Fludarabine Exposure Predicts Outcome after CD19 CAR T-Cell Therapy in Children and Young Adults with Acute Leukemia

Recent Advances in Therapeutic Drug Monitoring of Antineoplastic and Antimicrobial Agents in Children

Therapeutic drug monitoring (TDM) is used to optimize drug therapy by ensuring efficacy or preventing toxicity. For a limited number of cytotoxic antineoplastic drugs, for aminoglycoside antibiotics, and for vancomycin the use of TDM is common practice. In this article, we summarize recent advances and indications for the TDM of antineoplastic agents in children, focusing on protein kinase inhibitors and the cytotoxic drug fludarabine. We also summarize recent recommendations for antimicrobial TDM of beta-lactam antibiotics and vancomycin.

Low Peripheral Blood Counts and Elevated Proinflammatory Cytokines Signal a Poor CD19 CAR-T Response in ALL: Immune correlates of CAR-T response

BACKGROUND

CD19 chimeric antigen receptor T-cell (CAR-T) therapy has significantly improved outcomes for patients with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL). However, approximately 20% of patients fail to achieve a complete remission (CR), and some develop severe, life-threatening toxicities. Understanding the biological mechanisms underlying both dysfunctional responses and severe toxicity is essential for optimizing patient management and improving therapeutic efficacy.

OBJECTIVES

This study aimed to (1) characterize cytokine profiles associated with dysfunctional responses and severe toxicity following CAR-T infusion, (2) examine the timing and trajectory of cytokine changes in relation to treatment outcomes and evaluate potential strategies for mitigating toxicity and treatment failure.

STUDY DESIGN

We conducted a comprehensive analysis of serum cytokine profiles in 86 adult and pediatric patients undergoing autologous CD19 CAR-T therapy for B-ALL. Patients were categorized into three groups: 1. Dysfunctional response- Patients who failed to achieve a minimal residual disease-negative complete remission (MRD- CR) by Day 63 or who experienced recurrence of CD19+ disease in the setting ongoing CAR T cell detection before Day 63. 2. Functional response with severe cytokine release syndrome (CRS) and/or Neurotoxicity (NTX)- Patients with best response of MRD- CR by Day 63 who experienced grade 3 or higher CRS or NTX. 3. Functional response without severe CRS or NTX- Patients with best response of MRD- CR by Day 63 who did not experience grade ≥ 3 CRS or neurotoxicity. Cytokine levels were measured during the first week post-infusion and correlated with treatment efficacy, toxicity outcomes, complete blood counts (CBCs), and CAR-T expansion dynamics. This analysis aimed to better understand how cytokine profiles relate to patient outcomes and immune responses in CAR-T therapy.

RESULTS

Patients with dysfunctional response exhibited decreased neutrophils, platelets and levels of granulocytic cytokines (suggestive of low bone marrow reserve) alongside elevated pro inflammatory cytokines by Day 1. Functional response with severe toxicity patients showed a progressive rise in proinflammatory cytokines, reaching similar levels to dysfunctional response patients by Day 7. We observed that high cytokines at both the Day 1 and Day 7 timepoints were associated with poor survival. These findings remained significant when adjusting for high disease burden, a known predictor of severe inflammatory toxicity and lack of response.

CONCLUSION

Early post-CAR-T infusion inflammation is associated with both dysfunctional response and severe toxicity-even after adjusting for disease burden. This suggests that inflammation, in addition to disease burden, plays a role in determining patient outcome. Therefore, strategies aimed at reducing the pro-inflammatory state prior to or early after CAR T cell infusion may improve outcomes for R/R B-ALL patients.

Lymphodepletion chemotherapy in chimeric antigen receptor-engineered T (CAR-T) cell therapy in lymphoma

The development of chimeric antigen receptor (CAR) T-cells, engineered from peripheral T-lymphocytes of a patient with lymphoma, in order to specifically target tumor cells, has been a revolution in adoptive cell therapy (ACT). As outlined in this review, ACT was initiated by hematopoietic cell transplantation (HSCT) and re-injection of interleukin-boosted tumor-infiltrating lymphocytes (TIL). The innovative venture of genetically modifying autologous peripheral T-cells to target them to cell-surface tumoral antigens through an antibody-derived structure (i.e. independent of major histocompatibility antigen presentation, physiologically necessary for T-cell activation), and intracytoplasmic T-cell costimulatory peptides, via a novel membrane CAR, has been an outstanding breakthrough. Here, focusing on B-cell hematological malignancies and mostly non-Hodgkin lymphoma, attention is brought to the importance of providing an optimal microenvironment for such therapeutic cells to proliferate and positively develop anti-tumoral cytotoxicity. This, perhaps paradoxically, implies a pre-infusion step of deep lymphopenia and deregulation of immunosuppressive mechanisms enhanced by tumoral cells. Fludarabine and cyclophosphamide appear to be the most efficient lymphodepletive drugs in this context, dosage being of importance, as will be illustrated by a thorough literature review.

Safety and clinical efficacy of Relmacabtagene autoleucel (relma-cel) for systemic lupus erythematosus: a phase 1 open-label clinical trial

Background

Systemic lupus erythematosus (SLE) is a classic systemic autoimmune disease mediated by autoantibodies. Chimeric antigen receptor T (CAR-T) cell therapy, known for its success in cancer, has shown promise in achieving durable B cell depletion and long-term remission in SLE. Relmacabtagene autoleucel (relma-cel) is the second anti-CD19 CAR-T product approved for marketing by the National Medical Products Administration (NMPA) in China and demonstrates its long-term efficacy in relapsed/refractory (r/r) large B cell lymphoma (LBCL). We report the results from a phase I open-label clinical trial of relma-cel in treating patients with moderately to severely active SLE.

Methods

Eligible patients were aged 18-70 years, a ≥6-month history of SLE, and the disease had to remain active after at least 2 months of stable SLE standard treatment prior to screening. We evaluated four dose levels (DL) of relma-cel in a dose-escalation scheme: total dose of 25 × 106, 50 × 106, 75 × 106, and 100 × 106 anti-CD19 CAR-T cells. All patients received lymphodepletion chemotherapy with fludarabine and cyclophosphamide. The primary endpoints were the incidence of dose-limiting toxicities (DLTs) and adverse events (AEs). Secondary endpoints included the evaluation of standard cellular pharmacokinetic parameters, the SLE Responder Index (SRI) response rate, and changes from baseline in the Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI), British Isles Lupus Assessment Group 2004 (BILAG-2004) and Physician's Global Assessment (PGA) scores post-treatment. This trial is registered with ClinicalTrials.gov, NCT05765006.

Findings

Between March 28, 2023 and April 8, 2024, a total of 12 patients were screened for study inclusion, of whom 8 patients were enrolled and assigned to different dose levels: 25 × 106 cells (n = 3), 50 × 106 cells (n = 2), 75 × 106 cells (n = 2), and 100 × 106 cells (n = 1). No DLT was observed. The most common AEs included cytopenia (n = 8, 100%), cytokine release syndrome (CRS) (n = 7, 88%) and hypogammaglobulinemia (n = 5, 63%). No Grade 3 or higher immune effector cell-associated hematotoxicity (ICAHT) occurred. No cases of immune effector cell-associated neurotoxicity syndrome (ICANS) were reported. CRS was predominantly grade 1, characterized mainly by mild fever and muscle soreness. A rare severe adverse event, immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS), was observed in one patient. The median time to reach maximum CAR-T cell expansion (Cmax) was 9.5 days (range: 8-22 days). The median Cmax was 18.74 CD3+CAR+ cells/μL (range: 7.94-228.36) by flow cytometry and 81766.5 copies/μg DNA (range: 50,979-1,140,893) by quantitative real-time PCR (qPCR). In all patients treated with relma-cel, CD19+ B cells in peripheral blood were almost completely depleted within 11-15 days and gradually recovered within 2-6 months. All patients achieved SRI response. Four patients achieved Definition of Remission in SLE (DORIS) remission criteria and seven patients reached the Lupus Low Disease Activity State (LLDAS) criteria within 1-4 months following relma-cel infusion.

Interpretation

This study preliminarily demonstrated that relma-cel is an effective and safe CAR-T product for the treatment of patients with moderately to severely active SLE, providing valuable clinical insights into the management of rare complications. Further studies with larger sample sizes are warranted.

Funding

National Natural Science Foundation of China.

CAR T-cells for acute leukemias in children: current status, challenges, and future directions

CAR T-cells therapy is seen as one of the most promising immunotherapies for leukemias, since targeting CD19 has revolutionized the treatment of relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL) in children, adolescents, and young adults. Early phase clinical trials have shown a very high initial response rate confirmed by follow up and real-world studies. However, almost half of patients relapse with the available commercial product currently suggesting the need of a consolidative treatment after CAR T-cell infusion in well-defined cases, according to several pre- and post-CAR clinical and biological factors. This finding highlights that numerous challenges exist before the extension of CAR T-cell indications (first relapse and high-risk first line) in the field of B-ALL: to enhance persistence of CAR T-cells to avoid CD19-positive relapse and to avoid CD19-negative relapse by reducing tumor burden pre-CAR-T infusion and/or by multitargeting. Promising approaches with exciting early clinical data are emerging in the field of T-cell ALL. The use of CAR T-cells for acute myeloid leukemias remains challenging due to the lack of leukemia-specific antigens and to the immunosuppressive microenvironment.

The present and future of CAR T-cell therapy for adult B-cell ALL

ABSTRACT

Chimeric antigen receptor T-cell therapy (CAR-T) targeting CD19 has transformed the management of relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL), with the US Food and Drug Administration approval of tisagenlecleucel for pediatric/young adult patients and brexucabtagene autoleucel for adults. Efficacy is contingent upon several factors including disease burden. Emerging data suggest that bridging therapy, lymphodepletion, and, for some patients, consolidation therapy have an important role in the success of treatment. Furthermore, strategies to define and manage immunotoxic side effects including hematotoxicity is critical to safe delivery. Advancements in CAR-T design beyond CD19 represent an ongoing therapeutic evolution. Overall, CAR-T signifies a paradigm shift in B-ALL management, with the potential for improved remission and survival in a historically challenging patient population.

From Prospective Evaluation to Practice: Model-Informed Dose Optimization in Oncology

One dose does not fit all, especially in oncolytic drugs, where side effects and therapy failures highlight the need for personalized dosing approaches. In recent years, the quest to apply model-informed precision dosing to oncology drugs has gained significant momentum, reflecting its potential to revolutionize patient care by tailoring treatments to individual pharmacokinetic profiles. Despite this progress, model-informed precision dosing has not (yet) become widely integrated into routine clinical care. We aimed to explain model-informed precision dosing from a clinical viewpoint while addressing all prospective model-informed precision dosing implementation and validation studies in the field of oncology. We identified 16 different drugs for which prospective model-informed precision dosing validation/implementation has been performed. Although these studies are mostly focused on attaining adequate drug exposures and reducing inter-individual variability, improved clinical outcomes after performing model-informed precision dosing were shown for busulfan, and high-dose methotrexate. Toxicities were significantly reduced for busulfan and cyclophosphamide treatment. In contrast, for carboplatin, for which model-informed precision dosing has been used in the Calvert formula, no prospective validation on outcomes was deemed necessary as the therapeutic window had been extensively validated. Model-informed precision dosing has shown to be of added value in oncology and is expected to significantly change dosing regimens in the future.

Recommended approaches for integration of population pharmacokinetic modelling with precision dosing in clinical practice

Current methods of dose determination have contributed to suboptimal and inequitable health outcomes in underrepresented patient populations. The persistent demand to individualise patient treatment, alongside increasing technological feasibility, is leading to a growing adoption of model-informed precision dosing (MIPD) at point of care. Population pharmacokinetic (popPK) modelling is a technique that supports treatment personalisation by characterising drug exposure in diverse patient groups. This publication addresses this important shift in clinical approach, by collating and summarising recommendations from literature. It seeks to provide standardised guidelines on best practices for the development of popPK models and their use in MIPD software tools, ensuring the safeguarding and optimisation of patient outcomes. Moreover, it consolidates guidance from key regulatory and advisory bodies on MIPD software deployment, as well as technical requirements for electronic health record integration. It also considers the future application and clinical impact of machine learning algorithms in popPK and MIPD. Ultimately, this publication aims to facilitate the incorporation of high-quality precision-dosing solutions into standard clinical workflows, thereby enhancing the effectiveness of individualised dose selection at point of care.

Therapeutic drug monitoring in acute lymphoblastic leukemia-a deep dive into pharmacokinetics, -dynamics, and -genetics of antileukemic drugs

INTRODUCTION

Therapeutic drug monitoring (TDM) is important to optimize drug exposure and minimize toxicity for the individual patient.

AREAS COVERED

This narrative review covers the pharmacokinetics (PK), -dynamics (PD) and -genetics of classic chemotherapeutic drugs used in frontline therapy for acute lymphoblastic leukemia (ALL), including anthracyclines, asparaginase, busulfan, cyclophosphamide, cytarabine, glucocorticoids, methotrexate, nelarabine, thiopurines, tyrosine kinase inhibitors, and vincristine. Furthermore, novel immunotherapies including blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor T-cells that are rapidly moving into frontline therapy are addressed. This review focuses on TDM already used in clinical practice as well as the unused potential and feasibility of TDM. Finally, important factors affecting PK/PD such as obesity and transition to adolescence and young adulthood are discussed.

EXPERT OPINION

Investigation of TDM as standard of care for antileukemic agents is highly warranted to personalize curative yet toxic anticancer regimens within frontline ALL treatment. Some of the drugs have been used in ALL treatment regimens for decades, but a wide range of new compounds are being introduced, some like blinatumomab reaching standard-of-care designation. Not least, optimized drug efficacy and reduction of the risk of serious toxicities may render TDM implementation cost-effective.

Dual-targeting CAR T cells for B-cell acute lymphoblastic leukemia and B-cell non-Hodgkin lymphoma

ABSTRACT

Relapse after CD19-directed chimeric antigen receptor (CAR) T-cell therapy remains a major challenge in B-cell acute lymphoblastic leukemia (ALL) and B-cell non-Hodgkin lymphoma (B-NHL). One of the main strategies to avoid CD19-negative relapse has been the development of dual CAR T cells targeting CD19 and an additional target, such as CD22 or CD20. Different methods have been used to achieve this, including coadministration of 2 products targeting 1 single antigen, cotransduction of autologous T cells, use of a bicistronic vector, or the development of bivalent CARs. Phase 1 and 2 trials across all manufacturing strategies have shown this to be a safe approach with equivalent remission rates and initial product expansion. CAR T-cell persistence remains a significant issue, with the majority of relapses being antigen-positive after CAR T-cell infusion. Further, despite adding a second antigen, antigen-negative relapses have not yet been eliminated. This review summarizes the state of the art with dual-targeting CAR T cells for B-cell ALL and B-NHL, the challenges encountered, and possible next steps to overcome them.

Tisagenlecleucel in Practice: Real-World Lessons in Pediatric and Young Adult B-ALL

The global multi-institutional registration trial (ELIANA) of CD19.41BB.zeta chimeric antigen receptor (CAR) T cell therapy forged the path to the first FDA-approved CAR T product, tisagenlecleucel. Since its approval, extensive post-market experience with CAR T cells in children and young adults has amassed, allowing several multi-institutional efforts to leverage real-world data. Real-world data has validated clinical trial findings and provided insights into CAR T-cell use in patient groups not included in early clinical trials, such as children <3 years, patients with active CNS and isolated extramedullary disease, and patients treated in first relapse. Data from multi-centered consortia has also identified cohorts who experienced inferior outcomes post-tisagenlecleucel, informing high-risk groups for whom further treatment optimization is needed, and delineating treatment variables, such as CAR T cell dose and lymphodepleting chemotherapy pharmacokinetics, that impact outcomes. In this early stage of CAR T-cell therapies, real-world experience provides an increasingly rich data reservoir and an invaluable resource to investigate and address clinical gaps for CAR T recipients. This review highlights key insights gained from post-market studies that have informed clinical use of CAR T-cell therapy for children and young adults with B-ALL.

Clinical review of substitutions or alternatives for critical chemotherapy drug shortages in hematologic malignancies

PURPOSE

Over the past decade, drug shortages have become increasingly more problematic for clinicians, with over 300 drug shortages reported in the first quarter of 2023. Shortages of chemotherapy drugs can have a negative impact on patient care, as omission or delay of treatment can lead to worse outcomes. Although many articles have been published on this topic, currently no review articles discuss strategies for using alternative regimens or substitutions in the event of severe chemotherapy drug shortages.

SUMMARY

In this article, we review the literature on antineoplastic agents used to treat hematologic malignancies that experienced a drug shortage from 2010 through 2023, providing recommendations for substitutions and alternative regimens in the event of a critical shortage. In particular, we discuss how shortages of fludarabine, cytarabine, daunorubicin, methotrexate, and platinum agents may be addressed, including supporting clinical evidence.

CONCLUSION

Further publications assessing possible alternatives and substitutions for chemotherapy agents and examining the efficacy of previous strategies are needed to mitigate potentially devastating interruptions to care for patients with cancer during severe drug shortages.

The role of the conditioning regimen for autologous and ex vivo genetically modified hematopoietic stem cell-based therapies: recommendations from the ISCT stem cell engineering committee

BACKGROUND

The advent of autologous gene modified cell therapies to treat monogenic disorders has been a major step forward for the field of hematopoietic stem cell transplantation (HCT) and cellular therapies. The need for disease-specific conditioning to enable these products to provide a potential cure has required extrapolation from experience in myeloablative and non-myeloablative HCT for these disorders.

METHODS

In this manuscript, we review the current datasets and clinical experience using different conditioning regimens for autologous gene therapies in hemoglobinopathies, metabolic and lysosomal disorders, inborn errors of immunity (IEI) and bone marrow failure (BMF) syndromes.

RESULTS

The disease specific and unique conditioning requirements of each disorder are considered in order to achieve maximal benefit while minimizing associated toxicities.

CONCLUSIONS

Standardized recommendations based on these data are made for each set of disorders to harmonize treatment. Future directions and the possibility of non-genotoxic conditioning regimens for autologous gene therapies are also discussed. Ethical Statement: The authors followed all relevant ethical considerations in writing this manuscript.

Allogeneic chimeric antigen receptor cell therapies for cancer: progress made and remaining roadblocks

Chimeric antigen receptor (CAR) T cells are revolutionizing cancer therapy, particularly for haematological malignancies, conferring durable and sometimes curative responses in patients with advanced-stage disease. The CAR T cell products currently approved for clinical use are all autologous and are often effective; however, in patients who are lymphopenic and/or heavily pretreated with chemotherapy, autologous T cells can be difficult to harvest in sufficient numbers or have functional impairments that might ultimately render them less efficacious. Moreover, autologous products take several weeks to produce, and each product can be used in only one patient. By contrast, allogeneic CAR T cells can be produced for many patients using T cells from a single healthy donor, can be optimized for safety and efficacy, can be instantly available for 'off-the-shelf' use and, therefore, might also be more cost-effective. Despite these potential advantages, the development of allogeneic CAR T cells has lagged behind that of autologous products, owing to the additional challenges such as avoiding graft-versus-host disease and host-mediated graft rejection. Over the past few years, the development of advanced genome-editing techniques has facilitated the generation of novel allogeneic CAR T cell products. Furthermore, CAR cell products derived from other cell types such as induced pluripotent stem cells and natural killer cells are being investigated for clinical use. In this Review, we discuss the potential of allogeneic CAR cell products to expand life-saving immunotherapy to a much broader population of patients in the coming years, the progress made to date and strategies to overcome remaining hurdles.

Chimeric antigen receptor T-cell therapy for haematological malignancies: Insights from fundamental and translational research to bedside practice

Autologous chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of lymphoid malignancies, leading to the approval of CD19-CAR T cells for B-cell lymphomas and acute leukaemia, and more recently, B-cell maturation antigen-CAR T cells for multiple myeloma. The long-term follow-up of patients treated in the early clinical trials demonstrates the possibility for long-term remission, suggesting a cure. This is associated with a low incidence of significant long-term side effects and a rapid improvement in the quality of life for responders. In contrast, other types of immunotherapies require prolonged treatments or carry the risk of long-term side effects impairing the quality of life. Despite impressive results, some patients still experience treatment failure or ultimately relapse, underscoring the imperative to improve CAR T-cell therapies and gain a better understanding of their determinants of efficacy to maximize positive outcomes. While the next-generation of CAR T cells will undoubtingly be more potent, there are already opportunities for optimization when utilizing the currently available CAR T cells. This review article aims to summarize the current evidence from clinical, translational and fundamental research, providing clinicians with insights to enhance their understanding and use of CAR T cells.

Pharmacokinetics and Pharmacodynamics of Systemic Corticosteroids in Autoimmune and Inflammatory Diseases: A Review of Current Evidence

BACKGROUND AND OBJECTIVE

Systemic corticosteroids have a long history of use in the treatment of autoimmune and inflammatory diseases. Both efficacy and safety show large interindividual variability (IIV), suggesting that corticosteroids may have the potential for individualised dosing strategies to optimise therapy. This systematic review aims to provide an overview of current evidence on the pharmacokinetic (PK) and pharmacodynamic (PD) relationships of systemic corticosteroids in patients with autoimmune and inflammatory diseases.

METHODS

A systematic literature search was conducted in PubMed and Embase for PK/PD studies of systemic corticosteroids in autoimmune and inflammatory diseases in humans published until December 2023. Studies were scored from 1 to 5 according to criteria for the levels of evidence, as inspired by the Oxford Centre for Evidence-Based Medicine.

RESULTS

Twelve studies (1981-2016) were included. The majority of these studies had a small sample size. The corticosteroids involved were prednisone, prednisolone, methylprednisolone and budesonide. Substantial IIV of corticosteroid PK was described in all studies. Evidence for a relationship between the PK of corticosteroids and efficacy was inconclusive and limited. However, there was some evidence for a relationship between the PK of prednisolone and the severity of Cushingoid features.

CONCLUSION

There is insufficient evidence to draw firm conclusions on the potential associations between PK and clinical outcome of systemic corticosteroid treatment in autoimmune and inflammatory diseases. This is remarkable given the many decades that steroid drugs have been used in clinical care. Prospective research is recommended with robust and well-defined cohorts to fully quantify the PK/PD associations of corticosteroids.

Advancements and challenges in CAR T cell therapy in autoimmune diseases

Chimeric antigen receptor (CAR) T cells are highly effective at targeting and eliminating cells of the B cell lineage. CAR T cell therapy has become a standard-of-care treatment for patients with relapsed or refractory B cell malignancies. In addition, the administration of genetically modified T cells with the capacity to deplete B cells and/or plasma cells has tremendous therapeutic potential in autoimmune diseases. In the past few years, CD19-based and B cell maturation antigen (BCMA)-based CAR T cell therapies have been applied to various B cell-mediated autoimmune diseases including systemic lupus erythematosus, idiopathic inflammatory myopathy, systemic sclerosis, neuromyelitis optica spectrum disorder, myasthenia gravis and multiple sclerosis. The scientific rationale behind this approach is that deep depletion of B cells, including autoreactive B cell clones, could restore normal immune function, referred to as an immune reset. In this Review, we discuss important aspects of CAR T cell therapy in autoimmune disease, including considerations relating to patient selection, safety, efficacy and medical management. These considerations are based on the early experiences of CAR T cell therapy in autoimmune diseases, and as the field of CAR T cell therapy in autoimmune diseases continues to rapidly evolve, these issues will remain subject to ongoing refinement and adaptation.

Prediction of Response to FDA-Approved Targeted Therapy and Immunotherapy in Acute Lymphoblastic Leukemia (ALL)

OPINION STATEMENT

Acute lymphoblastic leukemia (ALL) represents the predominant cancer in pediatric populations, though its occurrence in adults is relatively rare. Pre-treatment risk stratification is crucial for predicting prognosis. Important factors for assessment include patient age, white blood cell (WBC) count at diagnosis, extramedullary involvement, immunophenotype, and cytogenetic aberrations. Minimal residual disease (MRD), primarily assessed by flow cytometry following remission, plays a substantial role in guiding management plans. Over the past decade, significant advancements in ALL outcomes have been witnessed. Conventional chemotherapy has remarkably reduced mortality rates; however, its intensive nature raises safety concerns and has led to the emergence of treatment-resistant cases with recurrence of relapses. Consequently, The U.S. Food and Drug Administration (FDA) has approved several novel treatments for relapsed/refractory ALL due to their demonstrated efficacy, as indicated by improved complete remission and survival rates. These treatments include tyrosine kinase inhibitors (TKIs), the anti-CD19 monoclonal antibody blinatumomab, anti-CD22 inotuzumab ozogamicin, anti-CD20 rituximab, and chimeric antigen receptor (CAR) T-cell therapy. Identifying the variables that influence treatment decisions is a pressing necessity for tailoring therapy based on heterogeneous patient characteristics. Key predictive factors identified in various observational studies and clinical trials include prelymphodepletion disease burden, complex genetic abnormalities, and MRD. Furthermore, the development of serious adverse events following treatment could be anticipated through predictive models, allowing for appropriate prophylactic measures to be considered. The ultimate aim is to incorporate the concept of precision medicine in the field of ALL through valid prediction platform to facilitate the selection of the most suitable treatment approach.

The Role of the JAK-STAT Pathway in Childhood B-Cell Acute Lymphoblastic Leukemia

B-cell lymphoblastic leukemia is a hematologic neoplasm that poses a serious health concern in childhood. Genetic aberrations, such as mutations in the genes IL-7, IL7R, JAK1, JAK2, TLSP, CRLF2, and KTM2A or gene fusions involving BCR::ABL1, ETV6::RUNX1, and PAX5::JAK2, often correlate with the onset of this disease. These aberrations can lead to malfunction of the JAK-STAT signaling pathway, which is implicated in various important biological processes, including those related to immunology. Understanding the mechanisms underlying the malfunction of the JAK-STAT pathway holds potential for research on drugs targeting its components. Available drugs that interfere with the JAK-STAT pathway include fludarabine, ruxolitinib, and fedratinib.

Prognostic differences between carmustine, etoposide, cytarabine and melphalan (BEAM) and carmustine, etoposide, cytarabine, melphalan and fludarabine (BEAMF) regimens before autologous stem cell transplantation plus chimeric antigen receptor T therapy in patients with refractory/relapsed B-cell non-Hodgkin-lymphoma

BACKGROUND AIMS

The combination therapy of autologous hematopoietic stem cell transplantation (ASCT) and chimeric antigen receptor T-cell (CART) therapy has been employed to improve outcomes for relapsed or refractory (R/R) B-cell non-Hodgkin-lymphoma (B-NHL). The widely used conditioning regimen before ASCT plus CART therapy reported in the literature was carmustine, etoposide, cytarabine and melphalan (BEAM). However, whether adding fludarabine to the BEAM regimen (BEAMF) can improve the survival of patients with R/R B-NHL remains unknown.

METHODS

In total, 39 and 19 patients with R/R B-NHL were enrolled to compare clinical outcomes in the BEAM and BEAMF regimens before ASCT plus CD19/22 CART therapy, respectively.

RESULTS

The objective response (OR) rates at 3 months to BEAM and BEAMF regimens before ASCT plus CD19/22 CART therapy were 71.8% and 94.7%, respectively (P = 0.093). The BEAMF regimen showed a trend towards a superior duration of response compared with the BEAM regimen (P = 0.09). After a median follow-up of 28 months (range: 0.93-51.9 months), the BEAMF regimen demonstrated superior 2-year progression-free survival (PFS) (89.5% versus 63.9%; P = 0.048) and 2-year overall survival (OS) (100% vs 77.3%; P = 0.035) compared with the BEAM regimen. In the multivariable Cox regression analysis, OR at month 3 (responders) was remarkably correlated with better OS (hazard ratio: 0.112, P = 0.005) compared with OR (non-responders).

CONCLUSIONS

For patients with R/R B-NHL, the BEAMF regimen before ASCT plus CD19/22 CART therapy was correlated with superior PFS and OS than the BEAM regimen, and the BEAMF regimen is a promising alternative conditioning regimen for ASCT plus CAR-T therapy.

Current Challenges in Chimeric Antigen Receptor T-cell Therapy in Patients With B-cell Lymphoid Malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a promising immunotherapy based on genetically engineered T cells derived from patients. The introduction of CAR T-cell therapy has changed the treatment paradigm of patients with B-cell lymphoid malignancies. However, challenging issues including managing life-threatening toxicities related to CAR T-cell infusion and resistance to CAR T-cell therapy, leading to progression or relapse, remain. This review summarizes the issues with currently approved CAR T-cell therapies for patients with relapsed or refractory B-cell lymphoid malignancies, including lymphoma and myeloma. We focus on unique toxicities after CAR T-cell therapy, such as cytokine-related events and hematological toxicities, and the mechanisms underlying post-CAR T-cell failure.

Busulfan with 400 centigray of total body irradiation and higher dose fludarabine: An alternative regimen for hematopoietic stem cell transplantation in pediatric acute lymphoblastic leukemia

BACKGROUND

Hematopoietic stem cell transplantation can be curative for children with difficult-to-treat leukemia. The conditioning regimen utilized is known to influence outcomes. We report outcomes of the conditioning regimen used at the Alberta Children's Hospital, consisting of busulfan (with pharmacokinetic target of 3750 μmol*min/L/day ±10%) for 4 days, higher dose (250 mg/m2 ) fludarabine and 400 centigray (cGy) of total body irradiation.

PROCEDURE

This retrospective study involved children receiving transplant for acute lymphoblastic leukemia (ALL). It compared children who fell within the target range for busulfan with those who were either not measured or were measured and fell outside this range. All other treatment factors were identical.

RESULTS

Twenty-nine children (17 within target) were evaluated. All subjects engrafted neutrophils with a median [interquartile range] time of 14 days [8-30 days]. The cumulative incidence of acute graft-versus-host disease was 44.8% [95% confidence interval, CI: 35.6%-54.0%], while chronic graft-versus-host disease was noted in 16.0% [95% CI: 8.7%-23.3%]. At 2 years, the overall survival was 78.1% [95% CI: 70.8%-86.4%] and event-free survival was 74.7% [95% CI: 66.4%-83.0%]. Cumulative incidence of relapse was 11.3% [95% CI: 5.1%-17.5%]. There were no statistically significant differences in between the group that received targeted busulfan compared with the untargeted group.

CONCLUSION

Our conditioning regiment for children with ALL resulted in outcomes comparable to standard treatment with acceptable toxicities and significant reduction in radiation dose. Targeting busulfan dose in this cohort did not result in improved outcomes.

Immune therapies of B-cell acute lymphoblastic leukaemia in children and adults

B-cell acute lymphoblastic leukaemia (B-cell ALL) is a common haematologic cancer in children and adults. About 10 percent of children and 50 percent of adults fail to achieve a histological complete remission or subsequently relapse despite current anti-leukaemia drug therapies and/or haematopoietic cell transplants. Several new immune therapies including monoclonal antibodies and chimeric antigen receptor (CAR)-T-cells are proved safe and effective in this setting. We review data on US Food and Drug Administration (FDA)-approved immune therapies for B-cell ALL in children and adults including blinatumomab, inotuzumab ozogamicin, tisagenlecleucel, and brexucabtagene autoleucel. We also summarize pharmaco-dynamics, pharmaco-kinetics, and pharmaco-economics of these interventions.

The Implementation of Chimeric Antigen Receptor (CAR) T-cell Therapy in Pediatric Patients: Where Did We Come From, Where Are We Now, and Where are We Going?

CD19-directed Chimeric Antigen Receptor (CAR) T-cell therapy has revolutionized the treatment of patients with B-cell acute lymphoblastic leukemia (B-ALL). Somewhat uniquely among oncologic clinical trials, early clinical development occurred simultaneously in both children and adults. In subsequent years however, the larger number of adult patients with relapsed/refractory (r/r) malignancies has led to accelerated development of multiple CAR T-cell products that target a variety of malignancies, resulting in six currently FDA-approved for adult patients. By comparison, only a single CAR-T cell therapy is approved by the FDA for pediatric patients: tisagenlecleucel, which is approved for patients ≤ 25 years with refractory B-cell precursor ALL, or B-cell ALL in second or later relapse. Tisagenlecleucel is also under evaluation in pediatric patients with relapsed/refractory B-cell non-Hodgkin lymphoma, but is not yet been approved for this indication. All the other FDA-approved CD19-directed CAR-T cell therapies available for adult patients (axicabtagene ciloleucel, brexucabtagene autoleucel, and lisocabtagene maraleucel) are currently under investigations among children, with preliminary results available in some cases. As the volume and complexity of data continue to grow, so too does the necessity of rapid assimilation and implementation of those data. This is particularly true when considering "atypical" situations, e.g. those arising when patients do not precisely conform to the profile of those included in pivotal clinical trials, or when alternative treatment options (e.g. hematopoietic stem cell transplantation (HSCT) or bispecific T-cell engagers (BITEs)) are also available. We have therefore developed a relevant summary of the currently available literature pertaining to the use of CD19-directed CAR-T cell therapies in pediatric patients, and sought to provide guidance for clinicians seeking additional data about specific clinical situations.

Comparison of high-throughput single-cell RNA-seq methods for ex vivo drug screening

Functional precision medicine (FPM) aims to optimize patient-specific drug selection based on the unique characteristics of their cancer cells. Recent advancements in high throughput ex vivo drug profiling have accelerated interest in FPM. Here, we present a proof-of-concept study for an integrated experimental system that incorporates ex vivo treatment response with a single-cell gene expression output enabling barcoding of several drug conditions in one single-cell sequencing experiment. We demonstrate this through a proof-of-concept investigation focusing on the glucocorticoid-resistant acute lymphoblastic leukemia (ALL) E/R+ Reh cell line. Three different single-cell transcriptome sequencing (scRNA-seq) approaches were evaluated, each exhibiting high cell recovery and accurate tagging of distinct drug conditions. Notably, our comprehensive analysis revealed variations in library complexity, sensitivity (gene detection), and differential gene expression detection across the methods. Despite these differences, we identified a substantial transcriptional response to fludarabine, a highly relevant drug for treating high-risk ALL, which was consistently recapitulated by all three methods. These findings highlight the potential of our integrated approach for studying drug responses at the single-cell level and emphasize the importance of method selection in scRNA-seq studies. Finally, our data encompassing 27 327 cells are freely available to extend to future scRNA-seq methodological comparisons.

INSPIRED Symposium Part 4B: Chimeric Antigen Receptor T Cell Correlative Studies-Established Findings and Future Priorities

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of B cell malignancies, with multiple CAR T cell products approved for numerous indications by regulatory agencies worldwide. However, significant work remains to be done to enhance these treatments. In March 2023, a group of experts in CAR T cell therapy assembled at the National Institutes of Health in Bethesda, Maryland at the Insights in Pediatric CAR T Cell Immunotherapy: Recent Advances and Future Directions (INSPIRED) Symposium to identify key areas for research for the coming years. In session 4B, correlative studies to be incorporated into future clinical trials and real-world settings were discussed. Active areas of research identified included (1) optimizing CAR T cell product manufacturing; (2) ensuring adequate lymphodepletion prior to CAR T cell administration; (3) overcoming immunoregulatory cells and tumor stroma present in the tumor microenvironment, particularly in solid tumors; (4) understanding tumor intrinsic properties that lead to CAR T cell immunotherapy resistance; and (5) uncovering biomarkers predictive of treatment resistance, treatment durability, or immune-related adverse events. Here we review the results of previously published clinical trials and real-world studies to summarize what is currently known about each of these topics. We then outline priorities for future research that we believe will be important for improving our understanding of CAR T cell therapy and ultimately leading to better outcomes for patients.

Emerging Biomarkers for Monitoring Chimeric Antigen Receptor T-Cell Therapy

BACKGROUND

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized treatment of hematologic malignancies and holds promise for solid tumors. While responses to CAR T-cell therapy have surpassed other available options for patients with refractory malignancies, not all patients respond the same way. The reason for this variability is not currently understood. Therefore, there is a strong need to identify characteristics of patients as well as cellular products that lead to an effective response to CAR T-cell therapy.

CONTENT

In this review, we discuss potential biomarkers that may predict clinical outcomes of CAR T-cell therapy. Based on correlative findings from clinical trials of both commercially available and early-phase products, we classify biomarkers into categories of pre- and post-infusion as well as patient and product-related markers. Among the biomarkers that have been explored, measures of disease burden both pre- and post-infusion, as well as CAR T-cell persistence post-infusion, are repeatedly identified as predictors of disease response. Higher proportions of early memory T cells at infusion appear to be favorable, and tracking T-cell subsets throughout treatment will likely be critical.

SUMMARY

There are a growing number of promising biomarkers of CAR T-cell efficacy described in the research setting, however, none of these have been validated for clinical use. Some potentially important predictors of response may be difficult to obtain routinely under the current CAR T-cell therapy workflow. A collaborative approach is needed to select biomarkers that can be validated in large cohorts and incorporated into clinical practice.

CAR-T Cell Therapy in B-Cell Acute Lymphoblastic Leukemia

Treatment of refractory and relapsed (R/R) B acute lymphoblastic leukemia (B-ALL) is an unmet medical need in both children and adults. Studies carried out in the last two decades have shown that autologous T cells engineered to express a chimeric antigen receptor (CAR-T) represent an effective technique for treating these patients. Antigens expressed on B-cells, such as CD19, CD20, and CD22, represent targets suitable for treating patients with R/R B-ALL. CD19 CAR-T cells induce a high rate (80-90%) of complete remissions in both pediatric and adult R/R B-ALL patients. However, despite this impressive rate of responses, about half of responding patients relapse within 1-2 years after CAR-T cell therapy. Allo-HSCT after CAR-T cell therapy might consolidate the therapeutic efficacy of CAR-T and increase long-term outcomes; however, not all the studies that have adopted allo-HSCT as a consolidative treatment strategy have shown a benefit deriving from transplantation. For B-ALL patients who relapse early after allo-HSCT or those with insufficient T-cell numbers for an autologous approach, using T cells from the original stem cell donor offers the opportunity for the successful generation of CAR-T cells and for an effective therapeutic approach. Finally, recent studies have introduced allogeneic CAR-T cells generated from healthy donors or unmatched, which are opportunely manipulated with gene editing to reduce the risk of immunological incompatibility, with promising therapeutic effects.

CAR-T cell therapy in hematological malignancies: Where are we now and where are we heading for?

Chimeric antigen receptor T (CAR-T) therapy has emerged as a revolutionary new pillar in cancer care, particularly in relapsed/refractory (r/r) B-cell malignancies. Following impressive clinical outcomes in hematological malignancies, the FDA-approved six CAR-T cell products for indications such as lymphoma, leukemia, and myeloma. Despite the numerous advantages of CAR-T cell treatment, several challenges exist that interfere with its therapeutic efficacy. Serious adverse effects connected with the treatment continue to be a major concern. In addition, poor persistence of therapeutics and antigen escape frequently result in tumor relapse. Exorbitant treatment cost further remains a significant barrier to its effective implementation, limiting its accessibility. This review presents progress of CAR-T research, the key obstacles that hamper promising outcomes for patients with hematological malignancies, and a few strategies to overcome them.

Lymphodepletion - an essential but undervalued part of the chimeric antigen receptor T-cell therapy cycle

Lymphodepletion (LD) or conditioning is an essential step in the application of currently used autologous and allogeneic chimeric antigen receptor T-cell (CAR-T) therapies as it maximizes engraftment, efficacy and long-term survival of CAR-T. Its main modes of action are the depletion and modulation of endogenous lymphocytes, conditioning of the microenvironment for improved CAR-T expansion and persistence, and reduction of tumor load. However, most LD regimens provide a broad and fairly unspecific suppression of T-cells as well as other hematopoietic cells, which can also lead to severe side effects, particularly infections. We reviewed 1271 published studies (2011-2023) with regard to current LD strategies for approved anti-CD19 CAR-T products for large B cell lymphoma (LBCL). Fludarabine (Flu) and cyclophosphamide (Cy) (alone or in combination) were the most commonly used agents. A large number of different schemes and combinations have been reported. In the respective schemes, doses of Flu and Cy (range 75-120mg/m2 and 750-1.500mg/m2) and wash out times (range 2-5 days) differed substantially. Furthermore, combinations with other agents such as bendamustine (benda), busulfan or alemtuzumab (for allogeneic CAR-T) were described. This diversity creates a challenge but also an opportunity to investigate the impact of LD on cellular kinetics and clinical outcomes of CAR-T. Only 21 studies explicitly investigated in more detail the influence of LD on safety and efficacy. As Flu and Cy can potentially impact both the in vivo activity and toxicity of CAR-T, a more detailed analysis of LD outcomes will be needed before we are able to fully assess its impact on different T-cell subsets within the CAR-T product. The T2EVOLVE consortium propagates a strategic investigation of LD protocols for the development of optimized conditioning regimens.

Advancing Diagnostics and Therapy to Reach Universal Cure in Childhood ALL

Systemic combination chemotherapy and intrathecal chemotherapy markedly increased the survival rate of children with ALL. In the past two decades, the use of minimal (measurable) residual disease (MRD) measurements early in therapy improved risk group stratification with subsequent treatment intensifications for patients at high risk of relapse, and enabled a reduction of treatment for low-risk patients. The recent development of more sensitive MRD technologies may further affect risk stratification. Molecular genetic profiling has led to the discovery of many new subtypes and their driver genetic alterations. This increased our understanding of the biological basis of ALL, improved risk classification, and enabled implementation of precision medicine. In the past decade, immunotherapies, including bispecific antibodies, antibody-drug conjugates, and cellular therapies directed against surface proteins, led to more effective and less toxic therapies, replacing intensive chemotherapy courses and allogeneic stem-cell transplantation in patients with relapsed and refractory ALL, and are now being tested in newly diagnosed patients. It has taken 50-60 years to increase the cure rate in childhood ALL from 0% to 90% by stepwise improvements in chemotherapy. This review provides an overview of how the developments over the past 10-15 years mentioned above have significantly changed the diagnostic and treatment approach in ALL, and discusses how the integrated use of molecular and immunotherapeutic insights will very likely direct efforts to cure those children with ALL who are not cured today, and improve the quality of life for survivors who should have decades of life ahead. Future efforts must focus on making effective, yet very expensive, new technologies and therapies available to children with ALL worldwide.

Has the shortage of fludarabine altered the current paradigm of lymphodepletion in favor of bendamustine?

The most common lymphodepletion regimen used prior to infusion of chimeric antigen receptor-T cells (CAR-T) is cyclophosphamide (CY) in combination with fludarabine (Flu) (CY-FLU). While cyclophosphamide (CY) possesses lymphotoxic effects, it concurrently preserves regulatory T cell activity, potentially affecting the efficacy of CAR-T cells. Moreover, the use of fludarabine (FLU) has been linked to neurotoxicity, which could complicate the early detection of immune effector cell-associated neurotoxicity syndrome (ICANS) observed in CAR-T cell therapy. Given the ongoing shortage of FLU, alternative lymphodepleting agents have become necessary. To date, only a limited number of studies have directly compared different lymphodepleting regimens, and most of these comparisons have been retrospective in nature. Herein, we review the current literature on lymphodepletion preceding CAR-T cell therapies for lymphoid hematologic malignancies, with a specific focus on the use of bendamustine (BEN). Recent evidence suggests that administering BEN before CAR-T cell infusion yields comparable efficacy, possibly with a more favorable toxicity profile when compared to CY-FLU. This warrants further investigation through randomized prospective studies.

Model-informed drug development of autologous CAR-T cell therapy: Strategies to optimize CAR-T cell exposure leveraging cell kinetic/dynamic modeling

Autologous Chimeric antigen receptor (CAR-T) cell therapy has been highly successful in the treatment of aggressive hematological malignancies and is also being evaluated for the treatment of solid tumors as well as other therapeutic areas. A challenge, however, is that up to 60% of patients do not sustain a long-term response. Low CAR-T cell exposure has been suggested as an underlying factor for a poor prognosis. CAR-T cell therapy is a novel therapeutic modality with unique kinetic and dynamic properties. Importantly, "clear" dose-exposure relationships do not seem to exist for any of the currently approved CAR-T cell products. In other words, dose increases have not led to a commensurate increase in the measurable in vivo frequency of transferred CAR-T cells. Therefore, alternative approaches beyond dose titration are needed to optimize CAR-T cell exposure. In this paper, we provide examples of actionable variables - design elements in CAR-T cell discovery, development, and clinical practice, which can be modified to optimize autologous CAR-T cell exposure. Most of these actionable variables can be assessed throughout the various stages of discovery and development as part of a well-informed research and development program. Model-informed drug development approaches can enable such study and program design choices from discovery through to clinical practice and can be an important contributor to cell therapy effectiveness and efficiency.

INSPIRED Symposium Part 2: Prevention and Management of Relapse Following Chimeric Antigen Receptor T Cell Therapy for B Cell Acute Lymphoblastic Leukemia

Although CD19-directed chimeric antigen receptor (CAR) T cell therapy (CAR-T) for relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) has been transformative in inducing and sustaining remission, relapse rates remain unacceptably high, with approximately 50% of children and young adults experiencing relapse within the first year postinfusion. Emerging strategies to extend the durability of remission involve the use of prognostic biomarkers to identify those at high risk of relapse or incorporate strategies aimed to enhancing functional CAR T cell persistence. Nonetheless, with antigen loss/down-regulation or evolution to lineage switch as major mechanisms of relapse, optimizing single antigen targeting alone is insufficient. Here, with a focus on relapse prevention strategies, including postinfusion surveillance and treatment approaches being explored to optimize post-CAR-T management (eg, combinatorial antigen targeting strategies, preemptive hematopoietic cell transplantation), we review the current state of the art in the prevention and management of post CAR-T relapse. We highlight the advancements in the field and identify gaps in the literature to guide future research in optimizing the prevention and management of post-CAR-T relapse in children and young adults with B-ALL.

Bendamustine lymphodepletion is a well-tolerated alternative to fludarabine and cyclophosphamide lymphodepletion for axicabtagene ciloleucel therapy for aggressive B-cell lymphoma

Fludarabine/cyclophosphamide (Flu/Cy) is established for lymphodepletion (LD) prior to standard-of-care CAR T-cell therapy for lymphoma. There is ongoing need to test alternative LD regimens to preserve efficacy, improve safety, and address challenges including the recent national fludarabine shortage. We retrospectively evaluated outcomes among patients with relapsed/refractory aggressive B-cell lymphoma who received bendamustine (n = 27) or Flu/Cy (n = 42) LD before axicabtagene ciloleucel (axi-cel) at our institution. The median change in absolute lymphocyte count from pre-LD to time of axi-cel infusion was -0.6×109 /L in bendamustine cohort and -0.7×109 /L in Flu/Cy cohort. The best overall response/complete response rates were 77.8% (95% CI: 57.7%-91.4%)/48.1% (95% CI: 28.7%-68.1%) among bendamustine cohort and 81.0% (95% CI: 65.9%-91.4%)/50.0% (95% CI: 34.2%-65.8%) among Flu/Cy cohort. Six-month progression-free survival were 43.8% (95% CI: 24.7%-61.3%) and 55.6% (95% CI: 39.0%-69.3%) in bendamustine and Flu/Cy cohorts, while 6-month overall survival were 81.5% (95% CI: 61.1%-91.8%) and 90.4% (95% CI: 76.4%-96.3%), respectively. Relative to Flu/Cy-treated patients, bendamustine-treated patients did not show an increase in hazards associated with experiencing progression/relapse/death (aHR:1.4 [95% CI: 0.7-2.8]; p = .32) or death (aHR:1.6 [95% CI: 0.5-5.6]; p = .46), after adjusting for baseline number of prior therapies and refractory disease. Any grade/grade ≥3 CRS were observed in 89%/3.7% and 86%/4.8% among bendamustine and Flu/Cy cohorts, while any grade ICANS/grade ≥3 ICANS were observed in 30%/19% and 55%/31% respectively. While more Flu/Cy-treated patients experienced grade ≥3 neutropenia compared with bendamustine-treated patients (100% vs. 68%), grade ≥3 infectious complications were comparable (24% vs. 19% respectively). More patients received bendamustine LD and axi-cel as outpatient than Flu/Cy cohort, without increased toxicities and with shorter median inpatient stays. In conclusion, we observed comparable efficacy and lower any grade ICANS among patients receiving bendamustine relative to Flu/Cy LD, followed by axi-cel.

CAR T-Cells for the Treatment of B-Cell Acute Lymphoblastic Leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is the most common subtype of acute leukemia in the pediatric population. The prognosis and treatment of B-ALL have dramatically improved over the past decade with the adoption of intensive and prolonged combination chemotherapy regimens. The advent of novel immunologic agents such as blinatumomab and inotuzumab has changed the treatment landscape of B-ALL. However, patients have continued to relapse, raising the need for novel therapies. Chimeric antigen receptor (CAR) T-cells have achieved a milestone in the treatment of B-ALL. Two CD19-targeting CAR T-cells were approved by the Food and Drug Administration and the European Medicines Agency for the treatment of relapsed and/or refractory B-ALL. In this review, we review the available data regarding CD19-targeting CAR T-cells with their safety profile as well as the mechanism of resistance to these agents and the way to overcome this resistance.

INSPIRED Symposium Part 1: Clinical Variables Associated with Improved Outcomes for Children and Young Adults treated with Chimeric Antigen Receptor T cells for B cell Acute Lymphoblastic Leukemia

Chimeric antigen receptor (CAR) T cell therapy (CAR-T) targeting the CD19 antigen on B cell acute lymphoblastic leukemia (B-ALL) has transitioned from a highly investigational therapy with limited access to a commercial therapy with established toxicities, response and survival rates, and access in numerous countries. With more than a decade of clinical study and 5 years of commercial access, data showing associations with success and failure have emerged. To address functional limitations of CAR-T and overcome constrained sample sizes when studying single-trial or single-center data, collaborative groups, including the Pediatric Real World CAR Consortium, the CAR-Multicenter Analysis, the Center for International Blood and Marrow Transplant Research, and the International BFM Study Group, among others, have been retrospectively interrogating the amassed clinical experience. The high patient numbers and varied clinical experiences compiled by these groups have defined clinical variables impacting CAR-T outcomes. Here we review published CAR-T trials and consortium/collaborative outcomes to establish variables associated with optimal response to CAR-T in children and young adults with B-ALL. We focus on findings with clinical relevance that have emerged, including data implicating pretreatment disease burden, presence of extramedullary disease, nonresponse to prior CD19 antigen targeting (blinatumomab therapy), CAR T cell dose, and fludarabine pharmacokinetics as factors impacting post-CAR-T survival. Additionally, we address the role of collaborative efforts going forward in guiding clinical practice evolution and further optimizing post-CAR-T outcomes.

Identifying an optimal fludarabine exposure for improved outcomes after axi-cel therapy for aggressive B-cell non-Hodgkin lymphoma

Fludarabine is one of the most common agents given for lymphodepletion before CD19 chimeric antigen receptor T cells, but its optimal therapeutic intensity is unknown. Using data from a multicenter consortium, we estimated fludarabine exposure (area under the curve [AUC]) using a population pharmacokinetic (PK) model in 199 adult patients with aggressive B-cell non-Hodgkin lymphomas who received commercial axicabtagene ciloleucel (Axi-cel). We evaluated the association of estimated fludarabine AUC with key outcomes, aiming to find an AUC that optimized efficacy and tolerability. We identified low (<18 mg × hour/L [mgh/L]), optimal (18-20 mgh/L), and high (>20 mgh/L) AUC groups for analyses; the 6-month cumulative incidences of relapse/progression of disease (relapse/POD) by AUC groups were 54% (45%-62%), 28% (15%-44%), and 30% (14%-47%), respectively; and the 1-year progression-free survival (PFS) rates were 39% (31%-48%), 66% (52%-84%), and 46% (30%-70%) and the overall survival (OS) rates were 58% (50%-67%), 77% (64%-92%), and 66% (50%-87%), respectively. In multivariable analyses compared with low AUC, an optimal AUC was associated with the highest PFS (hazard ratio [HR], 0.52; 0.3-0.91; P = .02) and lowest risk of relapse/POD (HR, 0.46; 0.25-0.84; P = .01) without an increased risk of any-grade cytokine release syndrome (HR, 1.1; 0.7-1.6; P = .8) or and immune effector cell-associated neurotoxicity syndrome (ICANS) (HR, 1.36; 0.83-2.3; P = .2). A high AUC was associated with the greatest risk of any-grade ICANS (HR, 1.9; 1.1-3.2; P = .02). Although the main cause of death in all groups was relapse/POD, nonrelapse-related deaths, including 3 deaths from ICANS, were more frequent in the high AUC group. These findings suggest that PK-directed fludarabine dosing to achieve an optimal AUC may result in improved outcomes for patients receiving axi-cel.

Rational Alternatives to Fludarabine and Cyclophosphamide-Based Pre-CAR Lymphodepleting Regimens in the Pediatric and Young Adult B-ALL Setting

PURPOSE OF REVIEW

Lymphodepleting chemotherapy (LD) has emerged as a key determinant of chimeric antigen receptor T cell (CAR) efficacy across pediatric/adult B cell malignancies. Clinical trials demonstrate the superiority of fludarabine/cyclophosphamide (Flu/Cy) regimens, resulting in the adoption of Flu/Cy as the pre-CAR LD standard. In the context of a global fludarabine shortage, consideration of alternative regimens is timely, yet limited clinical data exists, specifically in the pediatric B-ALL CAR setting.

RECENT FINDINGS

Bendamustine has been used as an effective LD prior to CD19-CAR in adult lymphoma. Although use in the pediatric CAR setting is limited, tolerability has been established in pediatric Hodgkin's lymphoma. Clofarabine is a purine nucleoside analog with mechanistic overlap with fludarabine; however, toxicity is high in the upfront leukemia setting, and thus use as an LD pre-CAR should be pursued with caution. We review the experience using bendamustine and clofarabine to serve as a resource when considering LD regimens as an alternative to fludarabine for pediatric B-ALL.

Mechanisms of Resistance and Treatment of Relapse after CAR T-cell Therapy for Large B-cell Lymphoma and Multiple Myeloma

Although chimeric antigen receptor (CAR) T cell therapy (CAR-T) has altered the treatment landscape for relapsed/refractory B cell malignancies and multiple myeloma, only a minority of patients attain long-term disease remission. The underlying reasons for CAR-T resistance are multifaceted and can be broadly divided into host-related, tumor-intrinsic, microenvironmental and macroenvironmental, and CAR-T-related factors. Emerging host-related determinants of response to CAR-T relate to gut microbiome composition, intact hematopoietic function, body composition, and physical reserve. Emerging tumor-intrinsic resistance mechanisms include complex genomic alterations and mutations to immunomodulatory genes. Furthermore, the extent of systemic inflammation prior to CAR-T is a potent biomarker of response and reflects a proinflammatory tumor micromilieu characterized by infiltration of myeloid-derived suppressor cells and regulatory T cell populations. The tumor and its surrounding micromilieu also can shape the response of the host to CAR-T infusion and the subsequent expansion and persistence of CAR T cells, a prerequisite for efficient eradication of tumor cells. Here, focusing on both large B cell lymphoma and multiple myeloma, we review resistance mechanisms, explore therapeutic avenues to overcome resistance to CAR-T, and discuss the management of patients who relapse after CAR-T.

The future of CAR T-cell therapy for B-cell acute lymphoblastic leukemia in pediatrics and adolescents

INTRODUCTION

Antigen down-regulation and early chimeric antigen receptor (CAR) T cell loss have emerged as 2 major challenges threatening outcomes following CD19-specific CAR T cell therapy for children and young adults with B-cell acute lymphoblastic leukemia (B-ALL). In addressing the future of CAR T cell therapy for B-ALL, innovative strategies to avert antigen downregulation and enhance CAR persistence warrant prioritized focus.

AREAS COVERED

We describe promising engineering strategies to refine CAR constructs to reverse exhaustion, develop regulatable CARs, optimize manufacturing, enrich for immune memory and disrupt immune inhibition. We additionally focus on alternative targeting to CD19-monospecific targeting and contextualize possibilities for expanded CAR utilization.

EXPERT OPINION

We describe research advances as they are independently reported, however anticipate an integrative strategy incorporating complementary modifications will be required to effectively address CAR loss, overcome antigen downregulation and enhance reliability and durability of CAR T cell responses for B-ALL.

Personalized hematopoietic stem cell transplantation for inborn errors of immunity

Patients with inborn errors of immunity (IEI) have been transplanted for more than 50 years. Many long-term survivors have ongoing medical issues showing the need for further improvements in how hematopoietic stem cell transplantation (HSCT) is performed if patients in the future are to have a normal quality of life. Precise genetic diagnosis enables early treatment before recurrent infection, autoimmunity and organ impairment occur. Newborn screening for severe combined immunodeficiency (SCID) is established in many countries. For newly described disorders the decision to transplant is not straight-forward. Specific biologic therapies are effective for some diseases and can be used as a bridge to HSCT to improve outcome. Developments in reduced toxicity conditioning and methods of T-cell depletion for mismatched donors have made transplant an option for all eligible patients. Further refinements in conditioning plus precise graft composition and additional cellular therapy are emerging as techniques to personalize the approach to HSCT for each patient.

How I use risk factors for success or failure of CD19 CAR T cells to guide management of children and AYA with B-cell ALL

By overcoming chemotherapeutic resistance, chimeric antigen receptor (CAR) T cells facilitate deep, complete remissions and offer the potential for long-term cure in a substantial fraction of patients with chemotherapy refractory disease. However, that success is tempered with 10% to 30% of patients not achieving remission and over half of patients treated eventually experiencing relapse. With over a decade of experience using CAR T cells in children, adolescents, and young adults (AYA) to treat relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL) and 5 years since the first US Food and Drug Administration approval, data defining the nuances of patient-specific risk factors are emerging. With the commercial availability of 2 unique CD19 CAR T-cell constructs for B-ALL, in this article, we review the current literature, outline our approach to patients, and discuss how individual factors inform strategies to optimize outcomes in children and AYA receiving CD19 CAR T cells. We include data from both prospective and recent large retrospective studies that offer insight into understanding when the risks of CAR T-cell therapy failure are high and offer perspectives suggesting when consolidative hematopoietic cell transplantation or experimental CAR T-cell and/or alternative immunotherapy should be considered. We also propose areas where prospective trials addressing the optimal use of CAR T-cell therapy are needed.

Chimeric Antigen Receptor T-Cell Therapy and Hematopoiesis

Chimeric Antigen Receptor (CAR) T-cell therapy is a promising treatment option for patients suffering from B-cell- and plasma cell-derived hematologic malignancies and is being adapted for the treatment of solid cancers. However, CAR T is associated with frequently severe toxicities such as cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), macrophage activation syndrome (MAS), and prolonged cytopenias-a reduction in the number of mature blood cells of one or more lineage. Although we understand some drivers of these toxicities, their mechanisms remain under investigation. Since the CAR T regimen is a complex, multi-step process with frequent adverse events, ways to improve the benefit-to-risk ratio are needed. In this review, we discuss a variety of potential solutions being investigated to address the limitations of CAR T. First, we discuss the incidence and characteristics of CAR T-related cytopenias and their association with reduced CAR T-cell efficacy. We review approaches to managing or mitigating cytopenias during the CAR T regimen-including the use of growth factors, allogeneic rescue, autologous hematopoietic stem cell infusion, and alternative conditioning regimens. Finally, we introduce novel methods to improve CAR T-cell-infusion products and the implications of CAR T and clonal hematopoiesis.

Relapsed or refractory large B-cell lymphoma after chimeric antigen receptor T-cell therapy: Current challenges and therapeutic options

Chimeric antigen receptor (CAR) T-cell (CAR-T) therapy can provide durable remission in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) after failure of chemoimmunotherapy. However, patients who are refractory or relapsing after CAR-T therapy have poor outcomes. Multiple mechanisms of CAR-T therapy failure have been proposed but management of these patients remains a challenge. As CAR-T therapy moves earlier in the treatment of DLBCL, we urgently need trials focused on patients with relapse after CAR-T therapy. Recent advances in novel immunotherapies such as bispecific antibodies, antibody-drug conjugates and next-generation CAR-T therapies may provide avenues for treatment. Here we review the available data on using these drugs after failure of CAR-T therapy and provide a framework for the ideal sequencing of these novel agents.

Switching from salvage chemotherapy to immunotherapy in adult B-cell acute lymphoblastic leukemia

About one-half of adults with acute B-cell lymphoblastic leukemia (B-ALL) who do not achieve molecular complete remission or who subsequently relapse are not cured by current chemo- or targeted therapies. Previously, the sole therapeutic option for such persons was a hematopoietic stem cell transplant. Recently, several immune therapies including monoclonal antibodies, bispecific T-cell engagers (BiTEs), antibody-drug conjugates (ADCs), and chimeric antigen receptor T-cells (CARs) have been shown safe and effective in this setting. In this manuscript, we summarize data on US FDA-approved immune therapies of advanced adult B-ALL including rituximab, blinatumomab, inotuzumab ozogamicin, tisagenlecleucel and brexucabtagene autoleucel. We consider the results of clinical trials focusing on efficacy, safety, and quality of life (QoL). Real-world evidence is presented as well. We also briefly discuss pharmacodynamics, pharmacokinetics, and pharmacoeconomics followed by risk-benefit analyses. Lastly, we present future directions of immune therapies for advanced B-ALL in adults.

Outcomes of CD19-Targeted Chimeric Antigen Receptor T Cell Therapy for Patients with Reduced Renal Function Including Dialysis

Patients with renal impairment (RI) are typically excluded from trials evaluating chimeric antigen receptor (CAR) T cell therapies. We evaluated the outcomes of patients with RI receiving standard of care (SOC) CAR T cell therapy for relapsed/refractory (R/R) diffuse large B cell lymphoma (DLBCL). In this retrospective, single-center cohort study of patients with R/R DLBCL treated with SOC axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) after 2 or more prior lines of therapy, renal and survival outcomes were compared based on RI and fludarabine dose reduction (DR) status. RI was defined by an estimated glomerular filtration rate <60 mL/min/1.73 m2 as determined by the Modification of Diet in Renal Disease equation using day -5 creatinine (Cr) values. Acute kidney injury (AKI) was identified and graded using standard Kidney Disease: Improving Global Outcomes criteria. Renal recovery was considered to occur if Cr was within .2 mg/mL of baseline by day +30. Fludarabine was considered DR if given at <90% of the recommended Food and Drug Administration label dose. Among 166 patients treated with CAR T cell therapy were 17 patients (10.2%) with baseline RI and 149 (89.8%) without RI. After CAR T cell infusion, the incidence of any grade AKI was not significantly different between patients with baseline RI and those without RI (42% versus 21%; P = .08). Similarly, severe grade 2/3 AKI was seen in 1 of 17 patients (5.8%) with baseline RI and in 11 of 149 patients (7.3%) without RI (P = 1). Decreased renal perfusion (28 of 39; 72%) was the most common cause of AKI, with cytokine release syndrome (CRS) contributing to 17 of 39 AKIs (44%). Progression-free survival (PFS) and overall survival (OS) did not differ between patients with RI and those without RI or between those who received standard-dose fludarabine and those who received reduced-dose fludarabine. In contrast, patients with AKI had worse clinical outcomes than those without AKI (multivariable PFS: hazard ratio [HR], 2.1; 95% confidence interval [CI], 1.2 to 3.7; OS: HR, 3.9; 95% CI, 2.1 to 7.4). Notably, peak inflammatory cytokine levels were higher in patients who experienced AKI. Finally, we describe 2 patients with end-stage renal disease (ESRD) on dialysis who received lymphodepletion and CAR T cell therapy. Baseline renal function did not affect renal or efficacy outcomes after CAR T cell therapy in DLBCL. On the other hand, patients with AKI went on to experience worse clinical outcomes. AKI was commonly related to CRS and high peak inflammatory cytokine levels. CAR T cell therapy is feasible in patients with ESRD and requires careful planning of lymphodepletion.