Cooperative CAR targeting to selectively eliminate AML and minimize escape

Hotspots evolution and frontiers of immunotherapy for the treatment of acute myeloid leukemia: A bibliometric analysis

Given the growing significance of immunotherapy in addressing the limitations of conventional acute myeloid leukemia (AML) treatments, this study aimed to elucidate the hotspot evolution and frontiers of immunotherapy in AML using bibliometric analysis. With a strict retrieval strategy applied in the Web of Science Core Collection, 2411 publications were obtained and exported. The temporal and geographical distributions of these publications and the countries, institutions, journals, and authors who contributed to the field were investigated. An in-depth content analysis was performed. The United States had various research institutions dedicated to AML immunotherapy. Frontiers in Immunology had the highest number of publications, but Blood had the highest H-index. Marion Subklewe was the most productive author. The current research hotspots of AML immunotherapy included chimeric antigen receptor-T-cell therapy, antibody-based immunotherapies, immune checkpoint blockade, and combination therapy, highlighting the key aspects of immunotherapy for AML treatment and providing comprehensive insights into the research status and advances in this field. Novel immunotherapies combined with chemotherapy may become the primary focus of AML treatment.

Insights into next-generation immunotherapy designs and tools: molecular mechanisms and therapeutic prospects

Immunotherapy has revolutionized the oncology treatment paradigm, and CAR-T cell therapy in particular represents a significant milestone in treating hematological malignancies. Nevertheless, tumor resistance due to target heterogeneity or mutation remains a Gordian knot for immunotherapy. This review elucidates molecular mechanisms and therapeutic potential of next-generation immunotherapeutic tools spanning genetically engineered immune cells, multi-specific antibodies, and cell engagers, emphasizing multi-targeting strategies to enhance personalized immunotherapy efficacy. Development of logic gate modulation-based circuits, adapter-mediated CARs, multi-specific antibodies, and cell engagers could minimize adverse effects while recognizing tumor signals. Ultimately, we highlight gene delivery, gene editing, and other technologies facilitating tailored immunotherapy, and discuss the promising prospects of artificial intelligence in gene-edited immune cells.

Strategies to enhance anti-leukaemia immunotherapy

Acute myeloid leukaemia (AML) was an incurable disease prior to allogeneic haematopoietic cell transplantation (allo-HCT), which was proven to be a potent cellular immunotherapy-approach. However, allo-HCT has major side effects, with disease relapse presenting as a frequent complication. Novel immunotherapies aim to reduce toxicity and increase the anti-leukaemia activity of allo-HCT. Technological advancements in genetic engineering approaches enable potent immunotherapeutic activity while limiting toxicities. A biology-driven application of small molecules that target AML vulnerabilities holds promise to enhance anti-leukaemia immunotherapy. Extensive preclinical testing of these approaches is essential to reduce toxicity and to find the ideal combination partners for future clinical testing.

Novel approaches to CAR T cell target identification in acute myeloid leukemia

Identifying safe and effective CAR T cell targets in acute myeloid leukemia (AML) is challenging due to the disease's complexity and overlap with normal hematopoiesis. This review highlights advances in target discovery for AML, emphasizing innovative approaches. Structural surfaceomics identifies tumor-specific protein conformations, while AI-driven single-cell RNA sequencing integrates multi-source data to pinpoint optimal targets. Refined cell surface capture technology maps the AML surfaceome without relying on predefined antibodies. These strategies enhance CAR T cell specificity and minimize off-tumor effects, offering promising pathways for safer and more effective AML treatments and broader cancer therapies.

GPR56/ADGRG1 induces biased Rho-ROCK-MLC and JAK-STAT3 signaling to promote amoeboid-like morphology and IL-6 upregulation in melanoma cells

BACKGROUND

GPR56/ADGRG1 is an adhesion G protein-coupled receptor involved in cell-matrix interactions and metastasis of human melanoma cells. Previously, we demonstrated that GPR56 activation in melanoma cells triggers Gα12/13-RhoA signaling, leading to increased IL-6 production and enhanced cell migration. Yet little is known of the downstream signaling effectors and their specific roles in regulating melanoma cellular phenotypes.

RESULTS

In this study, we show that GPR56 activation induces Rho-ROCK-MLC and JAK-STAT3 signaling, which temporally and differentially drive amoeboid-like morphology and IL-6 upregulation. Interestingly, GPR56-induced JAK-STAT3 activation is partially regulated by Rho-ROCK-MLC signaling but not vice versa. Moreover, receptor auto-proteolysis modulates the magnitude of GPR56-mediated signaling, and its unique intracellular regions contribute to the selective regulation of unique signaling pathways and associated cellular phenotypes.

CONCLUSION

Our findings reveal complex GPR56-mediated biased signaling through the Rho-ROCK-MLC and JAK-STAT3 pathways, highlighting these networks as potential therapeutic targets for modulating distinct tumorigenic phenotypes in human melanoma cells.

B7-H3 and CSPG4 co-targeting as Pan-CAR-T cell treatment of triple-negative breast cancer

PURPOSE

Chimeric antigen receptor T (CAR-T) cell therapy is under clinical investigation in patients with metastatic triple-negative breast cancer (TNBC). However, the identification of targetable antigens remains a high priority to avoid toxicity and prevent tumor escape.

EXPERIMENTAL DESIGN

Here we analyzed the gene expression of B7-H3 (CD276) and chondroitin sulfate proteoglycan 4 (CSPG4) in 98 TNBC samples identified in the AURORA US Network and Rapid Autopsy RNA sequencing data set at University of North Carolina (UNC). We then performed immunohistochemistry analysis for B7-H3 and CSPG4 protein expression in 151 TNBC samples collected at UNC. Finally, the validity of the proposed B7-H3 and CSGP4 co-targeting was tested in clinically relevant TNBC patient derived xenograft (PDX) models.

RESULTS

We observed that CD276 and CSPG4 genes are broadly and comparably expressed in TNBC samples, and gene expression is generally conserved in tumor metastases. None of the TNBC analyzed met the criteria for simultaneous low expression of CSPG4 and CD276 genes. Immunohistochemistry analysis showed a median H-score of 138 (105-168, lower and upper quartile, respectively) for B7-H3 expression and a median H-score of 33 (14-78 lower and upper quartile, respectively) for CSPG4 expression. Notably, 49% of the TNBC cores with B7-H3 H-score ≤105 exhibited a CSPG4 H-score exceeding its median value, and 37% and 18% of the TNBC cores with low B7-H3 expression scored CSPG4 expression above its median H-score or exceeded its upper quartile, respectively, confirming that at least one of these two proteins is expressed in 94% of the analyzed tumors. Finally, optimized dual-specific B7-H3 and CSPG4 CAR-T cells eradicated tumors with mixed antigen expression in TNBC PDX models.

CONCLUSIONS

These data highlight the clinical potential of the proposed approach that could be applicable to the great majority of patients with TNBC as well as most of patients with breast cancer in general.

Potentiating T cell tumor targeting using a combination of TCR with a Siglec-7 based CSR

Introduction

Tumors may utilize different strategies to escape T cell immunosurveillance. Besides the overexpression of checkpoint ligands (such as PDL1) or the secretion of immunosuppressive agents, several studies have shown that cancer aberrant sialylation can, through interaction with selected receptors such as those from the Siglec family, neutralize NK and T cell function.

Methods

Herein, we wanted to take advantage of the presence of inhibitory sialic acid ligands on the tumor cell surface to enhance T cell anti-tumor activity. To this end, we devised a novel chimeric receptor consisting of the extracellular portion of Siglec-7 and the intracellular portion of 41BB, which can convert inhibitory signals into stimulatory ones when expressed in human T-cells.

Results

This co-stimulatory chimeric switch receptor (CSR), when co-expressed with a tumor-specific TCR, facilitated higher cytokine secretion and activation profiles following co-culture with tumor cells. Additionally, T cells equipped with Siglec-7 CSR demonstrated improved anti-tumor function in vivo.

Discussion

Given the broad expression pattern of Siglec-7 ligands on tumor cells, our data suggest this CSR may act as a general adjuvant to boost TCR T cell function. Overall, this work provides an approach to improve engineered T-cell-based cancer treatment.

Engineering TCR-controlled fuzzy logic into CAR T cells enhances therapeutic specificity

Chimeric antigen receptor (CAR) T cell immunotherapy represents a breakthrough in the treatment of hematological malignancies, but poor specificity has limited its applicability to solid tumors. By contrast, natural T cells harboring T cell receptors (TCRs) can discriminate between neoantigen-expressing cancer cells and self-antigen-expressing healthy tissues but have limited potency against tumors. We used a high-throughput platform to systematically evaluate the impact of co-expressing a TCR and CAR on the same CAR T cell. While strong TCR-antigen interactions enhanced CAR activation, weak TCR-antigen interactions actively antagonized their activation. Mathematical modeling captured this TCR-CAR crosstalk in CAR T cells, allowing us to engineer dual TCR/CAR T cells targeting neoantigens (HHATL8F/p53R175H) and human epithelial growth factor receptor 2 (HER2) ligands, respectively. These T cells exhibited superior anti-cancer activity and minimal toxicity against healthy tissue compared with conventional CAR T cells in a humanized solid tumor mouse model. Harnessing pre-existing inhibitory crosstalk between receptors, therefore, paves the way for the design of more precise cancer immunotherapies.

Novel strategies to manage CAR-T cell toxicity

The immune-related adverse events associated with chimeric antigen receptor (CAR)-T cell therapy result in substantial morbidity as well as considerable cost to the health-care system, and can limit the use of these treatments. Current therapeutic strategies to manage immune-related adverse events include interleukin-6 receptor (IL-6R) blockade and corticosteroids. However, because these interventions do not always address the side effects, nor prevent progression to higher grades of adverse events, new approaches are needed. A deeper understanding of the cell types involved, and their associated signalling pathways, cellular metabolism and differentiation states, should provide the basis for alternative strategies. To preserve treatment efficacy, cytokine-mediated toxicity needs to be uncoupled from CAR-T cell function, expansion, long-term persistence and memory formation. This may be achieved by targeting CAR or independent cytokine signalling axes transiently, and through novel T cell engineering strategies, such as low-affinity CAR-T cells, reversible on-off switches and versatile adaptor systems. We summarize the current management of cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, and review T cell- and myeloid cell-intrinsic druggable targets and cellular engineering strategies to develop safer CAR-T cells.

The potential of chimeric antigen receptor -T cell therapy for endocrine cancer

Endocrine cancer, a relatively rare and heterogeneous tumor with diverse clinical features. The facile synthesis of hormones further complicates endocrine cancer treatment. Thus, the development of safe and effective systemic treatment approaches, such as chimeric antigen receptor (CAR) T cell therapy, is imperative to enhance the prognosis of patients with endocrine cancer. Although this therapy has achieved good results in the treatment of hematological malignancies, it encounters diverse complications and challenges in the context of endocrine cancer. This review delineates the generation of CAR-T cells, examines the potential of CAR-T cell therapy for endocrine cancer, enumerates pivotal antigens linked to endocrine cancer, encapsulates the challenges confronted with CAR-T cell therapy for endocrine cancer, and expounds upon strategies to overcome these limitations. The primary objective is to provide insightful perspectives that can contribute to the advancement of CAR-T cell therapy in the field of endocrine cancer.

Preclinical targeting of leukemia-initiating cells in the development future biologics for acute myeloid leukemia

INTRODUCTION

Leukemia-initiating cells (LICs) are a critical subset of cells driving acute myeloid leukemia (AML) relapse and resistance to therapy. They possess unique properties, including metabolic, epigenetic, and microenvironmental dependencies, making them promising therapeutic targets.

AREAS COVERED

This review summarizes preclinical advances in targeting AML LICs, including strategies to exploit metabolic vulnerabilities, such as the reliance on oxidative phosphorylation (OXPHOS), through the use of mitochondrial inhibitors; target epigenetic regulators like DOT1L (Disruptor of Telomeric Silencing 1-like) to disrupt LIC survival mechanisms; develop immunotherapies, including CAR (chimeric antigen receptor) T-cell therapy, and bispecific antibodies; and disrupt LIC interactions with the bone marrow microenvironment by inhibiting supportive niches.

EXPERT OPINION

LIC-targeted therapies hold significant promise for revolutionizing AML treatment by reducing relapse rates and improving long-term outcomes. However, challenges such as LIC heterogeneity, therapy resistance, and associated toxicity persist. Recent studies have illuminated the distinct biological characteristics of LICs, advancing our understanding of their behavior and vulnerabilities. These insights offer new opportunities to target LICs at earlier disease stages and to explore combination therapies with other targeted treatments, ultimately enhancing therapeutic efficacy and improving patient outcomes.

Recent advances of CAR-T cells in acute myeloid leukemia

Acute myeloid leukemia (AML), the most common type of leukemia in adults, is a highly heterogeneous and aggressive hematologic malignancy. Since the 20th century, the combination of cytosine arabinoside and anthracyclines has been the most common chemotherapy drug used to treat patients with AML. Although, new targeted medicines have emerged, such as midostaurin and gilteritinib targeting FMS-like tyrosine kinase 3 (FLT3), ivosidenib (isocitrate dehydrogenase 1 (IDH1) inhibitor) and enasidenib (IDH2 inhibitor) targeting IDH, and gemtuzumab ozogamicin targeting CD33, which have changed the treatment strategies of AML. But, until now, hematopoietic stem cell transplantation remains the best treatment option in most cases. However, treatment resistance and relapse are still the major consequences of disease progression in AML, highlighting the urgent need for novel therapeutic approaches. As an alternative, chimeric antigen receptor (CAR)-T cells are engineered T-cells developed as a breakthrough in cancer therapy in recent years, and explored and used in various tumor types. In particular, it has achieved remarkable efficacy in the field of relapsed and refractory B lymphocyte tumors. This review mainly summarizes and discusses the research progress and the clinical application of CAR-T cell immunotherapy in AML in recent years.

Development of multivalent CAR T cells as dual immunotherapy and conditioning agents

Hematopoietic stem cell transplantation (HSCT) is the only definitive cure for pediatric acute myeloid leukemia (AML). Despite adjustments in HSCT protocols and improvements in supportive care, 30% of high-risk patients who receive HSCT as part of their therapy still experience disease relapse with high transplant-related mortality. Relapsed AML has a dismal prognosis, and novel therapies are needed. To improve upon the status quo, HSCT would more effectively eliminate relapse-initiating leukemic cells and be delivered with safer, non-genotoxic conditioning. Here, we investigate hematopoietic cytokine receptors (HCRs) and identify that KIT, MPL, and FLT3 are collectively highly expressed in virtually all pediatric AML samples studied. Further, we establish proof-of-concept of a first-in-class chimeric antigen receptor (CAR) T cell that enables simultaneous targeting of KIT, MPL, and FLT3 through a single receptor, which we term the extracellularly linked concatemeric trivalent cytokine (ELECTRIC) CAR. ELECTRIC CARs exhibit potent cytotoxicity against normal and malignant hematopoietic cells in vitro and display anti-HCR activity in a murine xenograft model. We propose that the ELECTRIC system can be the foundation to developing a non-genotoxic, anti-leukemic conditioning regimen to enable safer, more durable efficacy with minimal toxicity.

Gene Signature-Based Prognostic Model for Acute Myeloid Leukemia: The Role of BATF, EGR1, PD-1, PD-L1, and TIM-3

Background: Acute myeloid leukemia (AML) is a malignancy of hematopoietic stem and progenitor cells, with T cell exhaustion linked to poor outcomes. Our previous research has shown that basic leucine zipper ATF-like transcription factor (BATF) and early growth response 1 (EGR1) play a role in chimeric antigen receptor T (CAR-T) cell exhaustion during AML tumor elimination. However, the roles of BATF and EGR1 and their association with immune checkpoint genes in AML prognosis remain underexplored. Methods: Bone marrow (BM) samples from 92 newly diagnosed AML patients at our clinical center (JUN-dataset) were analyzed to detect the expression levels of BATF, EGR1, programmed cell death 1 (PD-1), programmed death-ligand 1 (PD-L1), T cell immunoglobulin and mucin domain-containing protein 3 (TIM3) together with conducting a prognostic assessment. Our findings were validated using RNA sequencing data from 155 AML patients from the TCGA database and 199 AML patients from the Beat-AML database. Results: High BATF expression correlated with poor overall survival (OS) (P = 0.030), whereas high EGR1 expression indicated a favorable prognosis (P = 0.040). Patients with high BATF and low EGR1 expression had worst outcomes (P < 0.001). Among those receiving allogenic hematopoietic stem cell transplantation (allo-HSCT), high BATF expression was linked to shorter OS (P = 0.004). Moreover, a prognostic model incorporating BATF, EGR1, PD-1, PD-L1, and TIM-3 calculated a risk score, with high-risk patients demonstrating significantly shorter OS than low-risk patients in both total AML patients and allo-HSCT recipients (P < 0.001). Similar results were found in both the TCGA and Beat-AML datasets. Conclusions: We establish a prognostic model based on BATF, EGR1, PD-1, PD-L1, and TIM-3 expression that effectively predicts survival outcomes for AML patients and allo-HSCT recipients. This model may provide valuable insights for prognosis assessment and treatment strategies.

Multi-Targeting CAR-T Cell Strategies to Overcome Immune Evasion in Lymphoid and Myeloid Malignancies

BACKGROUND

Chimeric antigen receptor (CAR)-T cell therapy has become a groundbreaking treatment for hematological malignancies, particularly lymphomas and multiple myeloma, with high remission rates in refractory and relapsed patients. However, most CAR-T therapies target a single antigen, such as CD19, which can result in immune evasion through antigen escape. This mechanism describes the downregulation or complete loss of the targeted antigen by the tumor cells, eventually leading to relapse. To address this issue, multi-targeting strategies like logic-gated CARs, adapter CARs, or combination therapies can increase the potency of CAR-T cells. These approaches aim to minimize immune evasion by targeting multiple antigens simultaneously, thereby increasing treatment durability. Additionally, advanced tools such as next-generation sequencing (NGS), direct stochastic optical reconstruction microscopy (dSTORM), or multiparametric flow cytometry are helping to identify novel tumor-specific targets and improve therapy designs.

SUMMARY

This review explores the current landscape of CAR-T cell therapies in lymphoid and myeloid malignancies, highlights ongoing clinical trials, and discusses the future of these innovative multi-targeting approaches to improve patient outcome.

KEY MESSAGES

Antigen escape limits CAR-T cell therapy success, but multi-targeting strategies like logic gates and adapter CARs offer solutions. Optimizing antigen selection and CAR design, along with larger clinical trials, is essential for improving patient outcomes. Personalization using advanced technologies like CRISPR screening and single-cell RNA sequencing can enhance durability and effectiveness of treatments for heavily pretreated patients.

Honing CAR T cells to tackle acute myeloid leukemia

ABSTRACT

Acute myeloid leukemia (AML) remains a dismal disease with poor prognosis, particularly in the relapsed/refractory (R/R) setting. Chimeric antigen receptor (CAR) therapy has yielded remarkable clinical results in other leukemias and thus has, in principle, the potential to achieve similar outcomes in R/R AML. Redirecting the approved CD19-specific CAR designs against the myeloid antigens CD33, CD123, or CLEC12A has occasionally yielded morphologic leukemia-free states but has so far been marred by threatening myeloablation and early relapses. These safety and efficacy limitations are largely due to the challenge of identifying suitable target antigens and designing adequate receptors for effective recognition and safe elimination of AML. Building on lessons learned from the initial clinical attempts, a new wave of CAR strategies relying on alternative target antigens and innovative CAR designs is about to enter clinical evaluation. Adapted multiantigen targeting, logic gating, and emerging cell engineering solutions offer new possibilities to better direct T-cell specificity and sensitivity toward AML. Pharmacologic modulation and genetic epitope engineering may extend these approaches by augmenting target expression in AML cells or minimizing target expression in normal hematopoietic cells. On/off switches or CAR T-cell depletion may curb excessive or deleterious CAR activity. Investigation of AML-intrinsic resistance and leukemic microenvironmental factors is poised to reveal additional targetable AML vulnerabilities. We summarize here the findings, challenges, and new developments of CAR therapy for AML. These illustrate the need to specifically adapt CAR strategies to the complex biology of AML to achieve better therapeutic outcomes.

A review of common immunotherapy and nano immunotherapy for acute myeloid leukemia

Acute myeloid leukemia (AML) is a highly aggressive hematological malignancy. Traditional chemotherapy methods not only bring serious side effects, but also lead to high recurrence rate and drug resistance in some patients. However, as an emerging therapeutic strategy, immunotherapy has shown great potential in the field of AML treatment in recent years. At present, common immunotherapy methods for AML include monoclonal antibodies, CAR-T cell therapy, and immune checkpoint inhibitors. With the deepening of research and technological progress, especially the application of nanotechnology in medicine, new immunotherapy is expected to become one of the important means for the treatment of acute myeloid leukemia in the future.

Gene editing of CD3 epsilon to redirect regulatory T cells for adoptive T cell transfer

Adoptive transfer of antigen-specific regulatory T cells (Tregs) is a promising strategy to combat immunopathologies in transplantation and autoimmune diseases. However, their low frequency in peripheral blood poses challenges for both manufacturing and clinical application. Chimeric antigen receptors have been used to redirect the specificity of Tregs, using retroviral vectors. However, retroviral gene transfer is costly, time consuming, and raises safety issues. Here, we explored non-viral CRISPR-Cas12a gene editing to redirect Tregs, using human leukocyte antigen (HLA)-A2-specific constructs for proof-of-concept studies in transplantation models. Knock-in of an antigen-binding domain into the N terminus of CD3 epsilon (CD3ε) gene generates Tregs expressing a chimeric CD3ε-T cell receptor fusion construct (TRuC) protein that integrates into the endogenous TCR/CD3 complex. These CD3ε-TRuC Tregs exhibit potent antigen-dependent activation while maintaining responsiveness to TCR/CD3 stimulation. This enables preferential enrichment of TRuC-redirected Tregs over CD3ε knockout Tregs via repetitive CD3/CD28 stimulation in a good manufacturing practice-compatible expansion system. CD3ε-TRuC Tregs retained their phenotypic, epigenetic, and functional identity. In a humanized mouse model, HLA-A2-specific CD3ε-TRuC Tregs demonstrate superior protection of allogeneic HLA-A2+ skin grafts from rejection compared with polyclonal Tregs. This approach provides a pathway for developing clinical-grade CD3ε-TRuC-based Treg cell products for transplantation immunotherapy and other immunopathologies.

CD19 -targeted CAR T therapy treating hematologic malignancies: hidden danger is the next neighbor to security?

CD19-targeted chimeric antigen receptor (CAR) T-cell therapy has achieved marvelous results in the treatment of patients with relapsed and/or refractory B-cell lymphomas, B-cell acute lymphoblastic leukemia, and multiple myeloma. As a new treatment method that has changed the existing treatment paradigm, there has been a short time from its emergence to FDA approval. However, with the increasing number of cases and the passage of time, hidden problems have gradually been exposed. In this review, we summarize the short- and long-term toxicity, such as secondary T-cell tumors and lethal CAR tumors, of patients with hematologic malignancies treated with CD19-CAR-T cells, including cytokine release syndrome (CRS), ICANS, and secondary malignancies with low occurrence rates but high mortality, such as secondary T cell tumors and lethal CAR tumors, which may be related to the gene modification mechanism of viral vectors currently approved for CAR-T cells. We also discuss potential investigational strategies designed to improve the safety of CAR-T-cell therapy.

LILRB4 as a novel immunotherapeutic target for multiple diseases

Immune checkpoints are critical for maintaining autoimmune homeostasis and are implicated in various autoimmune diseases, with their significance increasingly recognized. Investigating the functions and mechanisms of these checkpoints is essential for the development of more effective treatments. Leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4) stands out as a unique immune checkpoint, with limited expression in most normal tissues but prominent presence in various hematological and solid tumors. It is also expressed on numerous immune and stromal cells, functioning as both a "Tumor Immune Checkpoint" and a "Tumor Stromal Immune Checkpoint." Due to its distinct expression profile, LILRB4 plays a pivotal role in tumors, autoimmune diseases, allergic reactions, and the maintenance of immune homeostasis during transplantation and pregnancy. A thorough understanding of its ligands, functions, mechanisms, and ongoing therapeutic strategies targeting LILRB4 will be crucial for the development of advanced therapeutic options. This review examines LILRB4 expression and function across multiple diseases and discusses therapeutic approaches targeting LILRB4 in various contexts. Additionally, the potential of combining current drugs with LILRB4-targeted therapies is explored. Challenges in developing LILRB4-targeting drugs are also addressed, offering valuable insights for future research.

Strategies to Overcome Antigen Heterogeneity in CAR-T Cell Therapy

Chimeric antigen receptor (CAR) gene-modified T-cell therapy has achieved significant success in the treatment of hematological malignancies. However, this therapy has not yet made breakthroughs in the treatment of solid tumors and still faces issues of resistance and relapse in hematological cancers. A major reason for these problems is the antigenic heterogeneity of tumor tissues. This review outlines the antigenic heterogeneity encountered in CAR-T cell therapy and the corresponding strategies to address it. These strategies include using combination therapy to increase the abundance of target antigens, optimizing the structure of CARs to enhance sensitivity to low-density antigens, developing multi-targeted CAR-T cells, and reprogramming the TME to activate endogenous immunity. These approaches offer new directions for overcoming tumor antigenic heterogeneity in CAR-T cell therapy.

Adoptive cell therapy in acute myeloid leukemia: the current landscape and emerging strategies

Efforts to produce adoptive cell therapies in AML have been largely unfruitful, despite the success seen in lymphoid malignancies. Identifying targetable antigens on leukemic cells that are absent on normal progenitor cells remains a major obstacle, as is the hostile tumor microenvironment created by AML blasts. In this review, we summarize the challenges in the development of adoptive cell therapies such as CAR-T, CAR-NK, and TCR-T cells in AML, discussing both autologous and allogeneic therapies. We also discuss methods to address myelotoxicity associated with these therapies, including rapidly switchable CAR platforms and CRISPR-Cas9 genetic engineering of hematopoietic stem cells. Finally, we present the current clinical landscape in these areas, along with future directions in the field.

The molecular receptor NKBB enhances the persistence and anti-hepatocellular carcinoma activity of GPC3 CAR-T cells

Chimeric antigen receptor (CAR) T cells have encouraging results in the treatment of hematological malignancies. However, CAR-T therapy still faces numerous challenges against solid tumors, such as hepatocellular carcinoma (HCC), owing to heterogeneous antigen expression in tumor cells, limited persistence of CAR-T cells, etc. Therefore, to treat HCC more effectively, we connected the molecular receptor NKBB to a second-generation glypican-3 (GPC3) CAR to construct GC3328z-NKBB CAR-T cells, which have double specific targets of GPC3 and NKG2DLs (natural killer group 2, member D ligands), dual co-stimulation of CD28 and 41BB, and a single CD3ζ chain. Our study showed that the molecular receptor NKBB conferred GPC3 CAR-T cells with enhanced migration and infiltration abilities towards HCC, higher central memory T (TCM) cell proportion and proliferation capacity, and reduced exhaustion level. GC3328z-NKBB CAR-T cells exhibited improved cytotoxicity against HCC cells and prolonged persistence. The cathepsin L/interleukin-17 (CTSL/IL-17) axis contributed to the superior anti-HCC activity of GC3328z-NKBB CAR-T cells. Overall, the molecular receptor NKBB significantly increased the persistence of GPC3 CAR-T cells, and GC3328z-NKBB CAR-T cells possessed potent anti-HCC activity in mice, providing a new strategy for the potential improvement of adoptive T cell therapy in the treatment of HCC.

Identification of hub genes and immune-related pathways in acute myeloid leukemia: insights from bioinformatics and experimental validation

Background

This study aims to identify the hub genes and immune-related pathways in acute myeloid leukemia (AML) to provide new theories for immunotherapy.

Methods

We use bioinformatics methods to find and verify the hub gene. At the same time, we use the results of GSEA enrichment analysis to find immune-related mediators. Through Mendelian randomization(MR) analysis, on the one hand, we look for related immune cells, and on the other hand, we use it to determine the causal relationship among immune cells, immune mediators, and AML. Finally, in vitro experiments are conducted to further verify and improve the reliability and physiological functions of the hub gene and its immune-related pathways.

Results

Complement Factor D(CFD) gene is identified as the highly expressed hub gene and is positively correlated with IL-2. IL-2 is also positively correlated with CD27 on CD24+CD27+B cells, JAK/STAT, and PI3K/Akt. The latter three are positively correlated with the occurrence and development of AML.

Conclusion

We conclude that CFD gene uses IL-2 as a mediator to promote the disease progression of AML by promoting the CD27 on CD24+CD27+B cells, JAK-STAT, and PI3K-Akt pathways.

CD33-CD123 IF-THEN Gating Reduces Toxicity while Enhancing the Specificity and Memory Phenotype of AML-Targeting CAR-T Cells

SIGNIFICANCE

Our study demonstrates the use of "IF-THEN" SynNotch-gated CAR-T cells targeting CD33 and CD123 in AML reduces off-tumor toxicity. This strategy enhances T-cell phenotype, improves expansion, preserves HSPCs, and mitigates cytokine release syndrome-addressing critical limitations of existing AML CAR-T therapies.

Correlative studies reveal factors contributing to successful CAR-T cell therapies in cancer

Cellular and targeted immunotherapies have revolutionized cancer treatments in the last several decades. Successful cellular therapies require both effective and durable cytotoxic activity from the immune cells as well as an accessible and susceptible response from targeted cancer cells. Correlative studies from clinical trials as well as real-world data from FDA-approved therapies have revealed invaluable insights about immune cell factors and cancer cell factors that impact rates of response and relapse to cellular therapies. This review focuses on the flagship cellular therapy of engineered chimeric antigen receptor T-cells (CAR-T cells). Within the CAR-T cell compartment, we discuss discoveries about T-cell phenotype, transcriptome, epigenetics, cytokine signaling, and metabolism that inform the cell manufacturing process to produce the most effective and durable CAR-T cells. Within the cancer cell compartment, we discuss mechanisms of resistance and relapse caused by mutations, alternative splicing, post-transcriptional modifications, and cellular reprogramming. Continued correlative and mechanistic studies are required to help us further optimize cellular therapies in a variety of malignancies.

Efficient combinatorial adaptor-mediated targeting of acute myeloid leukemia with CAR T-cells

CAR T-cell products targeting lineage-specific cell-of-origin antigens, thereby eliminating both tumor and healthy counterpart cells, are currently clinically approved therapeutics in B- and plasma-cell malignancies. While they represent a major clinical improvement, they are still limited in terms of efficacy by e.g. single, sometimes low-expressed antigen targeting, and in terms of safety by e.g., lack of on-off activity. Successful cell-of-origin non-discriminative targeting of heterogeneous hematopoietic stem and progenitor cell malignancies, such as acute myeloid leukemia (AML), will require antigen-versatile targeting and off-switching of effectors in order to then allow rescue by hematopoietic stem cell transplantation (HSCT), preventing permanent myeloablation. To address this, we developed adaptor-CAR (AdFITC-CAR) T-cells targeting fluoresceinated AML antigen-binding diabody adaptors. This platform enables the use of adaptors matching the AML-antigen-expression profile and conditional activity modulation. Combining adaptors significantly improved lysis of AML cells in vitro. In therapeutic xenogeneic mouse models, AdFITC-CAR T-cells co-administered with single diabody adaptors were as efficient as direct CAR T-cells, and combinatorial use of adaptors further enhanced therapeutic efficacy against both, cell lines and primary AML. Collectively, this study provides proof-of-concept that AdFITC-CAR T-cells and combinations of adaptors can efficiently enhance immune-targeting of AML.

Advances in cell therapy: progress and challenges in hematological and solid tumors

Cell-based therapies harness the endogenous ability of the immune system to fight cancer and have shown promising results in the treatment of hematological malignancies. However, their clinical application beyond B cell malignancies is hampered by numerous hurdles, ranging from relapsed disease to a hostile tumor microenvironment (TME). Recent advances in cell engineering and TME modulation may expand the applicability of these therapies to a wider range of cancers, creating new treatment possibilities. Breakthroughs in advanced gene editing and sophisticated cell engineering, have also provided promising solutions to longstanding challenges. In this review, we examine the challenges and future directions of the most prominent cell-based therapies, including chimeric antigen receptor (CAR)-T cells, tumor-infiltrating lymphocytes (TILs), and natural killer (NK) cells, and emerging modalities. We provide a comprehensive analysis of emerging cell types and combination strategies translated into clinical trials, offering insights into the next generation of cell-based cancer treatments.

A single-chain variable fragment-based bispecific T-cell activating antibody against CD117 enables T-cell mediated lysis of acute myeloid leukemia and hematopoietic stem and progenitor cells

Acute myeloid leukemia (AML) derives from hematopoietic stem and progenitor cells (HSPCs). To date, no AML-exclusive, non-HSPC-expressed cell-surface target molecules for AML selective immunotherapy have been identified. Therefore, to still apply surface-directed immunotherapy in this disease setting, time-limited combined immune-targeting of AML cells and healthy HSPCs, followed by hematopoietic stem cell transplantation (HSCT), might be a viable therapeutic approach. To explore this, we generated a recombinant single-chain variable fragment-based bispecific T-cell engaging and activating antibody directed against CD3 on T-cells and CD117, the surface receptor for stem cell factor, expressed by both AML cells and healthy HSPCs. Bispecific CD117xCD3 targeting induced lysis of CD117-positive healthy human HSPCs, AML cell lines and patient-derived AML blasts in the presence of T-cells at subnanomolar concentrations in vitro. Furthermore, in immunocompromised mice, engrafted with human CD117-expressing leukemia cells and human T-cells, the bispecific molecule efficiently prevented leukemia growth in vivo. Additionally, in immunodeficient mice transplanted with healthy human HSPCs, the molecule decreased the number of CD117-positive cells in vivo. Therefore, bispecific CD117xCD3 targeting might be developed clinically in order to reduce CD117-expressing leukemia cells and HSPCs prior to HSCT.

Fibroblast activation protein constitutes a novel target of chimeric antigen receptor T-cell therapy in solid tumors

With recent advances in tumor immunotherapy, chimeric antigen receptor T (CAR-T) cell therapy has achieved unprecedented success in several hematologic tumors, significantly improving patient prognosis. However, in solid tumors, the efficacy of CAR-T cell therapy is limited because of high antigen uncertainty and the extremely restrictive tumor microenvironment (TME). This challenge has led to the exploration of new targets, among which fibroblast activation protein (FAP) has gained attention for its relatively stable and specific expression in the TME of various solid tumors, making it a potential new target for CAR-T cell therapy. This study comprehensively analyzed the biological characteristics of FAP and discussed its potential application in CAR-T cell therapy, including the theoretical basis, and preclinical and clinical research progress of targeting FAP with CAR-T cell therapy for solid tumor treatment. The challenges and future optimization directions of this treatment strategy were also explored, providing new perspectives and strategies for CAR-T cell therapy in solid tumors.

Evolving strategies to overcome barriers in CAR-T cell therapy for acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) is a complex and heterogeneous disease characterized by an aggressive clinical course and limited efficacious treatment options in the relapsed/refractory (R/R) setting. Chimeric antigen receptor (CAR)-modified T (CAR-T) cell immunotherapy is an investigational treatment strategy for R/R AML that has shown some promise. However, obstacles to successful CAR-T cell immunotherapy for AML remain.

AREAS COVERED

In analyses of clinical trials of CAR-T cell therapy for R/R AML, complete responses without measurable residual disease have been reported, but the durability of those responses remains unclear. Significant barriers to successful CAR-T cell therapy in AML include the scarcity of suitable tumor-target antigens (TTA), inherent T cell functional deficits, and the immunoinhibitory and hostile tumor microenvironment (TME). This review will focus on these barriers to successful CAR-T cell therapy in AML, and discuss scientific advancements and evolving strategies to overcome them.

EXPERT OPINION

Achieving durable remissions in R/R AML will likely require a multifaceted approach that integrates advancements in TTA selection, enhancement of the intrinsic quality of CAR-T cells, and development of strategies to overcome inhibitory mechanisms in the AML TME.

Membrane Antigen Targeting in Acute Myeloid Leukemia Using Antibodies or CAR-T Cells

This review explores the emerging area of the therapeutic use of antibodies and chimeric antigen receptor (CAR)-T cells for the treatment of acute myeloid leukemia (AML). Through a detailed analysis of the existing literature, this paper highlights the different categories of AML antigens for immunotherapeutic targeting, the most recent applications on antibodies, including bispecific immune cell engagers and CAR-T cells, to the therapy of patients with refractory/relapsing AML The studies performed in AML patients using BisAbs and CAR-T cells have shown that only a limited number of AML patients show sustained responses to these therapies, thus underlying AML heterogeneity as a major challenge. Several studies have addressed the potential mechanisms underlying the resistance of AMLs to antibody-directed immunotherapies. A better understanding of the barriers hampering the successful development of AML immunotherapy is required. However, in spite of the limitations, the studies recently carried out have shown the peculiar sensitivity of some AML subtypes to immunotherapy and have provided the basis for future studies, such as multiplex antigen targeting, which hold the promise of successful development.

Revolutionizing cancer treatment: the emerging potential and potential challenges of in vivo self-processed CAR cell therapy

Chimeric antigen receptor (CAR) cell immunotherapies, including CAR-T, CAR-Macrophages, CAR-Natural Killer, CAR-γδ T, etc., have demonstrated significant advancements in the treatment of both hematologic malignancies and solid tumors. Despite the notable successes of traditional CAR cell manufacturing, its application remains constrained by the complicated production process and expensive costs. Consequently, efforts are focused on streamlining CAR cell production to enhance efficacy and accessibility. Among numerous proposed strategies, direct in vivo generation of CAR cells represents the most substantial technical challenge, yet holding great promise for achieving clinical efficacy. Herein, we outlined the current state-of-the-art in vivo CAR therapy, including CAR technology development, transfection vectors, and influence factors of construction of CAR in vivo. We also reviewed the types and characteristics of different delivery systems and summarized the advantages of in vivo CAR cell therapy, such as rapid preparation and cost-effectiveness. Finally, we discussed the limitations, including technical issues, challenges in target and signal design, and cell-related constraints. Meanwhile, strategies have correspondingly been proposed to advance the development of CAR cell therapy, in order to open the new horizons on cancer treatment.

CAR-T cell therapy in AML: recent progress and future perspectives

Despite several small-molecule drugs that have revolutionized the current treatment strategy for acute myeloid leukemia (AML), hematopoietic stem cell transplantation remains the only curative treatment in most cases to date. Chimeric antigen receptor (CAR)-T cell therapy is one of the most promising next-generation cancer therapies for hematological malignancies and is clinically available for treatment of AML. However, developing AML-targeted CAR-T therapy is challenging because of the heterogeneity of target antigen expression across leukemic cells and patients, the difficulty in excluding on-/off-target tumor effects, and the immunosuppressive tumor microenvironment. To date, various targets, including CD33, NKG2D, CD123, CLL-1, and CD7, have been actively studied for CAR-T cells. Although no CAR-T cell products are close to practical use, several clinical trials have shown promising results, particularly for CAR-T cells targeting CLL-1 or CD123. Meanwhile, research exploring the ideal target for AML-targeted CAR-T therapy continues. Furthermore, as collecting autologous lymphocytes from patients with AML is difficult, development of off-the-shelf CAR-T products is being actively pursued. This review discusses the challenges in AML-targeted CAR-T cell therapy development from the perspectives of target antigen characteristics and AML-specific on-target/off-tumor toxicity. Moreover, it discusses the clinical development and prospects of AML-targeting CAR-T cells.

Phase 1 study of CAR-37 T cells in patients with relapsed or refractory CD37+ lymphoid malignancies

ABSTRACT

We report a first-in-human clinical trial using chimeric antigen receptor (CAR) T cells targeting CD37, an antigen highly expressed in B- and T-cell malignancies. Five patients with relapsed or refractory CD37+ lymphoid malignancies were enrolled and infused with autologous CAR-37 T cells. CAR-37 T cells expanded in the peripheral blood of all patients and, at peak, comprised >94% of the total lymphocytes in 4 of 5 patients. Tumor responses were observed in 4 of 5 patients with 3 complete responses, 1 mixed response, and 1 patient whose disease progressed rapidly and with relative loss of CD37 expression. Three patients experienced prolonged and severe pancytopenia, and in 2 of these patients, efforts to ablate CAR-37 T cells, which were engineered to coexpress truncated epidermal growth factor receptor, with cetuximab were unsuccessful. Hematopoiesis was restored in these 2 patients after allogeneic hematopoietic stem cell transplantation. No other severe, nonhematopoietic toxicities occurred. We investigated the mechanisms of profound pancytopenia and did not observe activation of CAR-37 T cells in response to hematopoietic stem cells in vitro or hematotoxicity in humanized models. Patients with pancytopenia had sustained high levels of interleukin-18 (IL-18) with low levels of IL-18 binding protein in their peripheral blood. IL-18 levels were significantly higher in CAR-37-treated patients than in both cytopenic and noncytopenic cohorts of CAR-19-treated patients. In conclusion, CAR-37 T cells exhibited antitumor activity, with significant CAR expansion and cytokine production. CAR-37 T cells may be an effective therapy in hematologic malignancies as a bridge to hematopoietic stem cell transplant. This trial was registered at www.ClinicalTrials.gov as #NCT04136275.

Mapping the cancer surface proteome in search of target antigens for immunotherapy

Immune-based therapeutic interventions recognizing proteins localized on the cell surface of cancer cells are emerging as a promising cancer treatment. Antibody-based therapies and engineered T cells are now approved by the Food and Drug Administration to treat some malignancies. These therapies utilize a few cell surface proteins highly expressed on cancer cells to release the negative regulation of immune activation that limits antitumor responses (e.g., PD-1, PD-L1, CTLA4) or to redirect the T cell specificity toward blood cancer cells (e.g., CD19 and B cell maturation antigen). One limitation preventing broader application of these novel therapeutic strategies to all cancer types is the lack of suitable target antigens for all indications owing in part to the challenges in identifying such targets. Ideal target antigens are cell surface proteins highly expressed on malignant cells and absent in healthy tissues. Technological advances in mass spectrometry, enrichment protocols, and computational tools for cell surface protein isolation and annotation have recently enabled comprehensive analyses of the cancer cell surface proteome, from which novel immunotherapeutic target antigens may emerge. Here, we review the most recent progress in this field.

T cell-redirecting therapies in hematological malignancies: Current developments and novel strategies for improved targeting

T cell-redirecting therapies (TCRTs), such as chimeric antigen receptor (CAR) or T cell receptor (TCR) T cells and T cell engagers, have emerged as a highly effective treatment modality, particularly in the B and plasma cell-malignancy setting. However, many patients fail to achieve deep and durable responses; while the lack of truly unique tumor antigens, and concurrent on-target/off-tumor toxicities, have hindered the development of TCRTs for many other cancers. In this review, we discuss the recent developments in TCRT targets for hematological malignancies, as well as novel targeting strategies that aim to address these, and other, challenges.

CAR T-cell toxicities: from bedside to bench, how novel toxicities inform laboratory investigations

ABSTRACT

Multiple chimeric antigen receptor (CAR) T-cell therapies are US Food and Drug Administration-approved, and several are under development. Although effective for some cancers, toxicities remain a limitation. The most common toxicities, that is, cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, are well described. With increasing utilization, providers worldwide are reporting other emergent and often complicated toxicities. Given the evolving toxicity profiles and urgent need to catalog these emerging and emergent CAR T-cell toxicities and describe management approaches, the American Society of Hematology Subcommittee on Emerging Gene and Cell Therapies organized the first scientific workshop on CAR T-cell toxicities during the annual society meeting. The workshop functioned to (1) aggregate reports of CAR T-cell emergent toxicities, including movement disorders after B-cell maturation antigen CAR T cell, coagulation abnormalities, and prolonged cytopenia; (2) disseminate bedside-to-bench efforts elucidating pathophysiological mechanisms of CAR T-cell toxicities, including the intestinal microbiota and systemic immune dysregulation; and (3) highlight gaps in the availability of clinical tests, such as cytokine measurements, which could be used to expand our knowledge around the monitoring of toxicities. Key themes emerged. First, although clinical manifestations may develop before the pathophysiologic mechanisms are understood, they must be studied to aid in the detection and prevention of such toxicities. Second, systemic immune dysregulation appears to be central to these emergent toxicities, and research is needed to elucidate the links between tumors, CAR T cells, and microbiota. Finally, there was a consensus around the urgency to create a repository to capture emergent CAR T-cell toxicities and the real-world management.

Cell-Based Treatment in Acute Myeloid Leukemia Relapsed after Allogeneic Stem Cell Transplantation

Allogeneic stem cell transplant (ASCT) remains the only treatment option for patients with high-risk acute myeloid leukemia (AML). Recurrence of leukemic cells after ASCT represents a dramatic event associated with a dismal outcome, with a 2-year survival rate of around 20%. Adoptive cell therapy (ACT) is a form of cell-based strategy that has emerged as an effective therapy to treat and prevent post-ASCT recurrence. Lymphocytes are the principal cells used in this therapy and can be derived from a hematopoietic stem cell donor, the patient themselves, or healthy donors, after being engineered to express the chimeric antigen receptor (CAR-T and UniCAR-T). In this review, we discuss recent advances in the established strategy of donor lymphocyte infusion (DLI) and the progress and challenges of CAR-T cells.

Engineering focusing on cancer

While cancer research and care have benefited from revolutionary advances in the ability to manipulate and study living systems, the field is limited by a lack of synergy to leverage the power of engineering approaches. Cancer engineering is an emerging subfield of biomedical engineering that unifies engineering and cancer biology to better understand, diagnose, and treat cancer. We highlight cancer engineering's unique challenges, the importance of creating dedicated centers and departments that enable translational collaboration, and educational approaches to arm a new generation of scientists with engineering expertise and a fundamental understanding of cancer biology to transform clinical cancer care.

Recent Advances in Immune-Based Therapies for Acute Myeloid Leukemia

Despite advancements, acute myeloid leukemia (AML) remains unconquered by current therapies. Evidence of immune evasion during AML progression, such as HLA loss and T-cell exhaustion, suggests that antileukemic immune responses contribute to disease control and could be harnessed by immunotherapy. In this review, we discuss a spectrum of AML immunotherapy targets, encompassing cancer cell-intrinsic and surface antigens as well as targeting in the leukemic milieu, and how they can be tailored for personalized approaches. These targets are overviewed across major immunotherapy modalities applied to AML: immune checkpoint inhibitors, antibody-drug conjugates, therapeutic vaccines, bispecific/trispecific antibodies, and chimeric antigen receptor (CAR)-T and CAR-NK cells. Significance: Immune therapies in AML treatment show evolving promise. Ongoing research aims to customize approaches for varied patient profiles and clinical scenarios. This review covers immune surveillance mechanisms, therapy options like checkpoint inhibitors, antibodies, CAR-T/NK cells, and vaccines, as well as resistance mechanisms and microenvironment considerations.

Chimeric antigen receptor T-cell therapy in childhood acute myeloid leukemia: how far are we from a clinical application?

Recurrent and/or refractory (R/R) pediatric acute myeloid leukemia (AML) remains a recalcitrant disease with poor outcomes. Cell therapy with genetically modified immune effector cells holds the promise to improve outcomes for R/R AML since it relies on cytotoxic mechanisms that are distinct from chemotherapeutic agents. While T cells expressing chimeric antigen receptors (CAR T cells) showed significant anti-AML activity in preclinical models, early phase clinical studies have demonstrated limited activity, irrespective of the targeted AML antigen. Lack of efficacy is most likely multifactorial, including: (i) a limited array of AML-specific targets and target antigen heterogeneity; (ii) the aggressive nature of R/R AML and heavy pretreatment of patients; (iii) T-cell product manufacturing, and (iv) limited expansion and persistence of the CAR T cells, which is in part driven by the immunosuppressive AML microenvironment. Here we review the results of early phase clinical studies with AML-specific CAR T cells, and avenues investigators are exploring to improve their effector function.

Chimeric antigen receptor (CAR) modified T Cells in acute myeloid leukemia: limitations and expectations

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with a poor prognosis despite the advent of novel therapies. Consequently, a major need exists for new therapeutic options, particularly for patients with relapsed/refractory (R/R) AML. In recent years, it has been possible to individualize the treatment of a subgroup of patients, particularly with the emergence of multiple targeted therapies. Nonetheless, a considerable number of patients remain without therapeutic options, and overall prognosis remains poor because of a high rate of disease relapse. In this sense, cellular therapies, especially chimeric antigen receptor (CAR)-T cell therapy, have dramatically shifted the therapeutic options for other hematologic malignancies, such as diffuse large B cell lymphoma and acute lymphoblastic leukemia. In contrast, effectively treating AML with CAR-based immunotherapy poses major biological and clinical challenges, most of them derived from the unmet need to identify target antigens with expression restricted to the AML blast without compromising the viability of the normal hematopoietic stem cell counterpart. Although those limitations have hampered CAR-T cell therapy translation to the clinic, there are several clinical trials where target antigens, such as CD123, CLL-1 or CD33 are being used to treat AML patients showing promising results. Moreover, there are continuing efforts to enhance the specificity and efficacy of CAR-T cell therapy in AML. These endeavors encompass the exploration of novel avenues, including the development of dual CAR-T cells and next-generation CAR-T cells, as well as the utilization of gene editing tools to mitigate off-tumor toxicities. In this review, we will summarize the ongoing clinical studies and the early clinical results reported with CAR-T cells in AML, as well as highlight CAR-T cell limitations and the most recent approaches to overcome these barriers. We will also discuss how and when CAR-T cells should be used in the context of AML.

Peptide-scFv antigen recognition domains effectively confer CAR T cell multiantigen specificity

The emergence of immune escape is a significant roadblock to developing effective chimeric antigen receptor (CAR) T cell therapies against hematological malignancies, including acute myeloid leukemia (AML). Here, we demonstrate feasibility of targeting two antigens simultaneously by combining a GRP78-specific peptide antigen recognition domain with a CD123-specific scFv to generate a peptide-scFv bispecific antigen recognition domain (78.123). To achieve this, we test linkers with varying length and flexibility and perform immunophenotypic and functional characterization. We demonstrate that bispecific CAR T cells successfully recognize and kill tumor cells that express GRP78, CD123, or both antigens and have improved antitumor activity compared to their monospecific counterparts when both antigens are expressed. Protein structure prediction suggests that linker length and compactness influence the functionality of the generated bispecific CARs. Thus, we present a bispecific CAR design strategy to prevent immune escape in AML that can be extended to other peptide-scFv combinations.

Adhesion GPCRs in glioblastoma revisited

Glioblastoma is a devastating brain malignancy that has remained intractable to modern cancer treatments. Ravn-Boess et al.1 have discovered that the adhesion G protein-coupled receptor CD97/ADGRE5 contributes to glioblastogenesis and makes for an excellent molecular surface marker flagging the tumor cells.

Fine-tuning the antigen sensitivity of CAR T cells: emerging strategies and current challenges

Chimeric antigen receptor (CAR) T cells are "living drugs" that specifically recognize their target antigen through an antibody-derived binding domain resulting in T cell activation, expansion, and destruction of cognate target cells. The FDA/EMA approval of CAR T cells for the treatment of B cell malignancies established CAR T cell therapy as an emerging pillar of modern immunotherapy. However, nearly every second patient undergoing CAR T cell therapy is suffering from disease relapse within the first two years which is thought to be due to downregulation or loss of the CAR target antigen on cancer cells, along with decreased functional capacities known as T cell exhaustion. Antigen downregulation below CAR activation threshold leaves the T cell silent, rendering CAR T cell therapy ineffective. With the application of CAR T cells for the treatment of a growing number of malignant diseases, particularly solid tumors, there is a need for augmenting CAR sensitivity to target antigen present at low densities on cancer cells. Here, we discuss upcoming strategies and current challenges in designing CARs for recognition of antigen low cancer cells, aiming at augmenting sensitivity and finally therapeutic efficacy while reducing the risk of tumor relapse.

Broadening the horizon: potential applications of CAR-T cells beyond current indications

Engineering immune cells to treat hematological malignancies has been a major focus of research since the first resounding successes of CAR-T-cell therapies in B-ALL. Several diseases can now be treated in highly therapy-refractory or relapsed conditions. Currently, a number of CD19- or BCMA-specific CAR-T-cell therapies are approved for acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), multiple myeloma (MM), and follicular lymphoma (FL). The implementation of these therapies has significantly improved patient outcome and survival even in cases with previously very poor prognosis. In this comprehensive review, we present the current state of research, recent innovations, and the applications of CAR-T-cell therapy in a selected group of hematologic malignancies. We focus on B- and T-cell malignancies, including the entities of cutaneous and peripheral T-cell lymphoma (T-ALL, PTCL, CTCL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), classical Hodgkin-Lymphoma (HL), Burkitt-Lymphoma (BL), hairy cell leukemia (HCL), and Waldenström's macroglobulinemia (WM). While these diseases are highly heterogenous, we highlight several similarly used approaches (combination with established therapeutics, target depletion on healthy cells), targets used in multiple diseases (CD30, CD38, TRBC1/2), and unique features that require individualized approaches. Furthermore, we focus on current limitations of CAR-T-cell therapy in individual diseases and entities such as immunocompromising tumor microenvironment (TME), risk of on-target-off-tumor effects, and differences in the occurrence of adverse events. Finally, we present an outlook into novel innovations in CAR-T-cell engineering like the use of artificial intelligence and the future role of CAR-T cells in therapy regimens in everyday clinical practice.