Venetoclax in combination with cytarabine with or without idarubicin in children with relapsed or refractory acute myeloid leukaemia: a phase 1, dose-escalation study

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

INTRODUCTION

Children receiving treatment for acute myeloid leukemia (AML) are at high risk of invasive fungal disease (IFD). Evidence from pediatric studies support the efficacy of antifungal prophylaxis in reducing the burden of IFD in children receiving therapy for AML, yet existing antifungal agents have specific limitations and comparative data to inform the optimal prophylactic approach are lacking.

AREAS COVERED

This review summarizes the epidemiology of invasive fungal disease (IFD) and current antifungal prophylaxis recommendations for children with acute myeloid leukemia (AML). Challenges with currently available antifungal agents and considerations related to the changing landscape of AML therapy are reviewed. A keyword search was conducted to identify pediatric studies regarding IFD and antifungal prophylaxis in children with AML up to December 2023.

EXPERT OPINION

Children undergoing treatment for AML are recommended to receive antifungal prophylaxis to reduce risk of IFD, with tolerability, pharmacokinetics, feasibility of administration, and drug interactions all factors that require consideration in this context. With increased use of novel targeted agents for AML therapy, together with the development of new antifungal agents, data from well-designed clinical studies to optimize prophylactic approaches will be essential to limit the burden of IFD in this vulnerable cohort.

Real-world use of venetoclax in the treatment of paediatric and teenage/young adult haematological malignancies

Early-phase trials of venetoclax in children and teenagers/young adults with leukaemia have yielded promising results, but there remains a paucity of real-world data. To address this, we report a cohort of 41 children treated with venetoclax for a range of haematological malignancies, demonstrating complete remission in 43.6%, with most achieving minimal residual disease (MRD) negativity. Venetoclax was particularly effective as a bridge to transplant, with bridging successful in 75% of patients. Patients with MRD <1% at initiation of venetoclax were more likely to achieve MRD negativity (81.8% vs. 34.5%, p = 0.007) and had improved overall survival (54.5% vs. 17.9%, p = 0.004).

Mitochondria and Acute Leukemia: A Clinician's Perspective

Acute leukemia is a group of aggressive hematological malignancies, with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) being the most common types. The biology of acute leukemia involves complex genetic and epigenetic alterations that lead to uncontrolled cell proliferation and resistance to apoptosis. Mitochondrial dysfunction is a feature of acute leukemia that results in altered energy production, unregulated cell death pathways, and increased cancer cell survival. Apoptosis, particularly via the mitochondrial pathway, is crucial for cellular homeostasis and cancer prevention. In acute leukemia, disruption of apoptosis is pivotal in disease development and progression, with elevated levels of anti-apoptotic proteins conferring a survival advantage to leukemia cells and promoting resistance to conventional therapies. Targeting mitochondrial apoptosis using BH3 mimetics and anti-apoptotic protein inhibitors is a viable therapeutic strategy. Alterations in the mitochondrial membrane potential, metabolism, and dynamics also contribute to the pathogenesis of acute leukemia. Continued research is vital for developing novel therapies and enhancing survival outcomes in patients with acute leukemia while minimizing the long-term adverse effects of treatment. In this narrative review, we provide a birds-eye view of the available scientific literature on the importance of mitochondria in acute leukemia, and discuss the role of BH3 mimetics in targeting the mitochondrial internal apoptotic machinery.

NUP98 oncofusions in myeloid malignancies: An update on molecular mechanisms and therapeutic opportunities

Acute myeloid leukemia (AML) is an aggressive hematological malignancy with a heterogeneous molecular landscape. In the pediatric context, the NUP98 gene is a frequent target of chromosomal rearrangements that are linked to poor prognosis and unfavorable treatment outcomes in different AML subtypes. The translocations fuse NUP98 to a diverse array of partner genes, resulting in fusion proteins with novel functions. NUP98 fusion oncoproteins induce aberrant biomolecular condensation, abnormal gene expression programs, and re-wired protein interactions which ultimately cause alterations in the cell cycle and changes in cellular structures, all of which contribute to leukemia development. The extent of these effects is steered by the functional domains of the fusion partners and the influence of concomitant somatic mutations. In this review, we discuss the complex characteristics of NUP98 fusion proteins and potential novel therapeutic approaches for NUP98 fusion-driven AML.

Venetoclax: a new player in the treatment of children with high-risk myeloid malignancies?

ABSTRACT

Venetoclax selectively inhibits B-cell lymphoma 2 (BCL-2) and restores apoptotic signaling of hematologic malignant cells. Venetoclax, in combination with hypomethylating and low-dose cytotoxic agents, has revolutionized the management of older patients affected by acute myeloid leukemia (AML) and that of patients unfit to receive intensive chemotherapy. In a single phase 1 pediatric trial conducted on relapsed or refractory AML, the combination of venetoclax and intensive chemotherapy was shown to be safe and yielded promising response rates. In addition, several retrospective studies in children with AML reported that venetoclax, when combined with hypomethylating agents and cytotoxic drugs, seems to be a safe and efficacious bridge to transplant. The promising results on the use of venetoclax combinations in advanced myelodysplastic syndromes (MDS) and therapy-related MDS/AML have also been reported in small case series. This review summarizes the available current knowledge about venetoclax use in childhood high-risk myeloid neoplasms and discusses the possible integration of BCL-2 inhibition in the current treatment algorithm of these children. It also focuses on specific genetic subgroups potentially associated with response in preclinical and clinical studies.

Navigating Treatment Options and Communication in Relapsed Pediatric AML

Despite improved outcomes in newly diagnosed pediatric AML, relapsed disease remains a therapeutic challenge. Factors contributing to slow progress in improving outcomes include inherent challenges in pediatric clinical trial accrual and the scarcity of novel targeted/immunotherapy agents available for pediatric development. This paradigm is changing, however, as international collaboration grows in parallel with the development of promising targeted agents. In this review, we discuss the therapeutic landscape of relapsed pediatric AML, including conventional chemotherapy, targeted therapies, and the challenges of drug approvals in this patient population. We highlight current efforts to improve communication among academia, industry, and regulatory authorities and discuss the importance of international collaboration to improve access to new therapies. Among the therapeutic options, we highlight the approach to second hematopoietic stem cell transplant (HSCT) and discuss which patients are most likely to benefit from this potentially curative intervention. Importantly, we acknowledge the challenges in providing these high-risk interventions to our patients and their families and the importance of shared communication and decision making when considering early-phase clinical trials and second HSCT.

Clinical pharmacokinetics and pharmacodynamics of venetoclax, a selective B-cell lymphoma-2 inhibitor

Venetoclax, a highly potent BCL-2 inhibitor, is indicated for treatment of some hematologic malignancies as monotherapy, and/or in combination with other agents. Venetoclax pharmacokinetics has been extensively characterized in patients and healthy participants. After oral dosing, the median time to reach maximum plasma concentration ranged from 5 to 8 h and harmonic mean half-life ranged from 14 to 18 h. Food increases venetoclax bioavailability by 3-5-fold and venetoclax should be administered with food to ensure adequate and consistent bioavailability. Venetoclax is eliminated via cytochrome P450 (CYP)3A metabolism, and a negligible amount of unchanged drug is excreted in urine. Strong CYP3A/P-glycoprotein inhibitors increased venetoclax exposures (AUC) by 1.44- to 6.90-fold while a significant decrease (71%) has been observed when dosed with strong CYP3 inducers. Venetoclax does not inhibit or induce CYP enzymes or transporters. Venetoclax pharmacokinetics is not appreciably altered by age, weight, sex, but the exposure is up to twofold higher in participants from Asian countries. Mild-to-severe renal impairment or end-stage renal disease do not alter venetoclax exposures, and venetoclax is not cleared by dialysis. Although mild-to-moderate hepatic impairment does not affect venetoclax exposures, twofold higher exposure was observed in subjects with severe hepatic impairment. Venetoclax exposure is comparable across patients with different hematologic malignancies and healthy participants. Overall, venetoclax exposure is only affected by food and CYP3A modulators and is only higher in Asian subjects and subjects with severe hepatic impairment. Venetoclax exposure-response relationships are malignancy-dependent and can be different between monotherapy and combination therapy.

Venetoclax Combination Treatment of Acute Myeloid Leukemia in Adolescents and Young Adult Patients

Over the past two decades, the prognosis in adolescents and young adults (AYAs) diagnosed with acute myeloid leukemia (AML) has significantly improved. The standard intensive cytotoxic treatment approach for AYAs with AML, consisting of induction chemotherapy with anthracycline/cytarabine combination followed by consolidation chemotherapy or stem cell transplantation, has lately been shifting toward novel targeted therapies, mostly in the fields of clinical trials. One of the most recent advances in treating AML is the combination of the B-cell lymphoma 2 (Bcl-2) inhibitor venetoclax with hypomethylating agents, which has been studied in elderly populations and was approved by the Food and Drug Administration (FDA) for patients over 75 years of age or patients excluded from intensive chemotherapy induction schemas due to comorbidities. Regarding the AYA population, venetoclax combination therapy could be a therapeutic option for patients with refractory/relapsed (R/R) AML, although data from real-world studies are currently limited. Venetoclax is frequently used by AYAs diagnosed with advanced hematologic malignancies, mainly acute lymphoblastic leukemia and myelodysplastic syndromes, as a salvage therapeutic option with considerable efficacy and safety. Herein, we aim to summarize the evidence obtained from clinical trials and observational studies on venetoclax use in AYAs with AML. Based on the available evidence, venetoclax is a safe and effective therapeutic option for R/R AML AYA patients. However, further research in larger cohorts is needed to confirm these data, establishing the benefits of a venetoclax-based regimen for this special population.

Pediatric acute myeloid leukemia - novel approaches

PURPOSE OF REVIEW

Despite higher remission and survival rates than observed in adults, children with acute myeloid leukemia (AML) still suffer unacceptably high rates of treatment failure and late toxicities. Ongoing work aims to improve these long-term outcomes through improvements in the utilization of current therapies, the incorporation of novel chemotherapy agents, and improved use of current or novel cellular and immunotherapeutic approaches. In this review, we highlight recent advances and contextualize them within this evolving landscape.

RECENT FINDINGS

Novel agents such as the B-cell lymphoma 2 inhibitor venetoclax and the menin inhibitors have shown promising results with implications for large portions of the pediatric AML population. Older agents are being used in novel combinations (e.g. gemtuzumab ozogamicin) or are expanding into pediatrics after longer use in adults (e.g. Fms-like tyrosine kinase 3 inhibitors). Finally, immunotherapeutic approaches offer new options for patients with high-risk or relapsed disease.

SUMMARY

Recent findings have altered the landscape of pediatric AML therapy with exciting immediate and long-term implications. Ongoing studies may soon define this as standard as well. After many years in which few new therapies have become available for children with AML, recent and upcoming advances may soon dramatically alter the therapeutic landscape.

Characteristics and treatment results of refractory and relapsed acute myeloid leukaemia in paediatric patients treated in Polish Paediatric Leukaemia/Lymphoma Study Group institutions according to the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 and a review of novel treatment possibilities in paediatric acute myeloid leukaemia

Introduction

This study aimed to present the clinical features and results of treatment of patients diagnosed with refractory or relapsed acute myeloid leukaemia (AML) in Polish Paediatric Leukaemia/Lymphoma Study Group (PPL/LSG) institutions, treated in accordance with the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012, as their first-line therapy.

Material and methods

The outcome data of 10 patients with refractory AML (median age 9.5 years) and 30 with relapsed AML (median age 12 years) were analysed retrospectively. Re-induction was usually based on idarubicin, fludarabine, and cytarabine along with allogeneic haematopoietic stem cell transplant (allo-HSCT) in 5 patients with refractory AML and 7 relapsed AML children.

Results

37.5% (3/8) of refractory AML patients achieved second complete remission second complete remission (CRII). One of ten patients (1/10; 10%) was alive and stayed in complete remission for 34 months after the allo-HSCT. The probability of 3-year event-free survival (pEFS) in this group was 0.125 ±0.11. In the group of relapsed AML patients, the CRII was achieved in 9 patients (34%), and the probability of survival was: pEFS = 0.24 ±0.08; probability overall survival (pOS) = 0.34 ±0.09, with significantly better results achieved in patients who underwent allo-HSCT (pOS = 0.54 ±0.14 vs. 0.08 ±0.08, p < 0.0001).

Conclusions

The prognosis of refractory AML and the first AML recurrence in children who were first-line treated in PPL/LSG centres according to Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 is poor. Failures of re-induction treatment particularly result from difficulties in achieving remission. Allogeneic HSCT improves prognosis in children with refractory and first recurrent AML, under the condition it is performed in complete remission. Novel therapeutic approaches are needed to increase the remission rate and improve the outcomes.

Targeted Therapies in Pediatric Acute Myeloid Leukemia - Evolving Therapeutic Landscape

Acute myeloid leukemia (AML) accounts for 25% of all leukemia diagnosis and is characterized by distinct cytogenetic and molecular profile. Advances in the understanding of the causative driver mutations, risk-based therapy and better supportive care have led to an overall improvement in survival with frontline therapy. Despite these improvements, a significant number fail either because of primary refractory disease to the conventional 7+3 combination of anthracyclines and cytosine arabinoside (Cytarabine; Ara-C) or experience relapse post remission. Salvage therapy is complicated by the cardiotoxicity driven limitations on the reuse of anthracyclines and development of resistance to cytarabine. In this chapter authors will review the recent studies with targeted agents for refractory AML including targets for immunotherapeutic strategies.

Treatment outcomes of childhood PICALM::MLLT10 acute leukaemias

The prognostic impact of PICALM::MLLT10 status in childhood leukaemia is not well described. Ten International Berlin Frankfurt Münster-affiliated study groups and the Children's Oncology Group collaborated in this multicentre retrospective study. The presence of the PICALM::MLLT10 fusion gene was confirmed by fluorescence in situ hybridization and/or RNA sequencing at participating sites. Ninety-eight children met the study criteria. T-cell acute lymphoblastic leukaemia (T-ALL) and acute myeloid leukaemia (AML) predominated 55 (56%) and 39 (40%) patients, respectively. Most patients received a chemotherapy regimen per their disease phenotype: 58% received an ALL regimen, 40% an AML regimen and 1% a hybrid regimen. Outcomes for children with PICALM::MLLT10 ALL were reasonable: 5-year event-free survival (EFS) 67% and 5-year overall survival (OS) 76%, but children with PICALM::MLLT10 AML had poor outcomes: 5-year EFS 22% and 5-year OS 26%. Haematopoietic stem cell transplant (HSCT) did not result in a significant improvement in outcomes for PICALM::MLLT10 AML: 5-year EFS 20% for those who received HSCT versus 23% for those who did not (p = 0.6) and 5-year OS 37% versus 36% (p = 0.7). In summary, this study confirms that PICALM::MLLT10 AML is associated with a dismal prognosis and patients cannot be salvaged with HSCT; exploration of novel therapeutic options is warranted.

Relapsed/Refractory T- Acute Lymphoblastic Leukemia - Current Options and Future Directions

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. The T-cell subtype (T-ALL) accounts for 10-15% of pediatric ALL cases and has been historically associated with outcomes inferior to those of B-cell ALL (B-ALL). The prognosis of T-ALL has significantly improved with contemporary intensive pediatric regimens. However, most children with relapsed T-ALL have dismal outcomes and fewer therapeutic salvage options than those available for B-ALL. After demonstrating efficacy in relapsed T-ALL, nelarabine is being increasingly incorporated into frontline T-ALL regimens. The development of genomic sequencing has led to the identification of new T-ALL subgroups and potential targeted therapeutic approaches which could improve patients' outcomes and reduce the toxicity associated with current therapy. Immunotherapy and cellular therapy regimens are also under early investigation in T-cell malignancies. This review outlines the clinical and biological characteristics of T-ALL and provides an overview of novel treatment options for refractory and relapsed T-ALL.

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.

CBFA2T3::GLIS2 pediatric acute megakaryoblastic leukemia is sensitive to BCL-XL inhibition by navitoclax and DT2216

ABSTRACT

Acute megakaryoblastic leukemia (AMKL) is a rare, developmentally restricted, and highly lethal cancer of early childhood. The paucity and hypocellularity (due to myelofibrosis) of primary patient samples hamper the discovery of cell- and genotype-specific treatments. AMKL is driven by mutually exclusive chimeric fusion oncogenes in two-thirds of the cases, with CBFA2T3::GLIS2 (CG2) and NUP98 fusions (NUP98r) representing the highest-fatality subgroups. We established CD34+ cord blood-derived CG2 models (n = 6) that sustain serial transplantation and recapitulate human leukemia regarding immunophenotype, leukemia-initiating cell frequencies, comutational landscape, and gene expression signature, with distinct upregulation of the prosurvival factor B-cell lymphoma 2 (BCL2). Cell membrane proteomic analyses highlighted CG2 surface markers preferentially expressed on leukemic cells compared with CD34+ cells (eg, NCAM1 and CD151). AMKL differentiation block in the mega-erythroid progenitor space was confirmed by single-cell profiling. Although CG2 cells were rather resistant to BCL2 genetic knockdown or selective pharmacological inhibition with venetoclax, they were vulnerable to strategies that target the megakaryocytic prosurvival factor BCL-XL (BCL2L1), including in vitro and in vivo treatment with BCL2/BCL-XL/BCL-W inhibitor navitoclax and DT2216, a selective BCL-XL proteolysis-targeting chimera degrader developed to limit thrombocytopenia in patients. NUP98r AMKL were also sensitive to BCL-XL inhibition but not the NUP98r monocytic leukemia, pointing to a lineage-specific dependency. Navitoclax or DT2216 treatment in combination with low-dose cytarabine further reduced leukemic burden in mice. This work extends the cellular and molecular diversity set of human AMKL models and uncovers BCL-XL as a therapeutic vulnerability in CG2 and NUP98r AMKL.

The PedAL/EuPAL Project: A Global Initiative to Address the Unmet Medical Needs of Pediatric Patients with Relapsed or Refractory Acute Myeloid Leukemia

The prognosis of children with acute myeloid leukemia (AML) has improved incrementally over the last few decades. However, at relapse, overall survival (OS) is approximately 40-50% and is even lower for patients with chemo-refractory disease. Effective and less toxic therapies are urgently needed for these children. The Pediatric Acute Leukemia (PedAL) program is a strategic global initiative that aims to overcome the obstacles in treating children with relapsed/refractory acute leukemia and is supported by the Leukemia and Lymphoma Society in collaboration with the Children's Oncology Group, the Innovative Therapies for Children with Cancer consortium, and the European Pediatric Acute Leukemia (EuPAL) foundation, amongst others. In Europe, the study is set up as a complex clinical trial with a stratification approach to allocate patients to sub-trials of targeted inhibitors at relapse and employing harmonized response and safety definitions across sub-trials. The PedAL/EuPAL international collaboration aims to determine new standards of care for AML in a first and second relapse, using biology-based selection markers for treatment stratification, and deliver essential data to move drugs to front-line pediatric AML studies. An overview of potential treatment targets in pediatric AML, focused on drugs that are planned to be included in the PedAL/EuPAL project, is provided in this manuscript.

Venetoclax: A Game Changer in the Treatment of Younger AML Patients?

The combination approach based on venetoclax (VEN) with azacytidine (AZA) has significantly improved outcomes for elderly patients with acute myeloid leukemia (AML). This innovative approach has led to higher rates of overall response, measurable residual disease (MRD)-negative remissions, and overall survival compared with AZA monotherapy. As a result, this combination has emerged as the gold-standard treatment for elderly or unfit patients with AML who are not eligible for intensive therapy. In younger, fit patients with AML, intensive induction and consolidation chemotherapy is commonly used as a first-line approach; however, relapse continues to be the main reason for treatment failure in approximately 30-40% of patients. Efforts to improve MRD-negative response rates and to facilitate the transition to allogeneic hematopoietic stem cell transplantation, particularly in high-risk AML, have inspired trials exploring the combination of intensive chemotherapy with targeted agents. VEN, a first-in-class anti-BCL2 agent, combined with intensive chemotherapy regimens has shown deep MRD-negative remissions, producing prolonged event-free survival and enhancing the transition to allogeneic transplant in first-complete-remission patients. These benefits support the incremental advantages of adding VEN to intensive chemotherapy approaches across ELN risk subcategories, and provides a robust benchmark to design future trials. In this review, we will discuss current studies assessing the efficacy of frontline regimens integrating VEN into intensive chemotherapy in younger patients with AML and specific molecularly defined subgroups.

Emerging and Future Targeted Therapies for Pediatric Acute Myeloid Leukemia: Targeting the Leukemia Stem Cells

Acute myeloid leukemia (AML) is a rare subtype of acute leukemia in the pediatric and adolescent population but causes disproportionate morbidity and mortality in this age group. Standard chemotherapeutic regimens for AML have changed very little in the past 3-4 decades, but the addition of targeted agents in recent years has led to improved survival in select subsets of patients as well as a better biological understanding of the disease. Currently, one key paradigm of bench-to-bedside practice in the context of adult AML is the focus on leukemia stem cell (LSC)-targeted therapies. Here, we review current and emerging immunotherapies and other targeted agents that are in clinical use for pediatric AML through the lens of what is known (and not known) about their LSC-targeting capability. Based on a growing understanding of pediatric LSC biology, we also briefly discuss potential future agents on the horizon.

Addition of venetoclax to myeloablative conditioning regimens for allogeneic hematopoietic stem cell transplantation in high-risk AML

BACKGROUND

Venetoclax monotherapy is an effective option for patients with acute myeloid leukemia (AML). Venetoclax has also been used in non-myeloablative conditioning allogeneic hematopoietic stem cell transplantation (allo-HSCT) for high-risk AML with a tolerable toxicity profile. However, the efficacy and safety of a venetoclax-containing myeloablative conditioning (MAC) allo-HSCT regimen for high-risk AML have not been evaluated.

OBJECTIVE

To evaluate the safety and efficacy of a MAC regimen containing venetoclax for high-risk AML.

STUDY DESIGN

From 25 February 2021 to 4 September 2022, a total of 31 patients with high-risk AML who underwent allo-HSCT and a MAC regimen with venetoclax were analyzed.

RESULTS

At the time of transplantation, 21 patients were in first complete remission (CR1), 4 were in a second complete remission (CR2), and 6 in non-remission (NR). Twenty-four patients (77.4%) were minimal residual disease (MRD)-positive before transplant. The FLT3-ITD gene mutation was present in 51.6% of patients. NUP98 rearrangement, MLL rearrangement or MLL-PTD and DEK::CAN fusion genes were found in 5 (16.1%), 7(22.6%) and 2 (6.5%) patients, respectively. Twenty-nine (93.6%) patients underwent haploidentical allo-HSCT. The median follow-up time was 278 days (range: 52-632 days). The 100-day cumulative incidence of grade 3 to 4 acute graft-versus-host disease (aGVHD) was 16.1% (95%CI, 7.2-36.0%). The 180-day cumulative incidence of moderate to severe chronic graft-versus-host disease (cGVHD) was 7.1% (95%CI, 1.9-26.9%). Cumulative incidence of 100-day cytomegalovirus (CMV) viraemia and 100-day Epstein-Barr virus (EBV) viraemia was 61.6% (95%CI, 46.5-81.4%) and 3.2% (95%CI, 0.4-22.2%), respectively. The 600-day overall survival (OS) and leukemia-free survival (LFS) were 80.9% (95%CI, 63.5-93.6%) and 81.3% (95%CI, 64.2-93.7%), respectively. The 600-day relapse incidence (RI) and non-relapse mortality (NRM) was 6.9% (95%CI, 1.8-26.3%) and 11.7% (95%CI, 3.9-35.0%).

CONCLUSION

Our study shows that the addition of venetoclax to a MAC allo-HSCT was feasible, safe and effective for high-risk AML patients.

Recent Updates in Venetoclax Combination Therapies in Pediatric Hematological Malignancies

Venetoclax is a strongly effective B-cell lymphoma-2 inhibitor (BCL-2) with an ability to selectively restore the apoptotic potential of cancerous cells. It has been proven that in combination with immunotherapy, targeted therapies, and lower-intensity therapies such as hypomethylating agents (HMAs) or low-dose cytarabine (LDAC), the drug can improve overall outcomes for adult patients with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and multiple myeloma (MM), amongst other hematological malignancies, but its benefit in pediatric hematology remains unclear. With a number of preclinical and clinical trials emerging, the newest findings suggest that in many cases of younger patients, venetoclax combination treatment can be well-tolerated, with a safety profile similar to that in adults, despite often leading to severe infections. Studies aim to determine the activity of BCL-2 inhibitor in the treatment of both primary and refractory acute leukemias in combination with standard and high-dose chemotherapy. Although more research is required to identify the optimal venetoclax-based regimen for the pediatric population and its long-term effects on patients' outcomes, it can become a potential therapeutic agent for pediatric oncology.

A Review of Childhood Acute Myeloid Leukemia: Diagnosis and Novel Treatment

Acute myeloid leukemia (AML) is the second most common hematologic malignancy in children. The incidence of childhood AML is much lower than acute lymphoblastic leukemia (ALL), which makes childhood AML a rare disease in children. The role of genetic abnormalities in AML classification, management, and prognosis prediction is much more important than before. Disease classifications and risk group classifications, such as the WHO classification, the international consensus classification (ICC), and the European LeukemiaNet (ELN) classification, were revised in 2022. The application of the new information in childhood AML will be upcoming in the next few years. The frequency of each genetic abnormality in adult and childhood AML is different; therefore, in this review, we emphasize well-known genetic subtypes in childhood AML, including core-binding factor AML (CBF AML), KMT2Ar (KMT2A/11q23 rearrangement) AML, normal karyotype AML with somatic mutations, unbalanced cytogenetic abnormalities AML, NUP98 11p15/NUP09 rearrangement AML, and acute promyelocytic leukemia (APL). Current risk group classification, the management algorithm in childhood AML, and novel treatment modalities such as targeted therapy, immune therapy, and chimeric antigen receptor (CAR) T-cell therapy are reviewed. Finally, the indications of hematopoietic stem cell transplantation (HSCT) in AML are discussed.

Venetoclax plus cyclophosphamide and topotecan in heavily pre-treated relapsed metastatic neuroblastoma: a single center case series

The prognosis of relapsed/refractory (R/R) neuroblastoma (NB) is dismal, calling for new therapeutic strategies. Venetoclax (VEN) is a highly selective, potent, orally bioavailable, BCL-2 inhibitor small-molecule that showed a synergistic effect with cyclophosphamide and topotecan (Cy-Topo) in murine NB models. Our aim was to evaluate the feasibility of VEN plus Cy-Topo in children with R/R NB. Four patients, who had previously failed > 3 lines of treatment, were treated with VEN plus Cy-Topo based on a 28-day schedule in an outpatient setting. BCL-2 expression in immunochemistry on tumor samples at relapse and the BCL2 gene status was evaluated in all patients. The main toxicity was hematological, with grade 4 neutropenia and thrombocytopenia occurring in all courses and leading to transient VEN discontinuation. Grade 3 oral mucositis was observed in 1/8 courses. No other grade 2-4 toxicities were observed. BCL-2 was expressed in all tumors, while no molecular abnormalities in the BCL-2 genes were detected. A stable disease was observed in all patients, without any progression during the study period. VEN plus Cy-Topo is well tolerated, with encouraging results that may be improved by testing the schedule in less advanced patients.

Expert consensus guidelines for the prophylaxis and management of tumor lysis syndrome in the United States: Results of a modified Delphi panel

INTRODUCTION

Tumor lysis syndrome (TLS), which occurs spontaneously or in response to anticancer treatment, results in the release of intracellular potassium, phosphorus, and nucleic acids into the bloodstream, which results in secondary clinical complications that may be fatal. Prior TLS guidelines do not take into consideration potent novel oncologic agents or contemporary treatment paradigms with increased risk of TLS. Thus, a modified Delphi panel of experts was convened to provide an update for TLS management guidelines based upon a combination of supporting literature and practice consensus.

METHODS

A three-round modified Delphi process was implemented. For round 1, nine expert panelists completed a web-based questionnaire developed using published literature. In round 2, panelists were asked to reconsider their answers to questions that did not reach consensus (defined as ≥ 66% agreement among voting panelists). Round 3 was an unblinded, moderated virtual meeting to discuss any remaining questions that did not reach consensus.

RESULTS

Detailed recommendations are given for prophylaxis, monitoring, and management of TLS risks and complications, with hydration being a key element of TLS prophylaxis and management. Guidelines for the management of acute effects of TLS and prevention of long-term renal effects include management of hyperkalemia, hypocalcemia, hyperphosphatemia, and hyperuricemia.

DISCUSSION

Although the control of uric acid levels is quite effective with currently available agents, panelists emphasize the importance of monitoring and treating other dangerous electrolyte abnormalities such as hyperkalemia and hyperphosphatemia. Guidelines from this modified Delphi panel should aid clinicians in preventing and managing TLS.

Treatment of recurrent pediatric myelodysplastic syndrome post hematopoietic stem cell transplantation

Treatment of recurrent myelodysplastic syndrome (MDS) after hematopoietic cell transplantation (HCT) remains challenging. We present a 4-year-old girl experiencing early MDS relapse post-HCT treated with a multimodal strategy encompassing a second HCT and innovative targeted therapies. We underscore the potential of a comprehensive treatment approach in managing recurrent pediatric MDS.

Increased MCL1 dependency leads to new applications of BH3-mimetics in drug-resistant neuroblastoma

BACKGROUND

Neuroblastoma is a paediatric cancer that is characterised by poor prognosis for chemoresistant disease, highlighting the need for better treatment options. Here, we asked whether BH3-mimetics inhibiting BCL2 proteins may eliminate chemoresistant neuroblastoma cells.

METHODS

We utilised cisplatin-adapted neuroblastoma cell lines as well as patient tissues before and after relapse to study alterations of BCL2 proteins upon chemoresistance.

RESULTS

In a direct comparison of cisplatin-resistant cells we identified a prominent loss of sensitivity to BCL2/BCL-XL inhibitors that is associated with an increase in MCL1 dependency and high expression of MCL1 in patient tumour tissues. Screening of FDA-approved anti-cancer drugs in chemoresistant cells identified therapeutics that may be beneficial in combination with the clinically tested BH3-mimetic ABT263, but no synergistic drug interactions with the selective MCL1 inhibitor S63845. Further exploration of potential treatment options for chemoresistant neuroblastoma identified immunotherapy based on NK cells as highly promising, since NK cells are able to efficiently kill both parental and chemoresistant cells.

CONCLUSIONS

These data highlight that the application of BH3-mimetics may differ between first line treatment and relapsed disease. Combination of NK cell-based immunotherapy with BH3-mimetics may further increase killing of chemoresistant neuroblastoma, outlining a new treatment strategy for relapsed neuroblastoma.

AML under the Scope: Current Strategies and Treatment Involving FLT3 Inhibitors and Venetoclax-Based Regimens

Acute myeloid leukemia (AML) is a disease that mainly affects elderly patients who are more often unfit for intensive chemotherapy (median age of diagnosis is 68). The regimens, including venetoclax, a highly specific BCL-2 (B-cell lymphoma-2) inhibitor, are a common alternative because of their safer profile and fewer side effects. However, the resistance phenomenon of leukemic cells necessitates the search for drugs that would help to overcome the resistance and improve treatment outcomes. One of the resistance mechanisms takes place through the upregulation of MCL-1 and BCL-XL, preventing BAX/BAK-driven MOMP (mitochondrial outer membrane permeabilization), thus stopping the apoptosis process. Possible partners for BCL-2 inhibitors may include inhibitors from the FLT3i (FMS-like tyrosine kinase-3 inhibitor) group. They resensitize cancer cells through the downregulation of MCL-1 expression in the FLT3 mutated cells, resulting in the stronger efficacy of BCL-2 inhibitors. Also, they provide an additional pathway for targeting the clonal cell. Both preclinical and clinical data suggest that the combination might show a synergistic effect and improve patients' outcomes. The aim of this review is to determine whether the combination of venetoclax and FLT3 inhibitors can impact the therapeutic approaches and what other agents they can be combined with.

Pediatric acute myeloid leukemia: Insight into genetic landscape and novel targeted approaches

Acute myeloid leukemia (AML) is a very heterogeneous hematological malignancy that accounts for approximately 20% of all pediatric leukemia cases. The outcome of pediatric AML has improved over the last decades, with overall survival rates reaching up to 70%. Still, AML is among the leading types of pediatric cancers by its high mortality rate. Modulation of standard therapy, like chemotherapy intensification, hematopoietic stem cell transplantation and optimized supportive care, could only get this far, but for the significant improvement of the outcome in pediatric AML, development of novel targeted therapy approaches is necessary. In recent years the advances in genomic techniques have greatly expanded our knowledge of the AML biology, revealing molecular landscape and complexity of the disease, which in turn have led to the identification of novel therapeutic targets. This review provides a brief overview of the genetic landscape of pediatric AML, and how it's used for precise molecular characterization and risk stratification of the patients, and also for the development of effective targeted therapy. Furthermore, this review presents recent advances in molecular targeted therapy and immunotherapy with an emphasis on the therapeutic approaches with significant clinical benefits for pediatric AML.

Relapsed pediatric acute myeloid leukaemia: state-of-the-art in 2023

Although outcomes of children and adolescents with newly diagnosed acute myeloid leukemia (AML) have improved significantly over the past two decades, more than one-third of patients continue to relapse and experience suboptimal long-term outcomes. Given the small numbers of patients with relapsed AML and historical logistical barriers to international collaboration including poor trial funding and drug availability, the management of AML relapse has varied among pediatric oncology cooperative groups with several salvage regimens utilized and a lack of universally defined response criteria. The landscape of relapsed pediatric AML treatment is changing rapidly, however, as the international AML community harnesses collective knowledge and resources to characterize the genetic and immunophenotypic heterogeneity of relapsed disease, identify biological targets of interest within specific AML subtypes, develop new precision medicine approaches for collaborative investigation in early-phase clinical trials, and tackle challenges of universal drug access across the globe. This review provides a comprehensive overview of progress achieved to date in the treatment of pediatric patients with relapsed AML and highlights modern, state-of-the-art therapeutic approaches under active and emerging clinical investigation that have been facilitated by international collaboration among academic pediatric oncologists, laboratory scientists, regulatory agencies, pharmaceutical partners, cancer research sponsors, and patient advocates.

Risk-Stratified Therapy for Pediatric Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is the second most common type of leukemia in children. Recent advances in high-resolution genomic profiling techniques have uncovered the mutational landscape of pediatric AML as distinct from adult AML. Overall survival rates of children with AML have dramatically improved in the past 40 years, currently reaching 70% to 80% in developed countries. This was accomplished by the intensification of conventional chemotherapy, improvement in risk stratification using leukemia-specific cytogenetics/molecular genetics and measurable residual disease, appropriate use of allogeneic hematopoietic stem cell transplantation, and improvement in supportive care. However, the principle therapeutic approach for pediatric AML has not changed substantially for decades and improvement in event-free survival is rather modest. Further refinements in risk stratification and the introduction of emerging novel therapies to contemporary therapy, through international collaboration, would be key solutions for further improvements in outcomes.

Real-world experience with selinexor-containing chemotherapy-free or low-dose chemotherapy regimens for patients with relapsed/refractory acute myeloid leukemia and myeloid sarcoma

Introduction: Treatment of relapsed or refractory acute myeloid leukemia (R/R AML) and myeloid sarcoma (MS) has presented challenges for decades. Studies on selinexor in combination with various standard or intensive chemotherapy regimens for the treatment of R/R AML have demonstrated promising results. This study aimed to evaluate the efficacy and safety of chemotherapy-free or low-dose chemotherapy regimens with selinexor for R/R AML and MS patients. Methods: Ten patients with R/R AML or MS who received chemotherapy-free or low-dose chemotherapy regimens in combination with selinexor at Tongji Hospital from October 2021 to August 2022 were included in this study. The primary endpoint was overall response rate (ORR) and secondary endpoints included complete remission (CR), CR with incomplete hematological recovery (CRi), partial remission (PR), transplantation rate, and safety. Results: All patients were evaluable for response, achieving CR in four (40.0%) patients and CRi in two (20.0%) patients for a total CR/CRi of 60.0%. The ORR was 80.0% when patients with PR were included. Five (50.0%) patients underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) after treatment with selinexor-containing regimens. At the end of the follow-up, seven (70.0%) patients were alive, and three patients died of transplant-related complications or disease progression. The most frequently reported nonhematologic adverse events (AEs) in patients were grade 1 or 2 asymptomatic hyponatremia. Conclusion: The chemotherapy-free or low-dose chemotherapy regimens in combination with selinexor for R/R AML are feasible and tolerable and provide an opportunity for patients to receive transplantation.

Curing childhood cancer the "Natural" Way: Nature as the source of chemotherapy agents

For many centuries, products of natural origin from plants, marine, microbes and soil micro-organisms have been studied by numerous researchers across the world to yield many of the chemotherapeutic agents we use in this modern era. There has been a tremendous gain in knowledge from various screening and separating techniques which led to the discovery of biologically active small molecules from natural products. Preclinical studies testing the antitumor activities of these agents against tumor cell lines and xenograft animal models were the gateway to the clinical trials in humans leading to the approval of these agents that are in clinical use today. This review summarizes how various chemotherapeutic agents were discovered from products of natural origin, their preclinical development, and their indications in both pediatric and adult oncology. Many of these natural products have contributed to the very high cure rates of both pediatric leukemias and solid tumors.

Venetoclax in combination with chemotherapy as treatment for pediatric advanced hematologic malignancies

BACKGROUND

Venetoclax is frequently used as salvage treatment in pediatric, adolescent, and young adult (AYA) patients with advanced hematologic malignancies. However, more data are needed from real-world studies to guide the safe and appropriate use of venetoclax in this population.

PROCEDURE

We retrospectively reviewed the medical records of all patients diagnosed with hematologic malignancies less than 30 years of age treated with venetoclax outside of clinical trials at the University of California San Francisco Benioff Children's Hospitals from 2016 to 2022.

RESULTS

We identified 13 patients (acute myeloid leukemia, n = 8; B-acute lymphoblastic leukemia, n = 3; myelodysplastic syndrome, n = 2) aged 4 months to 27 years. A median of 3 prior lines of therapy weregiven (range 0-5). All patients received venetoclax in combination with either a hypomethylating agent or conventional chemotherapy. Three (23%) patients achieved complete remission (CR); two (15%) achieved partial remission (PR); 3 (23%) had stable disease (SD), and five (42%) had progressive disease. Median survival and time to progression from venetoclax initiation was 9 months (range 2.5-52 months) and 3 months (range 2 weeks to 7.5 months), respectively. Six patients (46%) developed grade 3 or higher infections while receiving venetoclax, including bacteremia due to atypical organisms, invasive pulmonary infections with Aspergillus, cytomegalovirus (CMV) viremia, skin infections, and encephalitis with bacterial brain abscesses.

CONCLUSIONS

Venetoclax in combination with hypomethylating agents or cytotoxic chemotherapy was effective in a subset of pediatric/AYA patients with advanced hematologic malignancies, but multiple severe infections were observed, particularly among patients who received venetoclax in combination with chemotherapy. Prospective studies will be required to determine the optimal dose and duration of venetoclax in this population.

Venetoclax Combined with Azacitidine and Homoharringtonine in Relapsed/Refractory AML: A Multicenter, Phase 2 Trial

BACKGROUND

Relapsed or refractory acute myeloid leukemia (R/R AML) has a dismal prognosis. The aim of this study was to investigate the activity and tolerability of venetoclax combined with azacitidine plus homoharringtonine (VAH) regimen for R/R AML.

METHODS

This phase 2 trial was done at ten hospitals in China. Eligible patients were R/R AML (aged 18-65 years) with an Eastern Cooperative Oncology Group performance status of 0-2. Patients received venetoclax (100 mg on day 1, 200 mg on day 2, and 400 mg on days 3-14) and azacitidine (75 mg/m² on days 1-7) and homoharringtonine (1 mg/m² on days 1-7). The primary endpoint was composite complete remission rate [CRc, complete response (CR) plus complete response with incomplete blood count recovery (CRi)] after 2 cycles of treatment. The secondary endpoints include safety and survival.

RESULTS

Between May 27, 2020, and June 16, 2021, we enrolled 96 patients with R/R AML, including 37 primary refractory AML and 59 relapsed AML (16 relapsed after chemotherapy and 43 after allo-HSCT). The CRc rate was 70.8% (95% CI 60.8-79.2). In the patients with CRc, measurable residual disease (MRD)-negative was attained in 58.8% of CRc patients. Accordingly, overall response rate (ORR, CRc plus partial remission (PR)) was 78.1% (95% CI 68.6-85.4). At a median follow-up of 14.7 months (95% CI 6.6-22.8) for all patients, median overall survival (OS) was 22.1 months (95% CI 12.7-Not estimated), and event-free survival (EFS) was 14.3 months (95% CI 7.0-Not estimated). The 1-year OS was 61.5% (95% CI 51.0-70.4), and EFS was 51.0% (95% CI 40.7-60.5). The most common grade 3-4 adverse events were febrile neutropenia (37.4%), sepsis (11.4%), and pneumonia (21.9%).

CONCLUSIONS

VAH is a promising and well-tolerated regimen in R/R AML, with high CRc and encouraging survival. Further randomized studies are needed to be explored. Trial registration clinicaltrials.gov identifier: NCT04424147.

Venetoclax Use in Paediatric Haemato-Oncology Centres in Poland: A 2022 Survey

Venetoclax, the best established BH3-mimetic, is a practice-changing proapoptotic drug in blood cancers in adults. In paediatrics the data are fewer but exciting results were recently presented in relapsed or refractory leukaemias demonstrating significant clinical activity. Importantly, the in-terventions could be potentially molecularly guided as vulnerabilities to BH3-mimetics were re-ported. Currently venetoclax is not incorporated into paediatric treatment schedules in Poland but it has been already used in patients that failed conventional therapy in Polish paediatric haemato-oncology departments. The aim of the study was to gather clinical data and correlates of all paediatric patients treated so far with venetoclax in Poland. We set out to gather this experience to help choose the right clinical context for the drug and stimulate further research. The questionnaire regarding the use of venetoclax was sent to all 18 Polish paediatric haemato-oncology centres. The data as available in November 2022 were gathered and analysed for the diagnoses, triggers for the intervention, treatment schedules, outcomes and molecular associations. We received response from 11 centres, 5 of which administered venetoclax to their patients. Clinical benefit, in most cases consistent with hematologic complete remission (CR), was reported in 5 patients out of ten, whereas 5 patient did not show clinical benefit from the intervention. Importantly, patients with CR included subtypes expected to show venetoclax vulnerability, such as poor-prognosis ALL with TCF::HLF fusion. We believe BH3-mimetics have clinical activity in children and should be available to pae-diatric haemato-oncology practitioners in well-selected applications.

Epigenomic machinery regulating pediatric AML: clonal expansion mechanisms, therapies, and future perspectives

Acute myeloid leukemia (AML) is a heterogeneous disease with a genetic, epigenetic, and transcriptional etiology mainly presenting somatic and germline abnormalities. AML incidence rises with age but can also occur during childhood. Pediatric AML (pAML) accounts for 15-20% of all pediatric leukemias and differs considerably from adult AML. Next-generation sequencing technologies have enabled the research community to "paint" the genomic and epigenomic landscape in order to identify pathology-associated mutations and other prognostic biomarkers in pAML. Although current treatments have improved the prognosis for pAML, chemoresistance, recurrence, and refractory disease remain major challenges. In particular, pAML relapse is commonly caused by leukemia stem cells that resist therapy. Marked patient-to-patient heterogeneity is likely the primary reason why the same treatment is successful for some patients but, at best, only partially effective for others. Accumulating evidence indicates that patient-specific clonal composition impinges significantly on cellular processes, such as gene regulation and metabolism. Although our understanding of metabolism in pAML is still in its infancy, greater insights into these processes and their (epigenetic) modulation may pave the way toward novel treatment options. In this review, we summarize current knowledge on the function of genetic and epigenetic (mis)regulation in pAML, including metabolic features observed in the disease. Specifically, we describe how (epi)genetic machinery can affect chromatin status during hematopoiesis, leading to an altered metabolic profile, and focus on the potential value of targeting epigenetic abnormalities in precision and combination therapy for pAML. We also discuss the possibility of using alternative epidrug-based therapeutic approaches that are already in clinical practice, either alone as adjuvant treatments and/or in combination with other drugs.

Venetoclax for Acute Myeloid Leukemia in Pediatric Patients: A Texas Medical Center Experience

The BCL-2 inhibitor venetoclax improves survival for adult patients with acute myeloid leukemia (AML) in combination with lower-intensity therapies, but its benefit in pediatric patients with AML remains unclear. We retrospectively reviewed two Texas Medical Center institutions’ experience with venetoclax in 43 pediatric patients with AML; median age 17 years (range, 0.6–21). This population was highly refractory; 44% of patients (n = 19) had ≥3 prior lines of therapy, 37% (n = 16) had received a prior bone marrow transplant, and 81% (n = 35) had unfavorable genetics KMT2A (n = 17), WT1 (n = 13), FLT3-ITD (n = 10), monosomy 7 (n = 5), TP53 (n = 3), Inv(3) (n = 3), IDH1/2 (n = 2), monosomy 5 (n = 1), NUP98 (n = 1) and ASXL1 (n = 1). The majority (86%) received venetoclax with a hypomethylating agent. Grade 3 or 4 adverse events included febrile neutropenia in 37% (n = 16), non-febrile neutropenia in 12% (n = 5), anemia in 14% (n = 6), and thrombocytopenia in 14% (n = 6). Of 40 patients evaluable for response, 10 patients (25%) achieved complete response (CR), 6 patients (15%) achieved CR with incomplete blood count recovery (CRi), and 2 patients (5%) had a partial response, (CR/CRi composite = 40%; ORR = 45%). Eleven (25%) patients received a hematopoietic stem cell transplant following venetoclax combination therapy, and six remain alive (median follow-up time 33.6 months). Median event-free survival and overall survival duration was 3.7 months and 8.7 months, respectively. Our findings suggest that in pediatric patients with AML, venetoclax is well-tolerated, with a safety profile similar to that in adults. More studies are needed to establish an optimal venetoclax-based regimen for the pediatric population.

Genetic characteristics predict response to venetoclax plus hypomethylating agents in relapsed or refractory acute myeloid leukemia

BACKGROUND

The heterogeneity of relapsed or refractory (R/R) acute myeloid leukemia (AML) leads to no response to venetoclax (VEN)-based therapy in more than half of the patients. Genetic characteristics are considered important predictors for response to treatment in adults with AML. However, the association of genetic characteristics with outcomes receiving VEN-based therapy is incompletely understood in R/R AML.

OBJECTIVE

To evaluate the efficacy of VEN combined with hypomethylating agents (HMA) and identify the potential genetic predictors of response in R/R AML.

METHODS

A total of 150 R/R AML patients treated with VEN combined with HMA were enrolled in this retrospective study. Outcomes of the response and overall survival (OS) were analyzed. The predictors of response and OS were analyzed by logistic regression or Cox proportional hazards model.

RESULTS

With a median of two (range, 1-4) cycles of therapy, the overall response rate was 56.2%, including 22.0% complete remission (CR), 21.3% CR with incomplete hematologic recovery, 2.0% morphologic leukemia-free state, and 10.7% partial remission, in which 25 patients achieved measurable residual disease (MRD)-negative response. With a median follow-up of 11.2 [95% confidence interval (CI), 7.2-14.8] months, 1- and 2-year OS were 46.9% (95% CI, 37.8%-58.1%) and 38.9% (95% CI, 28.7%-52.9%), respectively. Adverse cytogenetics and European Leukemia Net (ELN) risk predicted inferior response to VEN-based therapy. Mutations in IDH1/2, NPM1, ASXL1, and chromatin-cohesin genes predicted superior response to VEN-based therapy, whereas mutations in active signaling genes such as FLT3-ITD and K/NRAS predicted inferior response.

CONCLUSION

VEN combined with HMA was effective with R/R AML patients, and the response to treatment was associated with genetic characteristics.

High caspase 3 and vulnerability to dual BCL2 family inhibition define ETO2::GLIS2 pediatric leukemia

Pediatric acute myeloid leukemia expressing the ETO2::GLIS2 fusion oncogene is associated with dismal prognosis. Previous studies have shown that ETO2::GLIS2 can efficiently induce leukemia development associated with strong transcriptional changes but those amenable to pharmacological targeting remained to be identified. By studying an inducible ETO2::GLIS2 cellular model, we uncovered that de novo ETO2::GLIS2 expression in human cells led to increased CASP3 transcription, CASP3 activation, and cell death. Patient-derived ETO2::GLIS2+ leukemic cells expressed both high CASP3 and high BCL2. While BCL2 inhibition partly inhibited ETO2::GLIS2+ leukemic cell proliferation, BH3 profiling revealed that it also sensitized these cells to MCL1 inhibition indicating a functional redundancy between BCL2 and MCL1. We further show that combined inhibition of BCL2 and MCL1 is mandatory to abrogate disease progression using in vivo patient-derived xenograft models. These data reveal that a transcriptional consequence of ETO2::GLIS2 expression includes a positive regulation of the pro-apoptotic CASP3 and associates with a vulnerability to combined targeting of two BCL2 family members providing a novel therapeutic perspective for this aggressive pediatric AML subgroup.

Repurposing Atovaquone as a Therapeutic against Acute Myeloid Leukemia (AML): Combination with Conventional Chemotherapy Is Feasible and Well Tolerated

Survival of pediatric AML remains poor despite maximized myelosuppressive therapy. The pneumocystis jiroveci pneumonia (PJP)-treating medication atovaquone (AQ) suppresses oxidative phosphorylation (OXPHOS) and reduces AML burden in patient-derived xenograft (PDX) mouse models, making it an ideal concomitant AML therapy. Poor palatability and limited product formulations have historically limited routine use of AQ in pediatric AML patients. Patients with de novo AML were enrolled at two hospitals. Daily AQ at established PJP dosing was combined with standard AML therapy, based on the Medical Research Council backbone. AQ compliance, adverse events (AEs), ease of administration score (scale: 1 (very difficult)-5 (very easy)) and blood/marrow pharmacokinetics (PK) were collected during Induction 1. Correlative studies assessed AQ-induced apoptosis and effects on OXPHOS. PDX models were treated with AQ. A total of 26 patients enrolled (ages 7.2 months-19.7 years, median 12 years); 24 were evaluable. A total of 14 (58%) and 19 (79%) evaluable patients achieved plasma concentrations above the known anti-leukemia concentration (>10 µM) by day 11 and at the end of Induction, respectively. Seven (29%) patients achieved adequate concentrations for PJP prophylaxis (>40 µM). Mean ease of administration score was 3.8. Correlative studies with AQ in patient samples demonstrated robust apoptosis, OXPHOS suppression, and prolonged survival in PDX models. Combining AQ with chemotherapy for AML appears feasible and safe in pediatric patients during Induction 1 and shows single-agent anti-leukemic effects in PDX models. AQ appears to be an ideal concomitant AML therapeutic but may require intra-patient dose adjustment to achieve concentrations sufficient for PJP prophylaxis.

Targeted Therapy With Venetoclax and Daratumumab as Part of HSCT Preparative Regimen in Children With Chemorefractory Acute Myeloid Leukemia

The long-term outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in chemorefractory acute myeloid leukemia (AML) remains suboptimal because of a high relapse rate. Enhancement of conditioning regimens by the incorporation of targeted anti-leukemia agents is a potential approach to improve the efficacy of HSCT. In a pilot trial and extended access cohort, we evaluated the safety and potential value of adding combinations of venetoclax and daratumumab to a preparative regimen among children with chemorefractory acute myeloid leukemia grafted with αβ T-cell-depleted peripheral blood stem cells. All 20 patients had active disease status of AML at the time of transplantation. The preparative regimen included myeloablative conditioning based on either total body irradiation or treosulfan. A haploidentical related donor was used as a graft source for all patients. Engraftment was not compromised, and no excess toxicity was noted. Minimal residual disease-negative complete remission was achieved in 17 patients (85%). The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 17%, and the cumulative incidence of chronic GVHD was 7%. At 2 years, nonrelapse mortality was 10%, relapse incidence was 46%, event-free survival was 44%, and overall survival was 65%. Our data show the possibility of safely adding targeted agents to conditioning regimens; however, no evidence of a significant improvement in long-term transplantation outcomes in this cohort of patients was observed.

Homoharringtonine-Based Induction Therapy Reduces the Recurrence Rate of Pediatric Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is an effective treatment for acute myeloid leukemia (AML). Pediatric patients with AML who relapse after HSCT have an extremely poor prognosis. We performed a retrospective study of pediatric patients diagnosed with AML from August 2015 to October 2019 who were treated with HSCT. Kaplan-Meier analyses were used to evaluate overall survival (OS), event-free survival (EFS), and cumulative recurrence rate (CRR). Cox regression analysis was used to determine the association between the baseline characteristics and relapse. A total of 37 pediatric patients met the inclusion criteria. Twenty-eight (75.7%) patients survived, and 9 (24.3%) patients died. The OS rates of AML patients treated with HSCT were 89.2% ± 5.1%, 75.7% ± 7.1%, and 75.7% ± 7.1% at 1, 3, and 5 years, respectively, and the CRRs were 11.4% ± 5.4%, 24.7% ± 7.7%, and 33.1% ± 10.4% at 1, 3, and 5 years after HSCT, respectively; four of nine children who relapsed after transplantation died. Induction with etoposide rather than homoharringtonine and fungal infections could be high-risk factors for recurrence after transplantation. The association between homoharringtonine-based induction therapy and a low recurrence rate persisted after adjusting for age, sex, risk stratification, fusion genes, and fungal infections. This study clarifies the clinical features and poor prognosis of post-transplant relapse in pediatric AML and indicates the urgent need for effective therapy for patients who relapse after HSCT.

Ex Vivo Drug Sensitivity Correlates with Clinical Response and Supports Personalized Therapy in Pediatric AML

Acute myeloid leukemia (AML) is a heterogeneous disease that accounts for ~20% of all childhood leukemias, and more than 40% of children with AML relapse within three years of diagnosis. Although recent efforts have focused on developing a precise medicine-based approach towards treating AML in adults, there remains a critical gap in therapies designed specifically for children. Here, we present ex vivo drug sensitivity profiles for children with de novo AML using an automated flow cytometry platform. Fresh diagnostic blood or bone marrow aspirate samples were screened for sensitivity in response to 78 dose conditions by measuring the reduction in leukemic blasts relative to the control. In pediatric patients treated with conventional chemotherapy, comprising cytarabine, daunorubicin and etoposide (ADE), ex vivo drug sensitivity results correlated with minimal residual disease (r = 0.63) and one year relapse-free survival (r = 0.70; AUROC = 0.94). In the de novo ADE analysis cohort of 13 patients, AML cells showed greater sensitivity to bortezomib/panobinostat compared with ADE, and comparable sensitivity between venetoclax/azacitidine and ADE ex vivo. Two patients showed a differential response between ADE and bortezomib/panobinostat, thus supporting the incorporation of ex vivo drug sensitivity testing in clinical trials to further evaluate the predictive utility of this platform in children with AML.

The evolution of targeted therapy in pediatric AML: gemtuzumab ozogamicin, FLT3/IDH/BCL2 inhibitors, and other therapies

Despite the maximum intensification of chemotherapy and the increased use of hematopoietic stem cell transplantation (HCT) in pediatric patients with acute myeloid leukemia (AML), nearly 40% of patients still experience relapse, and cure in this setting remains a significant challenge. Recent improvements in AML characterization, including advances in flow cytometry and comprehensive genomic sequencing, have led to a better understanding of AML biology and the identification of multiple potential therapeutic targets. Novel agents targeting genomic lesions, cell surface antigens, and other mechanisms that permit oncogenesis or immune escape are being incorporated into current treatment strategies or are under investigation in efforts to improve outcomes and decrease the toxicities and late effects associated with traditional intensive chemotherapeutic and HCT treatment. However, multiple challenges still exist, including the biologic and immunophenotypic heterogeneity of childhood AML, the differences in underlying biology as compared to adult AML, and the significant potential for on-target/off-tumor toxicity associated with therapies directed at targets common to myeloid cells, both leukemic and normal. This article reviews the current landscape of genomic and cell surface targets for children with AML with a focus on the currently available targeted therapeutic agents, those in active clinical investigation, and those still in development.