Quizartinib versus salvage chemotherapy in relapsed or refractory FLT3-ITD acute myeloid leukaemia (QuANTUM-R): a multicentre, randomised, controlled, open-label, phase 3 trial

Discovery of cmpd D6 (FH-001) as a efficiency enhancement and myelosuppression degradation small-molecule fms-like tyrosine kinase 3 inhibitor for the treatment of FLT3-ITD positive acute myeloid leukemia

AML is the most common and lethal type of leukemia. The mutant of FLT3 kinase is the most common mutation in AML. Based on the structure analysis and deuteration modification of the cmpd 18 (CHMFL-FLT3-122), a potent and orally available FLT3 Kinase inhibitor, cmpd D6 (FH-001) was found, which demonstrated a remarkable inhibitory effect on the proliferation of FLT3 - ITD positive AML cancer cell lines. Specifically, it effectively suppressed the growth of the MV4-11 cell line (IC50 = 42.8 nM versus 17.1 nM). Similarly, notable inhibitory activity was observed in the MOLM-13 (IC50 = 20.8 nM versus 53.9 nM). More importantly, the IC50 of cmpd D6 to inhibit FLT3 kinase was 338.689 nM and the IC50 to inhibit c-KIT kinase was 3006.042 nM, which were much lower than the IC50 of cmpd 18 to the two kinases, indicating that cmpd D6 may effectively avoid the synthetic lethal myelosuppression toxicity caused by FLT3/c-KIT double inhibition. Pharmacokinetic experiments showed that the deuterated cmpd D6 could prolong the half-life (T1/2 = 4.333 h versus 3.646 h) and improve bioavailability (F = 42.51 % versus 35.93 %). Pharmacodynamic experiments of the three models showed that cmpd D6 (12.5 mg/kg) could significantly inhibit tumor growth compared with cmpd 18, and had no obvious toxicity. Based on the above results, cmpd D6 is a potential candidate drug for the future treatment of FLT3-ITD positive AML.

Comparison of clinical outcomes between preemptive and maintenance therapy after allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia

This study aimed to compare the efficacy and safety of preemptive and maintenance therapies as post-transplant therapy for acute myeloid leukemia (AML). Patients with AML who underwent allogeneic stem cell transplantation and received post-transplant therapy were eligible. Preemptive therapy was initiated if elevated Wilms' tumor-1 mRNA was detected in the peripheral blood. Twenty-nine patients received either preemptive (n = 12) or maintenance therapy (n = 17). The median age was 56 years (range, 18-70). The median time from transplantation to intervention was 77 days (range, 43-203) for maintenance and 346 days (range, 104-1027) for preemptive therapy. Maintenance therapy consisted of azacitidine (AZA) monotherapy in six patients, venetoclax (VEN) + AZA in five, and VEN + cytarabine (AraC) in six. Preemptive therapy consisted of AZA monotherapy in two patients, VEN + AZA in nine, and VEN + AraC in one. One-year overall survival from intervention was 92% for maintenance and 73% for preemptive therapy (P = 0.28), and 1-year event-free survival was 83% and 66%, respectively (P = 0.29). No serious adverse events or treatment-related mortality were observed in either group. Both therapies were safe and effective in preventing disease relapse. A prospective study comparing these two groups is warranted.

A Phase 2 Trial of CPX-351 Combined With Venetoclax in Relapsed or Refractory Acute Myeloid Leukemia

Outcomes in patients with relapsed/refractory (RR) AML are poor. We sought to investigate if CPX-531 in combination with venetoclax (CPX + VEN) was tolerable and effective in RR AML. This was a single institution phase 1b/2 trial of CPX + VEN. Patients aged ≥ 18 years with RR AML who were fit for intensive chemotherapy were eligible. Prior venetoclax exposure was allowed. The phase 1b portion followed a 3 + 3 design to identify the recommended phase 2 dose (RP2D) for the expansion cohort. At the starting dose level of -1, prolonged myelosuppression was observed, leading to dose level -2 (CPX-351 dosed at daunorubicin 44 mg/m2 on days 1,3, and 5 and venetoclax 300 mg days 2-8) being chosen as the RP2D. Thirty three patients with a median age of 58 years (range, 26-72) were treated. Patients were heavily pretreated, with 58% with prior venetoclax exposure, 44% in the second salvage or later, and 30% with prior stem cell transplant (SCT). Adverse cytogenetics were present in 51% of patients, with myelodysplasia-related mutations in 64%, and TP53mut in 21%. The overall response rate (ORR) was 46% (95% CI, 30-62), with a composite CR rate (CRc) of 39% (95% CI, 25-56). Patients in first salvage with wildtype TP53 had a CRc rate of 70% (95% CI, 40-89), with undetectable MRD in 71% (95% CI, 36-92) and a 2-year OS of 49% (95% CI, 23-100). Eleven (73%) responding patients underwent SCT. The 30-day mortality was 9%, with a 60-day mortality of 21%. The most common adverse events were related to myelosuppression. CPX + VEN has activity in RR AML, particularly when used in first salvage and in patients who do not harbor TP53 mutations. ClinicalTrials.gov Identifier: NCT03629171.

How I treat AML relapse after allogeneic HSCT

ABSTRACT

Allogeneic hematopoietic stem cell transplantation (HSCT) is one of the principal curative approaches in the treatment of acute myeloid leukemia (AML); however, relapse after transplantation remains a catastrophic event with poor prognosis. The incidence of relapse has remained unchanged over the last 3 decades despite an evolving understanding of the immunobiology of the graft-versus-leukemia effect and the immune escape mechanisms that lead to post-HSCT relapse. The approach to posttransplant relapse is highly individualized and is dictated both by disease biology and genomics as well as the patient's clinical status at the time of relapse and the interval between relapse and transplantation. With the help of 3 illustrative cases, we discuss our approach to early, late, and incipient relapse. Current therapeutic strategies incorporate immunosuppression taper when feasible, a variety of targeted and nontargeted chemotherapeutic agents, and consolidative cellular therapies including donor lymphocyte infusions or a second allogeneic transplant. We then summarize evolving frontiers in the treatment and prognostication of relapse, including the critical role of measurable residual disease. Finally, we emphasize enrollment on clinical trials and thoughtful discussions regarding goals of care and supporting frail patients as universal principles that should be incorporated in approaches to treatment of AML relapse after transplantation.

Next-generation sequencing for guiding matched targeted therapies in people with relapsed or metastatic cancer

BACKGROUND

Matched targeted therapies (MTT) given alone or in combination with systemic anti-cancer therapies have delivered proven survival benefit for many people with newly diagnosed cancer. However, there is little evidence of their effectiveness in the recurrent or late-stage setting. With this uncertainty, alongside the perception that late-stage cancers are too genetically heterogenous or too mutationally diverse to benefit from matched targeted therapies, next-generation sequencing (NGS) of tumours in people with refractory cancer remains a low priority. As a result, next-generation sequencing testing of recurrent or late-stage disease is discouraged. We lack evidence to support the utility of next generation sequencing in guiding matched targeted therapies in this setting.

OBJECTIVES

To evaluate the benefits and harms of matched targeted therapies in people with advanced cancers in randomised controlled trials.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ClinicalTrials.gov, and the World Health Organisation International Clinical Trials Registry Platform (WHO-ICTRP) search portal up to 30th October 2024. We also screened reference lists of included studies and also the publications that cited these studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that had enroled participants with advanced/refractory solid or haematological cancers who had progressed through at least one line of standard anti-cancer systemic therapy. To be eligible, all participants should have received matched targeted therapy based on next-generation sequencing carried out on their tumour (tumour tissue, blood or bone marrow).

DATA COLLECTION AND ANALYSIS

We systematically searched medical databases (e.g. MEDLINE, Embase) and trial registers for randomised controlled trials (RCTs). Outcomes of interest were progression-free survival (PFS), overall survival (OS), overall response rates (ORR), serious (grade 3 or 4) adverse events (AEs) and quality of life (QOL). We used a random-effects model to pool outcomes across studies and compared predefined subgroups using interaction tests. Grading of Recommendations Assessment, Development and Evaluation (GRADE) assessment of certainty was used to evaluate the quality of evidence.

MAIN RESULTS

We identified a total of 37 studies, out of which 35 studies (including 9819 participants) were included in the meta-analysis. All included studies compared a matched targeted therapy intervention to standard-of-care treatment, non-matched targeted therapies or no treatment (best supportive care): Matched targeted therapy versus standard-of-care treatment Matched targeted therapy (MTT) compared with standard systematic therapy probably reduces the risk of disease progression by 34% (hazard ratio (HR) = 0.66, 95% confidence interval (CI) 0.59 to 0.74; 14 studies, 3848 participants; moderate-certainty evidence). However, MTT might have little to no difference in risk of death (HR = 0.85, 95% CI 0.75 to 0.97; 14 studies, 3848 participants; low-certainty evidence) and may increase overall response rates (low-certainty evidence). There was no clear evidence of a difference in severe (grade 3/4) adverse events between matched targeted therapy and standard-of-care treatment (low-certainty evidence). There was limited evidence of a difference in quality of life between groups (very low-certainty of evidence). Matched targeted therapy in combination with standard-of-care treatment versus standard-of-care treatment alone Matched targeted therapy in combination with standard-of-care treatment compared with standard-of-care treatment alone probably reduces the risk of disease progression by 39% (HR = 0.61, 95% CI 0.53-0.70, 14 studies, 2,637 participants; moderate-certainty evidence) and risk of death by 21% (HR = 0.79, 95% CI 0.70 to 0.89; 11 studies, 2575 participants, moderate-certainty evidence). The combination of MTT and standard-of-care treatment may also increase overall response rates (low-certainty evidence). There was limited evidence of a difference in the incidence of severe adverse events (very low-certainty evidence) and quality of life between the groups (very low-certainty of evidence). Matched targeted therapy versus non-matched targeted therapy Matched targeted therapy compared with non-matched targeted therapy probably reduces the risk of disease progression by 24% (HR = 0.76, 95% CI 0.64 to 0.89; 3 studies, 1568 participants; moderate-certainty evidence) and may reduce the risk of death by 25% (HR = 0.75, 95% CI 0.65 to 0.86, 1307 participants; low-certainty evidence). There was little to no effect on overall response rates between MTT and non-MTT. There was no clear evidence of a difference in overall response rates (low-certainty evidence) and severe adverse events between MTT and non-MTT (low-certainty evidence). None of the studies comparing MTT and non-MTT reported quality of life. Matched targeted therapy versus best supportive care Matched targeted therapy compared with the best supportive care (BSC) i.e. no active treatment probably reduces the risk of disease progression by 63% (HR 0.37, 95% CI 0.28 to 0.50; 4 studies, 858 participants; moderate-certainty evidence). There was no clear evidence of a difference in overall survival between groups (HR = 0.88, 95% CI 0.73 to 1.06, 3 studies, 783 participants; low-certainty evidence). There was no clear evidence of a difference in overall response rates (very low-certainty of evidence) and incidence of severe adverse events (very low-certainty of evidence) between the groups. Quality of life was reported in a single study but did not provide composite scores. Risk of bias The overall risk of bias was judged low for eight studies, unclear for two studies, and the remaining 27 studies were high risk.

AUTHORS' CONCLUSIONS

Matched targeted therapies guided by next-generation sequencing in people with advanced cancer prolongs the time before cancer progresses compared to standard therapies. However, there is limited evidence to suggest that it prolongs overall survival, improves the quality of life or increases adverse events. Importantly, this review supports equitable access to next-generation sequencing technology for all people with advanced cancer and offers them the opportunity to access genotype-matched targeted therapies.

PSPC1 exerts an oncogenic role in AML by regulating a leukemic transcription program in cooperation with PU.1

Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy characterized by the blockage of myeloid cell differentiation and uncontrolled proliferation of immature myeloid cells. Here, we show that paraspeckle component 1 (PSPC1) is aberrantly overexpressed and associated with poor survival in AML patients. Using human AML cells and mouse models, we demonstrate that PSPC1 is not required for normal hematopoiesis, but it is critical and essential for AML cells to maintain their leukemic characteristics. PSPC1 loss induces robust differentiation, suppresses proliferation, and abolishes leukemogenesis in diverse AML cells. Mechanistically, PSPC1 exerts a pro-leukemia effect by regulating a unique leukemic transcription program via cooperative chromatin binding with PU.1 and activation of tumor-promoting genes, including NDC1, which is not previously implicated in AML. Our findings uncover a unique and crucial role of PSPC1 dependency in AML and highlight its potential as a promising therapeutic target for AML.

Treatment of Relapsed/Refractory AML-Novel Treatment Options Including Immunotherapy

Acute myeloid leukemia is a molecularly heterogenous disease caused by the rapid expansion and impaired differentiation of malignant myeloid progenitors. Overall, outcomes remain poor, and more than half of patients develop relapsed or refractory disease after front-line therapy. Allogeneic hematopoietic stem cell transplant (HCT) remains the best chance for cure for eligible patients, and the development of novel therapies including BCL2, FLT3, IDH1/2 and menin inhibitors, which are efficacious yet generally more tolerable, have enabled better bridging to prompt HCT. Despite the early success of targeted therapies, more generalized and efficacious therapeutic approaches remain in need, and numerous targeted immunotherapeutic agents (including CAR-T, bispecific and trispecific antibody therapies) are currently under investigation.

Resistance to FLT3 inhibitors involves different molecular mechanisms and reduces new DNA synthesis

Acute myeloid leukaemia (AML) is a hard to treat blood cancer. Mutations in FLT3 are common among the genetic aberrations that characterise the cancer. Patients initially react to FLT3 inhibitors but drug resistance is a hinder to successful therapy. To better understand the mechanisms leading to drug resistance, we generated four AML cell lines resistant to the inhibitors gilteritinib or FF-10101, and explored their resistance mechanisms. We further tested whether the novel inhibitor Chen-9u could be used to limit cell growth. The results showed that each of the four resistant cell lines became resistant through a different mechanism. Resistant cells showed decreased FLT3 and increased NRAS pathway activity and reduced DNA synthesis due to decrease in CDK4 activity. Resistance mechanisms included resistance mutations in FLT3 (C695F and N701K), and a novel mutation in NRAS (G12C). In a fourth line, resistance might have developed through a MYCN mutation. Cell growth was inhibited by Chen-9u and resistant clones could not be obtained with this inhibitor. The results highlight opportunities and limitations. On the one hand, resistant cells were produced due to different mechanisms, showing the versatility of tumour cells. Furthermore, resistance developed to the most advanced inhibitors, one of which is covalent and the other non-covalent but highly specific. On the other hand, it is shown that DNA synthesis is reduced, which means that resistance has evolutionary consequences. Finally, the novel drug-resistant cell lines may serve as useful models for better understanding of the cellular events associated with inherent and acquired drug resistance.

Getting the right combination to break the epigenetic code

Rapid advances in the field of epigenetics have facilitated the development of novel therapeutics targeting epigenetic mechanisms that are hijacked by cancer cells to support tumour growth and progression. Several epigenetic agents have been approved by the FDA for the treatment of cancer; however, the efficacy of these drugs is dependent on the underlying biology and drivers of the disease, with inherent differences between solid tumours and haematological malignancies. The efficacy of epigenetic drugs as single agents remains limited across most cancer types, which has spurred the clinical development of combination therapies, with the hope of attaining synergistic activity and/or overcoming treatment resistance. In this Review we discuss clinical advances that have been achieved with the use of epigenetic agents in combination with chemotherapies, immunotherapies or other targeted agents, including epigenetic-epigenetic combinations, as well as limitations and challenges associated with these combinatorial strategies. So far, the success of combination therapies targeting epigenetic mechanisms has generally been confined to haematological malignancies, with limited efficacy observed in patients with solid tumours. Nevertheless, this Review captures the field of epigenetic combination therapies across the spectra of haematology and oncology, highlighting opportunities for precision therapy to effectively harness the potential of epigenetic agents and produce meaningful improvements in clinical outcomes.

Changes in donor lymphocyte infusion for relapsed patients post-hematopoietic stem cell transplantation: a 30-year single-center experience

Introduction

Donor lymphocyte infusion (DLI) is a therapeutic approach for relapse after hematopoietic stem cell transplantation (HSCT). Despite their reported efficacy, the evolution of DLI practices over time remains underexplored.

Methods

This study provided a comprehensive analysis of DLI strategies and outcomes over 30 years at a single institution. A retrospective analysis was conducted on 75 patients who underwent DLI for disease relapse between April 1994 and March 2024. The primary endpoint was the 3-year overall survival (OS) rate after DLI. Secondary endpoints included the 100-day complete remission (CR) rate and incidence of acute graft-versus-host disease (GVHD).

Results

The median age at the first DLI was 49 years (range, 20-69 years). The most common underlying diseases in all 75 cases were acute myeloid leukemia (AML, n = 46) and myelodysplastic syndromes (MDS, n = 12). Until 2014, DLI was only performed in patients with AML (n = 14), MDS (n = 2), or chronic myeloid leukemia (n = 5). However, since 2015, patients with various diseases, including lymphoid malignancies, have also undergone DLI. Azacitidine was the most frequently used combination therapy with DLI (n = 34). Regimens including venetoclax and FLT3 inhibitors have been commonly used since 2019 (n = 18). The 3-year OS rate was 29.1% (95% CI, 18.8-40.2%). Factors negatively influencing OS included age ≥50 years and a high or very high refined disease risk index. The 100-day CR rate was 52.1%, and acute GVHD occurred in 25.3% of the patients, with no strong correlation between GVHD incidence and CR achievement. Among 18 patients who underwent three or more DLIs since 2018, 88.9% achieved remission following DLI or second HSCT, with a median follow-up of 949.5 days for survivors.

Conclusion

This study highlighted the evolving trends in DLI practices and the diversification of combination therapies. Future research should focus on further validating these findings and optimizing DLI protocols to improve patient outcomes.

Precision Medicine in Myeloid Neoplasia: Challenges and Opportunities

High-risk myeloid neoplasms encompass a group of hematologic malignancies known to cause significant cytopenias, which are accompanied by the risk of end-organ damage. They tend to have an aggressive clinical course and limit life expectancy in the absence of effective treatments. The adoption of precision medicine approaches has been limited by substantive diversity in somatic mutations, limited fraction of patients with targetable genetic lesions, and the prolonged turnaround times of pertinent genetic tests. Efforts to incorporate targeted agents into first-line treatment, rapidly determine pre-treatment molecular or cytogenetic aberrations, and evaluate functional vulnerabilities ex vivo hold promise for advancing the use of precision medicine in these malignancies. Given the relative accessibility of malignant cells from blood and bone marrow, precision medicine strategies hold great potential to shape future standard-of-care approaches to patients with high-risk myeloid malignancies. This review aims to summarize the development of the targeted therapies currently available to treat these blood cancers, most notably acute myeloid leukemia, and also evaluate future opportunities and challenges related to the integration of personalized approaches.

Targeting FMS-like tyrosine kinase 3 (FLT3) in acute myeloid leukemia: Novel molecular approaches and therapeutic challenges

Acute myeloid leukemia (AML), a heterogeneous hematologic malignancy, has generally a poor prognosis despite the recent advancements in diagnostics and treatment. Genetic instability, particularly mutations in the FMS-like tyrosine kinase 3 (FLT3) gene, is associated with severe outcomes. Approximately 30 % of AML patients harbor FLT3 mutations, which have been linked to higher relapse and reduced survival rates. Traditional AML treatments employ cytarabine and anthracyclines drugs. Furthermore, the development of FLT3 inhibitors has significantly improved therapy for FLT3-mutated AML patients. For example, the introduction of midostaurin, the first FLT3 inhibitor, improved patient outcomes. However, resistant AML cell clones continue to pose a challenge to the success of AML treatment. This review discusses FLT3 kinase, mutations, and role in AML pathogenesis. It explores the molecular mechanisms of FLT3 activation, signaling pathways, and the structure and function of the FLT3 receptor. Current and emerging therapeutic approaches are presented, while highlighting the latest FLT3 inhibitors in clinical use, and strategies to overcome drug resistance. Future directions, including personalized therapies and novel drug designs, are examined to provide updated insights into FLT3-targeted treatments. This comprehensive review aims to guide clinicians and researchers in the development of innovative therapies to improve AML patient outcomes.

A phase 1/2 study of gilteritinib in combination with chemotherapy in newly diagnosed patients with AML in Asia

OBJECTIVE

This interim analysis of a phase 1/2, open-label, single-arm study assessed the safety, efficacy, and pharmacokinetics of gilteritinib plus chemotherapy in adults with newly diagnosed FLT3 mutation-positive acute myeloid leukemia.

METHODS

In sequential phase 1 and 2 studies, induction and consolidation therapy with gilteritinib 120 mg/day plus chemotherapy (induction: idarubicin/cytarabine once daily; consolidation: cytarabine twice daily) was followed by maintenance gilteritinib 120 mg/day monotherapy. Endpoints included maximum tolerated dose (MTD), recommended expansion dose (RED), and dose-limiting toxicity (phase 1), and complete remission (CR) rate following induction therapy (primary endpoint), overall survival (OS), safety, and pharmacokinetics (phase 2).

RESULTS

In phase 1, MTD was not reached and RED was 120 mg/day. In phase 2, the CR rate was 50.0% after induction (90% confidence interval [CI] 40.4, 59.6); however, the lower confidence limit did not exceed the pre-defined 55% benchmark. Composite CR (CRc) rates were high following induction (86.6%, 95% CI [77.3, 93.1]), consolidation, and maintenance therapy (87.8%, 95% CI [78.7, 94.0], each). The probability of OS was 86.6% at 12 months. No new safety findings were reported.

CONCLUSION

In this interim analysis, gilteritinib 120 mg/day in combination with chemotherapy was well tolerated, with similar CRc rates to previous studies.

Quizartinib with donor lymphocyte infusion for post-transplant relapse of FLT3-ITD-positive acute myeloid leukemia

FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD)-positive acute myeloid leukemia (AML) has a poor prognosis, particularly with DNMT3A and NPM1 mutations. Quizartinib, a FLT3 inhibitor showing clinical benefit in FLT3-ITD-positive AML, has unclear safety and efficacy when combined with donor lymphocyte infusion (DLI). We report a case of FLT3-ITD-positive AML with DNMT3A and NPM1 mutations that relapsed after allogeneic hematopoietic stem cell transplantation (allo-HCT) and was treated with quizartinib and DLI. A 49-year-old man was diagnosed with AML. Target-sequencing analysis of the bone marrow revealed FLT3-ITD, DNMT3A R882, and NPM1 mutations. Although the patient achieved complete remission (CR) through induction therapy and received allo-HCT, he relapsed on day 71. Quizartinib was initiated on day 79, and the patient achieved CR with incomplete recovery on day 106. He did not desire a second allo-HCT and continued quizartinib in combination with DLI, which was started on day 156 and administered eight times every 2 to 3 months. The patient achieved hematological CR on day 163 and remained in molecular CR 3 years after allo-HCT without adverse effects. Quizartinib combined with DLI may be a feasible treatment for early relapse of FLT3-ITD-positive AML after allo-HCT, even with concurrent DNMT3A and NPM1 mutations.

Biology of post-transplant relapse: actionable features

In patients receiving allogeneic hematopoietic cell transplantation to cure acute myeloid leukemia (AML), recurrence of the underlying disease, or relapse, represents a crucial unanswered issue and prominent cause of mortality. Still, over recent years, advancements in omic technologies have allowed us to gain new insights into the dynamic changes occurring in cancer and the host over the course of treatments, providing a novel evolutionary perspective on the issue of disease relapse. In this review, we summarize current knowledge on the molecular features of relapsing AML, with a specific focus on changes in the mutational asset of the disease and in the interplay between the tumor and the donor-derived immune system. In particular, we discuss how this information can be translated into relevant indications for monitoring transplanted patients and selecting the most appropriate therapeutic options to prevent and treat relapse.

Mutation- and MRD-informed treatments for transplant-ineligible patients

The ongoing development of molecularly targeted therapies in addition to the new standard of care combination of azacitidine and venetoclax (AZA-VEN) has transformed the prognostic outlook for older, transplant-ineligible patients with acute myeloid leukemia (AML). While conventional treatments, such as standard anthracycline and cytarabine- based chemotherapy or hypomethylating agent (HMA) monotherapy, are associated with a generally poor prognosis in this patient population, the use of these novel regimens can result in long-lasting, durable remissions in select patient subgroups. Furthermore, the simultaneous discovery of resistance mechanisms to targeted therapies and AZA-VEN has enabled the identification of patient subgroups with inferior outcomes, leading to the development, of new risk-stratification models and clinical investigations incorporating targeted therapies using an HMA-VEN-based platform. Treatments inclusive of IDH1, IDH2, FLT3, and menin inhibitors combined with HMA-VEN have additionally demonstrated safety and high rates of efficacy in early-phase clinical trials, suggesting these regimens may further improve outcomes within select subgroups of patients with AML in the near future. Additional studies defining the prognostic role of measurable residual disease following VEN-based treatment have further advanced prognostication capabilities and increased the ability for close disease monitoring and early targeted intervention prior to morphologic relapse. This review summarizes these recent developments and their impact on the treatment and survival of transplant-ineligible patients living with AML.

How to improve AML outcomes?

Understanding the intricacies of the pathophysiology and genomic landscape has enhanced the long-term outcomes for patients with acute myeloid leukemia (AML). The identification of novel molecular targets has introduced new therapeutic strategies that attempt to surpass the dominance of the "7 + 3 regimen" established in the 1970s. In 2022, the World Health Organization and International Consensus Classification revised their definitions and approaches to AML, reflecting the current and evolving changes at the molecular level. The guidelines are now grounded in a definition of the disease that emphasizes genetic characteristics. Today, we recognize AML as a genetically diverse disease; a retrospective study identified 5234 driver mutations across 76 genes or genomic regions, with two or more drivers observed in 86% of patients (Papaemmanuil et al., N Engl J Med 374:2209-21, 2016).

Population pharmacokinetic analysis of quizartinib in patients with newly diagnosed FLT3-internal-tandem-duplication-positive acute myeloid leukemia

The population pharmacokinetics (PK) of quizartinib and its pharmacologically active metabolite AC886 have been previously described in healthy volunteers (HV) and relapsed/refractory (R/R) FLT3-internal-tandem-duplication-positive (FLT3-IDT-positive) acute myeloid leukemia (AML) patients receiving quizartinib monotherapy. In this analysis, we characterized the population PK of quizartinib and AC886 in newly diagnosed FLT3-ITD-positive AML patients receiving standard induction and consolidation chemotherapy as background treatment, using data from the Phase 3 QuANTUM-First trial and 12 earlier studies. Quizartinib PK were best described by a three-compartment model with sequential zero- and first-order absorption and first-order elimination. A two-compartment model with first-order metabolite formation and first-order elimination best fitted AC886 data. The PK of both moieties showed large interindividual variability (approximately 70% coefficient of variation for systemic clearances). The use of strong cytochrome P450 3A (CYP3A) inhibitors had the largest impact on exposure, increasing the steady-state area under the curve during the dosing interval (AUCss) by 1.8-fold. This is consistent with observations in HV and R/R AML patients and confirms the need for dose adjustments during coadministration. A novel finding in newly diagnosed AML patients was the phase-dependent change in steady-state quizartinib exposure: dose-normalized AUCss values were 0.6-fold during induction, similar during consolidation, and 1.4-fold during continuation compared to R/R AML patients receiving quizartinib monotherapy. The present analysis highlighted the comparison of quizartinib and AC886 PK between newly diagnosed AML patients and previously studied populations, informed dose modifications needed with strong CYP3A inhibitors, and supported the use of derived individual exposure metrics in separate exposure-response analyses.

Efficacy and safety of second‑generation FLT3 inhibitors in acute myeloid leukemia: A systematic review and meta‑analysis of randomized controlled trials

Acute myeloid leukemia (AML) is one of the most frequent forms of acute leukemia and the second most common leukemia subtype in adults. In 2020, the incidence of AML in the United States was estimated to be ~4 cases per 100,000 adults. The FMS-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) and tyrosine kinase domain (TKD) mutation are major prognostic indicators of AML. They are more frequently observed in younger AML patients (aged <60 years), likely due to their association with de novo. Additionally, these mutations have a stronger negative impact on survival in younger patients. Therefore, quizartinib and gilteritinib are second-generation FLT3 inhibitors that are frequently applied for treating patients with AML. However, to the best of our knowledge, few studies have compared the efficacy of second-generation FLT3 inhibitors for AML treatment. Therefore, the present study conducted a comprehensive search for studies on the efficacy and safety of FLT3 inhibitors across PubMed, Embase, the Cochrane Library and ClinicalTrials.gov. The search criteria were limited to randomized controlled trials (RCTs). Subsequently, a meta-analysis was performed on a total of five randomized controlled trials, involving 1,543 participants in total, using a random-effects model. In each RCT, compared to the salvage chemotherapy used in the control group, the groups that received second-generation FLT3 inhibitors experienced significant improvements in overall survival (hazard ratio, 0.717; 95% CI, 0.604-0.850; P<0.001). In addition, overall survival was found to be consistent across the different types of second-generation FLT3 inhibitors used and different types of AML. The risks associated with a prolonged heart-rate corrected QT interval (QTc) interval were next evaluated. Compared with the salvage chemotherapy used in the control group, the second-generation FLT3 inhibitor group exhibited a significantly higher risk of having a prolonged QTc interval (odds ratio, 6.311; 95% CI, 3.061-13.013; P<0.001). In conclusion, these findings suggest that second-generation FLT3 inhibitors can improve the overall survival of patients with AML. However, QTc prolongation is a potential adverse effect that should be monitored.

Salvage Therapy with Second-Generation Inhibitors for FLT3 Mutated Acute Myeloid Leukemia: A Real-World Study by the CETLAM and PETHEMA Groups

BACKGROUND/OBJECTIVES

Patients with relapsed/refractory (R/R) AML with FLT3 mutation (FLT3mut) have a dismal prognosis. FLT3mut offers a target for therapy in these patients. Gilteritinib (gilter) and quizartinib (quizar) have demonstrated efficacy as single agents in two phase 3 clinical trials.

METHODS

We retrospectively analyzed the characteristics, treatments, and outcomes of 50 patients with R/R FLT3mut AML who received gilter or quizar as monotherapy in 27 Spanish centers before their commercial availability. Forty-four patients were treated with gilter and six with quizar.

RESULTS

The median age was 62.5 years, and 52% were women. Most patients presented with FLT3-ITD mutations (80%); 46% had refractory disease and 54% had relapsed disease at treatment initiation. First-line treatment was chemotherapy in 80% of patients, with 40% of these also receiving midostaurin. Twenty-five patients (50%) had previously received FLT3 inhibitor, and twenty-eight (56%) had received more than one line treatment before starting gilter/quizar. The rates of complete remission (CR), CR without hematological recovery (CRi), and partial remission were 22%, 18%, and 16%, respectively. The median overall survival (OS) and disease-free survival were 4.74 months and 2.99 months, respectively. We observed a significant improvement in OS in patients who had received only one prior line of therapy compared to those who had received two or more therapies (10.77 months vs. 4.24 months, p = 0.016). Multivariate analysis identified failure to achieve CR/CRi, receiving more than one prior line of therapy, age, and white blood cells count as independent prognostic factors for OS. The most common toxicities were febrile neutropenia, liver function abnormalities, and QT interval prolongation.

CONCLUSIONS

Gilter/quizar monotherapy are effective and tolerable options for patients with R/R FLT3mut AML in a real-world setting. Response and toxicity rates are similar to those reported in the phase 3 trials, despite the more heterogeneous nature of the study population.

Quizartinib: a potent and selective FLT3 inhibitor for the treatment of patients with FLT3-ITD-positive AML

Mutations in FMS-related receptor tyrosine kinase 3 (FLT3) are among the most common alterations in acute myeloid leukemia (AML), present in ≈30% of newly diagnosed AML cases. Internal tandem duplications (ITD) in FLT3 (FLT3-ITD) occur in ≈25% of newly diagnosed AML cases and are associated with unfavorable outcomes. Quizartinib (formerly AC220) is a novel, second-generation, highly potent, and selective type II FLT3 inhibitor. Quizartinib is approved in Japan as monotherapy for the treatment of adult patients with FLT3-ITD-positive relapsed/refractory (R/R) AML. Quizartinib is also approved in the United States, Japan, Europe, and United Kingdom in combination with chemotherapy during induction and consolidation, and as maintenance monotherapy (but, in the United States, not after allogeneic hematopoietic cell transplantation [allo-HCT]), for the treatment of adult patients with newly diagnosed FLT3-ITD-positive AML. In this review, we summarize preclinical studies that established quizartinib as a potent and selective type II FLT3 inhibitor as well as early and pivotal phase 3 clinical studies (QuANTUM-R and QuANTUM-First) that led to the approvals of quizartinib. We also summarize mechanisms of resistance to quizartinib along with its safety profile. Furthermore, we review the ongoing post hoc analyses of the QuANTUM-First data elucidating the impact of allo-HCT, the presence of measurable residual disease, and number and length of ITD on the clinical outcomes of quizartinib. We also describe the impact of quizartinib on patient-reported outcomes. Finally, we highlight some of the ongoing studies that test quizartinib in patients with FLT3-ITD-positive AML, patients with FLT3-ITD-negative AML, in both the first-line and R/R settings, in patients fit or unfit for intensive chemotherapy, including studies for quizartinib-based combination with other compounds such as decitabine and venetoclax. Future research should aim to further optimize the clinical value of quizartinib and explore its use in additional clinical settings, which could be achieved by testing quizartinib with other drugs, better characterization of the mechanisms of resistance, identification of the role of quizartinib as a maintenance therapy after allo-HCT, and investigating quizartinib in patients with FLT3-ITD-negative AML.

OXPHOS mediators in acute myeloid leukemia patients: Prognostic biomarkers and therapeutic targets for personalized medicine

BACKGROUND

Despite significant advances in comprehending its tumorigenic role, the prognostic and therapeutic potential of targeting oxidative phosphorylation (OXPHOS) in acute myeloid leukemia (AML) remain obscure.

METHODS

The prognostic value of ~ 200 mitochondrial/OXPHOS genes as candidate biomarkers was examined in AML patients over ~ 10 years follow-up using Kaplan-Meier and Cox regression analyses. Furthermore, the transcript levels of the assessed markers were inspected in healthy bone marrow tissues and the dependencies of AML cells on the assessed genes were examined.

RESULTS

Elevated levels of NADH:ubiquinone oxidoreductase subunit A6 (NDUFA6), succinate dehydrogenase complex flavoprotein subunit A (SDHA), solute carrier family 25 member 12 (SLC25A12), electron transfer flavoprotein subunit beta (ETFB), carnitine palmitoyltransferase 1A (CPT1A) and glutathione peroxidase 4 (GPX4) were associated with poor overall survival of AML patients. SLC25A12, ETFB and CPT1A were overexpressed in AML compared to healthy tissues. Cytochrome B5 type A (CYB5A)high, SLC25A12high and GPX4high AML patients displayed higher levels of circulating and engrafted blasts compared to low-expressing cohorts. NPM1 and SRSF2 mutations were frequent in SDHAlow and CPT1Alow AML patients respectively. FLT3-ITD, NPM1 and IDH1 mutations were prevalent in CPT1Ahigh AML patients. FLT3-ITD AMLs were more dependent on OXPHOS.

CONCLUSIONS

This study identifies NDUFA6 and SDHA as novel companion prognostic biomarkers which might present a rational strategy for personalized therapy of AML patients.

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.

Recent advancements in biomarkers, therapeutics, and associated challenges in acute myeloid leukemia

Acute myeloid leukemia (AML) is a common type of leukemia that has a high mortality rate. The reasons for high mortality in patients with AML are therapeutic resistance, limited ability to predict duration of response, and likelihood of cancer relapse. Biomarkers, such as leukemic stem cell biomarkers, circulatory biomarkers, measurable residual disease biomarkers, and molecular biomarkers, are used for prognosis, diagnosis, and targeted killing to selectively eliminate AML cells. They also play an indispensable role in providing therapeutic resistance to patients with AML. Therefore, targeting these biomarkers will improve the outcome of AML patients. However, identifying biomarkers that can differentiate between treatment-responsive and non-responsive AML patients remains a challenge. This review discusses recent advancements in AML biomarkers, promising therapeutics, and associated challenges in the treatment of AML.

Concentration-QTcF analysis of quizartinib in patients with newly diagnosed FLT3-internal-tandem-duplication-positive acute myeloid leukemia

Quizartinib prolongs QT interval through inhibition of the slow delayed rectifier potassium current (IKs). We used non-linear mixed-effects modeling to explore the relationship between quizartinib and its pharmacologically active metabolite AC886 and the Fridericia-corrected QT interval (QTcF) in newly diagnosed acute myeloid leukemia (AML) patients. We evaluated linear and non-linear drug effect models, using triplicate QTcF measurements with available time-matched pharmacokinetic samples from the Phase 3 QuANTUM-First trial. The effect of intrinsic and extrinsic factors on model parameters was tested using stepwise covariate model building. Simulations were conducted to predict the change from baseline in QTcF (ΔQTcF) at the maximum concentration at steady-state (Cmax,ss) for quizartinib maintenance daily doses of 30 and 60 mg. The concentration-QTcF (C-QTcF) relationship was best described by a sigmoidal maximum effect model. After accounting for the effect of quizartinib, including AC886 concentrations did not further explain changes in QTcF. Circadian variations in QTcF were described using an empirical change from baseline based on clock times. Age and hypokalaemia were identified as statistically significant covariates on baseline QTcF; no covariates were found to impact the C-QTcF relationship. The median model-predicted ΔQTcF at Cmax,ss was 18.4 ms (90% confidence interval (CI): 16.3-20.5) at 30 mg and 24.1 ms (90% CI: 21.4-26.6) at 60 mg. In conclusion, in newly diagnosed AML patients, ΔQTcF increased non-linearly with increasing quizartinib concentrations. The predicted ΔQTcF increase at Cmax,ss supports the proposed dose adaptation based on observed QTcF and the dose reduction in case of strong cytochrome P450 3A (CYP3A) inhibitors coadministration.

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.

Advances in the pathogenesis of FLT3 -mutated acute myeloid leukemia and targeted treatments

PURPOSE OF REVIEW

FLT3 mutations are among the most common myeloid drivers identified in adult acute myeloid leukemia (AML). Their identification is crucial for the precise risk assessment because of the strong prognostic significance of the most recurrent type of FLT3 alterations, namely internal tandem duplications (ITDs). Recent advances in the pathogenesis and biology of FLT3 -mutated AML have opened an opportunity for development and application of selective inhibition of FLT3 pathway.

RECENT FINDINGS

In the last decade, at least three targeted treatments have been approved by regulatory agencies and several others are currently under investigations. Here, we review the latest advance in the role of FLT3 mutations in AML, providing an outline of the available therapeutic strategies, their mechanisms of actions and of resistance, as well as routes for potential improvement.

SUMMARY

The availability of FLT3 inhibitors has improved outcomes in AML harboring such mutations, currently also reflected in disease stratification and recommendations. Newer inhibitors are under investigations, and combinations with chemotherapy or other targeted treatments are being explored to further improve disease outcomes.

Anti-leukemic effects of Vernonia amygdalina extract

This study aimed to investigate the impact of Vernonia amygdalina leaf extract on FLT3 regulation. V. amygdalina was extracted with 96% ethanol (VAE-96), and its cytotoxicity against FLT3- cell lines (MOLM-13 and MV-4-11) was evaluated. The results indicated that VAE-96 induced apoptosis in these cells and inhibited the phosphorylation of AKT, MAPK, and FLT3. Additionally, VAE-96 substantially diminished the activity of the FLT3 promoter and the expression of FLT3 mRNA. The extract was found to contain alkaloids, saponin, reduced sugar compounds, and polyphenols, including tannins and flavonoids, as per the phytoconstituents analysis. The potential of alkaloid fractions on MOLM-13 cells was indicated by the robust cytotoxic effect of the alkaloid fractions, which resulted in over 50% cell mortality at 30 µg/ml. Our results suggest that VAE-96 may be a beneficial agent for the prevention and treatment of AML with FLT3-ITD mutation.

Relapse and resistance in acute myeloid leukemia post venetoclax: improving second lines therapy and combinations

INTRODUCTION

The combined use of the BCL-2 inhibitor venetoclax with azacitidine now is the standard of care for patients with acute myeloid leukemia (AML) unfit for intensive chemotherapy with outcomes exceeding those achieved with hypomethylating agents alone. Venetoclax in combination with intensive chemotherapy is also increasingly used both as frontline as well as salvage therapy. However, resistance to and relapse after venetoclax-based therapies are of major concern and outcomes after treatment failure remain poor.

AREAS COVERED

A comprehensive search was performed using PubMed database (up to April 2024). Studies evaluating venetoclax-based combination treatments in AML and studies assessing markers of response and resistance to venetoclax were investigated. We summarize the status of venetoclax-based therapies in the frontline and relapsed/refractory setting with focus on the main mechanisms of resistance to BCL-2 inhibition. Further, strategies to overcome resistance including combinatorial regimens of hypomethylating agent (HMA) + venetoclax + inhibitors targeting actionable mutations like IDH1/2 or FLT3-ITD and the introduction of novel agents like menin-inhibitors are addressed.

EXPERT OPINION

Although venetoclax is reshaping the treatment of unfit and fit AML patients, prognosis of patients after HMA/VEN failure remains dismal, and strategies to abrogate primary and secondary resistance are an unmet clinical need.

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.

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.

Key role of glutamine metabolism in persistence of leukemic cells upon exposition to FLT3 tyrosine kinase inhibitors

Acute myeloid leukemias are a group of hematological malignancies characterized by a poor prognosis for survival. The discovery of oncogenic mutations in the FMS-like tyrosine kinase 3 (FLT3) gene has led to the development of tyrosine kinase inhibitors such as quizartinib. However, achieving complete remission in patients remains challenging because these new tyrosine kinase inhibitors (TKIs) are unable to completely eradicate all leukemic cells. Residual leukemic cells persist during quizartinib treatment, leading to the rapid emergence of drug-resistant leukemia. Given that mitochondrial oxidative metabolism promotes the survival of leukemic cells after exposure to multiple anticancer drugs, we characterized the metabolism of leukemic cells that persisted during quizartinib treatment and developed metabolic strategies to eradicate them. In our study, employing biochemical and metabolomics approaches, we confirmed that the survival of leukemic cells treated with FLT3 inhibitors critically depends on maintaining mitochondrial metabolism, specifically through glutamine oxidation. We uncovered a synergistic interaction between the FLT3 inhibitor quizartinib and L-asparaginase, operating through antimetabolic mechanisms. Utilizing various models of persistent leukemia, we demonstrated that leukemic cells resistant to quizartinib are susceptible to L-asparaginase. This combined therapeutic strategy shows promise in reducing the development of resistance to FLT3 inhibitors, offering a potential strategy to enhance treatment outcomes.

Clonal Dynamics and Relapse Risk Revealed by High-Sensitivity FLT3-Internal Tandem Duplication Detection in Acute Myeloid Leukemia

The ability to detect low-level disease is key to our understanding of clonal heterogeneity in acute myeloid leukemia (AML) and residual disease that elude conventional assays and seed relapse. We developed a high-sensitivity next-generation sequencing (HS-NGS) clinical assay, able to reliably detect low levels (1 × 10-5) of FLT3-ITD, a frequent, therapeutically targetable and prognostically relevant mutation in AML. By applying this assay to 289 longitudinal samples from 62 patients at initial diagnosis and/or clinical follow-up (mean follow-up of 22 months), we reveal the frequent occurrence of FLT3-ITD subclones at diagnosis and demonstrate a significantly decreased relapse risk when FLT3-ITD is cleared after induction or thereafter. We perform pairwise sequencing of diagnosis and relapse samples from 23 patients to uncover more detailed patterns of FLT3-ITD clonal evolution at relapse than is detectable by less-sensitive assays. Finally, we show that rising ITD level during consecutive biopsies is a harbinger of impending relapse. Our findings corroborate the emerging clinical utility of high-sensitivity FLT3-ITD testing and expands our understanding of clonal dynamics in FLT3-ITD-positive AML.

Common Driver Mutations in AML: Biological Impact, Clinical Considerations, and Treatment Strategies

Next-generation sequencing of samples from patients with acute myeloid leukemia (AML) has revealed several driver gene mutations in adult AML. However, unlike other cancers, AML is defined by relatively few mutations per patient, with a median of 4-5 depending on subtype. In this review, we will discuss the most common driver genes found in patients with AML and focus on the most clinically relevant ones that impact treatment strategies. The most common driver gene mutations in AML occur in NPM1 and FLT3, accounting for ~30% each. There are now targeted therapies being tested or already approved for these driver genes. Menin inhibitors, a novel targeted therapy that blocks the function of the menin protein, are in clinical trials for NPM1 driver gene mutant AML after relapse. A number of FLT3 inhibitors are now approved for FLT3 driver gene mutant AML in combination with chemotherapy in the frontline and also as single agent in relapse. Although mutations in IDH1/2 and TP53 only occur in around 10-20% of patients with AML each, they can affect the treatment strategy due to their association with prognosis and availability of targeted agents. While the impact of other driver gene mutations in AML is recognized, there is a lack of data on the actionable impact of those mutations.

Molecular Features and Treatment Paradigms of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a common hematologic malignancy that is considered to be a disease of aging, and traditionally has been treated with induction chemotherapy, followed by consolidation chemotherapy and/or allogenic hematopoietic stem cell transplantation. More recently, with the use of next-generation sequencing and access to molecular information, targeted molecular approaches to the treatment of AML have been adopted. Molecular targeting is gaining prominence, as AML mostly afflicts the elderly population, who often cannot tolerate traditional chemotherapy. Understanding molecular changes at the gene level is also important for accurate disease classification, risk stratification, and prognosis, allowing for more personalized medicine. Some mutations are well studied and have an established gene-specific therapy, including FLT3 and IDH1/2, while others are being investigated in clinical trials. However, data on most known mutations in AML are still minimal and therapeutic studies are in pre-clinical stages, highlighting the importance of further research and elucidation of the pathophysiology involving these genes. In this review, we aim to highlight the key molecular alterations and chromosomal changes that characterize AML, with a focus on pathophysiology, presently available treatment approaches, and future therapeutic options.

Classification of FLT3 inhibitors and SAR analysis by machine learning methods

FMS-like tyrosine kinase 3 (FLT3) is a type III receptor tyrosine kinase, which is an important target for anti-cancer therapy. In this work, we conducted a structure-activity relationship (SAR) study on 3867 FLT3 inhibitors we collected. MACCS fingerprints, ECFP4 fingerprints, and TT fingerprints were used to represent the inhibitors in the dataset. A total of 36 classification models were built based on support vector machine (SVM), random forest (RF), eXtreme Gradient Boosting (XGBoost), and deep neural networks (DNN) algorithms. Model 3D_3 built by deep neural networks (DNN) and TT fingerprints performed best on the test set with the highest prediction accuracy of 85.83% and Matthews correlation coefficient (MCC) of 0.72 and also performed well on the external test set. In addition, we clustered 3867 inhibitors into 11 subsets by the K-Means algorithm to figure out the structural characteristics of the reported FLT3 inhibitors. Finally, we analyzed the SAR of FLT3 inhibitors by RF algorithm based on ECFP4 fingerprints. The results showed that 2-aminopyrimidine, 1-ethylpiperidine,2,4-bis(methylamino)pyrimidine, amino-aromatic heterocycle, [(2E)-but-2-enyl]dimethylamine, but-2-enyl, and alkynyl were typical fragments among highly active inhibitors. Besides, three scaffolds in Subset_A (Subset 4), Subset_B, and Subset_C showed a significant relationship to inhibition activity targeting FLT3.

Combination therapy with novel agents for acute myeloid leukaemia: Insights into treatment of a heterogenous disease

The treatment landscape of acute myeloid leukaemia (AML) is evolving rapidly. Venetoclax in combination with intensive chemotherapy or doublets or triplets with targeted or immune therapies is the focus of numerous ongoing trials. The development of mutation-targeted therapies has greatly enhanced the treatment armamentarium, with FLT3 inhibitors and isocitrate dehydrogenase inhibitors improving outcomes in frontline and relapsed/refractory (RR) AML, and menin inhibitors showing efficacy in RR NPM1mut and KMT2A-rearranged AML. With so many new drugs approved, the number of potential combinatorial approaches to leverage the maximal benefit of these agents has increased dramatically, while at the same time introducing clinical challenges, such as key preclinical and clinical data supporting the development of combinatorial therapy, how to optimally combine or sequence these novel agents, how to optimise dose and duration to maintain safety while enhancing efficacy, the optimal duration of therapy and the role of measurable residual disease in decision-making in both intensive and low-intensity therapy settings. In this review, we will outline the evidence leading to the approval of key agents in AML, their on-label current approvals and how they may be optimally combined in a safe and deliverable fashion to further improve outcomes in AML.

Clinical Outcomes and Treatment Patterns in Adults With FLT3-ITDmut+ Acute Myeloid Leukemia Undergoing Allogeneic Hemopoietic Cell Transplantation in the United States and Canada

Allogeneic hematopoietic cell transplantation (alloHCT) is used to treat patients with acute myeloid leukemia (AML) with internal tandem duplication of the FMS-like tyrosine kinase 3 gene (FLT3-ITDmut+). However, the effect of different characteristics on outcomes after transplant is not fully understood. The aim of this study was to determine the impact of patient, disease, and transplant characteristics on clinical outcomes and trends in maintenance therapy for patients with FLT3-ITDmut+ AML who underwent their first alloHCT. This was an observational cohort study of adults ≥18 years who were recipients of human leukocyte antigen identical sibling, haploidentical, 8/8 or 7/8 unrelated, or cord blood donor alloHCT in the United States and Canada between 2014 and 2019. Patient, disease, and transplant characteristics were collected from Center for International Blood & Marrow Transplant Research between 2014 and 2022. Patients enrolled in the MORPHO clinical trial (NCT02997202) were excluded. Clinical outcomes were measured from the time of alloHCT by disease status: first complete remission (CR1), second or greater complete remission (≥CR2), or relapsed/refractory (R/R). The primary endpoints of this study were overall survival (OS) and leukemia-free survival (LFS). Key secondary endpoints included relapse after alloHCT, nonrelapse mortality (NRM), time from diagnosis to complete remission, time from complete remission to alloHCT, and maintenance therapy before and after alloHCT. Univariate analyses were conducted with Gray's test and log-rank test, while multivariable analyses were conducted using Cox proportional hazards models. A total of 3147 eligible patients (CR1, n = 2389; ≥CR2, n = 340; R/R, n = 418) were included. Most patient, disease, and transplant characteristics were similar between different disease statuses. In univariate analyses, disease status of CR1 compared with ≥CR2 or R/R was significantly (P < .001) associated with improved OS and LFS, and decreased probability of relapse; NRM likely differed across cohorts after alloHCT (P = .003). In multivariable analyses, patients with a disease status of ≥CR2 and R/R compared with CR1 had significantly shorter OS (hazard ratio [HR] 95% confidence interval [CI], 1.43 [1.19 to 1.72], P = .0001, and 2.14 [1.88 to 2.44], P < .0001, respectively). Patients with a disease status of CR1 at ≤2.6 months had better LFS compared with ≥CR2 and R/R (HR [95% CI], 2.03 [1.56 to 2.63], P < .0001 and 3.98 [3.07 to 5.17], P < .0001, respectively). Patients with a ≥CR2 or R/R disease status at ≤2.6 months had an increased likelihood of relapse compared with CR1 (HR [95% CI], 2.46 [1.82 to 3.33], P < .0001 and 4.68 [3.46 to 6.34], P < .0001, respectively). Disease status was not significantly associated with NRM. We also identified several additional patient, disease, and transplant characteristics that may have been associated with inferior OS and/or LFS and greater relapse and/or NRM. Maintenance therapy usage after alloHCT increased from 2014 to 2019 primarily due to increased FLT3 inhibitor use. In this largest study to date of patients from the United States and Canada with FLT3-ITDmut+ AML, disease status of CR1 at the time of alloHCT was associated with better clinical outcomes. Additional factors were identified that may also impact clinical outcomes, and in total, have the potential to inform clinical decision-making.

Perspectives and challenges of small molecule inhibitor therapy for FLT3-mutated acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous clonal disease characterized overall by an aggressive clinical course. The underlying genetic abnormalities present in leukemic cells contribute significantly to the AML phenotype. Mutations in FMS-like tyrosine kinase 3 (FLT3) are one of the most common genetic abnormalities identified in AML, and the presence of these mutations strongly influences disease presentation and negatively impacts prognosis. Since mutations in FLT3 were identified in AML, they have been recognized as a valid therapeutic target resulting in decades of research to develop effective small molecule inhibitor treatment that could improve outcome for these patients. Despite the approval of several FLT3 inhibitors over the last couple of years, the treatment of patients with FLT3-mutated AML remains challenging and many questions still need to be addressed. This review will provide an up-to-date overview of our current understanding of FLT3-mutated AML and discuss what the current status is of the available FLT3 inhibitors for the day-to-day management of this aggressive disease.

Deciphering the mechanism of HM43239 inhibiting the mutant F691L resistant to gilteritinib in FMS-like tyrosine kinase 3

FMS-like tyrosine kinase (FLT3) has become the legitimate molecular therapeutic target for acute myeloid leukemia therapy. Though FLT3 inhibitors have impact on disease progression, drug resistance induced by secondary point mutations is the primary mechanism and urgent to overcome. Herein, we sought to decipher the mechanism of HM43239 inhibiting the mutant F691L resistant to gilteritinib in FLT3. A series of molecular modeling studies, including molecular dynamics (MD) simulation, dynamic cross-correlation (DCC) analysis, binding free energy (MM-GBSA) and docking study were explored to elucidate the differential tolerance mechanisms of two inhibitors to the same mutant. The F691L mutation had relatively larger effect on gilteritinib than HM43239, which showed as the changed and fixed conformation, respectively. These observations rationalized that the binding affinity of gilteritinib decreased more than that of HM43239 in the F691L mutant.Communicated by Ramaswamy H. Sarma.

Patient-Reported Outcomes in Phase 3 Clinical Trials for Blood Cancers: A Systematic Review

Importance

Published research suggests that patient-reported outcomes (PROs) are neither commonly collected nor reported in randomized clinical trials (RCTs) for solid tumors. Little is known about these practices in RCTs for hematological malignant neoplasms.

Objective

To evaluate the prevalence of PROs as prespecified end points in RCTs of hematological malignant neoplasms, and to assess reporting of PROs in associated trial publications.

Evidence Review

All issues of 8 journals known for publishing high-impact RCTs (NEJM, Lancet, Lancet Hematology, Lancet Oncology, Journal of Clinical Oncology, Blood, JAMA, and JAMA Oncology) between January 1, 2018, and December 13, 2022, were searched for primary publications of therapeutic phase 3 trials for adults with hematological malignant neoplasms. Studies that evaluated pretransplant conditioning regimens, graft-vs-host disease treatment, or radiotherapy as experimental treatment were excluded. Data regarding trial characteristics and PROs were extracted from manuscripts and trial protocols. Univariable analyses assessed associations between trial characteristics and PRO collection or reporting.

Findings

Ninety RCTs were eligible for analysis. PROs were an end point in 66 (73%) trials: in 1 trial (1%) as a primary end point, in 50 (56%) as a secondary end point, and in 15 (17%) as an exploratory end point. PRO data were reported in 26 of 66 primary publications (39%): outcomes were unchanged in 18 and improved in 8, with none reporting worse PROs with experimental treatment. Trials sponsored by for-profit entities were more likely to include PROs as an end point (49 of 55 [89%] vs 17 of 35 [49%]; P < .001) but were not significantly more likely to report PRO data (20 of 49 [41%] vs 6 of 17 [35%]; P = .69). Compared with trials involving lymphoma (18 of 29 [62%]) or leukemia or myelodysplastic syndrome (18 of 28 [64%]), those involving plasma cell disorders or multiple myeloma (27 of 30 [90%]) or myeloproliferative neoplasms (3 of 3 [100%]) were more likely to include PROs as an end point (P = .03). Similarly, compared with trials involving lymphoma (3 of 18 [17%]) or leukemia or myelodysplastic syndrome (5 of 18 [28%]), those involving plasma cell disorders or multiple myeloma (16 of 27 [59%]) or myeloproliferative neoplasms (2 of 3 [67%]) were more likely to report PROs in the primary publication (P = .01).

Conclusions and Relevance

In this systematic review, almost 3 of every 4 therapeutic RCTs for blood cancers collected PRO data; however, only 1 RCT included PROs as a primary end point. Moreover, most did not report resulting PRO data in the primary publication and when reported, PROs were either better or unchanged, raising concern for publication bias. This analysis suggests a critical gap in dissemination of data on the lived experiences of patients enrolled in RCTs for hematological malignant neoplasms.

Emerging DNA Methylome Targets in FLT3-ITD-Positive Acute Myeloid Leukemia: Combination Therapy with Clinically Approved FLT3 Inhibitors

OPINION STATEMENT

The internal tandem duplication (ITD) mutation of the FMS-like receptor tyrosine kinase 3 (FLT3-ITD) is the most common mutation observed in approximately 30% of acute myeloid leukemia (AML) patients. It represents poor prognosis due to continuous activation of downstream growth-promoting signaling pathways such as STAT5 and PI3K/AKT. Hence, FLT3 is considered an attractive druggable target; selective small FLT3 inhibitors (FLT3Is), such as midostaurin and quizartinib, have been clinically approved. However, patients possess generally poor remission rates and acquired resistance when FLT3I used alone. Various factors in patients could cause these adverse effects including altered epigenetic regulation, causing mainly abnormal gene expression patterns. Epigenetic modifications are required for hematopoietic stem cell (HSC) self-renewal and differentiation; however, critical driver mutations have been identified in genes controlling DNA methylation (such as DNMT3A, TET2, IDH1/2). These regulators cause leukemia pathogenesis and affect disease diagnosis and prognosis when they co-occur with FLT3-ITD mutation. Therefore, understanding the role of different epigenetic alterations in FLT3-ITD AML pathogenesis and how they modulate FLT3I's activity is important to rationalize combinational treatment approaches including FLT3Is and modulators of methylation regulators or pathways. Data from ongoing pre-clinical and clinical studies will further precisely define the potential use of epigenetic therapy together with FLT3Is especially after characterized patients' mutational status in terms of FLT3 and DNA methlome regulators.

The potential of triplet combination therapies for patients with FLT3-ITD -mutated acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) encompasses a heterogeneous group of aggressive myeloid malignancies, where FMS-like tyrosine kinase 3 (FLT3) mutations are prevalent, accounting for approximately 25-30% of adult patients. The presence of this mutation is related to a dismal prognosis and high relapse rates. In the lasts years many FLT3 inhibitors have been developed.

AREAS COVERED

This review provides a comprehensive overview of FLT3mut AML, summarizing the state of art of current treatment and available data about combination strategies including an FLT3 inhibitor.

EXPERT OPINION

In addition, the review discusses the emergence of drug resistance and the need for a nuanced approaches in treating patients who are ineligible for or resistant to intensive chemotherapy. Specifically, it explores the historical context of FLT3 inhibitors (FLT3Is) and their impact on treatment outcomes, emphasizing the pivotal role of midostaurin, as well as gilteritinib and quizartinib, and providing detailed insights into ongoing trials exploring the safety and efficacy of novel triplet combinations involving FLT3Is in different AML settings.

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.

Recent progress in chimeric antigen receptor therapy for acute myeloid leukemia

Although CAR-T cell therapy has been particularly successful as a treatment for B cell malignancies, effectively treating acute myeloid leukemia with CAR remains a greater challenge. Multiple preclinical studies and clinical trials are underway, including on AML-related surface markers that CAR-T cells can target, such as CD123, CD33, NKG2D, CLL1, CD7, FLT3, Lewis Y and CD70, all of which provide opportunities for developing CAR-T therapies with improved specificity and efficacy. We also explored specific strategies for CAR-T cell treatment of AML, including immune checkpoints, suicide genes, dual targeting, genomic tools and the potential for universal CAR. In addition, CAR-T cell therapy for AML still has certain risks and challenges, including cytokine release syndrome (CRS) and haematotoxicity. Despite these challenges, as a new targeting method for AML treatment, CAR-T cell therapy still has great prospects. Ongoing research aims to further optimize this treatment mode.

A practical algorithm for acute myeloid leukaemia diagnosis following the updated 2022 classifications

Disease classification of complex and heterogenous diseases, such as acute myeloid leukaemia (AML), is continuously updated to define diagnoses, appropriate treatments, and assist research and education. Recent availability of molecular profiling techniques further benefits the classification of AML. The World Health Organization (WHO) classification of haematolymphoid tumours and the International Consensus Classification of myeloid neoplasms and acute leukaemia from 2022 are two updated versions of the WHO 2016 classification. As a consequence, the European LeukemiaNet 2022 recommendations on the diagnosis and management of AML in adults have been also updated. The current review provides a practical interpretation of these guidelines to facilitate the diagnosis of AML and discusses genetic testing, disease genetic heterogeneity, and FLT3 mutations. We propose a practical algorithm for the speedy diagnosis of AML. Future classifications may need to incorporate gene mutation combinations to enable personalised treatment regimens in the management of patients with AML.

A phase 1 study of the irreversible FLT3 inhibitor FF-10101 in relapsed or refractory acute myeloid leukemia

ABSTRACT

FLT3 tyrosine kinase inhibitors (TKIs) have clinical efficacy for patients with FLT3-mutated AML (acute myeloid leukemia), but their impact is limited by resistance in the setting of monotherapy and by tolerability problems when used in combination therapies. FF-10101 is a novel compound that covalently binds to a cysteine residue near the active site of FLT3, irreversibly inhibiting receptor signaling. It is effective against most FLT3 activating mutations, and, unlike other inhibitors, is minimally vulnerable to resistance induced by FLT3 ligand. We conducted a phase 1 dose escalation study of oral FF-10101 in patients with relapsed and/or refractory AML, the majority of whom harbored FLT3-activating mutations and/or had prior exposure to FLT3 inhibitors. Fifty-four participants enrolled in cohorts receiving doses ranging from 10 to 225 mg per day and 50 to 100 mg twice daily (BID). The dose limiting toxicities were diarrhea and QT prolongation. Among 40 response-evaluable participants, the composite complete response rate was 10%, and the overall response rate (including partial responses) was 12.5%, including patients who had progressed on gilteritinib. Overall, 56% of participants had prior exposure to FLT3 inhibitors. The recommended phase 2 dose was 75 mg BID. FF-10101 potentially represents a next-generation advance in the management of FLT3-mutated AML. This trial was registered at www.ClinicalTrials.gov as #NCT03194685.

Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3

PURPOSE

Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit.

METHODS

Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS.

RESULTS

Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575).

CONCLUSION

Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

Crenolanib and Intensive Chemotherapy in Adults With Newly Diagnosed FLT3-Mutated AML

PURPOSE

Crenolanib is a second-generation tyrosine kinase inhibitor with activity against FLT3-ITD- and TKD-mutant AML. We conducted a trial of crenolanib plus intensive chemotherapy in adults with newly diagnosed FLT3-mutant AML.

METHODS

Eligible patients were 18 years and older. Induction chemotherapy consisted of cytarabine (100 mg/m2) continuous infusion on days 1-7 and anthracycline (daunorubicin 60-90 mg/m2 or idarubicin 12 mg/m2, once daily) on days 1-3 followed by consolidation with high-dose cytarabine (1-3 g/m2 twice daily on days 1, 3, 5) and/or allogeneic transplant. Crenolanib (100 mg thrice a day) was given from day 9 until 72 hours before the next cycle, after consolidation, and for 12 months after consolidation or transplant.

RESULTS

Forty-four patients (median age, 57; range, 19-75 years) were enrolled. Thirty-six had FLT3-ITD, and 11 had FLT3-TKD mutations. European LeukemiaNet 2017 disease risk was favorable in 34%, intermediate in 30%, and adverse in 36%. The overall response rate was 86% (complete remission [CR], 77%; CR with incomplete count recovery [CRi], 9%): 90% in patients 60 years and younger and 80% in older patients. Measurable residual disease-negative CR/CRi rates were 89% and 45%, respectively. With a 45-month follow-up, median overall survival has not been reached and the median event-free survival was 44.7 months. Among younger patients, the estimated 3-year survival was 71.4% with 15% cumulative incidence of relapse. Treatment-related serious adverse events included febrile neutropenia, diarrhea, and nausea. The median time to platelets ≥100,000/µL and absolute neutrophil count ≥1,000/µL during induction was 29 and 32 days, respectively. No new FLT3-mutant clones were detected at relapse in patients completing consolidation.

CONCLUSION

Crenolanib plus intensive chemotherapy in adults with newly diagnosed FLT3-mutant AML results in high rate of deep responses and long-term survival with acceptable toxicity. A randomized trial of crenolanib versus midostaurin plus chemotherapy in younger patients is ongoing.