Nelarabine: when and how to use in the treatment of T-cell acute lymphoblastic leukemia

ABSTRACT

T-cell acute lymphoblastic leukemia or lymphoblastic lymphoma (T-ALL/LBL) is a rare hematologic malignancy most commonly affecting adolescent and young adult males. Outcomes are dismal for patients who relapse, thus, improvement in treatment is needed. Nelarabine, a prodrug of the deoxyguanosine analog 9-β-arabinofuranosylguanine, is uniquely toxic to T lymphoblasts, compared with B lymphoblasts and normal lymphocytes, and has been developed for the treatment of T-ALL/LBL. Based on phase 1 and 2 trials in children and adults, single-agent nelarabine is approved for treatment of patients with relapsed or refractory T-ALL/LBL, with the major adverse effect being central and peripheral neurotoxicity. Since its approval in 2005, nelarabine has been studied in combination with other chemotherapy agents for relapsed disease and is also being studied as a component of initial treatment in pediatric and adult patients. Here, we review current data on nelarabine and present our approach to the use of nelarabine in the treatment of patients with T-ALL/LBL.

Subcellular Proteome Analysis Reveals Apoptotic Vulnerability of T-Cell Acute Lymphoblastic Leukemia

Targeting death receptor-mediated apoptosis in T-cell acute lymphoblastic leukemia (T-ALL), an aggressive disease with poor prognosis, is hindered by the inherent resistance of primary leukemia cells. Knowledge on therapeutic vulnerabilities in these malignant cells will provide opportunities for developing novel combinatory treatments for patients. Using label-free quantitative mass spectrometry and subcellular fractionation techniques, we systematically compared organelle-specific proteomes between Jurkat cells, an in vitro model for T-ALL, and a Jurkat mutant with increased resistance to death receptor-mediated apoptosis. By identifying several differentially regulated protein clusters, our data argued that extensive metabolic reprograming in the mitochondria, characterized by enhanced respiration and energy production, might allow cells to evade DR5-mediated cytotoxicity. Further analysis using clinical datasets demonstrated that the elevated expression of a three-gene signature, consisting of SDHA, IDH3A, and ANXA11, was significantly associated with poor survival of acute leukemia patients. Our analysis therefore provided a unique dataset for a mechanistic understanding of T-ALL and for the design of novel ALL treatments.

Changes in intracellular activation-related gene expression and induction of Akt contribute to acquired resistance toward nelarabine in CCRF-CEM cell line

Drug resistance is a major problem in treatment with nelarabine, and its resolution requires elucidation of the underlying mechanisms. We established two nelarabine-resistant subclones of the human T-cell lymphoblastic leukemia cell line CCRF-CEM. The resistant subclones showed changes in the expression of several genes related to nelarabine intracellular activation and inhibition of apoptosis. Activation of the Akt protein upon nelarabine treatment was observed in both subclones. The combination treatment with nelarabine and PI3K/Akt inhibitors was shown to inhibit cell growth. Cross-resistance was observed with ara-C and not with vincristine, daunorubicin, or etoposide treatment. Thus, changes in the expression of cellular activation-related genes, inhibition of apoptosis, and induction of Akt may be involved in the development of nelarabine resistance in the CCRF-CEM cell model. The use of different classes of chemotherapeutic agents and combination therapy with PI3K/Akt pathway inhibitors may be used to overcome resistance to nelarabine.

Acute Lymphoblastic Leukemia, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

The NCCN Guidelines for Acute Lymphoblastic Leukemia (ALL) focus on the classification of ALL subtypes based on immunophenotype and cytogenetic/molecular markers; risk assessment and stratification for risk-adapted therapy; treatment strategies for Philadelphia chromosome (Ph)-positive and Ph-negative ALL for both adolescent and young adult and adult patients; and supportive care considerations. Given the complexity of ALL treatment regimens and the required supportive care measures, the NCCN ALL Panel recommends that patients be treated at a specialized cancer center with expertise in the management of ALL This portion of the Guidelines focuses on the management of Ph-positive and Ph-negative ALL in adolescents and young adults, and management in relapsed settings.

Current and emerging therapeutic approaches for T-cell acute lymphoblastic leukaemia

T-cell ALL (T-ALL) is an aggressive malignancy of T-cell progenitors. Although survival outcomes in T-ALL have greatly improved over the past 50 years, relapsed and refractory cases remain extremely challenging to treat and those who cannot tolerate intensive treatment continue to have poor outcomes. Furthermore, T-ALL has proven a more challenging immunotherapeutic target than B-ALL. In this review we explore our expanding knowledge of the basic biology of T-ALL and how this is paving the way for repurposing established treatments and the development of novel therapeutic approaches.

Recent progress in the treatment of cancer in children

Although significant improvements have been made in the outcomes of children with cancer, the pace of improvement has slowed in recent years as the limits of therapy intensification may have been reached for many pediatric cancers. Furthermore, with increasing numbers of pediatric cancer survivors, the long-term side effects of treatment have become increasingly apparent. Therefore, attention has shifted to the use of molecularly targeted agents and immunotherapies to improve the outcomes of children who are not cured by traditional cytotoxic chemotherapies and to decrease exposure to cytotoxic chemotherapy and reduce late effects. This review describes the recent progress in the treatment of children with cancer, focusing in particular on diseases in which targeted and immunotherapeutic agents have made an impact.

Optimizing the treatment of acute lymphoblastic leukemia in younger and older adults: new drugs and evolving paradigms

In the past decade, the available treatments for patients with acute lymphoblastic leukemia (ALL) have rapidly expanded, in parallel with an increased understanding of the genomic features that impact the disease biology and clinical outcomes. With the development of the anti-CD22 antibody-drug conjugate inotuzumab ozogamicin, the CD3-CD19 bispecific T-cell engager antibody blinatumomab, CD19 chimeric antigen receptor T-cell therapy, and the potent BCR-ABL1 tyrosine kinase inhibitor ponatinib, the outlook of ALL in both younger and older adults has substantially improved. The availability of highly effective drugs raised important questions concerning the optimal combination and sequence of these agents, their incorporation into frontline regimens, and the role of hematopoietic stem cell transplantation. In this review, we discuss the rapidly evolving paradigms in the treatment of ALL, highlighting both established and effective regimens, as well as promising new therapies that are being evaluated in ongoing clinical trials. We specifically focus on novel combination regimens in both the frontline and salvage settings that are leading to new standards of care in the treatment of ALL.

Outcome of T-cell acute lymphoblastic leukemia/lymphoma: Focus on near-ETP phenotype and differential impact of nelarabine

Early T-cell precursor acute lymphoblastic leukemia/lymphoma (ETP-ALL/LBL) is characterized by a distinct immunophenotype (CD1a-negative, CD8-negative, CD5-negative or weak-positive <75%, myeloid/stem-cell markers positive) and poor clinical outcomes. Near-ETP ALL is transcriptionally similar to ETP-ALL but CD5 expression level is not low enough to meet the criteria of ETP immunophenotype. Outcomes of near-ETP ALL are not well characterized. We reviewed 171 patients with newly-diagnosed T-ALL/LBL. Patients were categorized into three groups; ETP (N = 27), near-ETP (N = 24), and non-ETP ALL/LBL (N = 120). ETP-ALL/LBL was associated with a significantly worse survival compared with non-ETP ALL/LBL: 5-year overall survival (OS) rates 32% versus 63% (p < .001). Outcome was similar between near-ETP and non-ETP ALL/LBL: 5-year OS rates 56% versus 63% (p = .543). Landmark analysis showed that allogeneic stem cell transplant (allo-SCT) in first remission was beneficial in ETP-ALL/LBL (5-year event-free survival rates 36% versus 18%, p = .030) but not in near-ETP or non-ETP ALL/LBL. Multivariate analysis selected the following as significant independent prognostic factors for OS: age ≥ 60 years (HR 3.11; p = .003); elevated WBC ≥100 × 10⁹ /L (HR 2.60; p = .005); and ETP immunophenotype (HR 2.29; p = .010). A survival advantage with adding nelarabine to hyper-CVAD was observed in non-ETP ALL (5-year OS rates 83% versus 38% with hyper-CVAD plus neralabine versus hyper-CVAD, p = .003). In conclusion, outcome of ETP-ALL/LBL was poor and improved with allo-SCT; outcome of near-ETP ALL/LBL was similar to non-ETP ALL/LBL; the addition of nelarabine to hyper-CVAD improved the survival in non-ETP ALL only.

The New Therapeutic Strategies in Pediatric T-Cell Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia is a genetically heterogeneous cancer that accounts for 10–15% of T-cell acute lymphoblastic leukemia (T-ALL) cases. The T-ALL event-free survival rate (EFS) is 85%. The evaluation of structural and numerical chromosomal changes is important for a comprehensive biological characterization of T-ALL, but there are currently no genetic prognostic markers. Despite chemotherapy regimens, steroids, and allogeneic transplantation, relapse is the main problem in children with T-ALL. Due to the development of high-throughput molecular methods, the ability to define subgroups of T-ALL has significantly improved in the last few years. The profiling of the gene expression of T-ALL has led to the identification of T-ALL subgroups, and it is important in determining prognostic factors and choosing an appropriate treatment. Novel therapies targeting molecular aberrations offer promise in achieving better first remission with the hope of preventing relapse. The employment of precisely targeted therapeutic approaches is expected to improve the cure of the disease and quality of life of patients. These include therapies that inhibit Notch1 activation (bortezomib), JAK inhibitors in ETP-ALL (ruxolitinib), BCL inhibitors (venetoclax), and anti-CD38 therapy (daratumumab). Chimeric antigen receptor T-cell therapy (CAR-T) is under investigation, but it requires further development and trials. Nelarabine-based regimens remain the standard for treating the relapse of T-ALL.

Clinical significance of novel subtypes of acute lymphoblastic leukemia in the context of minimal residual disease-directed therapy

We evaluate clinical significance of recently identified subtypes of acute lymphoblastic leukemia (ALL) in 598 children treated with minimal residual disease (MRD)-directed therapy. Among the 16 B-ALL and 8 T-ALL subtypes identified by next generation sequencing, ETV6-RUNX1, high-hyperdiploid and DUX4-rearranged B-ALL had the best five-year event-free survival rates (95% to 98.4%); TCF3-PBX1, PAX5alt, T-cell, ETP, iAMP21, and hypodiploid ALL intermediate rates (80.0% to 88.2%); and BCR-ABL1, BCR-ABL1-like and ETV6-RUNX1-like and KMT2A-rearranged ALL the worst rates (64.1% to 76.2%). All but three of the 142 patients with day-8 blood MRD <0.01% remained in remission. Among new subtypes, intensified therapy based on day-15 MRD≥1% improved outcome of DUX4-rearranged, BCR-ABL1-like, and ZNF384-rearranged ALL, and achievement of day-42 MRD<0.01% did not preclude relapse of PAX5alt, MEF2D-rearranged and ETV6-RUNX1-like ALL. Thus, new subtypes including DUX4-rearranged, PAX5alt, BCR-ABL1-like, ETV6-RUNX1-like, MEF2D-rearranged and ZNF384-rearranged ALL have important prognostic and therapeutic implications.

Pediatric Acute Lymphoblastic Leukemia, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Advancements in technology that enhance our understanding of the biology of the disease, risk-adapted therapy, and enhanced supportive care have contributed to improved survival rates. However, additional clinical management is needed to improve outcomes for patients classified as high risk at presentation (eg, T-ALL, infant ALL) and who experience relapse. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for pediatric ALL provide recommendations on the workup, diagnostic evaluation, and treatment of the disease, including guidance on supportive care, hematopoietic stem cell transplantation, and pharmacogenomics. This portion of the NCCN Guidelines focuses on the frontline and relapsed/refractory management of pediatric ALL.

Identification of prognostic factors in childhood T-cell acute lymphoblastic leukemia: Results from DFCI ALL Consortium Protocols 05-001 and 11-001

BACKGROUND/OBJECTIVES

While outcomes for pediatric T-cell acute lymphoblastic leukemia (T-ALL) are favorable, there are few widely accepted prognostic factors, limiting the ability to risk stratify therapy.

DESIGN/METHODS

Dana-Farber Cancer Institute (DFCI) Protocols 05-001 and 11-001 enrolled pediatric patients with newly diagnosed B- or T-ALL from 2005 to 2011 and from 2012 to 2015, respectively. Protocol therapy was nearly identical for patients with T-ALL (N = 123), who were all initially assigned to the high-risk arm. End-induction minimal residual disease (MRD) was assessed by reverse transcription polymerase chain reaction (RT-PCR) or next-generation sequencing (NGS), but was not used to modify postinduction therapy. Early T-cell precursor (ETP) status was determined by flow cytometry. Cases with sufficient diagnostic DNA were retrospectively evaluated by targeted NGS of known genetic drivers of T-ALL, including Notch, PI3K, and Ras pathway genes.

RESULTS

The 5-year event-free survival (EFS) and overall survival (OS) for patients with T-ALL was 81% (95% CI, 73-87%) and 90% (95% CI, 83-94%), respectively. ETP phenotype was associated with failure to achieve complete remission, but not with inferior OS. Low end-induction MRD (<10-4 ) was associated with superior disease-free survival (DFS). Pathogenic mutations of the PI3K pathway were mutually exclusive of ETP phenotype and were associated with inferior 5-year DFS and OS.

CONCLUSIONS

Together, our findings demonstrate that ETP phenotype, end-induction MRD, and PI3K pathway mutation status are prognostically relevant in pediatric T-ALL and should be considered for risk classification in future trials. DFCI Protocols 05-001 and 11-001 are registered at www.clinicaltrials.gov as NCT00165087 and NCT01574274, respectively.

Nelarabine as salvage therapy and bridge to allogeneic stem cell transplant in 118 adult patients with relapsed/refractory T-cell acute lymphoblastic leukemia/lymphoma. A CAMPUS ALL study

The outcome of relapsed or refractory (R/R) T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/T-LBL) in adults is poor, with less than 20% of patients surviving at 5 years. Nelarabine is the only drug specifically approved for R/R T-ALL/T-LBL, but the information to support its use is based on limited available data. The aim of this observational phase four study was to provide recent additional data on the efficacy and safety of nelarabine in adults with R/R T-ALL/T-LBL and to evaluate the feasibility and outcome of allogeneic hematopoietic stem cell transplant (SCT) after salvage with nelarabine therapy. The primary endpoints were overall response rate (ORR) and overall survival (OS). Additional endpoints were safety, SCT rate and post-SCT OS. Between May 2007 and November 2018, 118 patients received nelarabine salvage therapy at 27 Italian hematology sites. The median age was 37 years (range 18-74 years), 73% were male, 77 had a diagnosis of T-ALL and 41 of T-LBL, and 65/118 (55%) had received more than two lines of therapy. The median number of nelarabine cycles was two (range 1-4); 43/118 (36%) patients had complete remission (CR), 16 had partial remission (14%) and 59 (50%) were refractory, with an ORR of 50%. The probability of OS, from the first dose of nelarabine, was 37% at 1 year with a median survival of 8 months. The OS at 1 year was significantly better for the 47 patients (40%) who underwent SCT after nelarabine salvage therapy (58% vs 22%, log-rank P < .001). The probability of OS at 2 and 5 years from SCT was 46% and 38%, respectively. Seventy-five patients (64%) experienced one or more drug-related adverse events (AE). Grade III-IV neurologic toxicities were observed in 9/118 (8%) of cases and thrombocytopenia or/and neutropenia (grade III-IV) were reported in 41% and 43% of cases, respectively. In conclusion, this is one of the largest cohorts of adult patients with R/R T-ALL/T-LBL treated in real life with nelarabine. Taking into account the poor prognosis of this patient population, nelarabine represents an effective option with an ORR of 50% and a CR rate of 36%. In addition, 40% of cases following nelarabine salvage therapy could undergo SCT with an expected OS at 2 and 5 years of 46% and 38%, respectively. The safety profile of nelarabine was acceptable with only 8% of cases showing grade III-IV neurological AE.

Precision medicine in acute lymphoblastic leukemia

The cure rate of childhood acute lymphoblastic leukemia (ALL) has exceeded 90% in some contemporary clinical trials. However, the dose intensity of conventional chemotherapy has been pushed to its limit. Further improvement in outcome will need to rely more heavily on molecular therapeutic as well as immuno-and cellular-therapy approaches together with precise risk stratification. Children with ETV6-RUNX1 or hyperdiploid > 50 ALL who achieve negative minimal residual disease during early remission induction are suitable candidates for reduction in treatment. Patients with Philadelphia chromosome (Ph)-positive or Ph-like ALL with ABL-class fusion should be treated with dasatinib. BH3 profiling and other preclinical methods have identified several high-risk subtypes, such as hypodiplod, early T-cell precursor, immature T-cell, KMT2A-rearranged, Ph-positive and TCF-HLF-positive ALL, that may respond to BCL-2 inhibitor venetoclax. There are other fusions or mutations that may serve as putative targets, but effective targeted therapy has yet to be established. For other high-risk patients or poor early treatment responders who do not have targetable genetic lesions, current approaches that offer hope include blinatumomab, inotuzumab and CAR-T cell therapy for B-ALL, and daratumumab and nelarabine for T-ALL. With the expanding therapeutic armamentarium, we should start focus on rational combinations of targeted therapy with non-overlapping toxicities.

Successful Outcomes of Newly Diagnosed T Lymphoblastic Lymphoma: Results From Children's Oncology Group AALL0434

PURPOSE

The Children's Oncology Group (COG) protocol AALL0434 evaluated the safety and efficacy of multi-agent chemotherapy with Capizzi-based methotrexate/pegaspargase (C-MTX) in patients with newly diagnosed pediatric T-cell lymphoblastic lymphoma (T-LL) and gained preliminary data using nelarabine in high-risk patients.

PATIENTS AND METHODS

The trial enrolled 299 patients, age 1-31 years. High-risk (HR) patients had ≥ 1% minimal detectable disease (MDD) in the bone marrow at diagnosis or received prior steroid treatment. Induction failure was defined as failure to achieve a partial response (PR) by the end of the 4-week induction. All patients received the augmented Berlin-Frankfurt-Muenster (ABFM) C-MTX regimen. HR patients were randomly assigned to receive or not receive 6 5-day courses of nelarabine incorporated into ABFM. Patients with induction failure were nonrandomly assigned to ABFM C-MTX plus nelarabine. No patients received prophylactic cranial radiation; however, patients with CNS3 disease (CSF WBC ≥ 5/μL with blasts or cranial nerve palsies, brain/eye involvement, or hypothalamic syndrome) were ineligible.

RESULTS

At end-induction, 98.8% of evaluable participants had at least a PR. The 4-year event-free survival (EFS) and overall survival (OS) were 84.7% ± 2.3% and 89.0% ± 2.0%. The 4-year disease-free survival (DFS) from end-induction was 85.9% ± 2.6%. There was no difference in DFS observed between the HR and standard-risk groups (P = .29) or by treatment regimen (P = .55). Disease stage, tumor response, and MDD at diagnosis did not demonstrate thresholds that resulted in differences in EFS. Nelarabine did not show an advantage for HR patients. CNS relapse occurred in only 4 patients.

CONCLUSION

COG AALL0434 produced excellent outcomes in one of the largest trials ever conducted for patients with newly diagnosed T-LL. The COG ABFM regimen with C-MTX provided excellent EFS and OS without cranial radiation.

Optimal approach to the treatment of young adults with acute lymphoblastic leukemia in 2020

Akin to the introduction of tyrosine kinase inhibitors to Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL), pediatric-based asparaginase-heavy approaches have revolutionized the treatment of young adults with the Philadelphia chromosome-negative subset the past decades. Once again, we are approaching a new era. An era of precision medicine with immunotherapy and other molecularly targeted treatments that offers unique opportunities to customize treatment intensity with or without hematopoietic stem cell transplantation, reduce the burden of toxicities, and combat persistent residual disease. Recently approved agents for refractory/relapsed B-cell precursor ALL include the chimeric antigen receptor-modified T-cells, the anti-CD22 monoclonal antibody-drug conjugate, inotuzumab ozogamicin, and the bispecific anti-CD19 T-cell engager, blinatumomab. These agents are expected to move widely into the frontline setting along with the proteasome inhibitors, bortezomib and carfilzomib, as well as tyrosine kinase inhibitors for Philadelphia-like rearrangements that are especially frequent among young adults. To this add the BH3 mimetics, venetoclax and navitoclax, which are being widely explored in refractory/relapsed as well as frontline settings for B- and T-cell ALL. The promising anti-CD38 monoclonal antibody, daratumumab, is entering the scene of refractory/relapsed T-ALL, whereas the old purine analogue, nelarabine, is being evaluated in a new upfront setting. This review focuses on 2 main questions: How do we optimize frontline as well as salvage ALL treatment of young adults in the 2020s? Not least, how do we address the current burden of serious toxicities unique to young adults?

Bilateral breast masses as a presentation for T-cell acute lymphoblastic leukaemia

Here we describe a 27-year-old woman, 5 months post partum, who presented to the emergency department with bilateral breast masses. She was initially treated as lactational mastitis with no improvement. Breast ultrasound showed bilateral breast and axillary lymphadenopathy suggestive of metastatic/neoplastic process, and chest X-ray showed a large anterior mediastinal mass. Further work-up led to the diagnosis of T-cell acute lymphoblastic leukaemia. The patient was started on a paediatric regimen using the children's oncology group AALL0434 protocol. The patient achieved a complete remission following induction chemotherapy with resolution of her presenting symptoms.

Early precursor T-cell acute lymphoblastic leukemia: current paradigms and evolving concepts

Early precursor T cell-acute lymphoblastic leukemia (ETP-ALL) is a rare entity characterized by chemo-resistance and a paucity of data regarding optimal management. We review here the literature regarding the management of ETP-ALL and focus on the recent, emerging data, regarding the potential role of molecularly targeted approaches with a focus on venetoclax.

Relapsed T Cell ALL: Current Approaches and New Directions

PURPOSE OF REVIEW

Patients with relapsed T cell acute lymphoblastic leukemia (T-ALL) have limited therapeutic options and a poor prognosis. Although a variety of salvage chemotherapy regimens may be used, response rates are unsatisfactory. This article summarizes current approaches and promising emerging strategies for the treatment of relapsed T-ALL.

RECENT FINDINGS

Although nelarabine is the only agent approved specifically for T-ALL, recent studies have identified a variety of genetic alterations and signaling pathways that are critical in its pathogenesis. Based on these findings, a number of small-molecule inhibitors and other targeted therapies are being studied for relapsed T-ALL, including gamma-secretase inhibitors, BCL-2 inhibitors, cyclin-dependent kinase inhibitors, and mTOR inhibitors. In addition, pre-clinical studies of chimeric antigen receptor T cells targeting CD5 and CD7 as well as the monoclonal antibody daratumumab have shown promising results for T-ALL. Relapsed T-ALL currently remains challenging to treat, but recent pre-clinical studies of targeted and immunotherapeutic agents have shown encouraging results. A number of clinical trials investigating these approaches for T-ALL are currently underway.

Recent Advances in Adult Acute Lymphoblastic Leukemia

PURPOSE OF REVIEW

This article reviews the recent advances in the pathophysiology and management of acute lymphoblastic leukemia (ALL) in adults.

RECENT FINDINGS

Addition of rituximab to standard chemotherapy improves survival in the frontline treatment of B cell ALL, and measurable residual disease (MRD) is the most important prognostic factor. Tyrosine kinase inhibitors (TKI), particularly ponatinib, in combination with Hyper-CVAD significantly improve outcomes in Ph + ALL challenging the benefit of allogeneic stem cell transplant in first line for these patients. Blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor (CAR) T cells are better options than chemotherapy alone for the treatment of relapsed or refractory ALL. Combination of these agents with chemotherapy and their incorporation in the frontline setting show promises to improve cure rates of ALL. Development of monoclonal antibodies, CAR T, and potent TKI has improved the outcome of ALL. Advances in our understanding of ALL biology are expected to bring new therapeutic strategies in the upcoming years.

Evolving therapy of adult acute lymphoblastic leukemia: state-of-the-art treatment and future directions

Recent years have witnessed major advances that have improved outcome of adults with acute lymphoblastic leukemia (ALL). The emergence of the concept of measurable residual disease has fine-tuned our prognostic models and guided our treatment decisions. The treatment paradigms of ALL have been revolutionized with the advent of tyrosine kinase inhibitors targeting BCR-ABL1, monoclonal antibodies targeting CD20 (rituximab), antibody-drug conjugates targeting CD22 (inotuzumab ozogamicin), bispecific antibodies (blinatumomab), and CD19 chimeric antigen receptor T cell therapy (tisagenlecleucel). These highly effective new agents are allowing for novel approaches that reduce reliance on intensive cytotoxic chemotherapy and hematopoietic stem cell transplantation in first remission. This comprehensive review will focus on the recent advances and future directions in novel therapeutic strategies in adult ALL.

Biology and Treatment Paradigms in T Cell Acute Lymphoblastic Leukemia in Older Adolescents and Adults

OPINION STATEMENT

T cell acute lymphoblastic leukemia (T-ALL) occurs in approximately 25-30% of adult ALL diagnoses. Historically, B cell ALL (B-ALL) and T-ALL have been treated in the same fashion despite differences in the biology of disease. Outcomes in the adolescent/young adult (AYA) population have improved significantly with the utilization of pediatric-based regimens. In addition, there may now be a role for the addition of nelarabine to frontline treatment in the AYA population. In older adults, choices in which regimen to pursue should account for the potential toxicities associated with pediatric-based regimens. Measurable residual disease (MRD) has taken on increasing prognostic value in T-ALL and may help to identify which patients should receive an allogeneic stem cell transplant. T cell lymphoblastic lymphoma (T-LBL) has traditionally been treated similarly to T-ALL, but additional management questions must be considered. Mediastinal irradiation does not seem to clearly improve outcomes, and there is considerable heterogeneity in the central nervous system (CNS) prophylaxis strategy used in prospective trials. CNS prophylaxis in AYA patients with T-ALL, on the other hand, can be safely achieved with intrathecal chemotherapy alone. Prospective data regarding CNS prophylaxis strategies in older adults are currently not available. Nelarabine-based regimens currently remain the standard in relapsed/refractory T-ALL; however, novel therapies targeting molecular aberrations in T-ALL are actively being investigated.

Post-induction Measurable Residual Disease Using Multicolor Flow Cytometry Is Strongly Predictive of Inferior Clinical Outcome in the Real-Life Management of Childhood T-Cell Acute Lymphoblastic Leukemia: A Study of 256 Patients

Background: Measurable/minimal residual disease (MRD) status is suggested as a powerful indicator of clinical-outcome in T-cell lymphoblastic leukemia/lymphoma (T-ALL). Contrary to B-cell ALL, reports on T-ALL MRD are limited and mostly based on molecular methods, mainly from developed countries. Multicolor flow cytometry (MFC)-based T-ALL studies are very few. Clinically relevant cut-off levels and ideal time-point for MRD assessment are still inconclusive. In view of lack of T-ALL MRD data from the developing world, we evaluated the prognostic value of MFC-based post-induction (PI)-MRD assessment in T-ALL in the context of standard practice. Methods: We included 256 childhood-T-ALL patients (age < 15 years) treated with a modified-MCP841 protocol, which uses high-dose cytarabine during consolidation, as a part of standard hospital practice. MRD was studied using 10-color 11-antibody MFC with any level of detectable disease being considered positive. Post-induction (PI)-MRD was available in all patients, and post-consolidation (PC) MRD was available mostly in PI-MRD-positive patients (n = 88). Results: Three years cumulative-incidence-of-relapse (3years-CIR) in PI-MRD-positive patients was inferior to negative patients (46.3% vs. 18.4%). The median relapse-free-survival (RFS), event-free-survival (EFS) and overall-survival (OS) with hazard ratio (HR) of PI-MRD-positive patients were 21.4 months vs not reached (p < 0.0001, HR-4.7), 21.6 months vs. not-reached (p = 0.0003, HR-2.01) and 37.3 months vs. not reached (p = 0.026, HR-1.64) respectively. RFS, EFS and OS of patients with PI-MRD<0.01% (n = 17) were as inferior as PI-MRD ≥ 0.01% in comparison with MRD-negative patients with HR of 4.7 (p < 0.0001), 2.45 (p = 0.0003), and 2.5 (p = 0.029), respectively. Three-years-CIR of patients with hyperleukocytosis (≥100 × 109/L) was also higher (50.5 vs. 27.6%) with inferior RFS, EFS, and OS. Among PI-MRD-positive patients, 3years-CIR, RFS, EFS, and OS of PC-MRD-positive were also inferior to that of negative patients. On multivariate analysis any-level detectable PI-MRD and hyperleukocytosis remained independently associated with inferior RFS, EFS, and OS. A combination of PI-MRD-positive status and hyperleukocytosis identified the patients with the worst clinical outcomes. Conclusion: Detectable PI-MRD using MFC was found to be the strong predictive factor of inferior clinical outcome in T-ALL patients. The combination of PI-MRD status and hyperleukocytosis provides the most influential tool for the management of T-ALL in resource constrained settings from developing world.

The Genetics and Mechanisms of T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy derived from early T-cell progenitors. The recognition of clinical, genetic, transcriptional, and biological heterogeneity in this disease has already translated into new prognostic biomarkers, improved leukemia animal models, and emerging targeted therapies. This work reviews our current understanding of the molecular mechanisms of T-ALL.

Recent Advances in the Management of Acute Lymphoblastic Leukaemia

OPINION STATEMENT

The last few years have seen unprecedented advances in treatment options for patients diagnosed with acute lymphoblastic leukaemia (ALL) in adulthood. New targeted drug therapies have been shown in randomised trials to offer significant survival improvements above standard-of-care (SoC) for relapsed disease, whilst being relatively well tolerated. Chimeric antigen receptor T cell therapy (CAR-T) has offered spectacular promise amongst the young adult population, with the possibility of cure for refractory disease. It has reversed the paradigm that transplant is the only curative option at relapse. Data is awaited regarding its effectiveness in the older adult population. Nelarabine represents an advance, but there remains a pressing need to develop new therapies with efficacy against T-ALL, especially in the relapse setting.Outcomes for younger adults have improved with the adoption of paediatric-like regimens, with a focus on dose intensity and heavy use of pegylated asparaginase. Defining who falls into the "young adult" category and would benefit from this approach remains a controversial area. In elderly patients with ALL, the introduction of tyrosine kinase inhibitors (TKIs) and reduction in standard chemotherapy intensity (especially for those with Philadelphia-positive disease) have significantly reduced treatment-associated mortality and resulted in durable remissions with good quality of life.Bone marrow transplantation remains a key therapy in adult ALL, and is still the treatment of choice for relapsed disease. The mortality associated with a myeloablative approach can be substantially lowered by reduced intensity conditioning, without an apparently significant reduction in efficacy.

Pediatric-inspired protocols in adult acute lymphoblastic leukemia: are the results bearing fruit?

Observational findings demonstrating improved survival for younger adults following pediatric, as opposed to adult, acute lymphoblastic leukemia (ALL) regimens have been translated into international, prospective multicenter clinical trials testing the pediatric regimen in young adult ALL. The results of these studies confirm the feasibility of delivering the pediatric regimen in the adult oncology setting and establish the superiority of this approach relative to historical adult cooperative group regimen results. Specific toxicities, including thrombosis, hepatotoxicity, and osteonecrosis, are more prevalent in adults receiving the pediatric regimen relative to young children. Persistent minimal residual disease (MRD) is a strong prognostic indicator in adults receiving the pediatric regimen; sensitive, high-quality MRD evaluation should be performed in all patients receiving these therapies. Incorporation of targeted agents, particularly in the frontline and MRD+ setting, will usher in the next era of the pediatric regimen in adult ALL.

Targeted therapy paves the way for the cure of acute lymphoblastic leukaemia

The past decade has witnessed tremendous progress in the treatment of acute lymphoblastic leukaemia (ALL), primarily due to the development of targeted therapies, including tyrosine kinase inhibitors targeting BCR-ABL1 tyrosine kinase, monoclonal antibodies targeting cell surface antigens (CD19, CD20 and CD22), bispecific antibodies and chimeric antigen receptor T- cell therapy. A number of new therapies have been approved by the US Food and Drug Administration in the past 5 years, including blinatumomab in 2014, inotuzumab ozagamicin in 2017 and tisagenlecleucel in 2017 for relapsed/refractory ALL. This has led to tremendous improvement in long-term survival, of more than 50% in patients with precursor B-ALL [50-70% in patients with Philadelphia chromosome (Ph)-positive ALL)], 50-60% in T-ALL and 80% in mature B-ALL. Research is ongoing to optimize the benefit of targeted therapeutics with the goal of decreasing the use of cytotoxic therapies.

The treatment of adolescents and young adults with acute lymphoblastic leukemia

Adolescents and young adults (AYAs) with ALL represent a unique population in terms of their biology and treatment. Studies have demonstrated an improved outcome when these patients are treated with pediatric-inspired regimens. Novel antibody based therapies have demonstrated impressive results in relapsed/refractory B-ALL and are starting to be evaluated in the upfront setting. Immunotherapy with CAR T cells had great success in ALL and clinical trials are ongoing and further studies are being done to expand access to this therapy and decrease toxicities. Although our outcomes with this disease have improved significantly, transplant still plays a role for high risk patients in CR1 (based on MRD status) and for patients with relapsed/refractory ALL.

Comparative features and outcomes between paediatric T-cell and B-cell acute lymphoblastic leukaemia

Contemporary paediatric clinical trials have improved 5-year event-free survival above 85% and 5-year overall survival above 90% in B-cell acute lymphoblastic leukaemia (ALL) in many study groups, whilst outcomes for T-cell ALL are still lagging behind by 5-10% in most studies. Several factors have contributed to this discrepant outcome. First, patients with T-cell ALL are generally older than those with B-cell ALL and, therefore, have poorer tolerance to chemotherapy, especially dexamethasone and asparaginase, and have increased risk of extramedullary relapse. Second, a higher proportion of patients with B-cell ALL have favourable genetic subtypes (eg, ETV6-RUNX1 and high hyperdiploidy), which confer a superior outcome compared with favourable subtypes of T-cell ALL. Third, T-cell ALL blasts are generally more resistant to conventional chemotherapeutic drugs than are B-cell ALL blasts. Finally, patients with B-cell ALL are more amendable to available targeted therapies, such as Philadelphia chromosome-positive and some Philadelphia chromosome-like ALL cases to ABL-class tyrosine kinase inhibitors, and CD19-positive and CD22-postive B-cell ALL cases to a variety of immunotherapies. Several novel treatments under investigation might narrow the gap in survival between T-cell ALL and B-cell ALL, although novel treatment options for T-cell ALL are limited.

Treatment of higher risk acute lymphoblastic leukemia in young people (CCG-1961), long-term follow-up: a report from the Children's Oncology Group

Children's Cancer Group CCG-1882 improved outcome for 1-21-year old with high risk acute lymphoblastic leukemia and Induction Day 8 marrow blasts ≥25% (slow early responders, SER) with longer and stronger post induction intensification (PII). This CCG-1961 explored alternative PII strategies. We report 10-year follow-up for patients with rapid early response (RER) and for the first time details our experience for SER patients. A total of 2057 patients were enrolled, and 1299 RER patients were randomized to 1 of 4 PII regimens: standard vs. augmented intensity and standard vs. increased length. At the end of interim maintenance, 447 SER patients were randomized to idarubicin/cyclophosphamide or weekly doxorubicin in the delayed intensification phases. The 10-year EFS for RER were 79.4 ± 2.4% and 70.9 ± 2.6% (hazard ratio = 0.65, 95% CI 0.52-0.82, p < 0.001) for augmented and standard strength PII; the 10-year OS rates were 87.2 ± 2.0% and 81.0 ± 2.2% (hazard ratio = 0.64, 95% CI 0.48-0.86, p = 0.003). Outcomes remain similar for standard and longer PII, and for SER patients assigned to idarubicin/cyclophosphamide and weekly doxorubicin. The EFS and OS advantage of augmented PII is sustained at 10 years for RER patients. Longer PII for RER patients and sequential idarubicin/cyclophosphamide for SER patients offered no advantage. CCG-1961 is the platform for subsequent COG studies.

Lymphoblastic lymphoma in children and adolescents: review of current challenges and future opportunities

Lymphoblastic lymphoma (LBL) is the second most common type of Non-Hodgkin Lymphoma (NHL) in childhood and adolescence, accounting for 25-35% of all cases. The majority, 70-80%, is of T-lymphoblastic origin while 20-25% arise from B lymphoblasts. With current therapy, the event-free and overall survivals for paediatric LBL patients now exceeds 80%. Therapy, especially in T-LBL with large mediastinal tumours, is challenging, with both significant morbidity and late sequela. An additional challenge is the dismal prognosis of patients with refractory or relapsed disease. This review article will focus on the growing knowledge of the pathogenesis and biology of LBL, recent advances and challenges in the therapy of LBL, and ongoing and future efforts and opportunities in optimizing therapy and developing novel targeted treatment approaches.

Novel targeted therapeutic agents for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

Non-Hodgkin lymphomas (NHLs) are a heterogeneous group of malignancies. Most NHLs in children, adolescent and young adult patients are aggressive lymphomas that are generally treated with multi-agent chemotherapy or immunochemotherapy regimens. While overall survival is high, the treatment can lead to a high rate of acute and long-term toxicity. However, in the rarer instance of relapsed or refractory disease, outcomes are dismal. Novel therapeutic approaches to the treatment of both T-cell and B-cell NHLs are critical to improve outcomes while also minimising the associated toxicity of current treatment regimes. Potential therapeutic approaches in development include humoral and cellular immunotherapies, small molecule inhibitors of relevant signalling pathways and epigenetic modifying agents. In this review, we will highlight the current state of development of agents of interest with a focus on agents relevant to childhood, adolescent and young adult NHL.

Will my child do better if she enrolls in a clinical trial?

The question of whether children with cancer who enroll in clinical trials have superior outcomes compared with those who do not participate has been pursued for more than 4 decades, and recent studies have provided conflicting answers. Whether clinical trial participation influences outcome has important implications for how clinicians should present trial participation to patients and families. Methodological challenges limit generalizations about the impact of clinical trial participation on outcome compared with nonparticipation. Oncologists should inform patients and families that clinical trials are the engine for future progress because they identify more effective therapies and that clinical trial participation is a reasonable option to consider for children with cancer. However, as noted in by Truong and colleagues in this issue, the rationale for trial enrollment should not include an expectation of better outcomes compared with nonenrollment.