY

Novel drug combinations and strategies against FLT3 mutated AML are currently under investigation and will be the focus of future studies. The development of more selective and potent FLT3 inhibitors may further improve outcomes for patients with FLT3-positive AML. Monitoring minimal residual disease and overcoming resistance are key issues for the future.

A primary pediatric acute myelomonocytic leukemia with t(3;21)(q26;q22): A case report

RATIONALE

The rare t(3;21)(q26;q22) translocation results in gene fusion and generates multiple fusion transcripts, which are typically associated with therapy-related myelodysplastic syndrome, acute myeloid leukemia, and chronic myelogenous leukemia. Here, we report a rare case of de novo acute myelomonocytic leukemia in a young child with t(3;21)(q26;q22).

PATIENT CONCERNS

A 2-and-a-half-year-old female patient presented with abdominal pain, cough, paleness, and fever for 3 weeks, without any history of malignant diseases.

DIAGNOSES

Chest computed tomography revealed pneumonia. Bone marrow smear confirmed acute myelomonocytic leukemia. Cytogenetic analysis and Sanger sequencing identified RUNX1-MECOM and RUNX1-RPL22 fusion genes as a result of t(3;21)(q26;q22).

INTERVENTIONS

The patient received 3 courses of chemotherapy, but bone marrow smear examination showed no remission. According to the wishes of the patient family, the allogeneic hematopoietic stem cell transplantation (Allo-HSCT) was chosen.

OUTCOMES

The patient did not experience any adverse reactions after Allo-HSCT. The red blood cells and platelets increased without transfusion. The pneumonia recovered after antibiotic treatment.

LESSONS

The patient recovered well after Allo-HSCT. Therefore, for patients with RUNX1-MECOM and RUNX1-RPL22 fusion genes, transplantation may be a good choice when chemotherapy is not effective.

Impact of genetic patterns on sorafenib efficacy in patients with FLT3-ITD acute myeloid leukemia undergoing allogeneic hematopoietic stem cell transplantation: a multi-center, cohort study

Sorafenib therapy improves overall survival (OS) in patients with FLT3 internal tandem duplication (ITD) acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation. We explored the efficacy of sorafenib therapy in this population with different concomitant genetic patterns. In this multi-center, cohort study, we enrolled patients with FLT3-ITD AML undergoing allogenic hematopoietic cell transplantation. Patients with sorafenib maintenance post-transplantation for at least four weeks were allocated to the sorafenib group, and otherwise to the control group. Endpoints were OS, disease-free survival, and relapse for the whole cohort and OS for genetic pattern subgroups. Among 613 patients enrolled, 275 were in the sorafenib and 338 the control group. Median follow-up was 36.5 (interquartile range (IQR), 25.2-44.7) months post-transplantation. The 3-year OS post-transplantation was 79.6% (95% confidential interval (CI) 74.8%-84.6%) and 65.2% (95% CI 60.3%-70.6%) (Hazard ratio (HR) 0.50, 95% CI 0.37-0.69; P < 0.0001) in both groups. Sorafenib maintenance post-transplantation improved OS in the favorable (HR 0.33, 95% CI 0.14-0.77; P = 0.011) and adverse (HR 0.56, 95% CI 0.33-0.93; P = 0.026) ELN 2017 risk subgroups. Patients with mutated NPM1, DNMT3A, co-occurring NPM1/DNMT3A, "activated signaling" and "DNA methylation" genes benefited in OS from sorafenib maintenance, while those carrying CEBPA, "tumor suppressors" and "myeloid transcription factors" genes did not. Patients with FLT3-ITDhigh and FLT3-ITDlow AML both benefited in OS from sorafenib maintenance. Our results identify the response of genetic patterns to sorafenib maintenance, providing new viewpoints for the optimal use of sorafenib in FLT3-ITD AML in the transplantation setting.

Guadecitabine vs treatment choice in newly diagnosed acute myeloid leukemia: a global phase 3 randomized study

This phase 3 study evaluated the efficacy and safety of the new hypomethylating agent guadecitabine (n = 408) vs a preselected treatment choice (TC; n = 407) of azacitidine, decitabine, or low-dose cytarabine in patients with acute myeloid leukemia unfit to receive intensive induction chemotherapy. Half of the patients (50%) had poor Eastern Cooperative Oncology Group Performance Status (2-3). The coprimary end points were complete remission (19% and 17% of patients for guadecitabine and TC, respectively [stratified P = .48]) and overall survival (median survival 7.1 and 8.5 months for guadecitabine and TC, respectively [hazard ratio, 0.97; 95% confidence interval, 0.83-1.14; stratified log-rank P = .73]). One- and 2-year survival estimates were 37% and 18% for guadecitabine and 36% and 14% for TC, respectively. A large proportion of patients (42%) received <4 cycles of treatment in both the arms. In a post hoc analysis of patients who received ≥4 treatment cycles, guadecitabine was associated with longer median survival vs TC (15.6 vs 13.0 months [hazard ratio, 0.78; 95% confidence interval, 0.64-0.96; log-rank P = .02]). There was no significant difference in the proportion of patients with grade ≥3 adverse events (AEs) between guadecitabine (92%) and TC (88%); however, grade ≥3 AEs of febrile neutropenia, neutropenia, and pneumonia were higher with guadecitabine. In conclusion, no significant difference was observed in the efficacy of guadecitabine and TC in the overall population. This trial was registered at www.clinicaltrials.gov as #NCT02348489.

Sorafenib maintenance after allogeneic haemopoietic stem-cell transplantation in patients with FLT3-ITD acute myeloid leukaemia: long-term follow-up of an open-label, multicentre, randomised, phase 3 trial

BACKGROUND

Our open-label, multicentre, randomised, phase 3 trial showed that sorafenib maintenance after haematopoietic stem-cell transplantation (HSCT) improved overall survival and reduced relapse for patients with FLT3 internal tandem duplication (FLT3-ITD) acute myeloid leukaemia undergoing allogeneic HSCT. Here, we present a post-hoc analysis on the 5-year follow-up data of this trial.

METHODS

This phase 3 trial, done in seven hospitals in China, included patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic HSCT, who were aged 18-60 years, had an Eastern Cooperative Oncology Group performance status of 0-2, had composite complete remission before and after transplantation, and had haematopoietic recovery within 60 days after transplantation. Patients were randomly assigned (1:1) to receive sorafenib maintenance (400 mg orally twice daily) or non-maintenance (control) at 30-60 days after transplantation. Randomisation was done with permuted blocks (block size four) via an interactive web-based system. Investigators and participants were not masked to group assignment. The primary endpoint was the 1-year cumulative incidence of relapse, which was reported previously. For this updated analysis, the 5-year endpoints were overall survival; cumulative incidence of relapse; non-relapse mortality; leukaemia-free survival; graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS); cumulative incidence of chronic GVHD; and late effects in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, NCT02474290, and is complete.

FINDINGS

Between June 20, 2015, and July 21, 2018, 202 patients were randomly assigned to sorafenib maintenance (n=100) or non-maintenance (n=102). Median follow-up was 60·4 months (IQR 16·7-73·3). Extended follow-up showed improved overall survival (72·0% [95% CI 62·1-79·7] vs 55·9% [45·7-64·9]; hazard ratio [HR] 0·55, 95% CI 0·34-0·88; p=0·011), leukaemia-free survival (70·0% [60·0-78·0] vs 49·0% [39·0-58·3]; 0·47, 0·30-0·73; p=0·0007), and GRFS (58·0% [47·7-67·0] vs 39·2% [29·8-48·5]; 0·56, 0·38-0·83; p=0·0030), lower cumulative incidence of relapse (15·0% [8·8-22·7] vs 36·3% [27·0-45·6]; 0·33, 0·18-0·60; p=0·0003), and no increase in non-relapse mortality (15·0% [8·8-22·7] vs 14·7% [8·6-22·3]; 0·79, 0·39-1·62; p=0·98) for patients in the sorafenib group compared with those in the control group. The 5-year cumulative incidence of chronic GVHD (54·0% [43·7-63·2] vs 51·0% [40·8-60·3]; 0·82, 0·56-1·19; p=0·73) did not differ significantly between the two groups and we did not find substantial differences in late effects between the two groups. There were no treatment-related deaths.

INTERPRETATION

With extended follow-up, sorafenib maintenance after transplantation is associated with improved long-term survival and reduced relapse rates compared with non-maintenance, further supporting this strategy as a standard of care for patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic HSCT.

FUNDING

None.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

FMS-Like Tyrosine Kinase 3 Inhibitors in the Treatment of Acute Myeloid Leukemia: An Update on the Emerging Evidence and Safety Profile

FMS-like tyrosine kinase 3 (FLT3) is one of the most frequently mutated genes in acute myeloid leukemia (AML). Approximately 30% of the adult cases harbor an internal tandem duplication (FLT3-ITD) and 5-10% a tyrosine kinase domain (TKD) amino acid substitution (FLT3-TKD). The treatment paradigm of AML patients harboring FLT3 mutations (30%) has been modified by the discovery of tyrosine kinase inhibitors. First- and second-generation inhibitors classify FLT3 inhibitors according to FLT3 specificity: first-generation FLT3 inhibitors include sorafenib and midostaurin and second-generation inhibitors are represented by quizartinib, gilteritinib and crenolanib, among others. Activity of these inhibitors depends on their mechanism of receptor binding (active vs inactive conformation) and efficacy against the FLT3-ITD and -TKD mutations (type 1 inhibitors are active both on FLT3-ITD and TKD, whereas type 2 inhibitors are active only on FLT3-ITD). The FLT3 inhibitors sorafenib, midostaurin, quizartinib and gilteritinib have been tested in monotherapy in several settings including refractory or relapsed AML (R/R AML), post-transplant maintenance as well as in combination with intensive chemotherapy (ICT) or non-intensity regimens. The results of published randomized studies support the use of sorafenib in a post-transplant setting (SORMAIN trial), midostaurin in combination with ICT based (RATIFY trial) and gilteritinib for R/R AML (ADMIRAL trial). Gilteritinib in combination with hypomethylating agent as well as quizartinib are not supported by solid randomized trial results for their use in FLT3-mutated AML patients.