Exploring the Dilemma of Allogeneic Hematopoietic Cell Transplantation after Chimeric Antigen Receptor T Cell Therapy: To Transplant or Not?

Quartic CAR-T Cell Bridging to Twice Allo-HSCT Therapy in a Patient with Acute Lymphoblastic Leukemia

Introduction

Chimeric antigen receptor T (CAR-T) cell therapy is an effective bridging treatment for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in relapsed or refractory acute lymphoblastic leukemia (ALL). However, repetitive CAR-T cell therapy and allo-HSCT can only be performed in a few patients because of technical difficulties and patients' physical, economic, and social conditions.

Case Presentation

A 23-year-old female patient with second relapsed B-cell ALL (B-ALL) underwent human-murine chimeric CD19 CAR-T cell therapy twice, human-murine chimeric CD22 CAR-T cell therapy once, and humanized CD19 CAR-T cell therapy once. Moreover, she was sequentially bridged to her mother donor allo-HSCT once and cousin donor allo-HSCT once.

Conclusion

Repetitive CAR-T cell therapy bridging to repetitive allo-HSCT is still a safe and active therapeutic strategy for patients with relapsed or refractory ALL.

Optimizing CAR-T cell therapy in adults with B-cell acute lymphoblastic leukemia

Chimeric antigen receptor T-cell (CAR-T) therapy has demonstrated unprecedented success in the treatment of various hematologic malignancies including relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). Currently, there are two FDA-approved CD19-directed CAR-T cell products for the treatment of adults with R/R B-ALL. Despite high remission rates following CD19 CAR-T cell therapy in R/R B-ALL, remission durability remains limited in most adult patients, with relapse observed frequently in the absence of additional consolidation therapy. Furthermore, the burden of CAR-T cell toxicity remains significant in adults with R/R B-ALL and further limits the wide utilization of this effective therapy. In this review, we discuss patient and disease factors that are linked to CAR-T cell therapy outcomes in R/R B-ALL and strategies to optimize durability of response to reduce relapse and mitigate toxicity in the adult population. We additionally discuss future approaches being explored to maximize the benefit of CAR-T in adults with B-ALL.

The progress of novel strategies on immune-based therapy in relapsed or refractory diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) can be cured with standard front-line immunochemotherapy, whereas nearly 30-40% of patients experience refractory or relapse. For several decades, the standard treatment strategy for fit relapsed/refractory (R/R) DLBCL patients has been high-dose chemotherapy followed by autologous hematopoietic stem cell transplant (auto-SCT). However, the patients who failed in salvage treatment or those ineligible for subsequent auto-SCT have dismal outcomes. Several immune-based therapies have been developed, including monoclonal antibodies, antibody-drug conjugates, bispecific T-cell engaging antibodies, chimeric antigen receptor T-cells, immune checkpoint inhibitors, and novel small molecules. Meanwhile, allogeneic SCT and radiotherapy are still necessary for disease control for fit patients with certain conditions. In this review, to expand clinical treatment options, we summarize the recent progress of immune-related therapies and prospect the future indirections in patients with R/R DLBCL.

Phase 1 clinical trial of CRISPR-engineered CAR19 universal T cells for treatment of children with refractory B cell leukemia

Genome editing of allogeneic T cells can provide "off-the-shelf" alternatives to autologous chimeric antigen receptor (CAR) T cell therapies. Disruption of T cell receptor α chain (TRAC) to prevent graft-versus-host disease (GVHD) and removal of CD52 (cluster of differentiation 52) for a survival advantage in the presence of alemtuzumab have previously been investigated using transcription activator-like effector nuclease (TALEN)-mediated knockout. Here, we deployed next-generation CRISPR-Cas9 editing and linked CAR expression to multiplexed DNA editing of TRAC and CD52 through incorporation of self-duplicating CRISPR guide RNA expression cassettes within the 3' long terminal repeat of a CAR19 lentiviral vector. Three cell banks of TT52CAR19 T cells were generated and cryopreserved. A phase 1, open-label, non-randomized clinical trial was conducted and treated six children with relapsed/refractory CD19-positive B cell acute lymphoblastic leukemia (B-ALL) (NCT04557436). Lymphodepletion included fludarabine, cyclophosphamide, and alemtuzumab and was followed by a single infusion of 0.8 × 106 to 2.0 × 106 CAR19 T cells per kilogram with no immediate toxicities. Four of six patients infused with TT52CAR19 T cells exhibited cell expansion, achieved flow cytometric remission, and then proceeded to receive allogeneic stem cell transplantation. Two patients required biological intervention for grade II cytokine release syndrome, one patient developed transient grade IV neurotoxicity, and one patient developed skin GVHD, which resolved after transplant conditioning. Other complications were within expectations, and primary safety objectives were met. This study provides a demonstration of the feasibility, safety, and therapeutic potential of CRISPR-engineered immunotherapy.

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

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

Updates in the Management of Relapsed and Refractory Acute Lymphoblastic Leukemia: An Urgent Plea for New Treatments Is Being Answered!

The treatment of acute lymphoblastic leukemia (ALL) has dramatically changed over the past three decades. However, relapsed and/or refractory ALL still remains with a very low survival and high morbidity associated with its treatment. Here, we will review the outstanding progress that has been made in the treatment of relapsed and/or refractory ALL and discuss future directions and challenges that require further investigation.

Point-of-care anti-CD19 CAR T-cells for treatment of relapsed and refractory aggressive B cell lymphoma

BACKGROUND

Anti CD19 Chimeric Antigen Receptor (CAR) T-cell therapy has transformed the care of relapsed & refractory aggressive B cell Lymphoma. However, financial toxicity and manufacturing time represent barriers to its widespread implementation.

OBJECTIVE

Study applicability, toxicity, and efficacy of a locally produced autologous CD19-directed CAR-T cell product.

METHODS

We performed a phase 1b/2 clinical trial with a point-of-care (POC) CAR T-cell product that contains a CD28 costimulatory domain. Adult patients with aggressive B cell lymphoma or transformed low-grade lymphoma who received at least two prior regimens were eligible.

RESULTS

A total of 73 patients, with a median age of 49 years, met inclusion criteria. CAR-T production time from apheresis was 10 days (IQR 10-11), negating the need for bridging chemotherapy. Overall and complete response rates were 62.5% and 37.5%. Median progression-free and overall survival were 3.7 and 12.1 months, respectively. Overall and progression-free survival at 12 months were 52.1% (CI: 40.8%-66.5%) and 40% (CI: 30%-53.7%), respectively. Patients who achieved response had longer progression-free and overall survival. Grade 3-4 CRS was observed in 9.5% of the patients, and ICANS grade 3-4 in 21.9%. No deaths occurred due to CAR T-cell toxicity. Fifteen patients (20%) underwent allogeneic stem cell transplantation at a median time of 60 days post CAR T-cell therapy; 8 were alive at last follow-up. Of the six patients that underwent the transplant in complete response 2 deceased due to toxicity.

CONCLUSIONS

POC CAR-T cells are a feasible therapeutic option in aggressive B-cell lymphoma. They provide good efficacy while minimizing production time and the need for bridging therapy.

The Emerging Role of CAR T Cell Therapy in Relapsed/Refractory Hodgkin Lymphoma

Treatment for Hodgkin lymphoma (HL) has evolved considerably from the time it was originally described in the 19th century with many patients now being cured with frontline therapy. Despite these advances, upwards of 10% of patients experience progressive disease after initial therapy with an even higher percentage relapsing. Until recently there had been limited therapeutic options for relapsed and/or refractory HL outside of highly intensive chemotherapy with stem cell rescue. Improved understanding of the pathophysiology of HL, coupled with the emergence of more targeted therapeutics, has reshaped how we view the treatment of relapsed/refractory HL and its prognosis. With this, there has been an increased focus on immunotherapies that can reprogram the immune system to better overcome the immunosuppressive milieu found in HL for improved cancer cell killing. In particular, chimeric antigen receptor (CAR) T cells are emerging as a valuable therapeutic tool in this area. Building on the success of antibody-drug conjugates directed against CD30, CAR T cells engineered to recognize the same antigen are now reaching patients. Though still in its infancy, CAR T therapy for relapsed/refractory HL has shown exceptional promise in early-stage clinical trials with the potential for durable responses even in patients who had progressed through multiple lines of prior therapy. Here we will review currently available data on the use of CAR T cells in HL, strategies to optimize their effectiveness, and how this therapy may fit into the treatment paradigm of HL going forward.

Impact of High Disease Burden on Survival in Pediatric Patients with B-ALL Treated with Tisagenlecleucel

CD19-specific chimeric antigen receptor (CAR) T-cell therapies, including the FDA-approved tisagenlecleucel, induce high rates of remission in pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, post-treatment relapse remains an issue. Optimal management of B-ALL after tisagenlecleucel treatment remains elusive, and continued tracking of outcomes is necessary to establish a standard of care for this population. We sought to evaluate outcomes on the real-world use of tisagenlecleucel in a contemporary pediatric patient population and to identify risk factors influencing event-free survival (EFS) and overall survival (OS). Additionally, we aimed to describe post-tisagenlecleucel management strategies, including use of allogeneic hematopoietic cell transplantation (AlloHCT) or repeat CAR T-cell infusions. We report on 31 pediatric and adolescent and young adult patients (AYA) with B-ALL, treated with lymphodepleting chemotherapy followed by tisagenlecleucel. Patients were treated at Johns Hopkins Hospital and St. Jude Children's Research Hospital between March 2018 and November 2020. Data on patient, disease, and treatment characteristics were collected retrospectively from medical records and described. EFS and OS were estimated by the Kaplan-Meier method and compared by the log-rank test. Single-factor and multiple-factor analysis of EFS and OS were performed by fitting Cox regression models. Of the 30 evaluable patients, 25 (83.3%) experienced a complete response, with 21 having negative minimal residual disease. Treatment was well tolerated, with expected rates of cytokine release syndrome (61.3%) and immune effector cell-associated neurotoxicity (29%). After initial complete response, 12 patients (48%) had subsequent disease recurrence, with CD19-negative relapse (n = 6) occurring sooner than CD19-positive relapse (P = .0125). With a median follow-up time of 386 days (range 11-1187 days), the EFS for the entire cohort (n = 31) at 6 and 12 months after infusion was 47% (95% confidence interval [CI], 28.4%-63.4%) and 35.2% (95% CI, 18.4%-52.5%), respectively. In multivariate analysis, high pretreatment leukemic burden (≥5% bone marrow blasts) was an independent risk factor for inferior EFS (HR 5.98 [95% CI, 1.1-32.4], P = .0380) and OS (HR 4.2 [95% CI, 1.33-13.39], P = .0148). Tisagenlecleucel induced high initial response rates in a contemporary cohort of pediatric and AYA patients with B-ALL. However, 48% of patients experienced subsequent disease relapse, including 6 with antigen-escape variants. This highlights a considerable limitation of single-agent autologous CD19-CAR T-cell therapy. Pretreatment leukemic disease burden of ≥5% blasts was significantly associated with worse outcomes in this study, including lower EFS and OS. Our findings suggest that reducing preinfusion leukemic burden is a viable treatment strategy to improve outcomes of CAR T-cell therapy.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relapse Mechanism and Treatment Strategy After Chimeric Antigen Receptor T-Cell Therapy in Treating B-Cell Hematological Malignancies

Over the past few decades, immunotherapy has revolutionized the modern medical oncology field. Chimeric antigen receptor (CAR)-T cell therapy has a promising curative effect in the treatment of hematological malignancies. Anti-CD19 CAR-T cells are the most mature CAR-T cells recently studied and in recent years it has achieved a complete remission rate of approximately 90% in the treatment of B-cell acute lymphoblastic leukemia (B-ALL). Although CAR-T cell therapy has greatly alleviated the disease in patients with leukemia or lymphoma, some of them still relapse after treatment. Therefore, in this article, we discuss the factors that may contribute to disease relapse following CAR-T cell therapy and summarize potential strategies to overcome these obstacles, thus providing the possibility of improving standard treatment regimens.

Humanized Anti-CD19 CAR-T Cell Therapy and Sequential Allogeneic Hematopoietic Stem Cell Transplantation Achieved Long-Term Survival in Refractory and Relapsed B Lymphocytic Leukemia: A Retrospective Study of CAR-T Cell Therapy

Early response could be obtained in most patients with relapsed or refractory B cell lymphoblastic leukemia (R/R B-ALL) treated with chimeric antigen receptor T-cell (CAR-T) therapy, but relapse occurs in some patients. There is no consensus on treatment strategy post CAR-T cell therapy. In this retrospective study of humanized CD19-targeted CAR-T cell (hCART19s) therapy for R/R B-ALL, we analyzed the patients treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT) or received a second hCART19s infusion, and summarized their efficacy and safety. We retrospectively studied 28 R/R B-ALL patients treated with hCART19s in the Affiliated Hospital of Xuzhou Medical University from 2016 to 2020. After the first hCART19s infusion, 10 patients received allo-HSCT (CART+HSCT group), 7 patients received a second hCART19s infusion (CART2 group), and 11 patients did not receive HSCT or a second hCART19s infusion (CART1 group). The safety, efficacy, and long-term survival were analyzed. Of the 28 patients who received hCART19s treatment, 1 patient could not be evaluated for efficacy, and 25 (92.6%) achieved complete remission (CR) with 20 (74.7%) achieving minimal residual disease (MRD) negativity. Seven (25%) patients experienced grade 3-4 CRS, and one died from grade 5 CRS. No patient experienced ≥3 grade ICANS. The incidence of second CR is higher in the CART+HSCT group compared to the CART2 group (100% vs. 42.9%, p=0.015). The median follow-up time was 1,240 days (range: 709–1,770). Significantly longer overall survival (OS) and leukemia-free survival (LFS) were achieved in the CART+HSCT group (median OS and LFS: not reached, p=0.006 and 0.001, respectively) compared to the CART2 group (median OS: 482; median LFS: 189) and the CART1 group (median OS: 236; median LFS: 35). In the CART+HSCT group, the incidence of acute graft-versus-host disease (aGVHD) was 30% (3/10), and transplantation-related mortality was 30% (3/10). No chronic GVHD occurred. Multivariate analysis results showed that blasts ≥ 20% in the bone marrow and MRD ≥ 65.6% are independent factors for inferior OS and LFS, respectively, while receiving allo-HSCT is an independent factor associated with both longer OS and LFS. In conclusion, early allo-HSCT after CAR-T therapy can achieve long-term efficacy, and the adverse events are controllable.

CAR-T after Stem Cell Transplantation in B-Cell Lymphoproliferative Disorders: Are They Really Autologous or Allogenic Cell Therapies?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is one of the standard treatments for B-cell lymphoproliferative disorders; however, deep relapses are common after an allo-HSCT, and it is associated with poor prognosis. A successful approach to overcome these relapses is to exploit the body's own immune system with chimeric antigen receptor (CAR) T-cells. These two approaches are potentially combinatorial for treating R/R B-cell lymphoproliferative disorders. Several clinical trials have described different scenarios in which allo-HSCT and CAR-T are successively combined. Further, for all transplanted patients, assessment of chimerism is important to evaluate the engraftment success. Nonetheless, for those patients who previously received an allo-HSCT there is no monitorization of chimerism before manufacturing CAR T-cells. In this review, we focus on allo-HSCT and CAR-T treatments and the different sources of T-cells for manufacturing CAR T-cells.

Antibody and cellular immunotherapies for acute lymphoblastic leukemia in adults

Despite improvements in the outcomes of patients with acute lymphoblastic leukemia (ALL), traditional therapies (including hematopoietic stem cell transplant) often still fail. Antigen-specific immunotherapies for the treatment of ALL such as monoclonal antibodies, antibody-drug conjugates, bispecific T-cell engagers (BiTEs), and chimeric antigen receptor (CAR) T-cells have demonstrated remarkable clinical efficacy and are rapidly evolving. With indisputable activity in patients with relapsed or refractory ALL, efforts now hope to integrate these agents into earlier phases of treatment. In this review, we will discuss the available antibody and cellular-based immunotherapies for the treatment of patients with ALL and provide a clinical and biologic framework with which to inform treatment approaches.

Evolution of haematopoietic cell transplantation for canine blood disorders and a platform for solid organ transplantation

Pre-clinical haematopoietic cell transplantation (HCT) studies in canines have proven to be invaluable for establishing HCT as a highly successful clinical option for the treatment of malignant and non-malignant haematological diseases in humans. Additionally, studies in canines have shown that immune tolerance, established following HCT, enabled transplantation of solid organs without the need of lifelong immunosuppression. This progress has been possible due to multiple biological similarities between dog and mankind. In this review, the hurdles that were overcome and the methods that were developed in the dog HCT model which made HCT clinically possible are examined. The results of these studies justify the question whether HCT can be used in the veterinary clinical practice for more wide-spread successful treatment of canine haematologic and non-haematologic disorders and whether it is prudent to do so.

Hematopathologic Correlates of CAR T-Cell Therapy

CD19-targeting chimeric antigen rector (CAR) T-cell products are used for the treatment of relapsed/refractory B-acute lymphoblastic leukemia, diffuse large B-cell lymphoma, and mantle cell lymphoma. The success of CD19-CAR-T cells has led to the investigation of CAR T-cell products targeting different antigens in other hematological malignancies and solid tumors. Clinical laboratories play an important role in the manufacture, distribution, and monitoring of CAR T-cell therapy. Hence, it is important for laboratory professionals to be cognizant of clinicopathologic aspects of CAR T-cell therapy.

CD4+CD25+CD127low regulatory T cells associated with the effect of CD19 CAR-T therapy for relapsed/refractory B-cell acute lymphoblastic leukemia

BACKGROUND

CD19-specific chimeric antigen receptor T-cell (CAR-T) therapy has shown promising clinical outcomes in relapsed/refractory acute B-cell lymphoblastic leukemia (R/R B-ALL) patients. However, some patients did not respond to this therapy or relapsed after remission. Regulatory T cells (Tregs) have shown great importance in promoting tumor escape, but little is known about their role in R/R B-ALL patients with CAR-T therapy. Our previous study has proved that higher Tregs before infusion was an independent high-risk factor for relapse-free survival (RFS). To further clarify the relationship between Tregs and the efficacy of CAR-T therapy, the present study tested the levels of CD4⁺CD25⁺CD127^low Tregs in peripheral blood (PB) of R/R B-ALL patients at different stages of CD19 CAR-T therapy, and evaluate their impact on the efficacy and prognosis of CAR-T therapy.

METHODS

From November 2015 to May 2019, 47 R/R B-ALL patients successfully received CD19 CAR-T therapy at our institution and followed up for at least 1 month. Among them, one patient did not tested for Tregs, so 46 patients enrolled in this study. We collected clinical information of them and dynamically detected the frequency of CD4⁺CD25⁺CD127^low Tregs within CD4 + T cells at different time points (before infusion and at 1 week after infusion) by flow cytometry, and validated the relationship of circulating Tregs with clinical efficacy, OS, and recurrence of CAR-T therapy.

RESULTS

Circulating Tregs of R/R B-ALL patients in pre-infusion group (median 6.67%) and in 1 week after infusion group (median 6.80%) were all higher than that of the healthy control group (median 5.04%), with statistical significance (P < 0.05). The frequencies of Tregs in not remission (NR) group at baseline (pre-infusion) and at 1 week after infusion were all significantly higher than those in remission group. With cut-off values of 11.54% (before infusion) and 13.56% (1 week after infusion), the specificity for Tregs were 94.6% and 100% , respectively. In remission group, 11 patients underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) after achieving remission by Sino 19 cell therapy. No significant differences of Tregs expression were found between transplantation and non-transplantation groups. Time-dependent Cox model showed that transplantation group had lower risk of relapse and death when compared with non-transplantation group (HR = 0.664 for RFS and HR = 0.364 for OS), however, no statistical significances were found (P = 0.403 and 0.106, respectively). Higher Tregs before infusion and at 1 week after infusion were significant associated with shorter RFS and OS by Kaplan-Meier analysis. Multivariate analysis showed that higher Tregs at 1 week after infusion was the independently factor for poor RFS (P = 0.032) and shorter OS (P = 0.025) in R/R B-ALL patients with CD19 CAR-T therapy. Besides, Tregs levels before and at 1 week after infusion were negatively correlated with the persistence time of Sino 19 cell.

CONCLUSION

Higher circulating Tregs, especially 1 week after CD19 CAR-T cell infusion, was a poor predict indicator for CD19 CAR-T therapy in R/R B-ALL patients.

Integrating CAR T-Cell Therapy and Transplantation: Comparisons of Safety and Long-Term Efficacy of Allogeneic Hematopoietic Stem Cell Transplantation After CAR T-Cell or Chemotherapy-Based Complete Remission in B-Cell Acute Lymphoblastic Leukemia

Patients often undergo consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT) to maintain long-term remission following chimeric antigen receptor (CAR) T-cell therapy. Comparisons of safety and efficacy of allo-HSCT following complete remission (CR) achieved by CAR-T therapy versus by chemotherapy for B-cell acute lymphoblastic leukemia (B-ALL) has not been reported. We performed a parallel comparison of transplant outcomes in 105 consecutive B-ALL patients who received allo-HSCT after achieving CR with CAR-T therapy (n=27) or with chemotherapy (n=78). The CAR-T-allo-HSCT group had more patients in second CR compared to the chemotherapy-allo-HSCT group (78% vs. 37%; p<0.01) and more with complex cytogenetics (44% vs. 6%; p<0.001) but the proportion of patients with pre-transplant minimal residual disease (MRD) was similar. The median follow-up time was 49 months (range: 25-54 months). The CAR-T cohort had a higher incidence of Grade II-IV acute graft-versus-host disease (aGVHD 48.1% [95% CI: 46.1-50.1%] vs. 25.6% [95%CI: 25.2-26.0%]; p=0.016). The incidence of Grade III-IV aGVHD was similar in both groups (11.1% vs.11.5%, p=0.945). The overall incidence of chronic GVHD in the CAR-T group was higher compared to the chemotherapy group (73.3% [95%CI: 71.3-75.3%] vs. 55.0% [95%CI: 54.2-55.8%], p=0.107), but the rate of extensive chronic GVHD was similar (11.1% vs.11.9%, p=0.964). Efficacy measures 4 years following transplant were all similar in the CAR-T vs. the chemotherapy groups: cumulative incidences of relapse (CIR; 11.1% vs.12.8%; p=0.84), cumulative incidences of non-relapse mortality (NRM; 18.7% vs. 23.1%; p=0.641) leukemia-free survival (LFS; 70.2% vs. 64.1%; p=0.63) and overall survival (OS; 70.2% vs. 65.4%; p=0.681). We found that pre-transplant MRD-negative CR predicted a lower CIR and a higher LFS compared with MRD-positive CR. In conclusion, our data indicate that, in B-ALL patients, similar clinical safety outcomes could be achieved with either CD19 CAR T-cell therapy followed by allo-HSCT or chemotherapy followed by allo-HSCT. Despite the inclusion of more patients with advanced diseases in the CAR-T group, the 4-year LFS and OS achieved with CAR T-cells followed by allo-HSCT were as remarkable as those achieved with chemotherapy followed by allo-HSCT. Further confirmation of these results requires larger, randomized clinical trials.

Consolidative Hematopoietic Stem Cell Transplantation After CD19 CAR-T Cell Therapy for Acute Lymphoblastic Leukemia: A Systematic Review and Meta-analysis

BACKGROUND

This study aimed to systematically evaluate and compare the efficacy and safety of consolidative hematopoietic stem cell transplantation (HSCT) after CD19 chimeric antigen receptor T (CAR-T) therapy with non-HSCT in the treatment of acute lymphoblastic leukemia (ALL).

METHODS

The PubMed, Embase, Cochrane Library and Web of Science databases were searched for clinical trials. Pooled hazard ratios (HRs) for overall survival (OS), relapse rate, and leukemia-free survival (LFS) as well as overall incidence rates for transplant-related mortality (TRM), acute graft-versus-host disease (aGVHD), chronic graft-versus-host disease (cGVHD), and infections were calculated using Stata software.

RESULTS

We screened 3,441 studies and identified 19 eligible studies with 690 patients. Among the patients who achieved complete remission (CR) after CD19 CAR-T therapy, consolidative HSCT was beneficial for OS (HR = 0.34, 95% CI, 0.170.68, P = 0.003), the relapse rate (HR = 0.16, 95% CI, 0.100.25, P < 0.001), and LFS (HR = 0.15, 95% CI, 0.080.28, P < 0.001). For patients who achieved MRD-negative (neg) CR after CD19 CAR-T therapy, consolidative HSCT was beneficial for OS (0.57, 95% CI, 0.330.99, P = 0.045), the relapse rate (0.14, 95% CI, 0.060.31, P < 0.001), and LFS (0.21, 95% CI, 0.120.35, P < 0.001). Regarding safety, we calculated pooled incidence rates for TRM (8%, 95% CI, 0.020.15), aGVHD (44%, 95% CI, 0.230.67), cGVHD (36%, 95% CI, 0.170.56), and infections (39%, 95% CI, 0.030.83).

CONCLUSIONS

Compared with non-HSCT treatment, consolidative HSCT after CD19 CAR-T therapy for R/R B-ALL patients can prolong OS and LFS and reduce the risk of relapse. The incidence rates for adverse events are acceptable. More high-quality randomized controlled trials are required to avoid bias and further determine the efficacy of HSCT.

Anti-CD19 CAR-T cell therapy bridge to HSCT decreases the relapse rate and improves the long-term survival of R/R B-ALL patients: a systematic review and meta-analysis

Chimeric antigen receptor (CAR) T cell therapy improves the remission rate of refractory/relapsed B-acute lymphoblastic leukemia (R/R B-ALL) patients, but the relapse rate remains high. Recent studies suggest patients who underwent post-chimeric antigen receptor T cell therapy hematopoietic stem cell transplantation (post- HSCT) would achieve durable remission and better survival, but this remains controversial. To this end, we conducted a meta-analysis to assess the role of post-HSCT in R/R B-ALL. The Cochrane Library, Embase, and PubMed were used to identify relevant studies; the latest search update was on July 05, 2020. We used the Cochran Q test and I-squared statistics to test for heterogeneity among the studies analyzed. The fixed model and random model were used to combine results when appropriate. We performed all statistical analyses with Stata 12, and P < 0.05 was considered statistically significant. We included 18 studies with 758 patients in the meta-analysis. Our results indicated that post-HSCT was associated with lower relapse rate (RR: 0.40, 95% CI: 0.32-0.50, P = 0.000), better overall survival (HR: 0.37, 95% CI: 0.19-0.71, P = 0.003), better leukemia-free survival (HR: 0.20, 95% CI: 0.10-0.40, P = 0.000). However, post-HSCT did not influence OS in Caucasians, and CAR-T cells with CD28 co-stimulation factor bridged to HSCT did not influence OS. Post-HSCT decreased the relapse rate and improved the long-term survival of R/R B-ALL patients. R/R B-ALL patients would benefit from post-HSCT after CAR-T cell therapy.

Efficacy and safety of CD22 chimeric antigen receptor (CAR) T cell therapy in patients with B cell malignancies: a protocol for a systematic review and meta-analysis

BACKGROUND

Chimeric antigen receptor (CAR) T cell therapy has had great success in treating patients with relapsed or refractory B cell malignancies, with CD19-targeting therapies now approved in many countries. However, a subset of patients fails to respond or relapse after CD19 CAR T cell therapy, in part due to antigen loss, which has prompted the search for alternative antigen targets. CD22 is another antigen found on the surface of B cells. CARs targeting CD22 alone or in combination with other antigens have been investigated in several pre-clinical and clinical trials. Given the heterogeneity and small size of CAR T cell therapy clinical trials, systematic reviews are needed to evaluate their efficacy and safety. Here, we propose a systematic review of CAR T cell therapies targeting CD22, alone or in combination with other antigen targets, in B cell malignancies.

METHODS

We will perform a systematic search of EMBASE, MEDLINE, Web of Science, Cochrane Register of Controlled Trials, clinicaltrials.gov, and the International Clinical Trials Registry Platform. Ongoing and completed clinical trials will be identified and cataloged. Interventional studies investigating CD22 CAR T cells, including various multi-antigen targeting approaches, in patients with relapsed or refractory B cell malignancies will be eligible for inclusion. Only full-text articles, conference abstracts, letters, and case reports will be considered. Our primary outcome will be a complete response, defined as absence of detectable cancer. Secondary outcomes will include adverse events, overall response, minimal residual disease, and relapse, among others. Quality assessment will be performed using a modified Institute of Health Economics tool designed for interventional single-arm studies. We will report a narrative synthesis of clinical studies, presented in tabular format. If appropriate, a meta-analysis will be performed using a random effects model to synthesize results.

DISCUSSION

The results of the proposed review will help inform clinicians, patients, and other stakeholders of the risks and benefits of CD22 CAR T cell therapies. It will identify gaps or inconsistencies in outcome reporting and help to guide future clinical trials investigating CAR T cells.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42020193027.

Hematopoeitic Cell Transplantation and CAR T-Cell Therapy: Complements or Competitors?

Allogeneic hematopoietic cell transplantation (allo-HCT) and chimeric antigen receptor T cell (CAR T) therapy are the main modalities of adoptive cellular immunotherapy that have widely permeated the clinical space. The advent of both technologies revolutionized treatment of many hematologic malignancies, both offering the chance at sustained remissions for patients who would otherwise invariably succumb to their diseases. The understanding and exploitation of the nonspecific alloreactivity of allo-HCT and the graft-versus-tumor effect is contrasted by the genetically engineered precision of CAR T therapy. Historically, those with relapsed and refractory hematologic malignancies have often been considered for allo-HCT, although outcomes vary dramatically and are associated with potential acute and chronic toxicities. Such patients, mainly with B-lymphoid malignancies, may now be offered CAR T therapy. Yet, a lack of prospective data to guide decisions thereafter requires individualized approaches on whether to proceed to allo-HCT or observe. The continued innovations to make CAR T therapy more effective and accessible will continue to alter such approaches, but similar innovations in allo-HCT will likely result in similarly improved clinical outcomes. In this review, we describe the history of the two platforms, dissect the clinical indications emphasizing their intertwining and competitive roles described in trials and practice guidelines, and highlight innovations in which they complement or inform one another.