CD22 CAR T-cell therapy in refractory or relapsed B acute lymphoblastic leukemia

Programmed death‐ligand 1 expression on CD22‐specific chimeric antigen receptor‐modified T cells weakens antitumor potential

The molecules of programmed cell death protein‐1 (PD‐1) and ligand‐1 (PD‐L1) become new therapeutic targets for cancer therapy. Although tumor‐expressed PD‐L1 molecule is frequently dispensable for checkpoint blockade in some cancer patients, recent studies suggest that T cell‐expressed PD‐L1 molecule might play a crucial role in antitumor immunity. Here, to investigate CD22 chimeric antigen receptor (CAR)‐T cell therapy, we have generated the different CD22 CAR‐T constructs. We noticed that tumor cells induced PD‐L1 expression on the surface of CD22 CAR‐T cells. The induced PD‐L1 might limit immunogenic responses of CAR‐T cells. T cell‐expressed PD‐L1 leads to a suppressive signal by PD‐1/PD‐L1 engagement of CD22 CAR‐T cells. Meanwhile, PD‐L1 suppresses CD22 CAR‐T cell differentiation into memory T cells and negatively affected secretions of several essential cytokines, such as interleukin‐2 (IL‐2) and tumor necrosis factor (TNF)‐α. We further observed that anti‐PD‐L1 monoclonal antibodies rescued cytokine secretion of CD22 CAR‐T cells rather than anti‐PD‐1 monoclonal antibodies. Our current studies provide a potential mechanism to understand the functions and roles of T cell‐expressed PD‐L1 in tumor microenvironment. These results will encourage the physicians to re‐recognize the important roles of PD‐L1 in cancer immunotherapy studies and provide the helpful guidance for clinical operation of PD‐L1 inhibition drugs.

Practical guidance for the diagnosis and management of secondary hypogammaglobulinemia: A Work Group Report of the AAAAI Primary Immunodeficiency and Altered Immune Response Committees

Secondary hypogammaglobulinemia (SHG) is characterized by reduced immunoglobulin levels due to acquired causes of decreased antibody production or increased antibody loss. Clarification regarding whether the hypogammaglobulinemia is secondary or primary is important because this has implications for evaluation and management. Prior receipt of immunosuppressive medications and/or presence of conditions associated with SHG development, including protein loss syndromes, are histories that raise suspicion for SHG. In patients with these histories, a thorough investigation of potential etiologies of SHG reviewed in this report is needed to devise an effective treatment plan focused on removal of iatrogenic causes (eg, discontinuation of an offending drug) or treatment of the underlying condition (eg, management of nephrotic syndrome). When iatrogenic causes cannot be removed or underlying conditions cannot be reversed, therapeutic options are not clearly delineated but include heightened monitoring for clinical infections, supportive antimicrobials, and in some cases, immunoglobulin replacement therapy. This report serves to summarize the existing literature regarding immunosuppressive medications and populations (autoimmune, neurologic, hematologic/oncologic, pulmonary, posttransplant, protein-losing) associated with SHG and highlights key areas for future investigation.

Efficacy and safety of CD19 CAR-T cell therapy for patients with B cell acute lymphoblastic leukemia involving extramedullary relapse

OBJECTIVE

To evaluate the efficacy and safety of CD19 chimeric antigen receptor (CAR) T cell therapy for patients with B cell acute lymphoblastic leukemia (B-ALL) involving extramedullary relapse.

METHODS

Fifteen patients with B-ALL involving extramedullary relapse who received CD19 CAR-T cell therapy in the First Affiliated Hospital, Zhejiang University School of Medicine from January 2016 to October 2021 were enrolled in this study. The overall survival and leukemia-free survival of patients were analyzed using Kaplan-Meier curves, and the response of extramedullary lesions in different locations following the CD19 CAR-T cell therapy was observed. Cytokine release syndrome (CRS), hematological toxicity, and immune effector cell-associated neurotoxicity syndrome (ICANS) during CD19 CAR-T cell therapy were analyzed.

RESULTS

The median follow-up time was 7 (3-71) months, and 11 cases (73.3%) achieved complete response, median duration of complete response was 6 (2-27) months; 3 cases (20.0%) achieved partial response; 1 case (6.7%) got progressive disease. The overall response rate was 93.3% (14/15), and the overall survival rate was 80.0% (12/15) at the end of follow-up. The cumulative incidence of relapse was 40.0% (6/15) and relapse mortality rate was 20.0% (3/15). Until last follow-up date, 9 cases (60.0%) were still in disease-free survival. Among the 15 patients, 13 cases (86.7%) developed cytokine release syndrome (CRS) after cell infusion, including 7 cases with grade 1-2 CRS, 6 cases with grade 3 CRS; 1 case suffered from reversible ICANS; 15 cases (100.0%) developed B cell dysplasia; 12 cases (80.0%) developed severe hematologic adverse reactions; 2 cases (13.3%) had abnormal liver function; 1 case (6.7%) had abnormal renal function; 4 cases (26.7%) developed infection. The adverse reactions mentioned above were well controlled.

CONCLUSION

CD19 CAR-T cell therapy shows explicit efficacy and controllable adverse reactions for B-ALL patients with extramedullary relapse.

Recent Advances in Treatment Options for Childhood Acute Lymphoblastic Leukemia

Simple Summary

Acute lymphoblastic leukemia is the most common blood cancer in pediatric patients. Despite the enormous progress in ALL treatment, which is reflected by a high 5-year overall survival rate that reaches up to 96% in the most recent studies, there are still patients that cannot be saved. Treatment of ALL is based on conventional methods, including chemotherapy and radiotherapy. These methods carry with them the risk of very high toxicities. Severe complications related to conventional therapies decrease their effectiveness and can sometimes lead to death. Therefore, currently, numerous studies are being carried out on novel forms of treatment. In this work, classical methods of treatment have been summarized. Furthermore, novel treatment methods and the possibility of combining them with chemotherapy have been incorporated into the present work. Targeted treatment, CAR-T-cell therapy, and immunotherapy for ALL have been described. Treatment options for the relapse/chemoresistance ALL have been presented.

Abstract

Acute lymphoblastic leukemia is the most common blood cancer in pediatric patients. There has been enormous progress in ALL treatment in recent years, which is reflected by the increase in the 5-year OS from 57% in the 1970s to up to 96% in the most recent studies. ALL treatment is based primarily on conventional methods, which include chemotherapy and radiotherapy. Their main weakness is severe toxicity, which prompts dose reduction, decreases the effectiveness of the treatment, and, in some cases, can lead to death. Currently, numerous modifications in treatment regimens are applied in order to limit toxicities emerging from conventional approaches and improve outcomes. Hematological treatment of pediatric patients is reaching for more novel treatment options, such as targeted treatment, CAR-T-cells therapy, and immunotherapy. These methods are currently used in conjunction with chemotherapy. Nevertheless, the swift progress in their development and increasing efficacity can lead to applying those novel therapies as standalone therapeutic options for pediatric ALL.

Humanized CD19 CAR-T cells in relapsed/refractory B-ALL patients who relapsed after or failed murine CD19 CAR-T therapy

BACKGROUND

For CD19-positive relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL) after treatment with murine CD19 (mCD19) CAR-T, the reinfusion of mCD19 CAR-T cells may be ineffective due to anti-mouse single-chain variable fragment (scFv) antibody caused by mCD19 CAR. To overcome this immunogenicity, we applied humanized CD19 (hCD19) CAR-T cells to treat r/r B-ALL patients with prior mCD19 CAR-T therapy.

METHODS

Nineteen pediatric and adult patients were included, 16 relapsed after and 3 were primarily resistant to mCD19 CAR-T. All patients presented with more than 5% blasts in bone marrow and/or extramedullary disease, and still showed CD19 antigen expression. Humanized CD19-CARs were lentiviral vectors carrying a second generation CAR with 4-1-BB co-stimulatory and CD3ζ signaling domains. Patient-derived cells were collected for producing CAR-T cells, the median dose of infused hCD19 CAR-T cells was 2.4 × 10⁵/kg (range, 1.0-18.0 × 10⁵/kg).

RESULTS

hCD19 CAR-T resulted in a complete remission (CR) rate of 68% (13/19). Among 13 remission patients, 11 underwent allogeneic hematopoietic cell transplantation (allo-HCT) (3 were second HCT) and 10 remained in CR; the event-free survival rates at 12-18 months were 91% in 11 patients received following allo-HCT and 69% in all CR patients. Six cases had no response to hCD19 CAR-T, 3 died of disease progression; another 3 received salvage second transplantation, of them, 2 relapsed again (one died). Cytokine release syndrome (CRS) occurred in 95% (18/19) of patients, most CRS events were grade 1 and grade 2 (n = 17), there was only one grade 4 CRS. Two cases experienced grade 1 neurotoxicity.

CONCLUSIONS

Humanized CD19 CAR-T cell therapy could be a treatment option for CD19-positive B-ALL patients who relapsed after or resisted prior murine CD19 CAR-T, hCD19 CAR-T followed by allo-HCT provided a longer remission in CR patients. Nevertheless, the prognosis of non-responders to hCD19 CAR-T remained dismal.

TRIAL REGISTRATION

Chinese Clinical Trial Registry/WHO International Clinical Trial Registry ( ChiCTR1900024456 , URL: www.chictr.org.cn ); registered on July 12, 2019.

Reprogramming the tumor microenvironment by genome editing for precision cancer therapy

The tumor microenvironment (TME) is essential for immune escape by tumor cells. It plays essential roles in tumor development and metastasis. The clinical outcomes of tumors are often closely related to individual differences in the patient TME. Therefore, reprogramming TME cells and their intercellular communication is an attractive and promising strategy for cancer therapy. TME cells consist of immune and nonimmune cells. These cells need to be manipulated precisely and safely to improve cancer therapy. Furthermore, it is encouraging that this field has rapidly developed in recent years with the advent and development of gene editing technologies. In this review, we briefly introduce gene editing technologies and systematically summarize their applications in the TME for precision cancer therapy, including the reprogramming of TME cells and their intercellular communication. TME cell reprogramming can regulate cell differentiation, proliferation, and function. Moreover, reprogramming the intercellular communication of TME cells can optimize immune infiltration and the specific recognition of tumor cells by immune cells. Thus, gene editing will pave the way for further breakthroughs in precision cancer therapy.

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

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

CAR-NK cells for cancer immunotherapy: from bench to bedside

Natural killer (NK) cells are unique innate immune cells and manifest rapid and potent cytotoxicity for cancer immunotherapy and pathogen removal without the requirement of prior sensitization or recognition of peptide antigens. Distinguish from the T lymphocyte-based cythotherapy with toxic side effects, chimeric antigen receptor-transduced NK (CAR-NK) cells are adequate to simultaneously improve efficacy and control adverse effects including acute cytokine release syndrome (CRS), neurotoxicity and graft-versus-host disease (GVHD). Moreover, considering the inherent properties of NK cells, the CAR-NK cells are “off-the-shelf” product satisfying the clinical demand for large-scale manufacture for cancer immunotherapy attribute to the cytotoxic effect via both NK cell receptor-dependent and CAR-dependent signaling cascades. In this review, we mainly focus on the latest updates of CAR-NK cell-based tactics, together with the opportunities and challenges for cancer immunotherapies, which represent the paradigm for boosting the immune system to enhance antitumor responses and ultimately eliminate malignancies. Collectively, we summarize and highlight the auspicious improvement in CAR-NK cells and will benefit the large-scale preclinical and clinical investigations in adoptive immunotherapy.

Recent Advances and Next Breakthrough in Immunotherapy for Cancer Treatment

With the huge therapeutic potential, cancer immunotherapy is expected to become the mainstream of cancer treatment. In the current field of cancer immunotherapy, there are mainly five types. Immune checkpoint blockade therapy is one of the most promising directions. Adoptive cell therapy is an important component of cancer immunotherapy. The therapy with the cancer vaccine is promising cancer immunotherapy capable of cancer prevention. Cytokine therapy is one of the pillars of cancer immunotherapy. Oncolytic immunotherapy is a promising novel component of cancer immunotherapy, which with significantly lower incidence of serious adverse reactions. The recent positive results of many clinical trials with cancer immunotherapy may herald good clinical prospects. But there are still many challenges in the broad implementation of immunotherapy. Such as the immunotherapy cannot act on all tumors, and it has serious adverse effects including but not limited to nonspecific and autoimmunity inflammation. Here, we center on recent progress made within the last 5 years in cancer immunotherapy. And we discuss the theoretical background, as well as the opportunities and challenges of cancer immunotherapy.

Two for one: targeting BCMA and CD19 in B-cell malignancies with off-the-shelf dual-CAR NK-92 cells

Background

Chimeric antigen receptor (CAR) T-cell therapy has proven to be a valuable new treatment option for patients with B-cell malignancies. However, by applying selective pressure, outgrowth of antigen-negative tumor cells can occur, eventually resulting in relapse. Subsequent rescue by administration of CAR-T cells with different antigen-specificity indicates that those tumor cells are still sensitive to CAR-T treatment and points towards a multi-target strategy. Due to their natural tumor sensitivity and highly cytotoxic nature, natural killer (NK) cells are a compelling alternative to T cells, especially considering the availability of an off-the-shelf unlimited supply in the form of the clinically validated NK-92 cell line.

Methods

Given our goal to develop a flexible system whereby the CAR expression repertoire of the effector cells can be rapidly adapted to the changing antigen expression profile of the target cells, electrotransfection with CD19-/BCMA-CAR mRNA was chosen as CAR loading method in this study. We evaluated the functionality of mRNA-engineered dual-CAR NK-92 against tumor B-cell lines and primary patient samples. In order to test the clinical applicability of the proposed cell therapy product, the effect of irradiation on the proliferative rate and functionality of dual-CAR NK-92 cells was investigated.

Results

Co-electroporation of CD19 and BMCA CAR mRNA was highly efficient, resulting in 88.1% dual-CAR NK-92 cells. In terms of CD107a degranulation, and secretion of interferon (IFN)-γ and granzyme B, dual-CAR NK-92 significantly outperformed single-CAR NK-92. More importantly, the killing capacity of dual-CAR NK-92 exceeded 60% of single and dual antigen-expressing cell lines, as well as primary tumor cells, in a 4h co-culture assay at low effector to target ratios, matching that of single-CAR counterparts. Furthermore, our results confirm that dual-CAR NK-92 irradiated with 10 Gy cease to proliferate and are gradually cleared while maintaining their killing capacity.

Conclusions

Here, using the clinically validated NK-92 cell line as a therapeutic cell source, we established a readily accessible and flexible platform for the generation of highly functional dual-targeted CAR-NK cells.

A novel and efficient tandem CD19- and CD22-directed CAR for B cell ALL

CD19-directed chimeric antigen receptor (CAR) T cells have yielded impressive response rates in refractory/relapse B cell acute lymphoblastic leukemia (B-ALL); however, most patients ultimately relapse due to poor CAR T cell persistence or resistance of either CD19⁺ or CD19^- B-ALL clones. CD22 is a pan-B marker whose expression is maintained in both CD19⁺ and CD19^- relapses. CD22-CAR T cells have been clinically used in B-ALL patients, although relapse also occurs. T cells engineered with a tandem CAR (Tan-CAR) containing in a single construct both CD19 and CD22 scFvs may be advantageous in achieving higher remission rates and/or preventing antigen loss. We have generated and functionally validated using cutting-edge assays a 4-1BB-based CD22/CD19 Tan-CAR using in-house-developed novel CD19 and CD22 scFvs. Tan-CAR-expressing T cells showed similar in vitro expansion to CD19-CAR T cells with no increase in tonic signaling. CRISPR-Cas9-edited B-ALL cells confirmed the bispecificity of the Tan-CAR. Tan-CAR was as efficient as CD19-CAR in vitro and in vivo using B-ALL cell lines, patient samples, and patient-derived xenografts (PDXs). Strikingly, the robust antileukemic activity of the Tan-CAR was slightly more effective in controlling the disease in long-term follow-up PDX models. This Tan-CAR construct warrants a clinical appraisal to test whether simultaneous targeting of CD19 and CD22 enhances leukemia eradication and reduces/delays relapse rates and antigen loss.

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

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

Nanobody-based anti-CD22-chimeric antigen receptor T cell immunotherapy exhibits improved remission against B-cell acute lymphoblastic leukemia

Chimeric antigen receptor (CAR) T-cell immunotherapies targeting CD19 can achieve impressive clinical remission rates in the treatment of B-cell non-Hodgkin lymphoma and B-cell acute lymphoblastic leukemia. However, relapse after CD19-CAR T treatment remains a major issue, with CD19 antigen-negative relapse being one of the main reasons. CD22, another antigen expressed in a B-cell lineage-specific pattern, is retained following CD19 loss. Accordingly, we hypothesized that CD22 could represent an alternative target to alleviate or compensate for the ineffectiveness of CD19-CAR T therapy. To this end, we generated camelid-derived CD22 nanobodies, whose smaller size, greater stability, and lower immunogenicity offer better quality than classical antibodies, and we used them to construct third-generation CD22-CARs containing 4-1BB and ICOS co-stimulatory domains. The novel CD22-CAR T cells exhibited impressive cytotoxicity both in vitro and in vivo and significantly prolonged the overall survival of tumor-bearing NSG mice. These findings provide the basis for further translational studies employing CD22-CARs.

Insights into Modern Therapeutic Approaches in Pediatric Acute Leukemias

Pediatric cancers predominantly constitute lymphomas and leukemias. Recently, our knowledge and awareness about genetic diversities, and their consequences in these diseases, have greatly expanded. Modern solutions are focused on mobilizing and impacting a patient’s immune system. Strategies to stimulate the immune system, to prime an antitumor response, are of intense interest. Amid those types of therapies are chimeric antigen receptor T (CAR-T) cells, bispecific antibodies, and antibody–drug conjugates (ADC), which have already been approved in the treatment of acute lymphoblastic leukemia (ALL)/acute myeloid leukemia (AML). In addition, immune checkpoint inhibitors (ICIs), the pattern recognition receptors (PRRs), i.e., NOD-like receptors (NLRs), Toll-like receptors (TLRs), and several kinds of therapy antibodies are well on their way to showing significant benefits for patients with these diseases. This review summarizes the current knowledge of modern methods used in selected pediatric malignancies and presents therapies that may hold promise for the future.

Imaging Primer on Chimeric Antigen Receptor T-Cell Therapy for Radiologists

Chimeric antigen receptor (CAR) T-cell therapy is a recently approved breakthrough treatment that has become a new paradigm in treatment of recurrent or refractory B-cell lymphomas and pediatric or adult acute lymphoid leukemia. CAR T cells are a type of cellular immunotherapy that artificially enhances T cells to boost eradication of malignancy through activation of the native immune system. The CAR construct is a synthetically created functional cell receptor grafted onto previously harvested patient T cells, which bind to preselected tumor-associated antigens and thereby activate host immune signaling cascades to attack tumor cells. Advantages include a single treatment episode of 2-3 weeks and durable disease elimination, with remission rates of over 80%. Responses to therapy are more rapid than with conventional chemotherapy or immunotherapy, with intervening short-interval edema. CAR T-cell administration is associated with therapy-related toxic effects in a large percentage of patients, notably cytokine release syndrome, immune effect cell-associated neurotoxicity syndrome, and infections related to immunosuppression. Knowledge of the expected evolution of therapy response and potential adverse events in CAR T-cell therapy and correlation with the timeline of treatment are important to optimize patient care. Some toxic effects are radiologically evident, and familiarity with their imaging spectrum is key to avoiding misinterpretation. Other clinical toxic effects may be occult at imaging and are diagnosed on the basis of clinical assessment. Future directions for CAR T-cell therapy include new indications and expanded tumor targets, along with novel ways to capture T-cell activation with imaging. An invited commentary by Ramaiya and Smith is available online. Online supplemental material is available for this article. ^©RSNA, 2022.

CAR T Cell Immunotherapy Beyond Haematological Malignancy

Chimeric antigen receptor (CAR) T cells, which express a synthetic receptor engineered to target specific antigens, have demonstrated remarkable potential to treat haematological malignancies. However, their transition beyond haematological malignancy has so far been unsatisfactory. Here, we discuss recent challenges and improvements for CAR T cell therapy against solid tumors: Antigen heterogeneity which provides an effective escape mechanism against conventional mono-antigen-specific CAR T cells; and the immunosuppressive tumor microenvironment which provides physical and molecular barriers that respectively prevent T cell infiltration and drive T cell dysfunction and hypoproliferation. Further, we discuss the application of CAR T cells in infectious disease and autoimmunity.

BCMA CAR-T Therapy Is Safe and Effective for Refractory/Relapsed Multiple Myeloma With Central Nervous System Involvement

Central nervous system (CNS) involvement is a rare complication of multiple myeloma (MM) that portends an extremely poor prognosis. Although chimeric antigen receptor (CAR)-T cell therapy is considered a promising strategy for patients with MM, the role of CAR-T cell therapy in MM involving the CNS has not been fully elucidated. In this study, we retrospectively analyzed 4 cases of B-cell maturation antigen CAR-T cell therapy for patients with relapsed/refractory MM involving the CNS. Patients received a range of 2-7 lines of prior therapy, including 1 autologous hematopoietic stem cell transplant. The most common adverse event was cytokine release syndrome, which was observed in all 4 patients, including 2 with grade 1 and 2 with grade 2. No patient was complicated with immune effector cell-associated neurotoxicity syndrome. Within the follow-up (median: 257 d, range: 116-392 d), 3 of 4 patients reached complete remission (CR), and 1 patient reached partial response. At the data cutoff, 1 patient continued to remain in CR at day 220, and the patient with partial response died at day 116. The other 2 patients relapsed at 317 and 111 days with CR durations of 287 and 81 days, respectively. Our results show promising effectiveness and acceptable safety of CAR-T cell therapy for heavily pretreated patients with CNS MM.

Use of CAR T-cell for acute lymphoblastic leukemia (ALL) treatment: a review study

Acute lymphoblastic leukemia (ALL) is a cancer-specific lymphoid cell. Induction and consolidation chemotherapy alone or in combination with different therapeutic approaches remain the main treatment. Although complete or partial remission of the disease can be achieved, the risk of relapse or refractory leukemia is still high. More effective and safe therapy options are yet unmet needs. In recent years' new therapeutic approaches have been widely used. Hematopoietic Stem Cell Transplantation (HSCT) presents significant limitations and the outcome of the consolidation treatment is patient dependent. Side effects such as Graft versus Host Disease (GvHD) in allogeneic hematopoietic stem cell transplantation are extremely common, therefore, using alternative methods to address these challenges for treatment seems crucial. In the last decade, T cells genetically engineered with Chimeric Antigen Receptor (CAR) treatment for the ALL are largely studied and represent the new era of strategy. According to the Phase I/II clinical trials, this technology results seem very promising and can be used in the next future as an effective and safe treatment for ALL treatment. In this review different generations, challenges, and clinical studies related to chimeric antigen receptor (CAR) T-cells for ALL treatment are discussed.

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.

Allogeneic Vγ9Vδ2 T-Cell Therapy Promotes Pulmonary Lesion Repair: An Open-Label, Single-Arm Pilot Study in Patients With Multidrug-Resistant Tuberculosis

The WHO’s “Global tuberculosis report 2020” lists tuberculosis (TB) as one of the leading causes of death globally. Existing anti-TB therapy strategies are far from adequate to meet the End TB Strategy goals set for 2035. Therefore, novel anti-TB therapy protocols are urgently needed. Here, we proposed an allogeneic Vγ9Vδ2 T-cell-based immunotherapy strategy and clinically evaluated its safety and efficacy in patients with multidrug-resistant TB (MDR-TB). Eight patients with MDR-TB were recruited in this open-label, single-arm pilot clinical study. Seven of these patients received allogeneic Vγ9Vδ2 T-cell therapy adjunct with anti-TB drugs in all therapy courses. Cells (1 × 10⁸) were infused per treatment every 2 weeks, with 12 courses of cell therapy conducted for each patient, who were then followed up for 6 months to evaluate the safety and efficacy of cell therapy. The eighth patient initially received four courses of cell infusions, followed by eight courses of cell therapy plus anti-MDR-TB drugs. Clinical examinations, including clinical response, routine blood tests and biochemical indicators, chest CT imaging, immune cell surface markers, body weight, and sputum Mycobacterium tuberculosis testing, were conducted. Our study revealed that allogeneic Vγ9Vδ2 T cells are clinically safe for TB therapy. These cells exhibited clinical efficacy in multiple aspects, including promoting the repair of pulmonary lesions, partially improving host immunity, and alleviating M. tuberculosis load in vivo, regardless of their application in the presence or absence of anti-TB drugs. This pilot study opens a new avenue for anti-TB treatment and exhibits allogeneic Vγ9Vδ2 T cells as promising candidates for developing a novel cell drug for TB immunotherapy.

Will immunotherapy lead to a breakthrough in the treatment of older adults with ALL?

Historically, older adults with B-cell acute lymphoblastic leukemia (ALL) have done poorly with chemotherapy-based treatment. Therefore, new innovative approaches are urgently needed to improve outcomes for this population. CD19-targeted immunotherapies such as blinatumomab and chimeric antigen receptor (CAR) T cell therapy have produced remarkable responses in relapsed/refractory (r/r) B-cell ALL, including clearance of minimal residual disease (MRD). Available data support the efficacy and safety of blinatumomab in older adults with advanced B-cell ALL. Therefore, its application is being extended to frontline regimens for B-cell ALL, particularly in older adults. There are several studies actively examining the role of blinatumomab alone or in combination with attenuated dosing of conventional chemotherapy or novel agents in older adults with newly diagnosed ALL and early data are encouraging. While CD19-targeted CAR (CD19CAR) T cell therapy is active in children and young adults with r/r B-cell ALL, data supporting its efficacy and safety in older adults with ALL is scarce. Furthermore, the commercially FDA approved CD19CAR T cell therapy product for r/r ALL is restricted only to patients ≤25 years of age. Although there are concerns about older adults tolerating the expected toxicities associated with CAR T cell therapy, which may be life threatening, tailored approaches for prophylactic and pre-emptive interventions combined with utilization of safer CAR T cell platforms may improve tolerability and further extend the use of this promising treatment to older patients with ALL. In this review, we will discuss the progress in immunotherapies for older adults with B-cell ALL and their potential for transforming frontline therapy for newly diagnosed patients.

Peripheral leukemia burden at time of apheresis negatively affects the clinical efficacy of CART19 in refractory or relapsed B-ALL

Our previous clinical study achieved complete remission (CR) rates of >90% following chimeric antigen receptor T cells targeting CD19 (CART19) treatment of refractory/relapsed B cell acute lymphoblastic leukemia (r/r B-ALL); however, the influence of the leukemia burden in peripheral blood (PB) blasts remains unclear. Here, we retrospectively analyzed 143 patients treated with CART19 (including 36 patients with PB blasts) to evaluate the effect of peripheral leukemia burden at the time of apheresis. One hundred seventeen patients with high disease burdens achieved 91.5% CR or incomplete count recovery CR and 86.3% minimal residual disease-negative CR, and 26 patients with low disease burdens obtained 96.2% MRD⁻ CR. Collectively, 9 of 36 (25%) patients with PB blasts and 2 of 107 (1.87%) patients without PB blasts did not respond to CART19 therapy. The leukemia burden in PB negatively influenced ex vivo cell characteristics, including the transduction efficiency of CD3⁺ T cells and their fold expansion, and in vivo cell dynamics, including peak CART19 proportion and absolute count, fold expansion, and persistence duration. Further studies showed that these patients had higher programmed death-1 expression in CART19 products. Our data imply that PB blasts negatively affected CART19 production and the clinical efficacy of CART19 therapy in patients with r/r B-ALL.

Risk Factors Associated with Durable Progression-Free Survival in Patients with Relapsed or Refractory Multiple Myeloma Treated with Anti-BCMA CAR T-cell Therapy

PURPOSE

B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy results in high remission rates in patients with relapsed/refractory (R/R) multiple myeloma. However, the factors associated with prognosis following CAR T-cell therapy are unknown.

PATIENTS AND METHODS

Between July 1, 2018 and July 31, 2020, 61 patients with R/R multiple myeloma received anti-BCMA CAR T-cell therapy (Chictr.org number, ChiCTR1800017404). Step-wise multivariate Cox regression and competing risk analyses were conducted to identify poor prognosis-associated risk factors.

RESULTS

Sixty patients (98.4%) experienced cytokine release syndrome (CRS), including 33, 23, and 4 cases of CRS grades 1 to 2, 3, and 4, respectively. The objective response rate (ORR) was 98.3%, and the complete remission (CR) rate was 70.3%. With a median follow-up period of 21.1 months, the 1-year overall survival (OS) and progression-free survival (PFS) rates were 78.0% and 50.2%, respectively. The median PFS was 12.7 months. Cox modeling revealed that poor PFS was associated with extramedullary disease [HR = 2.59, 95% confidence interval (95% CI) = 1.29-5.21, P = 0.008], light chain multiple myeloma (HR = 2.53, 95% CI = 1.03-5.97, P = 0.035), high-risk cytogenetics (HR = 2.80, 95% CI = 1.27-6.14, P = 0.01), and prior treatment with more than 3 therapeutic lines (HR = 3.14, 95% CI = 1.34-7.34, P = 0.008). Among the 41 CR cases, competing risk analyses demonstrated higher relapse predispositions in those with extramedullary disease (HR = 4.51, 95% CI = 1.86-10.9, P = 0.001), light chain multiple myeloma (HR = 4.89, 95% CI = 1.52 - 15.7, P = 0.008), or high-risk cytogenetics (HR = 5.09, 95% CI = 1.63-15.9, P = 0.005).

CONCLUSIONS

Anti-BCMA CAR T-cell therapy is safe and effective for R/R multiple myeloma. For patients with high-risk factors, improvements to extend remission and more specific individualized therapies are needed.

Paediatric Strategy Forum for medicinal product development of chimeric antigen receptor T-cells in children and adolescents with cancer: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T-cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first- or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplantation and be definitive therapy versus those in whom it provides a more effective bridge to haematopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully humanised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prioritisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary mediastinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this population. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials. CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell therapies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success. The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies. Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regulatory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially important as these are very expensive therapies. The model for drug development for cell therapy in paediatric oncology could also involve a 'later stage handoff' to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies.

Mechanisms of Immunosuppressive Tumor Evasion: Focus on Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a malignancy with high heterogeneity in its biological features and treatments. Although the overall survival (OS) of patients with ALL has recently improved considerably, owing to the application of conventional chemo-therapeutic agents, approximately 20% of the pediatric cases and 40-50% of the adult patients relapse during and after the treatment period. The potential mechanisms that cause relapse involve clonal evolution, innate and acquired chemoresistance, and the ability of ALL cells to escape the immune-suppressive tumor response. Currently, immunotherapy in combination with conventional treatment is used to enhance the immune response against tumor cells, thereby significantly improving the OS in patients with ALL. Therefore, understanding the mechanisms of immune evasion by leukemia cells could be useful for developing novel therapeutic strategies.

Siglecs as Therapeutic Targets in Cancer

Hypersialylation is a common post-translational modification of protein and lipids found on cancer cell surfaces, which participate in cell-cell interactions and in the regulation of immune responses. Sialic acids are a family of nine-carbon α-keto acids found at the outermost ends of glycans attached to cell surfaces. Given their locations on cell surfaces, tumor cells aberrantly overexpress sialic acids, which are recognized by Siglec receptors found on immune cells to mediate broad immunomodulatory signaling. Enhanced sialylation exposed on cancer cell surfaces is exemplified as "self-associated molecular pattern" (SAMP), which tricks Siglec receptors found on leukocytes to greatly down-regulate immune responsiveness, leading to tumor growth. In this review, we focused on all 15 human Siglecs (including Siglec XII), many of which still remain understudied. We also highlighted strategies that disrupt the course of Siglec-sialic acid interactions, such as antibody-based therapies and sialic acid mimetics leading to tumor cell depletion. Herein, we introduced the central roles of Siglecs in mediating pro-tumor immunity and discussed strategies that target these receptors, which could benefit improved cancer immunotherapy.

Regulation of Adaptive Tumor Immunity by Non-Coding RNAs

Cancer immunology research has mainly focused on the role of protein-coding genes in regulating immune responses to tumors. However, despite more than 70% of the human genome is transcribed, less than 2% encodes proteins. Many non-coding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), have been identified as critical regulators of immune cell development and function, suggesting that they might play important roles in orchestrating immune responses against tumors. In this review, we summarize the scientific advances on the role of ncRNAs in regulating adaptive tumor immunity, and discuss their potential therapeutic value in the context of cancer immunotherapy.

Influence of TP53 Mutation on Survival of Diffuse Large B-Cell Lymphoma in the CAR T-Cell Era

Simple Summary

The genetic landscape of diffuse large B-cell lymphoma (DLBCL) is heterogenous. So far, detailed studies about TP53 mutations in DLBCL treated with anti-CD19 chimeric antigen receptor T-cell (CAR T cells) therapy are still missing. Chemotherapy resistance is one of the challenges in TP53 mutated tumors. New immunomodulatory agents, such as different inhibitors or CAR T cells, have shown durable responses in refractory/relapsed DLBCL in recent years. Although our CAR T cell treated cohort was small, we aimed to investigate the influence of TP53 mutations on overall survival of patients treated with CAR T cells compared to DLBCL patients without CAR T-cell therapy. Identification of risk factors for treatment failure may aid in choosing the most promising treatment in every setting.

Abstract

Refractory/relapsed diffuse large B-cell lymphoma (DLBCL) is associated with poor outcome. The clinical behavior and genetic landscape of DLBCL is heterogeneous and still not fully understood. TP53 mutations in DLBCL have been identified as markers of poor prognosis and are often associated with therapeutic resistance. Chimeric antigen receptor T-cell therapy is an innovative therapeutic concept and represents a game-changing therapeutic option by supporting the patient’s own immune system to kill the tumor cells. We investigated the impact of TP53 mutations on the overall survival of refractory/relapsed DLBCL patients treated with comparable numbers of therapy lines. The minimum number of therapy lines was 2 (median 4), including either anti-CD19 CAR T-cell therapy or conventional salvage therapy. A total of 170 patients with DLBCL and high-grade B-cell lymphoma with MYC, BCL2, and/or BCL6 rearrangements (DHL/THL), diagnosed and treated in our hospital between 2000 and 2021, were included. Twenty-nine of them received CAR T-cell therapy. TP53 mutations were found in 10/29 (35%) and 31/141 (22%) of patients in the CAR T-cell and conventional groups, respectively. Among the 141 patients not treated with CAR T cells, TP53 mutation was an independent prognostic factor for overall survival (OS) (median 12 months with TP53 vs. not reached without TP53 mutation, p < 0.005), but in the CAR T cell treated group, this significance could not be shown (median OS 30 vs. 120 months, p = 0.263). The findings from this monocentric retrospective study indicate that TP53 mutation status does not seem to affect outcomes in DLBCL patients treated with CAR T-cell therapy. Detailed evaluation in large cohorts is warranted.

Clinical determinants of relapse following CAR-T therapy for hematologic malignancies: Coupling active strategies to overcome therapeutic limitations

The advent of chimeric antigen receptor (CAR)-T cell therapy has been hailed as a major breakthrough in the treatment of B cell acute lymphoblastic leukemia (B-ALL) and diffuse large B-cell lymphoma (DLBCL). While multiple promising CAR-T cell clinical trials continue to receive approval from the FDA and the Chinese Clinical Trial Register (ChiCTR), many hematologic malignancies patients nonetheless experience disease relapse following treatment as a consequence of genetic mutations, antigen escape, lineage switching, poor CAR-T cell persistence, CAR T cell exhaustion, and immunogenicity against CAR T cells. In this article, we summarize the structural characteristics of CAR constructs and discuss clinical factors known to be related to relapse following CAR-T cell treatment. By better understanding the mechanistic basis for such disease recurrence, it will be possible to fully realize the potential of this potent therapeutic modality in the future. This review will focus on current activate strategies aimed at overcoming known limitations to CAR-T cell therapy in an effort to improve hematologic malignancies patient outcomes.

Upregulation of CD22 by Chidamide promotes CAR T cells functionality

Treatment failure or relapse due to tumor escape caused by reduction in target antigen expression has become a challenge in the field of CART therapy. Target antigen density is closely related to the effectiveness of CART therapy, and reduced or lost target antigen expression limits the efficacy of CART therapy and hinders the durability of CAR T cells. Epigenetic drugs can regulate histones for molecular modifications to regulate the transcriptional, translational and post-translational modification processes of target agents, and we demonstrated for the first time the role in regulating CD22 expression and its effect on the efficacy of CD22 CART. In this paper, we found that Chidamide promoted the expression of CD22 on the surface of B-cell tumor cells in vitro and in vivo, and enhanced the function of CD22 CART. As for mechanisms, we demonstrated that Chidamide did not affect CD22 mRNA transcription, but significantly increased the expression of total CD22 protein, indicating that Chidamide may upregulate cell surface CD22 expression by affecting the distribution of CD22 protein. In summary, our results suggest that Chidamide may enhance the efficacy of CD22 CART by inhibiting histone deacetylases to regulate post-transcriptional modifications that affect protein distribution to increase the expression of CD22 on the cell surface.

Efficient elimination of primary B-ALL cells in vitro and in vivo using a novel 4-1BB-based CAR targeting a membrane-distal CD22 epitope

Background

There are few therapeutic options available for patients with B-cell acute lymphoblastic leukemia (B-ALL) relapsing as CD19^– either after chemotherapy or CD19-targeted immunotherapies. CD22-chimeric antigen receptor (CAR) T cells represent an attractive addition to CD19-CAR T cell therapy because they will target both CD22⁺CD19^– B-ALL relapses and CD19^– preleukemic cells. However, the immune escape mechanisms from CD22-CAR T cells, and the potential contribution of the epitope binding of the anti-CD22 single-chain variable fragment (scFv) remain understudied.

Methods

Here, we have developed and comprehensively characterized a novel CD22-CAR (clone hCD22.7) targeting a membrane-distal CD22 epitope and tested its cytotoxic effects against B-ALL cells both in in vitro and in vivo assays.

Results

Conformational epitope mapping, cross-blocking, and molecular docking assays revealed that the hCD22.7 scFv is a high-affinity binding antibody which specifically binds to the ESTKDGKVP sequence, located in the Ig-like V-type domain, the most distal domain of CD22. We observed efficient killing of B-ALL cells in vitro, although the kinetics were dependent on the level of CD22 expression. Importantly, we show an efficient in vivo control of patients with B-ALL derived xenografts with diverse aggressiveness, coupled to long-term hCD22.7-CAR T cell persistence. Remaining leukemic cells at sacrifice maintained full expression of CD22, ruling out CAR pressure-mediated antigen loss. Finally, the immunogenicity capacity of this hCD22.7-scFv was very similar to that of other CD22 scFv previously used in adoptive T cell therapy.

Conclusions

We report a novel, high-affinity hCD22.7 scFv which targets a membrane-distal epitope of CD22. 4-1BB-based hCD22.7-CAR T cells efficiently eliminate clinically relevant B- CD22^high and CD22^low ALL primary samples in vitro and in vivo. Our study supports the clinical translation of this hCD22.7-CAR as either single or tandem CD22–CD19-CAR for both naive and anti-CD19-resistant patients with B-ALL.

Characterization of HLH-Like Manifestations as a CRS Variant in Patients Receiving CD22 CAR T-Cells

CAR T-cell toxicities resembling hemophagocytic lymphohistiocytosis (HLH) occur in a subset of patients with cytokine release syndrome (CRS). As a variant of conventional CRS, a comprehensive characterization of CAR T-cell associated HLH (carHLH) and investigations into associated risk factors are lacking. In the context of 59 patients infused with CD22 CAR T-cells where a substantial proportion developed carHLH, we comprehensively describe the manifestations and timing of carHLH as a CRS variant and explore factors associated with this clinical profile. Amongst 52 subjects with CRS, 21 (40.4%) developed carHLH. Clinical features of carHLH included hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, hepatic transaminitis, hyperbilirubinemia, severe neutropenia, elevated lactate dehydrogenase and occasionally hemophagocytosis. Development of carHLH was associated with pre-infusion NK-cell lymphopenia and higher bone marrow T/NK-cell ratio, which was further amplified with CAR T-cell expansion. Following CRS, more robust CAR T-cell and CD8 T-cell expansion in concert with pronounced NK-cell lymphopenia amplified pre-infusion differences in those with carHLH without evidence for defects in NK-cell mediated cytotoxicity. CarHLH was further characterized by persistent elevation of HLH-associated inflammatory cytokines, which contrasted with declining levels in those without carHLH. In the setting of CAR T-cell mediated expansion, clinical manifestations and immunophenotypic profiling in those with carHLH overlap with features of secondary HLH, prompting consideration of an alternative framework for identification and management of this toxicity profile to optimize outcomes following CAR T-cell infusion.

Sequential different B cell antigen-targeted CAR T-cell therapy for pediatric refractory/relapsed Burkitt Lymphoma

Sequential CAR T-cell therapy may result in a durable response and is safe in pediatric patients with R/R Burkitt lymphoma.

Sequential CAR T-cell therapy may benefit pediatric patients with R/R Burkitt lymphoma with CNS involvement.

Single antigen–targeted chimeric antigen receptor (CAR) T-cell therapy may be insufficient to induce a durable response in pediatric aggressive B-cell lymphomas. This clinical trial examined the feasibility of sequential different B-cell antigen–targeted CAR T-cell therapy for pediatric relapsed/refractory (R/R) Burkitt lymphoma. Twenty-three patients received the first CD19 CAR T-cell infusion. The patients who did not achieve an ongoing complete response (CR) underwent 1 or more sequential infusions of CAR T-cell therapy that targeted CD22 followed by CD20 according to their disease status and CAR T-cell persistence after each infusion. The median time from the last infusion to the cutoff date was 17 months (range, 15-23 months). The estimated 18-month CR rate was 78% (95% confidence interval [CI], 54%-91%). The estimated 18-month progression-free survival rate was 78% (95% CI, 55%-90%), with 78% (95% CI, 37%-94%) in patients with bulky disease and 60% (95% CI, 25%-83%) in patients with central nervous system (CNS) involvement. During the first CD19 CAR T-cell infusion, grade ≥3 cytokine release syndrome (CRS) occurred in 34.8% and neurotoxicity occurred in 21.7% of all patients. During subsequent infusions, there were only a few incidences of grade >2 CRS and neurotoxicity. All adverse events were reversible. The severity of neurotoxicity was not significantly different between patients with CNS involvement and those who did not have CNS involvement. Sequential CAR T-cell therapy may result in a durable response and is safe in pediatric R/R Burkitt lymphoma. Patients with CNS involvement may benefit from sequential CAR T-cell therapy. This trial was registered at www.chictr.org.cn/index.aspx as #ChiCTR1800014457.

Tisagenlecleucel for treatment of children and young adults with relapsed/refractory B-cell acute lymphoblastic leukemia

The treatment landscape for cancer therapy has changed drastically over the past decade. Tisagenlecleucel, the first genetically engineered adoptive cellular therapy approved by the United States Food and Drug Administration, has revolutionized this field by demonstrating impressive clinical success in children and young adults with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL). Now 3 years since its approval, we have gained a deeper understanding on the basic immunobiology and clinical efficacy of this drug. This review will provide an updated summary of tisagenlecleucel in childhood and young adults with r/r B-ALL, common side effects and their associated management strategies, as well as barriers that remain to be addressed in order to realize the maximum potential of this drug.

Structural details of monoclonal antibody m971 recognition of the membrane-proximal domain of CD22

Cluster of differentiation-22 (CD22) belongs to the sialic acid-binding immunoglobulin (Ig)-like lectin family of receptors that is expressed on the surface of B cells. It has been classified as an inhibitory coreceptor for the B-cell receptor because of its function in establishing a baseline level of B-cell inhibition. The restricted expression of CD22 on B cells and its inhibitory function make it an attractive target for B-cell depletion in cases of B-cell malignancies. Genetically modified T cells with chimeric antigen receptors (CARs) derived from the m971 antibody have shown promise when used as an immunotherapeutic agent against B-cell acute lymphoblastic leukemia. A key aspect of the efficacy of this CAR-T was its ability to target a membrane-proximal epitope on the CD22 extracellular domain; however, the molecular details of m971 recognition of CD22 have thus far remained elusive. Here, we report the crystal structure of the m971 fragment antigen-binding in complex with the two most membrane-proximal Ig-like domains of CD22 (CD22d6-d7). The m971 epitope on CD22 resides at the most proximal Ig domain (d7) to the membrane, and the antibody paratope contains electrostatic surfaces compatible with interactions with phospholipid head groups. Together, our data identify molecular details underlying the successful transformation of an antibody epitope on CD22 into an effective CAR immunotherapeutic target.

Surface Proteomics Reveals CD72 as a Target for In Vitro-Evolved Nanobody-Based CAR-T Cells in KMT2A/MLL1-Rearranged B-ALL

Alternative strategies are needed for patients with B-cell malignancy relapsing after CD19-targeted immunotherapy. Here, cell surface proteomics revealed CD72 as an optimal target for poor-prognosis KMT2A/MLL1-rearranged (MLLr) B-cell acute lymphoblastic leukemia (B-ALL), which we further found to be expressed in other B-cell malignancies. Using a recently described, fully in vitro system, we selected synthetic CD72-specific nanobodies, incorporated them into chimeric antigen receptors (CAR), and demonstrated robust activity against B-cell malignancy models, including CD19 loss. Taking advantage of the role of CD72 in inhibiting B-cell receptor signaling, we found that SHIP1 inhibition increased CD72 surface density. We establish that CD72-nanobody CAR-T cells are a promising therapy for MLLr B-ALL. SIGNIFICANCE: Patients with MLLr B-ALL have poor prognoses despite recent immunotherapy advances. Here, surface proteomics identifies CD72 as being enriched on MLLr B-ALL but also widely expressed across B-cell cancers. We show that a recently described, fully in vitro nanobody platform generates binders highly active in CAR-T cells and demonstrate its broad applicability for immunotherapy development.This article is highlighted in the In This Issue feature, p. 1861.

A deep insight into CRISPR/Cas9 application in CAR-T cell-based tumor immunotherapies

To date, two chimeric antigen receptors (CAR)-T cell products from autologous T cells have been approved by The United States Food and Drug Administration (FDA). The case-by-case autologous T cell generation setting is largely considered as a pivotal restraining cause for its large-scale clinical use because of the costly and prolonged manufacturing procedure. Further, activated CAR-T cells mainly express immune checkpoint molecules, including CTLA4, PD1, LAG3, abrogating CAR-T anti-tumor activity. In addition, CAR-T cell therapy potently results in some toxicity, such as cytokine releases syndrome (CRS). Therefore, the development of the universal allogeneic T cells with higher anti-tumor effects is of paramount importance. Thus, genome-editing technologies, in particular, clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 are currently being used to establish "off-the-shelf" CAR-T cells with robust resistance to immune cell-suppressive molecules. In fact, that simultaneous ablation of PD-1, T cell receptor alpha constant (TRAC or TCR), and also β-2 microglobulin (B2M) by CRISPR-Cas9 technique can support the manufacture of universal CAR-T cells with robust resistance to PD-L1. . Indeed, the ablation of β2M or TARC can severely hinder swift elimination of allogeneic T cells those express foreign HLA-I molecules, and thereby enables the generation of CAR-T cells from allogeneic healthy donors T cells with higher persistence in vivo. Herein, we will deliver a brief overview of the CAR-T cell application in the context of tumor immunotherapy. More importantly, we will discuss recent finding concerning the application of genome editing technologies for preparing universal CAR-T cells or cells that can effectively counter tumor escape, with a special focus on CRISPR-Cas9 technology.

CD19/CD22 Dual-Targeted CAR T-cell Therapy for Relapsed/Refractory Aggressive B-cell Lymphoma: A Safety and Efficacy Study

Chimeric antigen receptor (CAR) T-cell therapies that target either CD19 or CD22 alone have potent antilymphoma effects. However, antigen escape-mediated relapse often occurs. CAR T cells targeting both CD19 and CD22 may overcome this limitation. In this study, we developed bispecific CAR T cells simultaneously recognizing CD19- and CD22-expressing targets and assessed their safety and efficacy profiles in patients with relapsed/refractory aggressive B-cell lymphoma. Twenty-four patients were screened, and 16 were found eligible for the study. CAR T-cell-associated toxicities were recorded. Responses, overall survival (OS), and progression-free survival (PFS) were assessed. Of the 16 eligible patients, 14 (87.5%) achieved objective response and 10 (62.5%) achieved complete response (CR). The 2-year OS and PFS rates were 77.3% and 40.2%, respectively. Achieving CR (P = 0.046) and the number of prior chemotherapy lines (n = 2; P = 0.047) were independent prognostic factors associated with favorable PFS. The 2-year OS and PFS among patients who achieved CR were higher than among those who did not (P = 0.015 and P < 0.001, respectively). The 2-year PFS among patients who received two prior lines of chemotherapy was higher than that among patients who received more than two lines of chemotherapy (P = 0.049); OS did not differ between the groups. Severe grade 4 cytokine-release syndrome (CRS) was observed in 1 patient; 4 and 11 patients had grades 1 and 2 CRS, respectively. No patients developed neurotoxicity. CD19/CD22 dual-targeted CAR T cells may be a safe, potent antilymphoma cell-based targeted immunotherapy.

Exploiting Single-Cell Tools in Gene and Cell Therapy

Single-cell molecular tools have been developed at an incredible pace over the last five years as sequencing costs continue to drop and numerous molecular assays have been coupled to sequencing readouts. This rapid period of technological development has facilitated the delineation of individual molecular characteristics including the genome, transcriptome, epigenome, and proteome of individual cells, leading to an unprecedented resolution of the molecular networks governing complex biological systems. The immense power of single-cell molecular screens has been particularly highlighted through work in systems where cellular heterogeneity is a key feature, such as stem cell biology, immunology, and tumor cell biology. Single-cell-omics technologies have already contributed to the identification of novel disease biomarkers, cellular subsets, therapeutic targets and diagnostics, many of which would have been undetectable by bulk sequencing approaches. More recently, efforts to integrate single-cell multi-omics with single cell functional output and/or physical location have been challenging but have led to substantial advances. Perhaps most excitingly, there are emerging opportunities to reach beyond the description of static cellular states with recent advances in modulation of cells through CRISPR technology, in particular with the development of base editors which greatly raises the prospect of cell and gene therapies. In this review, we provide a brief overview of emerging single-cell technologies and discuss current developments in integrating single-cell molecular screens and performing single-cell multi-omics for clinical applications. We also discuss how single-cell molecular assays can be usefully combined with functional data to unpick the mechanism of cellular decision-making. Finally, we reflect upon the introduction of spatial transcriptomics and proteomics, its complementary role with single-cell RNA sequencing (scRNA-seq) and potential application in cellular and gene therapy.

Anti-CD22 CAR-T Cell Therapy as a Salvage Treatment in B Cell Malignancies Refractory or Relapsed After Anti-CD19 CAR-T therapy

Background

To observe efficacy of the anti-CD22 chimeric antigen receptor modified (anti-CD22-CAR) T cell salvage therapy in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) and B cell acute lymphoid leukemia (B-ALL) patients whose disease did not reach CR or progressed again after anti-CD19-CAR T cell therapy.

Methods

In our study, seven R/R DLBCL patients reached stable disease (SD) or progression of disease (PD) after their anti-CD19-CAR T cell therapy. Only three in all the six R/R B-ALL patients obtained complete response (CR)/CR with incomplete count recovery (Cri) in their anti-CD19-CAR T cell therapy, but they relapsed again in the following three, six and one months. Then, all these thirteen R/R DLBCL and B-ALL patients received anti-CD22 CAR-T cell salvage therapy because their disease did not reach CR or progressed again.

Results

Four R/R DLBCL patients obtained CR, while two R/R DLBCL patients achieved PR and one patient achieved SD. But only two R/R B-ALL patients obtained Cri in their anti-CD22 CAR-T cell salvage therapy. The overall survival (OS) of R/R DLBCL patients after the anti-CD22 CAR-T cell therapy was 6.142±3.395 months until August 31, 2020. There was no different of the median expansion peaks of the two kinds of CAR T cells (P=0.920). The time of anti-CD22-CAR T cell proportion peak days was later than that of the time of anti-CD19-CAR T cell peak days post infusion (P=0.022). Their cytokine release syndrome (CRS) was graded 2-4 in their anti-CD19-CAR T cell therapy, while the notable CRS was graded 1-2 in their anti-CD22-CAR T cell therapy. But there was no difference in the CRS and the immune effect or cell associated neurotoxic syndrome (ICANS) grades in the two kinds of therapies. And there was no difference in the hematological toxicity grades in the two kinds of therapies.

Conclusion

The anti-CD22-CAR T cell salvage therapy is highly effective in R/R DLBCL patients than in R/R B-ALL patients who failed in anti-CD19-CAR T cell therapy before. We need to expand the number of R/R DLBCL or B-ALL patients and continue to observe.

Trial Registration

ChiCTR-ONN-16009862 and ChiCTR1800019298.

Toxicity and effectiveness of CD19 CAR T therapy in children with high-burden central nervous system refractory B-ALL

INTRODUCTION

Although recent clinical trials have demonstrated the efficacy of CD19-directed chimeric antigen receptor (CAR) T-cell therapy for refractory or relapsed B acute lymphoblastic leukemia (r/r B-ALL), most trials exclude patients with high-burden CNS leukemia (CNSL) to avoid the risk of severe neurotoxicity. There were only sparse cases describing the effect of CAR T cells on low-burden CNSL, and the safety and effectiveness of CAR T cells in high-burden CNSL remains unknown.

METHODS

Here, we retrospectively analyzed the results of CD19 CAR T-cell therapy in 12 pediatric patients that had low (Blasts < 20/μL in CSF) or high-burdens (Blasts or intracranial solid mass) of CNS B-ALL, that are enrolled in three clinical trials and one pilot study at Beijing Boren Hospital RESULTS: Eleven patients (91.7%) achieved complete remission (CR) on day 30, and one patient got CR on day 90 after infusion. Most patient experienced mild cytokine-release syndrome. However, of the five patients who retained > 5/μL blasts in CSF or a solid mass before CAR T-cell expansion, four developed severe (grade 3-4) neurotoxicity featured by persistent cerebral edema and seizure, and they fully recovered after intensive managements. Sustained remission was achieved in 9 of the 12 patients, resulted in a 6-month leukemia-free survival rate of 81.8% (95% CI 59.0-100). Only one patient has CNS relapse again.

CONCLUSION

Our study demonstrates that CAR T cells are effective in clearing both low- and high-burden CNSL, but a high CNSL burden before CAR T-cell expansion may cause severe neurotoxicity requiring intense intervention.

Busulfan-containing conditioning regimens in allogeneic hematopoietic stem cell transplantation for acute lymphoblastic leukemia: A Taiwan observational study

Background

Allogeneic stem cell transplantation (allo‐HSCT) is the ultimate cure for acute lymphoblastic leukemia (ALL).

Aim

This study was performed to compare the outcomes of ALL patients receiving busulfan (Bu) with cyclophosphamide (Cy)‐based or total body irradiation (TBI)‐based regimen in a Chinese population.

Methods

We enrolled 224 adult patients with ALL who received allo‐HSCT at National Taiwan University Hospital between 1997 and 2016.

Results

The median age at transplantation was 33 years. Before allo‐HSCT, 75.9% of patients attained first or late complete remission. A total of 141 patients (62.9%) received Bu/Cy‐based conditioning, either myeloablative (MA) or reduced‐intensity stem cell transplantation (RIST), and 83 patients received a TBI‐based regimen (MA‐TBI). Patients receiving the MA‐Bu regimen had longer relapse‐free survival (RFS) than those receiving the MA‐TBI regimen (median, 24.1 vs. 6.7 months, p = .044). There was no difference in overall survival (OS, MA‐Bu vs. MA‐TBI vs. RIST‐Bu: 39.4 vs. 28.2 vs. 13.1 months, p = .276), treatment‐related mortality (TRM), or incidences of grade 3–4 acute graft‐versus‐host disease (GvHD). Among patients receiving identical GvHD prophylactic regimens, there was no difference between MA‐Bu and MA‐TBI groups regarding the incidence of grade 3–4 acute GvHD, grade 2–4, and all‐grade chronic GvHD. In subgroup analysis, patients receiving oral busulfan had comparable RFS and OS to the intravenous busulfan group (p = .436 and p = .236, respectively), but a higher TRM (25% vs. 9.8%, p = .016). In the multivariable analysis, disease status before allo‐HSCT was the only risk factor impacting RFS and OS.

Conclusion

In summary, patients receiving Bu/Cy‐based or TBI‐based regimens as conditioning had similar results in terms of OS, TRM, and acute GvHD, whereas the use of myeloablative Bu/Cy resulted in a better RFS. A Bu‐based regimen could be an alternative conditioning choice for patients who are ineligible to receive TBI. Prospective and randomized controlled trials are warranted to validate the long‐term outcomes.

Combination of CD19 and CD22 CAR-T cell therapy in relapsed B-cell acute lymphoblastic leukemia after allogeneic transplantation

The prognosis of relapsed acute lymphoblastic leukemia (ALL) after allogeneic transplantation is dismal when treated with conventional approaches. While single-target CD19 or CD22 chimeric antigen receptor (CAR) T-cell therapy has achieved high complete remission (CR) rates in refractory/relapsed B-ALL, it could not maintain a durable remission in most patients. To prolong relapse-free survival, we sequentially combined CD19 and CD22 CAR-T cells to treat post-transplant relapsed B-ALL patients with both CD19/CD22 antigen expression on lymphoblasts. Patient-derived donor cells were collected to produce CAR-T cells that were transfected by lentiviral vectors encoding second generation CARs composed of CD3ζ and 4-1BB. The second T-cell infusion was scheduled at least 1 month, and usually within 6 months after the first CAR-T treatment. Twenty-seven adult and pediatric patients, including 11 (41%) with extramedullary diseases (EMD), received the first CD19 CAR-T and 23 (85%) achieved CR. Subsequently, 21 out of 27 patients received the second CD22 CAR-T and were followed-up for a median of 19.7 (range, 5.6-27.3) months; 14 cases remained in CR, seven relapsed and two of them died from disease progression; Kaplan-Meier survival analysis showed overall survival and event-free survival rates of 88.5% and 67.5%, respectively, at both 12 months and 18 months. CAR-T associated graft-versus-host disease (GVHD) occurred in 23% of patients, with 8% new-onset acute GVHD and 15% persistent or worsened pre-existing cGVHD before CAR-T. This combination strategy of sequential CD19 and CD22 CAR-T therapy significantly improved the long-term survival in B-ALL patients who relapsed after transplantation.

The Potential Role of the Intestinal Micromilieu and Individual Microbes in the Immunobiology of Chimeric Antigen Receptor T-Cell Therapy

Cellular immunotherapy with chimeric antigen receptor (CAR)-T cells (CARTs) represents a breakthrough in the treatment of hematologic malignancies. CARTs are genetically engineered hybrid receptors that combine antigen-specificity of monoclonal antibodies with T cell function to direct patient-derived T cells to kill malignant cells expressing the target (tumor) antigen. CARTs have been introduced into clinical medicine as CD19-targeted CARTs for refractory and relapsed B cell malignancies. Despite high initial response rates, current CART therapies are limited by a long-term loss of antitumor efficacy, the occurrence of toxicities, and the lack of biomarkers for predicting therapy and toxicity outcomes. In the past decade, the gut microbiome of mammals has been extensively studied and evidence is accumulating that human health, apart from our own genome, largely depends on microbes that are living in and on the human body. The microbiome encompasses more than 1000 bacterial species who collectively encode a metagenome that guides multifaceted, bidirectional host-microbiome interactions, primarily through the action of microbial metabolites. Increasing knowledge has been accumulated on the role of the gut microbiome in T cell-driven anticancer immunotherapy. It has been shown that antibiotics, dietary components and gut microbes reciprocally affect the efficacy and toxicity of allogeneic hematopoietic cell transplantation (allo HCT) as the prototype of T cell-based immunotherapy for hematologic malignancies, and that microbiome diversity metrics can predict clinical outcomes of allo HCTs. In this review, we will provide a comprehensive overview of the principles of CD19-CART immunotherapy and major aspects of the gut microbiome and its modulators that impact antitumor T cell transfer therapies. We will outline i) the extrinsic and intrinsic variables that can contribute to the complex interaction of the gut microbiome and host in CART immunotherapy, including ii) antibiotic administration affecting loss of colonization resistance, expansion of pathobionts and disturbed mucosal and immunological homeostasis, and ii) the role of specific gut commensals and their microbial virulence factors in host immunity and inflammation. Although the role of the gut microbiome in CART immunotherapy has only been marginally explored so far, this review may open a new chapter and views on putative connections and mechanisms.

The evolving role of allogeneic haematopoietic cell transplantation in the era of chimaeric antigen receptor T-cell therapy

Chimaeric antigen receptor T-cell (CAR T) therapy has revolutionized the management of many haematological malignancies. It is associated with impressive disease responses in relapsed or refractory high-grade B-cell non-Hodgkin lymphoma (B-NHL) and acute lymphoblastic leukaemia (B-ALL) with durable remissions in a subset of patients. Historically, haematopoietic cell transplantation (HCT) has been the standard consolidation strategy for many of these patients who are now being treated with CAR T. Relapses are frequent after CD19 CAR T therapy in B-ALL and consolidation with allogeneic HCT (allo-HCT) may improve survival of patients with high-risk disease. There appears to be a clear difference in B-ALL outcomes between paediatric and adult patients, with the latter having a much higher risk of relapse after CAR T therapy. Late relapses are infrequent in patients with B-NHL and consolidation with allo-HCT may not be needed in patients who achieve a complete remission after CAR T therapy. Future registry-based and prospective studies will hopefully provide the needed data in the future to risk-stratify the recipients of CAR T therapy. Meanwhile, we provide guidance on patient selection and practical issues with performing allo-HCT after CAR T therapy.

[In vitro studies on the transfer of CAR into leukemia cells due to their residue in the autologous CAR-T cell preparation system for acute B-cell acute lymphoblastic leukemia]

Objective: To investigate the characteristics and cytotoxicity in vitro of the residual leukemia cells in the culture system that caused the accidental transfer of CD19 chimeric antigen receptor (CAR) into leukemia cells during the preparation of autologous CD19 CAR-T cells of relapsed/refractory B-cell acute lymphoblastic leukemia. Methods: ①Peripheral blood mononuclear cells (PBMC) of 30 patients with relapsed/refractory B-cell acute lymphoblastic anemia (R/R B-ALL) who accepted CD19 CAR-T cell therapy and six healthy volunteers were collected. ②The residual leukemia cells were analyzed by flow cytometry in the system after the PBMCs of R/R B-ALL patients were sorted by CD3 magnetic beads. ③ CD3(+) T cells from patients and healthy volunteers were transfected with CD19 CAR and CD22 CAR lentivirus to prepare CD19 CAR-T and CD22 CAR-T cells. ④The Nalm-6 cell line was resuscitated and the Nalm-6 cells with CD19 CAR lentivirus were transfected to prepare CD19 CAR-Nalm-6 cells. The patient's primary ALL cells were transfected with CD19 CAR lentivirus at the same time. ⑤The transfection rates were analyzed by flow cytometer, the cell proliferation was analyzed by the CCK-8 method, and the cell-killing activities were detected by the lactate dehydrogenase method. Results: ① Among the 30 R/R B-ALL patients who received CD19 CAR-T cell therapy, two patients had 2.04% and 3.32% residual leukemia cells in CD3(+) T cells. After 4 days in culture, the residual leukemia cells disappeared and could not be detected by a flow cytometer with prolonged cultivation in vitro. ② The proliferation of CD19 CAR-Nalm-6 cells was higher than that of the Nalm-6 cells. ③ The killing activity of the CD19 CAR-T cells on Nalm-6 cells was higher than that of the CD19 CAR-Nalm6 cells at a target ratio of 1∶1 on 24, 48, 72 h, respectively. The cytotoxicity of CD22 CAR-T cells on CD19 CAR-Nalm-6 cells was significantly higher than that of CD19 CAR-T cells. ④ The cytotoxicity of CD22 CAR-T alone on CD19 CAR-Nalm-6 cells was higher than that of CD19 CAR-T combined with CD22 CAR-T at the same target ratio. Conclusion: The residual leukemia cells in the culture system in the preparation of CD19 CAR-T cells may lead to the introduction of CD19 CAR into leukemia cells and results in the failure of the CD19 CAR-T cell therapy. Detecting the residual leukemia cells in the culture system via flow cytometry before transfection with CD19 CAR lentivirus is needed. Thus, CD22 CAR-T cell therapy could be used as one of the salvage treatments.

Nanoparticles for Enhanced Adoptive T Cell Therapies and Future Perspectives for CNS Tumors

Adoptive T cell therapy has emerged as a revolutionary immunotherapy for treating cancer. Despite immense promise and clinical success in some hematologic malignancies, limitations remain that thwart its efficacy in solid tumors. Particularly in tumors of the central nervous system (CNS), T cell therapy is often restricted by the difficulty in intratumoral delivery across anatomical niches, suboptimal T cell specificity or activation, and intratumoral T cell dysfunction due to immunosuppressive tumor microenvironments (TMEs). Nanoparticles may offer several advantages to overcome these limitations of T cell therapy, as they can be designed to robustly and specifically activate T cells ex vivo prior to adoptive transfer, to encapsulate T cell stimulating agents for co-localized stimulation, and to be conjugated onto T cells for added functionality. This perspective highlights recent preclinical advances in using nanoparticles to enhance T cell therapy, and discusses the potential applicability and constraints of nanoparticle-enhanced T cells as a new platform for treating CNS tumors.

Chimeric Antigen Receptor T-Cell Therapy for B-Cell Acute Lymphoblastic Leukemia: Current Landscape in 2021

ABSTRACT

Immunotherapy with T cells engineered to express a chimeric antigen receptor (CAR T cells) is reshaping the management of patients with relapsed or refractory B-cell malignancies. High efficacy of CD19-targeted CAR T cells has been reported in children and adults with B-cell acute lymphoblastic leukemia (B-ALL), with complete responses without detectable minimal residual disease occurring in approximately 80% to 90% of patients. This led to the approval of tisagenlecleucel (Kymriah) by the Food and Drug Administration based on the results of the ELIANA trial. Although CD19 CAR T-cell therapy may be curative in children, responses are short-lived in most adult B-ALL patients. In addition, CAR T-cell therapy can be associated with severe, potentially life-threatening, toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. Here, we review the recent advances in CAR T-cell therapy for R/R B-ALL and discuss strategies to improve its efficacy while minimizing toxicities.