How I treat relapsed acute lymphoblastic leukemia in the pediatric population

Enrichment of cancer-predisposing germline variants in adult and pediatric patients with acute lymphoblastic leukemia

Despite recent progress in acute lymphoblastic leukemia (ALL) therapies, a significant subset of adult and pediatric ALL patients has a dismal prognosis. Better understanding of leukemogenesis and recognition of germline genetic changes may provide new tools for treating patients. Given that hematopoietic stem cell transplantation, often from a family member, is a major form of treatment in ALL, acknowledging the possibility of hereditary predisposition is of special importance. Reports of comprehensive germline analyses performed in adult ALL patients are scarce. Aiming at fulfilling this gap of knowledge, we investigated variants in 93 genes predisposing to hematologic malignancies and 70 other cancer-predisposing genes from exome data obtained from 61 adult and 87 pediatric ALL patients. Our results show that pathogenic (P) or likely pathogenic (LP) germline variants in genes associated with predisposition to ALL or other cancers are prevalent in ALL patients: 8% of adults and 11% of children. Comparison of P/LP germline variants in patients to population-matched controls (gnomAD Finns) revealed a 2.6-fold enrichment in ALL cases (CI 95% 1.5–4.2, p = 0.00071). Acknowledging inherited factors is crucial, especially when considering hematopoietic stem cell transplantation and planning post-therapy follow-up. Harmful germline variants may also predispose patients to excessive toxicity potentially compromising the outcome. We propose integrating germline genetics into precise ALL patient care and providing families genetic counseling.

Immunotherapy for Pediatric Acute Lymphoblastic Leukemia: Recent Advances and Future Perspectives

Pediatric acute lymphoblastic leukemia (ALL) is the most common subtype of childhood leukemia, which is characterized by the abnormal proliferation and accumulation of immature lymphoid cell in the bone marrow. Although the long-term survival rate for pediatric ALL has made significant progress over years with the development of contemporary therapeutic regimens, patients are still suffered from relapse, leading to an unsatisfactory outcome. Since the immune system played an important role in the progression and relapse of ALL, immunotherapy including bispecific T-cell engagers and chimeric antigen receptor T cells has been demonstrated to be capable of enhancing the immune response in pediatric patients with refractory or relapsed B-cell ALL, and improving the cure rate of the disease and patients’ quality of life, thus receiving the authorization for market. Nevertheless, the resistance and toxicities associated with the current immunotherapy remains a huge challenge. Novel therapeutic options to overcome the above disadvantages should be further explored. In this review, we will thoroughly discuss the emerging immunotherapeutics for the treatment of pediatric ALL, as well as side-effects and new development.

Comparisons of Long-Term Survival and Safety of Haploidentical Hematopoietic Stem Cell Transplantation After CAR-T Cell Therapy or Chemotherapy in Pediatric Patients With First Relapse of B-Cell Acute Lymphoblastic Leukemia Based on MRD-Guided Treatment

Measurable residual disease (MRD) positivity before haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is an independent prognostic factor in determining outcomes in patients with B-cell acute lymphoblastic leukemia (ALL). In this study, we conducted a parallel comparison of the efficacy and safety in patients with suboptimal MRD response after reinduction who underwent haplo-HSCT after chimeric antigen receptor T-cell (CAR-T) therapy or chemotherapy. Forty B-cell ALL patients who relapsed after first-line chemotherapy and with an MRD ≥0.1% after reinduction were analyzed. The median pre-HSCT MRD in the CAR-T group (n = 26) was significantly lower than that in the chemotherapy group (n = 14) (0.009% vs. 0.3%, p = 0.006). The CAR-T group exhibited a trend toward improved 3-year leukemia-free survival and a significantly improved 3-year overall survival compared to the chemotherapy group [71.8% (95% confidence interval (CI): 53.9–89.6) vs. 44.4% (95% CI: 15.4–73.4), p = 0.19 and 84.6% (95% CI: 70.6–98.5) vs. 40.0% (95% CI: 12.7–67.2), p = 0.008; respectively]. Furthermore, no increased risk of graft-versus-host disease, treatment-related mortality, or infection was observed in the CAR-T group. Our study suggests that CAR-T therapy effectively eliminates pre-HSCT MRD, resulting in better survival in the context of haplo-HSCT.

Impact of KIR-ligand mismatch on pediatric T-cell acute lymphoblastic leukemia in unrelated cord blood transplantation

BACKGROUND

Currently, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered to be indicated for children and adolescents with high-risk or relapsed T-cell acute lymphoblastic leukemia (T-ALL); however, the outcomes are unsatisfactory. Killer cell immunoglobulin-like receptors (KIRs) are the main receptors on natural killer (NK) cells that play an important role in the graft-versus-leukemia effect after allo-HSCT. In allo-HSCT, when the recipient lacks a donor KIR-ligand (KIR-ligand mismatch in the graft-versus-host [GVH] direction), donor NK cells will be activated against recipient cells. KIR-ligand mismatch in the GVH direction improves outcomes after unrelated cord blood transplantation (UCBT) with acute myeloid leukemia, but the effect in T-ALL is unclear.

OBJECTIVE

We evaluated the impact of KIR-ligand mismatch in the GVH direction on the transplant outcomes of children and adolescents with T-ALL who received UCBT.

STUDY DESIGN

We conducted a retrospective study using a nationwide registry of the Japanese Society for Transplantation and Cellular Therapy. Patients diagnosed with T-ALL, aged 0-19 years, and underwent first UCBT between 1999 and 2017 were included.

RESULTS

A total of 91 patients were included in this study. In all, 23 (25.3%) percent of patients had KIR-ligand mismatch in the GVH direction. The 5-year leukemia-free survival (LFS) and overall survival (OS) rates after UCBT were 65.8% and 69.6%, respectively. In a multivariate analysis, KIR-ligand mismatch in the GVH direction was associated with a significant reduction in the relapse rate (hazard ratio [HR], 0.19; P = 0.002), resulting in better LFS (HR, 0.18; P = 0.010) and OS (HR, 0.26; P = 0.048) without increasing non-relapse mortality (NRM; HR, 1.90; P = 0.264). The cumulative incidence of GVH disease (GVHD) did not differ between patients with and without KIR-ligand mismatch (grade II-IV acute GVHD, 39.1% versus 36.8%, P = 0.648, grade III-IV acute GVHD, 13.0% versus 11.8%, P = 0.857, and chronic GVHD, 26.1% versus 22.9%, P = 0.736, respectively). Furthermore, acute and chronic GVHD were not associated with good patient outcomes. Notably, no relapse was observed in patients who received KIR-ligand mismatched UCBT in complete remission.

CONCLUSION

KIR-ligand mismatch in the GVH direction improved LFS and decreased relapse rates without increasing NRM in children and adolescents with T-ALL who received UCBT, which was not mediated by GVHD.

Combinational treatment of TPEN and TPGS induces apoptosis in acute lymphoblastic and chronic myeloid leukemia cells in vitro and ex vivo

TPEN and TPGS have recently shown selective cytotoxic effects in vitro and ex vivo leukemia cells. In this study, we aimed to test the synergistic effect of combined TPEN and TPGS agents (thereafter, T2 combo) on Jurkat (clone-E61), K562, Ba/F3, and non-leukemia peripheral blood lymphocytes (PBL). The ED50 doses (i.e., TPEN ED50: 3.2 μM and TPGS ED50: 34 μM, potency ratio R = 10.62 = TPGS (ED50)/TPEN (ED50)) were identified as dose-effect curve (%DNA fragmentation (sub-G₁ phase) versus agent concentration). The most effective synergistic doses were determined according to isobole analysis. The apoptotic and oxidative stress effects of combined doses (TPEN 0.1, 0.5, 1 μM) and TPGS (5, 10, 20 μM)) were evaluated by DNA fragmentation (sub-G₁ phase), mitochondrial membrane potential, oxidation of stress sensor protein DJ-1, and activation of executer protein CASPASE-3. They testified to the synergistic effect of the T2 combo (e.g., TPEN 1: TPGS 20, combination index (CI) 0.90 < 1; 1/3.2+ 20/34, > 90% induced apoptosis) in all 3 cell lines. As proof of principle, we challenged complete bone marrow (n = 5) or isolated cells from bone marrow (n = 3) samples from acute pediatric acute B-cell patients and found that T2 combo (1:20; 10:200) dramatically reduced (- 50%) the CD34+/CD19+cell population and increased significantly CD19+/CASP-3+ positive B-ALL cells up to 960%. The T2 combo neither induced DNA fragmentation, altered ΔΨm, nor induced oxidation of stress sensor protein DJ-1, nor activated CASP-3 in PBL cells. We conclude that by using different combinations of TPEN and TPGS, a more efficient treatment strategy can be developed for leukemia patients.

Immunotherapy and Allogeneic Bone Marrow Transplantation in B Acute Lymphoblastic Leukemia: How to Sequence?

Long-term disease control is achieved in 80–90% of patients with acute lymphoblastic leukemia of B origin (B-ALL). About half of adult and 10% of pediatric patients develop refractory or relapsed disease, whereas survival after relapse accounts about 10% in adults and 30–50% in children. Allogeneic bone marrow transplantation offers remarkable benefit in cases with unfavorable outcome. Nevertheless, novel immunotherapeutic options have been approved for patients with adverse prognosis. Immunotherapeutic agents, nowadays, are preferred over standard chemotherapy for patients with relapsed or refractory B-ALL The mode of action, efficacy and safety data of immunotherapeutic agents released, indications and sequence of those therapies over the course of treatment, are herein reviewed.

Isolated CNS Relapse in 2 High-Risk B-cell Acute Lymphoblastic Leukemia Patients Following SARS-CoV-2 Infection

B-cell acute lymphoblastic leukemia (B-ALL) is the most common pediatric malignancy with a highly favorable overall prognosis. Central nervous system (CNS) relapse of B-ALL is relatively rare and is associated with inferior survival outcomes. We present two patients with B-ALL who developed isolated CNS relapse following confirmed infection with severe acute respiratory syndrome coronavirus 2. In addition to individual and disease factors, we posit that delays in therapy together with immune system modulation because of severe acute respiratory syndrome coronavirus 2 may account for these 2 cases of CNS relapsed B-ALL. We report on this clinical observation to raise awareness of this potential association.

Preparing for CAR T cell therapy: patient selection, bridging therapies and lymphodepletion

Chimeric antigen receptor (CAR) T cells have emerged as a potent therapeutic approach for patients with certain haematological cancers, with multiple CAR T cell products currently approved by the FDA for those with relapsed and/or refractory B cell malignancies. However, in order to derive the desired level of effectiveness, patients need to successfully receive the CAR T cell infusion in a timely fashion. This process entails apheresis of the patient's T cells, followed by CAR T cell manufacture. While awaiting infusion at an authorized treatment centre, patients may receive interim disease-directed therapy. Most patients will also receive a course of pre-CAR T cell lymphodepletion, which has emerged as an important factor in enabling durable responses. The time between apheresis and CAR T cell infusion is often not a simple journey, with each milestone being a critical step that can have important downstream consequences for the ability to receive the infusion and the strength of clinical responses. In this Review, we provide a summary of the many considerations for preparing patients with B cell non-Hodgkin lymphoma or acute lymphoblastic leukaemia for CAR T cell therapy, and outline current limitations and areas for future research.

Bispecific Antibodies and Other Non-CAR Targeted Therapies and HSCT: Decreased Toxicity for Better Transplant Outcome in Paediatric ALL?

This review will address the place of innovative, non-chemotherapy, non-CAR-T targeted therapies in the treatment of Acute Lymphoblastic Leukaemia (ALL), focusing on their use in the hematopoietic stem cell transplant (HSCT) context. The focus will be on the agent with the most experience to date, namely the bispecific T-cell engater (BiTE) blinatumomab, but references to antibody-drug conjugates (ADCs) such as inotuzumab ozogamicin and monoclonal antibodies such as daratumamab will be made as well. Specific issues to be addressed include: (1) The use of these agents to reduce measurable residual disease (MRD) prior to HSCT and their potential for improved transplant outcomes due to reduced toxicity compared to traditional chemotherapy salvage, as well as potentially increased toxicity with HSCT with particular agents; (2) the appropriate sequencing of innovative therapies, i.e., when to use BiTEs or antibodies versus CARs pre- and/or post-HSCT; this will include also the potential for impact on response of one group of agents on response to the other; (3) the role of these agents particularly in the post-HSCT relapse setting, or as maintenance to prevent relapse in this setting; (4) special populations in which these agents may substitute for traditional chemotherapy during induction or consolidation in patients with predisposing factors for toxicity with traditional therapy (e.g., Trisomy 21, infants), or those who develop infectious complications precluding delivery of full standard-of-care (SOC) chemotherapy during induction/consolidation (e.g., fungal infections); (5) the evidence we have to date regarding the potential for substitution of blinatumomab for some of the standard chemotherapy agents used pre-HSCT in patients without the above risk factors for toxicity, but with high risk disease going into transplant, in an attempt to decrease current rates of transplant-related mortality as well as morbidity; (6) the unique toxicity profile of these agents and concerns regarding particular side effects in the HSCT context. The manuscript will include both the data we have to date regarding the above issues, ongoing studies that are trying to explore them, and suggestions for future studies to further refine our knowledge base.

Chimeric Antigen Receptor T-Cell Therapy in Paediatric B-Cell Precursor Acute Lymphoblastic Leukaemia: Curative Treatment Option or Bridge to Transplant?

Chimeric antigen receptor T-cell therapy (CAR-T) targeting CD19 has been associated with remarkable responses in paediatric patients and adolescents and young adults (AYA) with relapsed/refractory (R/R) B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). Tisagenlecleucel, the first approved CD19 CAR-T, has become a viable treatment option for paediatric patients and AYAs with BCP-ALL relapsing repeatedly or after haematopoietic stem cell transplantation (HSCT). Based on the chimeric antigen receptor molecular design and the presence of a 4-1BB costimulatory domain, tisagenlecleucel can persist for a long time and thereby provide sustained leukaemia control. "Real-world" experience with tisagenlecleucel confirms the safety and efficacy profile observed in the pivotal registration trial. Recent guidelines for the recognition, management and prevention of the two most common adverse events related to CAR-T - cytokine release syndrome and immune-cell-associated neurotoxicity syndrome - have helped to further decrease treatment toxicity. Consequently, the questions of how and for whom CD19 CAR-T could substitute HSCT in BCP-ALL are inevitable. Currently, 40-50% of R/R BCP-ALL patients relapse post CD19 CAR-T with either CD19- or CD19+ disease, and consolidative HSCT has been proposed to avoid disease recurrence. Contrarily, CD19 CAR-T is currently being investigated in the upfront treatment of high-risk BCP-ALL with an aim to avoid allogeneic HSCT and associated treatment-related morbidity, mortality and late effects. To improve survival and decrease long-term side effects in children with BCP-ALL, it is important to define parameters predicting the success or failure of CAR-T, allowing the careful selection of candidates in need of HSCT consolidation. In this review, we describe the current clinical evidence on CAR-T in BCP-ALL and discuss factors associated with response to or failure of this therapy: product specifications, patient- and disease-related factors and the impact of additional therapies given before (e.g., blinatumomab and inotuzumab ozogamicin) or after infusion (e.g., CAR-T re-infusion and/or checkpoint inhibition). We discuss where to position CAR-T in the treatment of BCP-ALL and present considerations for the design of supportive trials for the different phases of disease. Finally, we elaborate on clinical settings in which CAR-T might indeed replace HSCT.

Blinatumomab in Children and Adolescents with Relapsed/Refractory B Cell Precursor Acute Lymphoblastic Leukemia: A Real-Life Multicenter Retrospective Study in Seven AIEOP (Associazione Italiana di Ematologia e Oncologia Pediatrica) Centers

Five-year event-free survival in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) currently exceeds 80-85%. However, 15-20% of patients still experience a relapsed/refractory disease. From 1 January 2015 to 31 December 2020, thirty-nine patients, 0-21 years old with r/r BCP-ALL were treated with blinatumomab with the aim of inducing remission (n = 13) or reducing MRD levels (n = 26) in the frame of different multiagent chemotherapy schedules, in seven AIEOP centers. Patients were treated in compassionate and/or off-label settings and were not enrolled in any controlled clinical trials. Treatment was well tolerated; 22 (56.4%) patients reported adverse events (AE) on a total of 46 events registered, of which 27 (58.7%) were ≤2 grade according to CTCAE. Neurological AEs were 18 (39.1%); only two patients required transient blinatumomab discontinuation. Complete remission (CR) rate was 46% for the 13 patients treated with ≥5% blasts and 81% PCR/FC MRD negativity in the 26 patients with blasts < 5%. Median relapse-free survival was 33.4 months (95% CI; 7.5-59.3); median overall survival was not reached over a mean follow-up of 16 months. In our study, as in other real-life experiences, blinatumomab proved to be effective and well-tolerated, able to induce a high rate of CR and MRD negativity.

Blinatumomab In pediatric relapsed/refractory B-cell acute lymphoblastic leukemia: RIALTO expanded access study final analysis

The safety and efficacy of blinatumomab, a CD3/CD19-directed bispecific T-cell engager molecule, for treatment of pediatric relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R B-ALL) were examined in an open-label, single-arm, expanded access study (RIALTO). Children (>28 days, <18 years) with CD19+ R/R B-ALL received up to five cycles of blinatumomab by continuous infusion (cycle: 4 weeks on/2 weeks off). The primary endpoint was incidence of adverse events. Secondary endpoints included complete response (CR) and measurable residual disease (MRD) response within the first two cycles, relapse-free survival (RFS), overall survival (OS) and allogeneic hematopoietic stem cell transplant (alloHSCT) after treatment. At final data cutoff (1/10/20), 110 patients were enrolled (median age, 8.5 years; 88% ≥5% blasts at baseline). Blinatumomab treatment resulted in a low incidence of grade 3-4 cytokine release syndrome (n=2 [1.8%]) and neurologic events (n=4 [3.6%]). No blinatumomab-related fatal adverse events were reported. The probability of response was not affected by the presence of cytogenetic/molecular abnormalities. Median OS was 14.6 months (95%CI: 11.0─not estimable) and was significantly greater for MRD responders versus MRD non-responders (not estimable vs 9.3; HR 0.18, 95%CI: 0.08─0.39). One-year OS probability was higher for patients who received alloHSCT versus without alloHSCT post-blinatumomab (87% versus 29%). Median RFS for MRD responders (n=57) was 8.0 months (95%CI:3.4─10.1) versus 2.8 months (95%CI: 0.3─9.2) for MRD non-responders (n=10). Of patients achieving CR after 2 cycles, 73.5% (95%CI: 61.4%-83.5%) proceeded to alloHSCT. These findings support the use of blinatumomab as a safe and efficacious treatment for pediatric R/R B-ALL. (ClinicalTrials.gov identifier NCT02187354).

Novel Treatments for Pediatric Relapsed or Refractory Acute B-Cell Lineage Lymphoblastic Leukemia: Precision Medicine Era

With the markedly increased cure rate for children with newly diagnosed pediatric B-cell acute lymphoblastic leukemia (B-ALL), relapse and refractory B-ALL (R/R B-ALL) remain the primary cause of death worldwide due to the limitations of multidrug chemotherapy. As we now have a more profound understanding of R/R ALL, including the mechanism of recurrence and drug resistance, prognostic indicators, genotypic changes and so on, we can use newly emerging technologies to identify operational molecular targets and find sensitive drugs for individualized treatment. In addition, more promising and innovative immunotherapies and molecular targeted drugs that are expected to kill leukemic cells more effectively while maintaining low toxicity to achieve minimal residual disease (MRD) negativity and better bridge hematopoietic stem cell transplantation (HSCT) have also been widely developed. To date, the prognosis of pediatric patients with R/R B-ALL has been enhanced markedly thanks to the development of novel drugs. This article reviews the new advancements of several promising strategies for pediatric R/R B-ALL.

Blinatumomab for treating pediatric B-lineage acute lymphoblastic leukemia: A retrospective real-world study

OBJECTIVES

Blinatumomab was shown to be safe and effective for consolidation therapy in B-cell acute lymphoblastic leukemia (B-ALL). This study aimed to investigate the effectiveness and safety of blinatumomab in pediatric B-ALL patients in a real-world setting.

METHODS

This was a retrospective, observational study that included patients who initiated blinatumomab treatment between October 1, 2020 and June 20, 2022. Patients with B-ALL diagnosis, age below 18 years, and at least one blinatumomab treatment cycle were included. Treatment-related toxicities were assessed.

RESULT

Totally 23 pediatric patients were included in this study, with a median age of 6 years (range, 2 to 11 years). Blinatumomab therapy was applied for MRD-positive (disease ≥0.01%, n = 3) or chemotherapy-ineligible (n = 20) B-ALL cases. The median follow-up time was 9 months, and all evaluable patients achieved complete molecular remission with undetectable MRD. Four relapsed B-ALL cases proceeded to hematopoietic stem cell transplantation (HSCT) without further bridging therapy, while the others underwent maintenance chemotherapy after blinatumomab treatment. Grade ≥3 febrile neutropenia, white blood cell decrease and seizure were observed in 57%, 48% and 4.3% of patients, respectively. One case discontinued therapy due to neurologic toxicities. Elevated cytokine levels were observed in 4 patients. In all 23 patients, increased T-cell and low B-cell counts (<10/μl) were detected during blinatumomab therapy.

CONCLUSION

These encouraging results suggest blinatumomab in pediatric B-ALL patients with MRD⁺ or chemotherapy-related toxicities is effective and safe in the short run, although long-term follow-up is still needed.

Use of blinatumomab and CAR T-cell therapy in children with relapsed/refractory leukemia: A case series study

BACKGROUND

The 5-year event-free survival rate for childhood acute lymphoblastic leukemia (ALL) has increased to more than 85%. However, the 5-year overall survival rate in children with relapsed/refractory ALL did not exceed 50%. In the past decade, immunotherapies (such as blinatumomab and chimeric antigen receptor T-cell therapy) were approved for relapsed/refractory B-ALL, transforming the treatment environment for children with relapsed/refractory ALL.

OBJECTIVE

This study aimed to explore how immunotherapy can be incorporated into salvage regimens for pediatric patients with relapsed/refractory ALL by retrospectively analyzing the diagnosis and treatment process of seven children with relapsed/refractory leukemia and observing the side effects of the two strategies and long-term survival.

METHODS

The clinical features and treatment responses of patients aged <14 years with relapsed/refractory leukemia who received immunotherapy (including Chimeric Antigen Receptor T cell treatment and blinatumomab) at Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology between February 2014 and April 2022 were retrospectively analyzed.

RESULTS

Seven children underwent immunotherapy. Five patients received immunotherapy and sequential allogeneic hematopoietic stem cell transplantation (HSCT), whereas the other two received only immunotherapy. Five patients achieved complete remission (71.4%). None of the patients had severe cytokine release syndrome. However, one developed grade 3 immune effector cell-associated neurotoxicity syndrome with prior leukoencephalopathy. The median follow-up period was 541 days (range, 186-3,180 days). No deaths were related to treatment. Three patients relapsed, two had CD19-negative recurrences, and the third showed CD19 antigen reduction. One patient died after disease progression, whereas the other died of HSCT-related complications. One patient abandoned the treatment after relapse and was lost to follow-up.

CONCLUSION

Blinatumomab and CAR T-cell therapy showed excellent remission rates and manageable toxicity in pediatric patients with relapsed/refractory leukemia. However, the duration of the remission was limited. Therefore, further prospective randomized clinical studies should be conducted to improve the long-term efficacy of immunotherapy.

Supportive methods for childhood acute lymphoblastic leukemia then and now: A compilation for clinical practice

Survival of childhood acute lymphoblastic leukemia has significantly improved over the past decades. In the early years of chemotherapeutic development, improvement in survival rates could be attained only by increasing the cytostatic dose, also by modulation of the frequency and combination of chemotherapeutic agents associated with severe short- and long-time side-effects and toxicity in a developing child's organism. Years later, new treatment options have yielded promising results through targeted immune and molecular drugs, especially in relapsed and refractory leukemia, and are continuously added to conventional therapy or even replace first-line treatment. Compared to conventional strategies, these new therapies have different side-effects, requiring special supportive measures. Supportive treatment includes the prevention of serious acute and sometimes life-threatening events as well as managing therapy-related long-term side-effects and preemptive treatment of complications and is thus mandatory for successful oncological therapy. Inadequate supportive therapy is still one of the main causes of treatment failure, mortality, poor quality of life, and unsatisfactory long-term outcome in children with acute lymphoblastic leukemia. But nowadays it is a challenge to find a way through the flood of supportive recommendations and guidelines that are available in the literature. Furthermore, the development of new therapies for childhood leukemia has changed the range of supportive methods and must be observed in addition to conventional recommendations. This review aims to provide a clear and recent compilation of the most important supportive methods in the field of childhood leukemia, based on conventional regimes as well as the most promising new therapeutic approaches to date.

Venetoclax for Children and Adolescents with Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma

Simple Summary

Pediatric patients with relapsed or refractory acute lymphoblastic leukemia (ALL) or lymphoma (LBL) currently have unsatisfactory outcomes, and novel treatment options are needed. Venetoclax is approved for adult patients with several types of leukemia and is being investigated in the pediatric population. Here, we retrospectively reviewed the safety and efficacy of venetoclax for the treatment of ALL/LBL in the pediatric and young adult populations. The purpose of this study is to provide evidence that venetoclax is safe and effective to use in pediatric patients with ALL/LBL and should be considered in both the relapsed and upfront settings.

Abstract

Venetoclax is approved for adult patients with chronic lymphocytic leukemia and acute myeloid leukemia. Expanding its use to the pediatric population is currently under investigation, but more robust data are needed. We retrospectively analyzed the safety and efficacy of venetoclax in children/AYA with ALL/LBL. We identified 18 patients (T-cell ALL, n = 7; T-cell LBL, n = 6; B-cell ALL, n = 5) aged 6–22 years. No new venetoclax safety signals were identified; the most common toxicity was myelosuppression. No deaths occurred within 30 days from the start of the therapy. A mean of 2.6 (range 0–8) prior lines of therapy were given. The mean duration of venetoclax was 4.06 months (range 0.2–24.67 months). Complete remission was achieved in 11 (61%) patients. Of the eight patients who remain alive, four are continuing on venetoclax combination therapy, and four proceeded to hematopoietic stem cell transplantation. Three patients who initially achieved CR, later relapsed, and are deceased. Nine patients are deceased, and one patient was lost to follow-up. Overall survival is 9.14 months (range 1.1–33.1), and progression-free survival is 7.34 months (range 0.2–33.1). This is the largest cohort of pediatric/AYA patients who received venetoclax for ALL/LBL. Our data support the consideration of venetoclax-based regimens in pediatric patients with R/R ALL/LBL and its investigation as upfront therapy for T-cell ALL/LBL.

Allogeneic Hematopoietic Stem Cell Transplantation for Children With Acute Lymphoblastic Leukemia: Shifting Indications in the Era of Immunotherapy

Pediatric acute lymphoblastic leukemia generally carries a good prognosis, and most children will be cured and become long-term survivors. However, a portion of children will harbor high-risk features at the time of diagnosis, have a poor response to upfront therapy, or suffer relapse necessitating more intensive therapy, which may include allogeneic hematopoietic stem cell transplant (HSCT). Recent advances in risk stratification, improved detection and incorporation of minimal residual disease (MRD), and intensification of upfront treatment have changed the indications for HSCT over time. For children in first complete remission, HSCT is generally reserved for those with the highest risk of relapse. These include patients with unfavorable features/cytogenetics who also have a poor response to induction and consolidation chemotherapy, usually reflected by residual blasts after prednisone or by detectable MRD at pre-defined time points. In the relapsed setting, children with first relapse of B-cell ALL are further stratified for HSCT depending on the time and site of relapse, while all patients with T-cell ALL are generally consolidated with HSCT. Alternatives to HSCT have also emerged over the last decade including immunotherapy and chimeric antigen receptor (CAR) T-cell therapy. These novel agents may spare toxicity while attempting to achieve MRD-negative remission in the most refractory cases and serve as a bridge to HSCT. In some situations, these emerging therapies can indeed be curative for some children with relapsed or resistant disease, thus, obviating the need for HSCT. In this review, we seek to summarize the role of HSCT in the current era of immunotherapy.

Cardiac Relapse of Acute Lymphoblastic Leukemia Following Hematopoietic Stem Cell Transplantation: A Case Report and Review of Literature

Isolated extramedullary relapse of acute lymphoblastic leukemia (ALL) occurs in soft tissues and various organs outside the testis and central nervous system. Treatments such as hematopoietic stem cell transplantation and more novel modalities such as immunotherapy have eradicated ALL at extramedullary sites. In some instances, survival times for relapsed ALL at these sites are longer than those for relapsed disease involving only the bone marrow. Isolated relapse of ALL in the myocardium is rare, especially in children, making diagnosis and treatment of it difficult. More recent treatment options such as chimeric antigen receptor T-cell therapy carry a high risk of cytokine release syndrome and associated risk of worsening cardiac function. Herein we present the case of an 11-year-old boy who presented with relapsed symptomatic B-cell ALL in the myocardium following allogeneic hematopoietic stem cell transplantation. This is an unusual presentation of relapsed ALL and this case demonstrates the associated challenges in its diagnosis and treatment. The case report is followed by a literature review of the advances in treatment of pediatric leukemia and their application to extramedullary relapse of this disease in particular.

T-Cell Acute Lymphoblastic Leukemia-Current Concepts in Molecular Biology and Management

T-cell acute lymphoblastic leukemia (T-ALL) is an uncommon, yet aggressive leukemia that accounts for approximately one-fourth of acute lymphoblastic leukemia (ALL) cases. CDKN2A/CDKN2B and NOTCH1 are the most common mutated genes in T-ALL. Children and young adults are treated with pediatric intensive regimens and have superior outcomes compared to older adults. In children and young adults, Nelarabine added to frontline chemotherapy improves outcomes and end of consolidation measurable residual disease has emerged as the most valuable prognostic marker. While outcomes for de-novo disease are steadily improving, patients with relapsed and refractory T-ALL fare poorly. Newer targeted therapies are being studied in large clinical trials and have the potential to further improve outcomes. The role of allogeneic stem cell transplant (HSCT) is evolving due to the increased use of pediatric-inspired regimens and MRD monitoring. In this review we will discuss the biology, treatment, and outcomes in pediatric and adult T-ALL.

Role of chimeric antigen receptor T-cell therapy: bridge to transplantation or stand-alone therapy in pediatric acute lymphoblastic leukemia

PURPOSE OF REVIEW

To discuss the curative potential for chimeric antigen receptor T-cell (CAR-T) therapy, with or without consolidative hematopoietic stem cell transplantation (HCT) in the treatment of children and young adults with B lineage acute lymphoblastic leukemia (B-ALL).

RECENT FINDINGS

CAR-T targeting CD19 can induce durable remissions and prolong life in patients with relapsed/refractory B-ALL. Whether HCT is needed to consolidate remission and cure relapse/refractory B-ALL following a CD19 CAR-T induced remission remains controversial. Preliminary evidence suggests that consolidative HCT following CAR-T in HCT-naïve children improves leukemia-free survival. However, avoiding HCT-related late effects is a desirable goal, so identification of patients at high risk of relapse is needed to appropriately direct those patients to HCT when necessary, while avoiding HCT in others. High disease burden prior to CAR-T infusion, loss of B-cell aplasia and detection of measurable residual disease by flow cytometry or next-generation sequencing following CAR-T therapy associate with a higher relapse risk and may identify patients requiring consolidative HCT for relapse prevention.

SUMMARY

There is a pressing need to determine when CD19 CAR-T alone is likely to be curative and when a consolidative HCT will be required. We discuss the current state of knowledge and future directions.

Effect of time on quality of parent-child communication in pediatric cancer

BACKGROUND

A diagnosis of childhood cancer results in new parent-child communication challenges. Little is known about how communication changes over time after diagnosis or relapse. The objective of this study was to determine the effect of time since diagnosis and relapse on quality of parent-child communication. We hypothesized that there would be a positive correlation between time and quality of parent-child communication.

METHODS

Cross-sectional study in children (7-17 years) with relapsed/refractory cancer and their caregivers, who spoke English, were not cognitively impaired, and had internet access. Parents were recruited through Facebook ads. Parents and children completed the Parent-Adolescent Communication Scale (PACS), a 20-item measure of communication quality, with openness and problem subscales. Spearman's rho (r_s ) coefficients assessed correlations between PACS scores and time since diagnosis/relapse.

RESULTS

There was a statistically significant negative correlation between parent PACS scores and time since child's cancer diagnosis (r_s  = -0.21, p = .02), indicating a tendency for overall worsening communication as time since diagnosis increased. There was a positive correlation between the parent PACS problem scores and time since diagnosis (r_s  = +0.22, p = .01), indicating more problematic communication as time since diagnosis increased. Correlations of time since relapse and PACS scores were small and not statistically significant.

CONCLUSION

Parent-child communication worsens over time following a child's cancer diagnosis with more communication problems, contrary to our hypothesis. Future studies are needed to evaluate intervention timing to best support parent-child communication beyond the new-diagnosis period.

CAR T-Cell Therapy in Hematological Malignancies

Chimeric antigen receptor (CAR) T-cells (CAR T-cells) are a promising therapeutic approach in treating hematological malignancies. CAR T-cells represent engineered autologous T-cells, expressing a synthetic CAR, targeting tumor-associated antigens (TAAs) independent of major histocompatibility complex (MHC) presentation. The most common target is CD19 on B-cells, predominantly used for the treatment of lymphoma and acute lymphocytic leukemia (ALL), leading to approval of five different CAR T-cell therapies for clinical application. Despite encouraging clinical results, treatment of other hematological malignancies such as acute myeloid leukemia (AML) remains difficult. In this review, we focus especially on CAR T-cell application in different hematological malignancies as well as strategies for overcoming CAR T-cell dysfunction and increasing their efficacy.

Antibody-Drug Conjugates for the Treatment of Acute Pediatric Leukemia

The clinical development of antibody-drug conjugates (ADCs) has gained momentum in recent years and these agents are gradually moving into frontline regimens for pediatric acute leukemias. ADCs consist of a monoclonal antibody attached to a cytotoxic payload by a cleavable linker. This structure allows for highly cytotoxic agents to be directly delivered to leukemia cells leading to cell death and avoids excessive off-tumor toxicity. Near universal expression on B-cell acute lymphoblastic leukemia (ALL) blasts and the ability of rapid internalization has rendered CD22 an ideal target for ADC in B-ALL. Inotuzumab ozogamicin, the anti-CD22 antibody linked to calicheamicin led to complete remission rates of 60-80% in patients with relapsed/refractory B-ALL. In acute myeloid leukemia (AML), the CD33 targeting gemtuzumab ozogamicin has demonstrated modest improvements in survival and is the only ADC currently licensed in the United States for pediatric patients with de novo AML. Several other ADCs have been developed and tested clinically for leukemia but have achieved limited success to date. The search for additional leukemia-specific targets and optimization of ADC structure and specificity are ongoing efforts to improve their therapeutic window. This review provides a comprehensive overview of ADCs in acute leukemias, with a focus on pediatric ALL and AML.

Testicular involvement of acute lymphoblastic leukemia in children and adolescents: Diagnosis, biology, and management

Acute lymphoblastic leukemia (ALL) in children and adolescents can involve the testes at diagnosis or upon relapse. The testes were long considered pharmacologic sanctuary sites, presumably because of the blood-testis barrier, which prevents the entry of large-molecular-weight compounds into the seminiferous tubule. Patients with testicular involvement were historically treated with testicular irradiation or orchiectomy. With the advent of contemporary intensive chemotherapy, including high-dose methotrexate, vincristine/glucocorticoid pulses, and cyclophosphamide, testicular leukemia present at diagnosis can be eradicated, with the risk of testicular relapse being 2% or lower. However, the management of testicular leukemia is not well described in the recent literature and remains relevant in low- and middle-income countries where testicular relapse is still experienced. Chemotherapy can effectively treat late, isolated testicular B-cell ALL relapses without the need for irradiation or orchiectomy in patients with an early response and thereby preserve testicular function. For refractory or early-relapse testicular leukemia, newer treatment approaches such as chimeric antigen receptor-modified T (CAR-T) cell therapy are under investigation. The control of testicular relapse with CAR-T cells and their penetration of the blood-testis barrier have been reported. The outcome of pediatric ALL has been improved remarkably by controlling the disease in the bone marrow, central nervous system, and testes, and such success should be extended globally. LAY SUMMARY: Acute lymphoblastic leukemia (ALL) in children and adolescents can involve the testes at diagnosis or upon relapse. Modern intensive chemotherapy has largely eradicated testicular relapse in high-income countries. Consequently, most current clinicians are not familiar with how to manage it if it does occur, and testicular relapse continues to be a significant problem in low- and middle-income countries that have not had access to modern intensive chemotherapy. The authors review the historical progress made in eradicating testicular ALL and use the lessons learned to make recommendations for treatment.

A novel and highly effective mitochondrial uncoupling drug in T-cell leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy. Despite recent advances in treatments with intensified chemotherapy regimens, relapse rates and associated morbidities remain high. In this context, metabolic dependencies have emerged as a druggable opportunity for the treatment of leukemia. Here, we tested the antileukemic effects of MB1-47, a newly developed mitochondrial uncoupling compound. MB1-47 treatment in T-ALL cells robustly inhibited cell proliferation via both cytostatic and cytotoxic effects as a result of compromised mitochondrial energy and metabolite depletion, which severely impaired nucleotide biosynthesis. Mechanistically, acute treatment with MB1-47 in primary leukemias promoted AMPK activation and downregulation of mTOR signaling, stalling anabolic pathways that support leukemic cell survival. Indeed, MB1-47 treatment in mice harboring either murine NOTCH1-induced primary leukemias or human T-ALL PDXs led to potent antileukemic effects with a significant extension in survival without overlapping toxicities. Overall, our findings demonstrate a critical role for mitochondrial oxidative phosphorylation in T-ALL and uncover MB1-47-driven mitochondrial uncoupling as a novel therapeutic strategy for the treatment of this disease.

Establishment and characterization of HXWMF-1: the first mouse fibroblastic tumor cell line derived from leukemia-associated fibroblasts

Background

Chemo-resistance is still a major obstacle in leukemia treatment. Accumulating evidence indicates that cancer-associated fibroblasts (CAFs), the most abundant stromal cells in tumor microenvironment (TME), play a crucial role in cancer progression and response to chemotherapy. To Figure out the role of leukemia-associated fibroblasts (LAFs) in relapsed/refractory leukemia, we constructed the first leukemia-associated fibroblastic tumor cell line, HXWMF-1.

Methods

A cell culture technique was used to establish the leukemia-associated fibroblastic tumor cell line. Molecular and cellular biological techniques including flow cytometry, MTT assay, western blotting, and short tandem repeat (STR) analysis were used to characterize the cell line. Nude mice were used for xenograft studies.

Results

We established a LAFs derived tumor cell line HXWMF-1, originated from the subcutaneous xenografts of HXEX-ALL1, a cell line originated from a patient with acute lymphoblastic leukemia (ALL) at the second relapse. The HXWMF-1 cell line was authenticated as a tumor cell line and being derived from CAFs based on morphologic, immunophenotypic, cytogenetic and STR analyses and tumorigenicity test in nude mice. To clarify the reliability of the method, we got the LAFs derived tumor cells from three different tumor mass of HXEX-ALL1 xenografts.

Conclusions

To our knowledge, HXWMF-1 is the first fibroblastic tumor cell line derived from LAFs or CAFs. In addition, the cell line provided firm evidence for that leukemia cells may induce LAFs/CAFs malignant transformation, which may help to develop brand new theory and therapeutic strategies for patients with relapsed /refractory ALL.

Use of cardiac radiation therapy as bridging therapy to CAR-T for relapsed pediatric B-cell acute lymphoblastic leukemia

The use of radiotherapy as bridging therapy to chimeric antigen receptor T-cell therapy (CAR-T) in pre-B acute lymphoblastic leukemia (B-ALL) has been minimally explored. Here, we present a boy with B-ALL who relapsed after allogeneic bone marrow transplant with disseminated disease, including significant symptomatic cardiovascular and gastrointestinal (GI) involvement. The cardiac and GI leukemic infiltrates were successfully treated with bridging radiation therapy (BRT) prior to CAR-T infusion. Using this approach, he successfully tolerated CAR-T with no evidence of disease or sequelae on 3-month follow-up. This is the first reported case of safe and effective delivery of cardiac BRT in B-ALL.