B-Cell Precursor-Acute Lymphoblastic Leukemia With EBF1-PDGFRB Fusion Treated With Hematopoietic Stem Cell Transplantation and Imatinib: A Case Report and Literature Review

A 9-year-old girl was diagnosed with B-cell precursor-acute lymphoblastic leukemia (BCP-ALL). Although she entered remission after induction therapy, she relapsed 15 months after maintenance therapy cessation. Since further investigation revealed EBF1-PDGFRB fusion, her condition was treated as BCR-ABL1-like acute lymphoblastic leukemia. She was started on a tyrosine kinase inhibitor, imatinib, and chemotherapy and underwent umbilical cord blood transplantation following reduced intensity conditioning. She has remained in complete remission for 36 months after cord blood transplantation. This case demonstrates the successful use of a tyrosine kinase inhibitor to treat BCP-ALL with a fusion transcript and highlights the need for a standardized treatment protocol.

Use of microarrays and MLPA for integrating diagnostics and personalizing treatment - Case report of a patient with Ph-like acute B-cell lymphoblastic leukemia

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common childhood cancer. A special subtype of high risk BCP-ALL is Philadelphia-like ALL (Ph-like ALL), in which the gene expression profile is similar to BCR-ABL1-positive leukemia; however, fusion of the mentioned genes does not occur. The unfavourable clinical course and incidence of 15% of cases means that the diagnosis and therapeutic strategy of Ph-like ALL must be carefully developed and implemented into clinical practice. The study presents the case of a patient with diagnosed Ph-like ALL. The use of molecular analytical techniques has made it possible to identify a patient who is likely to relapse and who may benefit from personalized therapy This study shows the advantages of using genomic analyses to identify therapeutic targets, which is especially important for patients with high-risk disease. This model of management could be extended to other cancer subtypes, allowing for tailored diagnosis.

Chimeric antigen receptor T cells for mature B-cell lymphoma and Burkitt lymphoma

Chimeric antigen receptor (CAR) T-cell therapy has changed the landscape of immunotherapy for B-cell malignancies, including mature B-cell lymphomas. Although two CD19 CAR T-cell products have been commercially approved to treat relapsed/refractory B-cell lymphomas, outcomes in these patients remain inferior to those of patients with B-cell leukemia, regardless of therapy. Recent clinical studies and preclinical reports suggest that certain characteristics, such as the suppressive lymphoma tumor microenvironment and inferior endogenous T-cell fitness, may contribute to discrepant responses in these patients. In addition, these studies revealed that limited CAR T-cell persistence and tumor antigen escape, which also impact B-cell acute lymphoblastic leukemia, may play a more prominent role in lymphoma. Multiple promising strategies to overcome these barriers have advanced to clinical trials. In this review, we assess CAR T-cell therapies for pediatric relapsed/refractory mature B-cell lymphomas, potential obstacles diminishing antitumor activity and limiting CAR T-cell persistence, and current strategies to overcome these obstacles.

CAR T cells vs allogeneic HSCT for poor-risk ALL

For subgroups of children with B-cell acute lymphoblastic leukemia (B-ALL) at very high risk of relapse, intensive multiagent chemotherapy has failed. Traditionally, the field has turned to allogeneic hematopoietic stem cell transplantation (HSCT) for patients with poor outcomes. While HSCT confers a survival benefit for several B-ALL populations, often HSCT becomes standard-of-care in subsets of de novo ALL with poor risk features despite limited or no data showing a survival benefit in these populations, yet the additive morbidity and mortality can be substantial. With the advent of targeted immunotherapies and the transformative impact of CD19-directed chimeric antigen receptor (CAR)-modified T cells on relapsed or refractory B-ALL, this approach is currently under investigation in frontline therapy for a subset of patients with poor-risk B-ALL: high-risk B-ALL with persistent minimal residual disease at the end of consolidation, which has been designated very high risk. Comparisons of these 2 approaches are fraught with issues, including single-arm trials, differing eligibility criteria, comparisons to historical control populations, and vastly different toxicity profiles. Nevertheless, much can be learned from available data and ongoing trials. We will review data for HSCT for pediatric B-ALL in first remission and the efficacy of CD19 CAR T-cell therapy in relapsed or refractory B-ALL, and we will discuss an ongoing international phase 2 clinical trial of CD19 CAR T cells for very-high-risk B-ALL in first remission.

CAR T cells for other pediatric non-B-cell hematologic malignancies

As CAR T-cell therapy has advanced in B-cell acute lymphoblastic leukemia, research is now underway to develop similar therapies for other lymphoid and myeloid malignancies for pediatric patients. Barriers, including antigen selection and on-target/off-tumor toxicity, have prevented the rapid development of immune-based therapies for T-lineage and myeloid malignancies. More recently, unique strategies have been developed to overcome these barriers, with several products advancing to clinical trials. For T-lineage diseases, targets have focused on CD5, CD7, and CD38, whereas myeloid disease targets have predominately focused on CD123, CD33, and, more recently, CLL-1. This review provides a comprehensive overview of these targets and approaches to overcoming safety concerns in the development of CAR T-cell therapies for pediatric patients with T-lineage and myeloid malignancies.

Sleeping Beauty-engineered CAR T cells achieve antileukemic activity without severe toxicities

BACKGROUNDChimeric antigen receptor (CAR) T cell immunotherapy has resulted in complete remission (CR) and durable response in highly refractory patients. However, logistical complexity and high costs of manufacturing autologous viral products limit CAR T cell availability.METHODSWe report the early results of a phase I/II trial in B cell acute lymphoblastic leukemia (B-ALL) patients relapsed after allogeneic hematopoietic stem cell transplantation (HSCT) using donor-derived CD19 CAR T cells generated with the Sleeping Beauty (SB) transposon and differentiated into cytokine-induced killer (CIK) cells.RESULTSThe cellular product was produced successfully for all patients from the donor peripheral blood (PB) and consisted mostly of CD3+ lymphocytes with 43% CAR expression. Four pediatric and 9 adult patients were infused with a single dose of CAR T cells. Toxicities reported were 2 grade I and 1 grade II cytokine-release syndrome (CRS) cases at the highest dose in the absence of graft-versus-host disease (GVHD), neurotoxicity, or dose-limiting toxicities. Six out of 7 patients receiving the highest doses achieved CR and CR with incomplete blood count recovery (CRi) at day 28. Five out of 6 patients in CR were also minimal residual disease negative (MRD-). Robust expansion was achieved in the majority of the patients. CAR T cells were measurable by transgene copy PCR up to 10 months. Integration site analysis showed a positive safety profile and highly polyclonal repertoire in vitro and at early time points after infusion.CONCLUSIONSB-engineered CAR T cells expand and persist in pediatric and adult B-ALL patients relapsed after HSCT. Antileukemic activity was achieved without severe toxicities.TRIAL REGISTRATIONClinicalTrials.gov NCT03389035.FUNDINGThis study was supported by grants from the Fondazione AIRC per la Ricerca sul Cancro (AIRC); Cancer Research UK (CRUK); the Fundación Científica de la Asociación Española Contra el Cáncer (FC AECC); Ministero Della Salute; Fondazione Regionale per la Ricerca Biomedica (FRRB).

Cost-effectiveness of Anti-CD19 chimeric antigen receptor T-Cell therapy in pediatric relapsed/refractory B-cell acute lymphoblastic leukemia. A societal view

INTRODUCTION

In several studies, the chimeric antigen receptor T-cell therapy tisagenlecleucel demonstrated encouraging rates of remission and lasting survival benefits in pediatric patients with relapsed/refractory (r/r) acute lymphoblastic leukemia (ALL). We assessed the cost-effectiveness of tisagenlecleucel (list price: 320 000 EUR) among these patients when compared to clofarabine monotherapy (Clo-M), clofarabine combination therapy (Clo-C), and blinatumomab (Blina) from both a healthcare and a societal perspective. We also assessed future medical and future non-medical consumption costs.

METHODS

A three-state partitioned survival model was used to simulate a cohort of pediatric patients (12 years of age) through different disease states until the end of life (lifetime horizon). Relevant outcomes were life years, quality-adjusted life years (QALYs), healthcare costs, societal costs, and the incremental cost-effectiveness ratio (ICER). Uncertainty was explored through deterministic and probabilistic sensitivity analyses as well as through several scenario analyzes.

RESULTS

Total discounted costs for tisagenlecleucel were 552 679 EUR from a societal perspective, which was much higher than the total discounted costs from a healthcare perspective (ie, 409 563 EUR). Total discounted societal costs for the comparator regimens ranged between 160 803 EUR for Clo-M and 267 259 EUR for Blina. Highest QALYs were estimated for tisagenlecleucel (11.26), followed by Blina (2.25), Clo-C (1.70) and Clo-M (0.74). Discounted societal ICERs of tisagenlecleucel ranged between 31 682 EUR/QALY for Blina and 37 531 EUR/QALY for Clo-C and were considered cost-effective with a willingness-to-pay (WTP) threshold of 80 000 EUR/QALY. None of the scenarios exceeded this threshold, and more than 98% of the iterations in the probabilistic sensitivity analysis were cost-effective.

DISCUSSION

At the current price and WTP threshold, tisagenlecleucel is cost-effective from both a healthcare and a societal perspective. Nevertheless, long-term effectiveness data are needed to validate the several assumptions that were necessary for this model.

Bovine pestivirus is a new alternative virus for multiple myeloma oncolytic virotherapy

BACKGROUND

The oncolytic viruses have shown promising results for the treatment of multiple myeloma. However, the use of human viruses is limited by the patients' antiviral immune response. In this study, we investigated an alternative oncolytic strategy using non-human pathogen viruses as the bovine viral diarrhea virus (BVDV) that were able to interact with CD46.

METHODS

We treated several human myeloma cell lines and non-myeloma cell lines with BVDV to evaluate the expression of CD46 and to study the effect on cell viability by flow cytometry. The possible synergistic effect of bortezomib in combination with BVDV was also tested. Moreover, we infected the bone marrow mononuclear cells obtained from myeloma patients and we checked the BVDV effect on different cell populations, defined by CD138, CD14, CD3, CD19, and CD56 expression evaluated by flow cytometry. Finally, the in vivo BVDV effect was tested in NOD-SCID mice injected subcutaneously with myeloma cell lines.

RESULTS

Human myeloma cells were selectively sensitive to BVDV treatment with an increase of cell death and, consequently, of apoptotic markers. Consistently, bone marrow mononuclear cells isolated from myeloma patients treated with BVDV, showed a significant selective decrease of the percentage of viable CD138+ cells. Interestingly, bortezomib pre-treatment significantly increased the cytotoxic effect of BVDV in myeloma cell lines with a synergistic effect. Finally, the in vitro data were confirmed in an in vivo myeloma mouse model showing that BVDV treatment significantly reduced the tumoral burden compared to the vehicle.

CONCLUSIONS

Overall, our data indicate, for the first time, a direct oncolytic effect of the BVDV in human myeloma cells suggesting its possible use as novel alternative anti-myeloma virotherapy strategy.

Recent advances in CAR-T cell engineering

Chimeric antigen receptor T (CAR-T) cell therapy is regarded as an effective solution for relapsed or refractory tumors, particularly for hematological malignancies. Although the initially approved anti-CD19 CAR-T therapy has produced impressive outcomes, setbacks such as high relapse rates and resistance were experienced, driving the need to discover engineered CAR-T cells that are more effective for therapeutic use. Innovations in the structure and manufacturing of CAR-T cells have resulted in significant improvements in efficacy and persistence, particularly with the development of fourth-generation CAR-T cells. Paired with an immune modifier, the use of fourth-generation and next-generation CAR-T cells will not be limited because of cytotoxic effects and will be an efficient tool for overcoming the tumor microenvironment. In this review, we summarize the recent transformations in the ectodomain, transmembrane domain, and endodomain of the CAR structure, which, together with innovative manufacturing technology and improved cell sources, improve the prospects for the future development of CAR-T cell therapy.

The Biology of B-Progenitor Acute Lymphoblastic Leukemia

Genomic analyses have revolutionized our understanding of the biology of B-progenitor acute lymphoblastic leukemia (ALL). Studies of thousands of cases across the age spectrum have revised the taxonomy of B-ALL by identifying multiple new subgroups with diverse sequence and structural initiating events that vary substantially by age at diagnosis and prognostic significance. There is a growing appreciation of the role of inherited genetic variation in predisposition to ALL and drug responsiveness and of the nature of genetic variegation and clonal evolution that may be targeted for improved diagnostic, risk stratification, disease monitoring, and therapeutic intervention. This review provides an overview of the current state of knowledge of the genetic basis of B-ALL, with an emphasis on recent discoveries that have changed our approach to diagnosis and monitoring.

Extensive Remodeling of the Immune Microenvironment in B Cell Acute Lymphoblastic Leukemia

A subset of B cell acute lymphoblastic leukemia (B-ALL) patients will relapse and succumb to therapy-resistant disease. The bone marrow microenvironment may support B-ALL progression and treatment evasion. Utilizing single-cell approaches, we demonstrate B-ALL bone marrow immune microenvironment remodeling upon disease initiation and subsequent re-emergence during conventional chemotherapy. We uncover a role for non-classical monocytes in B-ALL survival, and demonstrate monocyte abundance at B-ALL diagnosis is predictive of pediatric and adult B-ALL patient survival. We show that human B-ALL blasts alter a vascularized microenvironment promoting monocytic differentiation, while depleting leukemia-associated monocytes in B-ALL animal models prolongs disease remission in vivo. Our profiling of the B-ALL immune microenvironment identifies extrinsic regulators of B-ALL survival supporting new immune-based therapeutic approaches for high-risk B-ALL treatment.

New targets for therapy: antigen identification in adults with B-cell acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) in adults is a rare and difficult-to-treat cancer that is characterised by excess lymphoblasts in the bone marrow. Although many patients achieve remission with chemotherapy, relapse rates are high and the associated impact on survival devastating. Most patients receive chemotherapy and for those whose overall fitness supports it, the most effective treatment to date is allogeneic stem cell transplant that can improve overall survival rates in part due to a 'graft-versus-leukaemia' effect. However, due to the rarity of this disease, and the availability of mature B-cell antigens on the cell surface, few new cancer antigens have been identified in adult B-ALL that could act as targets to remove residual disease in first remission or provide alternative targets for escape variants if and when current immunotherapy strategies fail. We have used RT-PCR analysis, literature searches, antibody-specific profiling and gene expression microarray analysis to identify and prioritise antigens as novel targets for the treatment of adult B-ALL.

Chimeric antigen receptor-modified T-cell therapy for bone marrow and skin relapse Philadelphia chromosome-like acute lymphoblastic leukemia: A case report

RATIONALE

Chimeric antigen receptor-modified T-cell (CART) therapy has revolutionized the treatment of patients with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL). However, the capacity of CART therapy has not yet been fully elucidated.

PATIENT CONCERNS

An 18-year-old Chinese male patient presented with multiple firm masses on the skin all over his body following regular chemotherapy.

DIAGNOSES

Bone marrow smear and skin biopsy confirmed that it was a bone marrow and skin relapse from the initial B-cell ALL.

INTERVENTIONS

CD19 CART-cell therapy was performed to manage the bone marrow and skin of the relapsed B-cell ALL.

OUTCOMES

During CART-cell therapy, cytokine release syndrome and central nervous encephalopathy occurred. Eventually, the lesions disappeared, and the bone marrow and skin tested minimal residual disease (MRD) negative. The patient achieved complete remission (CR). Fourteen days after testing MRD negative, he received allogeneic hematopoietic stem-cell transplantation and has remained disease free to date.

LESSONS

The CR of this patient with leukemia cutis demonstrated that CART exhibited efficacy in this case. While further research is still required, this treatment could potentially be used as a therapy for skin leukemia, lymphoma, and other primary skin cancers.

Efficacy and safety of humanized anti-CD19-CAR-T therapy following intensive lymphodepleting chemotherapy for refractory/relapsed B acute lymphoblastic leukaemia

We studied the efficacy and safety of humanized CAR-T therapy following intensive chemotherapy for refractory/relapsed (R/R) acute lymphoblastic leukaemia (B-ALL). Twenty-three patients with R/R B-ALL were pretreated with intensive chemotherapy (fludarabine combined with medium-dose cytarabine) 12 days before CAR-T therapy. Adverse events (AEs), curative effects, infection indicators and cytokine release syndrome (CRS) were monitored. Each of the 23 patients received a dose of 1·0 × 10⁶ cells/kg CAR-T cell infusion on day 0. After 14 days, 19 patients (82·61%) achieved complete response (CR) or CR with incomplete count recovery. No survival benefit was achieved with consolidative haematopoietic stem-cell transplantation (HSCT), with a median follow-up of 14·0 months (range, 1·5-21·0 months). The notable AEs were grade 1-2 CRS in 18 patients, while the other five patients were grade 3 CRS. No patients died of CRS. Only one patient died of respiratory failure due to cytomegalovirus infection 24 days after infusion. The proportion of leukaemic cells in bone marrow on infusion day and the peaks of IL-6, TNF-α and IL-8 levels were correlated with CRS levels. A lower disease burden was achieved by intensive lymphodepleting chemotherapy, and the subsequent CAR-T therapy had a high response and manageable toxicity. Trial registration: The patients were enrolled in a clinical trial of ChiCTR-ONN-16009862, and ChiCTR1800019622.

Toxicity and response after CD19-specific CAR T-cell therapy in pediatric/young adult relapsed/refractory B-ALL

Chimeric antigen receptor (CAR) T cells have demonstrated clinical benefit in patients with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). We undertook a multicenter clinical trial to determine toxicity, feasibility, and response for this therapy. A total of 25 pediatric/young adult patients (age, 1-22.5 years) with R/R B-ALL were treated with 19-28z CAR T cells. Conditioning chemotherapy included high-dose (3 g/m2) cyclophosphamide (HD-Cy) for 17 patients and low-dose (≤1.5 g/m2) cyclophosphamide (LD-Cy) for 8 patients. Fifteen patients had pretreatment minimal residual disease (MRD; <5% blasts in bone marrow), and 10 patients had pretreatment morphologic evidence of disease (≥5% blasts in bone marrow). All toxicities were reversible, including severe cytokine release syndrome in 16% (4 of 25) and severe neurotoxicity in 28% (7 of 25) of patients. Treated patients were assessed for response, and, among the evaluable patients (n = 24), response and peak CAR T-cell expansion were superior in the HD-Cy/MRD cohorts, as compared with the LD-Cy/morphologic cohorts without an increase in toxicity. Our data support the safety of CD19-specific CAR T-cell therapy for R/R B-ALL. Our data also suggest that dose intensity of conditioning chemotherapy and minimal pretreatment disease burden have a positive impact on response without a negative effect on toxicity. This trial was registered at www.clinicaltrials.gov as #NCT01860937.

Preemptive mitigation of CD19 CAR T-cell cytokine release syndrome without attenuation of antileukemic efficacy

Immunotherapy with the adoptive transfer of T cells redirected with CD19-specific chimeric antigen receptors (CARs) for B-lineage acute lymphoblastic leukemia (ALL) can salvage >80% of patients having relapsed/refractory disease. The therapeutic index of this emerging modality is attenuated by the occurrence of immunologic toxicity syndromes that occur upon CAR T-cell engraftment. Here, we report on the low incidence of severe cytokine release syndrome (CRS) in a subject treated with a CAR T-cell product composed of a defined ratio CD4:CD8 T-cell composition with a 4-1BB:zeta CAR targeting CD19 who also recieved early intervention treatment. We report that early intervention with tocilizumab and/or corticosteroids may reduce the frequency at which subjects transition from mild CRS to severe CRS. Although early intervention doubled the numbers of subjects dosed with tocilizumab and/or corticosteroids, there was no apparent detrimental effect on minimal residual disease-negative complete remission rates or subsequent persistence of functional CAR T cells compared with subjects who did not receive intervention. Moreover, early intervention therapy did not increase the proportion of subjects who experience neurotoxicity or place subjects at risk for infectious sequelae. These data support the contention that early intervention with tocilizumab and/or corticosteroids in subjects with early signs of CRS is without negative impact on the antitumor potency of CD19 CAR T cells. This intervention serves to enhance the therapeutic index in relapsed/refractory patients and provides the rationale to apply CAR T-cell therapy more broadly in ALL therapy. This trial was registered at www.clinicaltrials.gov as #NCT020284.

Mechanisms of and approaches to overcoming resistance to immunotherapy

Immunotherapies have been successfully developed for the treatment of B-cell acute lymphoblastic leukemia (B-ALL) with FDA approval of blinatumomab, inotuzumab, and tisagenlecleucel for relapsed or refractory patients. These agents target either CD19 or CD22, which are both expressed on the surface of the leukemic blasts in the majority of patients. The use of these agents has greatly transformed the landscape of available treatment, and it has provided curative therapy in some patients. As the field has matured, we are learning that for most patients, the currently available immunotherapies are not curative. Leukemic resistance to both CD19 and CD22 pressure has been described and is a major component of developed resistance to these therapies. Patients with B-ALL have developed CD19- or CD22-negative B-ALL, and in more rare cases, they have undergone lineage switch to acute myeloid leukemia. Current efforts are focusing on overcoming antigen escape, either by forced antigen expression or by dual-targeting therapies. A functional immune system is also required for maximal benefit of immunotherapy, particularly with chimeric antigen receptor (CAR) T-cell therapies. Data are now being produced that may allow for the prospective identification of patients whose immune deficits may be identified up front and predict failure. Preclinical work is focusing on additional engineering of CAR T cells to overcome these inherent immune deficits. Last, with improved knowledge of which patients are likely to benefit from immunotherapy as definitive treatment, those patients who are predicted to develop resistance may be prospectively recommended to undergo a consolidative hematopoietic cell transplant to lessen the recurrence risk.

Hematopoietic Stem-Cell Transplantation Does Not Improve the Poor Outcome of Children With Hypodiploid Acute Lymphoblastic Leukemia: A Report From Children's Oncology Group

PURPOSE

Children and young adults with hypodiploid B-lymphoblastic leukemia (B-ALL) fare poorly and hematopoietic stem-cell transplantation (HSCT) is often pursued in first complete remission (CR1). We retrospectively reviewed the outcomes of children and young adults with hypodiploid B-ALL who were enrolled in recent Children's Oncology Group (COG) trials to evaluate the impact of HSCT on outcome.

PATIENTS AND METHODS

Cytogenetic analyses and DNA index were performed at COG-approved laboratories, and hypodiploidy was defined as modal chromosome number less than 44 and/or DNA index less than 0.81. Minimal residual disease (MRD) was determined centrally using flow cytometry at two reference laboratories. Patients with hypodiploid ALL came off protocol therapy postinduction and we retrospectively collected details on their subsequent therapy and outcomes. Event-free survival (EFS) and overall survival (OS) were estimated for the cohort.

RESULTS

Between 2003 and 2011, 8,522 patients with National Cancer Institute standard-risk and high-risk B-ALL were enrolled in COG AALL03B1 ( ClinicalTrials.gov identifier: NCT00482352). Hypodiploidy occurred in 1.5% of patients (n = 131), 98.3% of whom achieved CR after induction therapy. Five-year EFS and OS were 52.2% ± 4.9% and 58.9% ± 4.8%, respectively. Outcomes for patients undergoing CR1 HSCT were not significantly improved: 5-year EFS and OS were 57.4% ± 7.0% and 66.2% ± 6.6% compared with 47.8% ± 7.5% and 53.8% ± 7.6%, respectively ( P = .49 and .34, respectively) for those who did not undergo transplantation. Patients with MRD of 0.01% or greater at the end of induction had 5-year EFS and OS of 26.7% ± 9.3% and 29.3% ± 10.1%, respectively, and HSCT had no significant impact on outcomes.

CONCLUSION

Children and young adults with hypodiploid B-ALL continue to fare poorly and do not seem to benefit from CR1 HSCT. This is especially true for patients with MRD of 0.01% or greater at the end of induction. New treatment strategies are urgently needed for these patients.

A successful multidisciplinary approach for treatment and for preserving the reproductive potential in a rare case of acute lymphocytic leukemia during pregnancy

Leukemia in pregnancy is a rare condition with the prevalence of 1 in 75,000-100,000 pregnancies. In this case report, we present a successful multidisciplinary management strategy for treatment and for preserving the reproductive potential in a rare case of acute lymphocytic leukemia (ALL) during pregnancy. Several complex challenges existed and necessitated a multidisciplinary approach with strong coordination and collaboration between oncologists, gynecologists, reproductive cryobiologists, obstetricians, and neonatologists in order to improve the maternal and fetal outcome. Pregnancy in the second trimester is neither a contraindication for ALL treatment nor for emergency fertility preservation via ovarian tissue extraction and further cryopreservation.

Clinical Pharmacology of Tisagenlecleucel in B-cell Acute Lymphoblastic Leukemia

PURPOSE

Tisagenlecleucel is an anti-CD19 chimeric antigen receptor (CAR19) T-cell therapy approved for the treatment of children and young adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL).

PATIENTS AND METHODS

We evaluated the cellular kinetics of tisagenlecleucel, the effect of patient factors, humoral immunogenicity, and manufacturing attributes on its kinetics, and exposure-response analysis for efficacy, safety and pharmacodynamic endpoints in 79 patients across two studies in pediatric B-ALL (ELIANA and ENSIGN).

RESULTS

Using quantitative polymerase chain reaction to quantify levels of tisagenlecleucel transgene, responders (N = 62) had ≈2-fold higher tisagenlecleucel expansion in peripheral blood than nonresponders (N = 8; 74% and 104% higher geometric mean Cmax and AUC0-28d, respectively) with persistence measurable beyond 2 years in responding patients. Cmax increased with occurrence and severity of cytokine release syndrome (CRS). Tisagenlecleucel continued to expand and persist following tocilizumab, used to manage CRS. Patients with B-cell recovery within 6 months had earlier loss of the transgene compared with patients with sustained clinical response. Clinical responses were seen across the entire dose range evaluated (patients ≤50 kg: 0.2 to 5.0 × 10⁶/kg; patients >50 kg: 0.1 to 2.5 × 10⁸ CAR-positive viable T cells) with no relationship between dose and safety. Neither preexisting nor treatment-induced antimurine CAR19 antibodies affected the persistence or clinical response.

CONCLUSIONS

Response to tisagenlecleucel was associated with increased expansion across a wide dose range. These results highlight the importance of cellular kinetics in understanding determinants of response to chimeric antigen receptor T-cell therapy.

Are CAR T cells better than antibody or HCT therapy in B-ALL?

Multicenter trials in children and young adults using second-generation CD19-targeted chimeric antigen receptor (CAR) T cells have shown dramatic levels of remission in patients with multiply relapsed/refractory disease (80% to ≥90%). Early results in adult trials have also shown significant responses, and strategies aimed at mitigating toxicities associated with the therapy have improved tolerability. Therefore, if available, CAR T-cell therapy deserves consideration for salvage of children and adults with B-lineage acute lymphoblastic leukemia (B-ALL) who are multiply relapsed, refractory, or relapsed after a previous allogeneic transplantation. For patients with a first relapse or who have persistent minimal residual disease (MRD) after initial or relapse therapy, treatment with blinatumomab or inotuzumab is reasonable to help patients achieve MRD- remission before definitive therapy with allogeneic hematopoietic cell transplantation (HCT). A number of studies in younger patients using 4-1BB-based CAR T-cell constructs lentivirally transduced into patient T cells and then optimally expanded have resulted in long-term persistence without further therapy. In 1 study using CD28-based CARs in adults, the benefit of HCT after CAR T-cell therapy was not clear, because a group of patients experienced long-term remissions without HCT. These data suggest that CAR T-cell therapy may be able to substitute for transplantation in many patients, avoiding the risks and long-term consequences of HCT. With this is mind, and with emerging data better defining ways of enhancing CAR T-cell persistence and avoiding relapse through antigen escape, CAR T cells will have a growing role in treatment of both pediatric and adult B-ALLs in the coming years.

Chimeric Antigen Receptor Therapy in Acute Lymphoblastic Leukemia Clinical Practice

Over half of patients diagnosed with B-cell acute lymphoblastic leukemia (ALL) develop relapsed or refractory disease. Traditional chemotherapy salvage is inadequate, and new therapies are needed. Chimeric antigen receptor (CAR) T cell therapy is a novel, immunologic approach where T cells are genetically engineered to express a CAR conferring specificity against a target cell surface antigen, most commonly the pan-B-cell marker CD19. After infusion, CAR T cells expand and persist, allowing ongoing tumor surveillance. Several anti-CD19 CAR T cell constructs have induced high response rates in heavily pre-treated populations, although durability of response varied. Severe toxicity (cytokine release syndrome and neurotoxicity) is the primary constraint to broad implementation of CAR T cell therapy. Here, we review the experience of CAR T cell therapy for ALL and ongoing efforts to modify existing technology to improve efficacy and decrease toxicity. As an anti-CD19 CAR T cell construct may be FDA approved soon, we focus on issues relevant to practicing clinicians.