Optimizing adoptive polyclonal T cell immunotherapy of lymphomas, using a chimeric T cell receptor possessing CD28 and CD137 costimulatory domains

Synthetic dual co-stimulation increases the potency of HIT and TCR-targeted cell therapies

Chimeric antigen receptor T cells have dramatically improved the treatment of hematologic malignancies. T cell antigen receptor (TCR)-based cell therapies are yet to achieve comparable outcomes. Importantly, chimeric antigen receptors not only target selected antigens but also reprogram T cell functions through the co-stimulatory pathways that they engage upon antigen recognition. We show here that a fusion receptor comprising the CD80 ectodomain and the 4-1BB cytoplasmic domain, termed 80BB, acts as both a ligand and a receptor to engage the CD28 and 4-1BB pathways, thereby increasing the antitumor potency of human leukocyte antigen-independent TCR (HIT) receptor- or TCR-engineered T cells and tumor-infiltrating lymphocytes. Furthermore, 80BB serves as a switch receptor that provides agonistic 4-1BB co-stimulation upon its ligation by the inhibitory CTLA4 molecule. By combining multiple co-stimulatory features in a single antigen-agnostic synthetic receptor, 80BB is a promising tool to sustain CD3-dependent T cell responses in a wide range of targeted immunotherapies.

Clinical efficacy and safety of combined anti-BCMA and anti-CD19 CAR-T cell therapy for relapsed/refractory multiple myeloma: a systematic review and meta-analysis

Background

The low rates of durable response against relapsed/refractory multiple myeloma (RRMM) in recent studies prompt that chimeric antigen receptor (CAR)-T cell therapies are yet to be optimized. The combined anti-BCMA and anti-CD19 CAR-T cell therapy showed high clinical efficacy in several clinical trials for RRMM. We here conducted a meta-analysis to confirm its efficacy and safety.

Methods

We collected data from Embase, Web of Science, PubMed, CNKI, Wanfang and Cochrane databases up to April 2023. We extracted and evaluated data related to the efficacy and safety of combined anti-BCMA and anti-CD19 CAR-T cell therapies in RRMM patients. The data was then analyzed using RevMan5.4 and StataSE-64 software. PROSPERO number was CRD42023455002.

Results

Our meta-analysis included 12 relevant clinical trials involving 347 RRMM patients who were treated with combined anti-BCMA and anti-CD19 CAR-T cell therapies. For efficacy assessment, the pooled overall response rate (ORR) was 94% (95% CI: 91%-98%), the complete response rate (CRR) was 50% (95% CI: 29%-71%), and the minimal residual disease (MRD) negativity rate within responders was 73% (95% CI: 66%-80%). In terms of safety, the pooled all-grade cytokine release syndrome (CRS) rate was 98% (95% CI: 97%-100%), grade≥3 CRS rate was 9% (95% CI: 4%-14%), and the incidence of neurotoxicity was 8% (95% CI: 4%-11%). Of hematologic toxicity, neutropenia was 82% (95% CI: 75%-89%), anemia was 71% (95% CI: 53%-90%), thrombocytopenia was 67% (95% CI: 40%-93%) and infection was 42% (95% CI: 9%-76%). The median progression-free survival (PFS) was 12.97 months (95% CI: 6.02-19.91), and the median overall survival (OS) was 26.63 months (95% CI: 8.14-45.11).

Conclusions

As a novel immunotherapy strategy with great potential, the combined anti-BCMA and anti-CD19 CAR-T cell therapy showed high efficacy in RRMM, but its safety needs further improvement. This meta-analysis suggests possible optimization of combined CAR-T therapy.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023455002.

Chimeric antigen receptor T-cell therapy in hematologic malignancies: Successes, challenges, and opportunities

The success of chimeric antigen receptor T-cell (CAR-T) therapy in hematologic malignancies has realized a longstanding effort toward harnessing the immune system to fight cancer in a truly personalized fashion. Second generation chimeric antigen receptors (CAR) incorporating co-stimulatory molecules like 4-1BB or CD28 were able to overcome some of the hindrances with initial CAR constructs resulting in efficacious products. Many second-generation CAR-T products have been approved in the treatment of relapsed/refractory hematologic malignancies including multiple myeloma (MM), non-Hodgkin lymphoma (NHL), and acute lymphoblastic leukemia. However, challenges remain in optimizing the manufacturing, timely access, limiting the toxicity from CAR-T infusions and improving sustainability of responses derived with CAR-T therapy. Here, we summarize the clinical trial data leading to approval CAR-T therapies in MM and NHL, discuss the limitations with current CAR-T therapy strategies and review emerging strategies for overcoming these limitations.

Chimeric antigen receptor-based natural killer cell immunotherapy in cancer: from bench to bedside

Immunotherapy has rapidly evolved in the past decades in the battle against cancer. Chimeric antigen receptor (CAR)-engineered T cells have demonstrated significant success in certain hematologic malignancies, although they still face certain limitations, including high costs and toxic effects. Natural killer cells (NK cells), as a vital component of the immune system, serve as the "first responders" in the context of cancer development. In this literature review, we provide an updated understanding of NK cell development, functions, and their applications in disease therapy. Furthermore, we explore the rationale for utilizing engineered NK cell therapies, such as CAR-NK cells, and discuss the differences between CAR-T and CAR-NK cells. We also provide insights into the key elements and strategies involved in CAR design for engineered NK cells. In addition, we highlight the challenges currently encountered and discuss the future directions in NK cell research and utilization, including pre-clinical investigations and ongoing clinical trials. Based on the outstanding antitumor potential of NK cells, it is highly likely that they will lead to groundbreaking advancements in cancer treatment in the future.

Programmable synthetic receptors: the next-generation of cell and gene therapies

Cell and gene therapies hold tremendous promise for treating a range of difficult-to-treat diseases. However, concerns over the safety and efficacy require to be further addressed in order to realize their full potential. Synthetic receptors, a synthetic biology tool that can precisely control the function of therapeutic cells and genetic modules, have been rapidly developed and applied as a powerful solution. Delicately designed and engineered, they can be applied to finetune the therapeutic activities, i.e., to regulate production of dosed, bioactive payloads by sensing and processing user-defined signals or biomarkers. This review provides an overview of diverse synthetic receptor systems being used to reprogram therapeutic cells and their wide applications in biomedical research. With a special focus on four synthetic receptor systems at the forefront, including chimeric antigen receptors (CARs) and synthetic Notch (synNotch) receptors, we address the generalized strategies to design, construct and improve synthetic receptors. Meanwhile, we also highlight the expanding landscape of therapeutic applications of the synthetic receptor systems as well as current challenges in their clinical translation.

Advances in promoting chimeric antigen receptor T cell trafficking and infiltration of solid tumors

T cells engineered to express chimeric antigen receptors (CARs) have demonstrated robust response rates in treating hematological malignancies. However, solid tumors present multiple challenges that hinder the antitumor efficacy of CAR-T cells, including antigen heterogeneity, off-tumor and systemic toxicities, and the immunosuppressive milieu of the tumor microenvironment (TME). Notably, the TME of solid tumors is characterized by chemokine dysregulation and a dense architecture consisting of tumor stroma, extracellular matrix, and aberrant vasculature that impede migration of CAR-T cells to the tumor site as well as infiltration into the solid-tumor mass. In this review, we highlight recent advances to improve CAR-T-cell trafficking to and infiltration of solid tumors to promote effective antigen recognition by CAR-T cells.

F77 antigen is a promising target for adoptive T cell therapy of prostate cancer

Adoptive immunotherapy using chimeric antigen receptor (CAR) T cells has made significant success in treating hematological malignancies, paving the way for solid tumors like prostate cancer. However, progress is impeded by a paucity of suitable target antigens. A novel carbohydrate antigen, F77, is expressed on both androgen-dependent and androgen-independent prostate cancer cells, making it a potential immunotherapy target. This study entails the generation and evaluation of a second-generation CAR against a carbohydrate antigen on malignant prostate cancer cells. Using a single chain fragment variable (scFv) from an F77-specific mouse monoclonal antibody, we created second-generation CARs with CD28 and CD137 (4-1BB) costimulatory signals. F77 expressing lentiviral CAR T cells produce cytokines and kill tumor cells in a F77 expression-dependent manner. These F77-specific CAR T cells eradicate prostate tumors in a human xenograft model employing PC3 cells. These findings validate F77 as a promising immunotherapeutic target for prostate cancer and other malignancies with this aberrant carbohydrate structure.

CAR T-Cells in Acute Lymphoblastic Leukemia: Current Status and Future Prospects

The currently available treatment for acute lymphoblastic leukemia (ALL) is mainly dependent on the combination of chemotherapy, steroids, and allogeneic stem cell transplantation. However, refractoriness and relapse (R/R) after initial complete remission may reach up to 20% in pediatrics. This percentage may even reach 60% in adults. To overcome R/R, a new therapeutic approach was developed using what is called chimeric antigen receptor-modified (CAR) T-cell therapy. The Food and Drug Administration (FDA) in the United States has so far approved four CAR T-cells for the treatment of ALL. Using this new therapeutic strategy has shown a remarkable success in treating R/R ALL. However, the use of CAR T-cells is expensive, has many imitations, and is associated with some adverse effects. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are two common examples of these adverse effects. Moreover, R/R to CAR T-cell therapy can take place during treatment. Continuous development of this therapeutic strategy is ongoing to overcome these limitations and adverse effects. The present article overviews the use of CAR T-cell in the treatment of ALL, summarizing the results of relevant clinical trials and discussing future prospects intended to improve the efficacy of this therapeutic strategy and overcome its limitations.

A systems and computational biology perspective on advancing CAR therapy

In the recent decades, chimeric antigen receptor (CAR) therapy signaled a new revolutionary approach to cancer treatment. This method seeks to engineer immune cells expressing an artificially designed receptor, which would endue those cells with the ability to recognize and eliminate tumor cells. While some CAR therapies received FDA approval and others are subject to clinical trials, many aspects of their workings remain elusive. Techniques of systems and computational biology have been frequently employed to explain the operating principles of CAR therapy and suggest further design improvements. In this review, we sought to provide a comprehensive account of those efforts. Specifically, we discuss various computational models of CAR therapy ranging in scale from organismal to molecular. Then, we describe the molecular and functional properties of costimulatory domains frequently incorporated in CAR structure. Finally, we describe the signaling cascades by which those costimulatory domains elicit cellular response against the target. We hope that this comprehensive summary of computational and experimental studies will further motivate the use of systems approaches in advancing CAR therapy.

ICOS and OX40 tandem co-stimulation enhances CAR T-cell cytotoxicity and promotes T-cell persistence phenotype

Chimeric Antigen Receptor (CAR) T-cell therapies have emerged as an effective and potentially curative immunotherapy for patients with relapsed or refractory malignancies. Treatment with CD19 CAR T-cells has shown unprecedented results in hematological malignancies, including heavily refractory leukemia, lymphoma, and myeloma cases. Despite these encouraging results, CAR T-cell therapy faces limitations, including the lack of long-term responses in nearly 50-70% of the treated patients and low efficacy in solid tumors. Among other reasons, these restrictions are related to the lack of targetable tumor-associated antigens, limitations on the CAR design and interactions with the tumor microenvironment (TME), as well as short-term CAR T-cell persistence. Because of these reasons, we developed and tested a chimeric antigen receptor (CAR) construct with an anti-ROR1 single-chain variable-fragment cassette connected to CD3ζ by second and third-generation intracellular signaling domains including 4-1BB, CD28/4-1BB, ICOS/4-1BB or ICOS/OX40. We observed that after several successive tumor-cell in vitro challenges, ROR1.ICOS.OX40ζ continued to proliferate, produce pro-inflammatory cytokines, and induce cytotoxicity against ROR1+ cell lines in vitro with enhanced potency. Additionally, in vivo ROR1.ICOS.OX40ζ T-cells showed anti-lymphoma activity, a long-lasting central memory phenotype, improved overall survival, and evidence of long-term CAR T-cell persistence. We conclude that anti-ROR1 CAR T-cells that are activated by ICOS.OX40 tandem co-stimulation show in vitro and in vivo enhanced targeted cytotoxicity associated with a phenotype that promotes T-cell persistence.

Development of a Novel CD26-Targeted Chimeric Antigen Receptor T-Cell Therapy for CD26-Expressing T-Cell Malignancies

Chimeric-antigen-receptor (CAR) T-cell therapy for CD19-expressing B-cell malignancies is already widely adopted in clinical practice. On the other hand, the development of CAR-T-cell therapy for T-cell malignancies is in its nascent stage. One of the potential targets is CD26, to which we have developed and evaluated the efficacy and safety of the humanized monoclonal antibody YS110. We generated second (CD28) and third (CD28/4-1BB) generation CD26-targeted CAR-T-cells (CD26-2G/3G) using YS110 as the single-chain variable fragment. When co-cultured with CD26-overexpressing target cells, CD26-2G/3G strongly expressed the activation marker CD69 and secreted IFNgamma. In vitro studies targeting the T-cell leukemia cell line HSB2 showed that CD26-2G/3G exhibited significant anti-leukemia effects with the secretion of granzymeB, TNFα, and IL-8, with 3G being superior to 2G. CD26-2G/3G was also highly effective against T-cell lymphoma cells derived from patients. In an in vivo mouse model in which a T-cell lymphoma cell line, KARPAS299, was transplanted subcutaneously, CD26-3G inhibited tumor growth, whereas 2G had no effect. Furthermore, in a systemic dissemination model in which HSB2 was administered intravenously, CD26-3G inhibited tumor growth more potently than 2G, resulting in greater survival benefit. The third-generation CD26-targeted CAR-T-cell therapy may be a promising treatment modality for T-cell malignancies.

Racing CARs to veterinary immuno-oncology

Chimeric antigen receptors (CARs) have demonstrated remarkable promise in human oncology over the past two decades, yet similar strategies in veterinary medicine are still in development. CARs are synthetically engineered proteins comprised of a specific antigen-binding single chain variable fragment (ScFv) fused to the signaling domain of a T cell receptor and co-receptors. Patient T cells engineered to express a CAR are directed to recognize and kill target cells, most commonly hematological malignancies. The U.S Food and Drug Administration (FDA) has approved multiple human CAR T therapies, but translation of these therapies into veterinary medicine faces many challenges. In this review, we discuss considerations for veterinary use including CAR design and cell carrier choice, and discuss the future promise of translating CAR therapy into veterinary oncology.

Potential of chimeric antigen receptor (CAR)-redirected immune cells in breast cancer therapies: Recent advances

Despite substantial developments in conventional treatments such as surgery, chemotherapy, radiotherapy, endocrine therapy, and molecular-targeted therapy, breast cancer remains the leading cause of cancer mortality in women. Currently, chimeric antigen receptor (CAR)-redirected immune cell therapy has emerged as an innovative immunotherapeutic approach to ameliorate survival rates of breast cancer patients by eliciting cytotoxic activity against cognate tumour-associated antigens expressing tumour cells. As a crucial component of adaptive immunity, T cells and NK cells, as the central innate immune cells, are two types of pivotal candidates for CAR engineering in treating solid malignancies. However, the biological distinctions between NK cells- and T cells lead to differences in cancer immunotherapy outcomes. Likewise, optimal breast cancer removal via CAR-redirected immune cells requires detecting safe target antigens, improving CAR structure for ideal immune cell functions, promoting CAR-redirected immune cells filtration to the tumour microenvironment (TME), and increasing the ability of these engineered cells to persist and retain within the immunosuppressive TME. This review provides a concise overview of breast cancer pathogenesis and its hostile TME. We focus on the CAR-T and CAR-NK cells and discuss their significant differences. Finally, we deliver a summary based on recent advancements in the therapeutic capability of CAR-T and CAR-NK cells in treating breast cancer.

CAR T-Cell Targeting of Macrophage Colony-Stimulating Factor Receptor

Macrophage colony-stimulating factor receptor (M-CSFR) is found in cells of the mononuclear phagocyte lineage and is aberrantly expressed in a range of tumours, in addition to tumour-associated macrophages. Consequently, a variety of cancer therapies directed against M-CSFR are under development. We set out to engineer chimeric antigen receptors (CARs) that employ the natural ligands of this receptor, namely M-CSF or interleukin (IL)-34, to achieve specificity for M-CSFR-expressing target cells. Both M-CSF and IL-34 bind to overlapping regions of M-CSFR, although affinity of IL-34 is significantly greater than that of M-CSF. Matched second- and third-generation CARs targeted using M-CSF or IL-34 were expressed in human T-cells using the SFG retroviral vector. We found that both M-CSF- and IL-34-containing CARs enable T-cells to mediate selective destruction of tumour cells that express enforced or endogenous M-CSFR, accompanied by production of both IL-2 and interferon (IFN)-γ. Although they contain an additional co-stimulatory module, third-generation CARs did not outperform second-generation CARs. M-CSF-containing CARs mediated enhanced cytokine production and cytolytic activity compared to IL-34-containing CARs. These data demonstrate the feasibility of targeting M-CSFR using ligand-based CARs and raise the possibility that the low picomolar affinity of IL-34 for M-CSFR is detrimental to CAR function.

Umbilical Cord Blood as a Source of Less Differentiated T Cells to Produce CD123 CAR-T Cells

Simple Summary

We used fresh or thawed Umbilical Cord Blood (UCB) to produce CAR-T cells directed against CD123, and we compared their functionality to Peripheral Blood (PB) CAR-T cells. T cells expressing CD123 CAR, derived from UCB, was exhibited through a high transduction rate, activation status, and cytotoxic potential in vitro as PB derived CAR-T cells. Moreover, we obtained T cells that had a less differentiated profile than the PB-derived T cells. UCB derived CAR-T can significantly control tumor progression in mice models. CAR-T obtained from thawed or fresh UCB gives the same results.

Abstract

Chimeric Antigen Receptor (CAR) therapy has led to great successes in patients with leukemia and lymphoma. Umbilical Cord Blood (UCB), stored in UCB banks, is an attractive source of T cells for CAR-T production. We used a third generation CD123 CAR-T (CD28/4-1BB), which was previously developed using an adult’s Peripheral Blood (PB), to test the ability of obtaining CD123 CAR-T from fresh or cryopreserved UCB. We obtained a cell product with a high and stable transduction efficacy, and a poorly differentiated phenotype of CAR-T cells, while retaining high cytotoxic functions in vitro and in vivo. Moreover, CAR-T produced from cryopreserved UCB are as functional as CAR-T produced from fresh UCB. Overall, these data pave the way for the clinical development of UCB-derived CAR-T. UCB CAR-T could be transferred in an autologous manner (after an UCB transplant) to reduce post-transplant relapses, or in an allogeneic setting, thanks to fewer HLA restrictions which ease the requirements for a match between the donor and recipient.

CD123 and More: How to Target the Cell Surface of Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia derived from plasmacytoid dendritic cells (pDCs). It is associated with a remarkably poor prognosis and unmet need for better therapies. Recently, the first-in-class CD123-targeting therapy, tagraxofusp, was approved for treatment of BPDCN. Other CD123-targeting strategies are in development, including bispecific antibodies and combination approaches with tagraxofusp and other novel agents. In other blood cancers, adoptive T-cell therapy using chimeric antigen receptor (CAR)-modified T cells represents a promising new avenue in immunotherapy, showing durable remissions in some relapsed hematologic malignancies. Here, we report on novel and innovative therapies in development to target surface molecules in BPDCN currently in clinical trials or in preclinical stages. We also discuss new cell surface targets that may have implications for future BPDCN treatment.

Evaluation PD-L1, CD8 and CD20 as early predictor and tracking markers for breast cancer (BC) in Egypt

Background

Breast cancer (BC) is considered as a common type of cancer threatening women throughout the world. Therefore, development of early predication biomarkers for BC got more concern especially for Egyptian females. This study was aimed to evaluate PD-L1, CD8, and CD20 as early prediction breast cancer biomarkers.

Methods

Flow cytometry (FC), immunohistochemistry (IHC), Western Blot, and q-PCR were used to compare PD-L1, CD20, and CD8 levels in tissues and blood samples of Breast Cancer and controls.

Results

Blood samples showed a significant increase in PD-L1, CD20, and CD8 compared to controls (p˂0.005). A Significant correlation was shown between PD-L1, CD8, and CD20 in tissue and breast cancer subtypes. Whereas, invasive lobular carcinoma (ILC) was characterized by superior PD-L1 and CD20 levels compared to invasive ductal carcinoma (IDC). FC studies on Blood showed 83% and 45.7% PD-L1 expressions for IDC and ILC, respectively. CD20 in ILC and IDC were 78.2% and 62.5%, respectively. Nevertheless, CD8 was 74.2% for IDC and 67.7% for ILC. Whereas, FC studies for PD-L1, CD20, and CD8 in ILC in tissues gave 34.4%, 30.2% and 35.1%, respectively. In addition, IDC tissue samples showed 16%, 12.5, and 13.5% for PD-L1, CD20, and CD8. The moderate stage of adenocarcinoma caused expression of PD-L1 within inflammatory cells, while expression was within neoplastic glandular cells in late stage.

Conclusion

PD-L1, CD8, and CD20 are considered as early predictor and tracking markers for breast cancer.

A carcinoembryonic antigen-specific cell therapy selectively targets tumor cells with HLA loss of heterozygosity in vitro and in vivo

The CEACAM5 gene product [carcinoembryonic antigen (CEA)] is an attractive target for colorectal cancer because of its high expression in virtually all colorectal tumors and limited expression in most healthy adult tissues. However, highly active CEA-directed investigational therapeutics have been reported to be toxic, causing severe colitis because CEA is expressed on normal gut epithelial cells. Here, we developed a strategy to address this toxicity problem: the Tmod dual-signal integrator. CEA Tmod cells use two receptors: a chimeric antigen receptor (CAR) activated by CEA and a leukocyte Ig-like receptor 1 (LIR-1)-based inhibitory receptor triggered by human leukocyte antigen (HLA)-A*02. CEA Tmod cells exploit instances of HLA heterozygous gene loss in tumors to protect the patient from on-target, off-tumor toxicity. CEA Tmod cells potently killed CEA-expressing tumor cells in vitro and in vivo. But in contrast to a traditional CEA-specific T cell receptor transgenic T cell, Tmod cells were highly selective for tumor cells even when mixed with HLA-A*02-expressing cells. These data support further development of the CEA Tmod construct as a therapeutic candidate for colorectal cancer.

Human epidermal growth factor receptor 2 (HER2)-specific chimeric antigen receptor (CAR) for tumor immunotherapy; recent progress

Due to the overexpression or amplification of human epidermal growth factor receptor 2 (HER2) with poor prognosis in a myriad of human tumors, recent studies have focused on HER2-targeted therapies. Deregulation in HER2 signaling pathways is accompanied by sustained tumor cells growth concomitant with their migration and also tumor angiogenesis and metastasis by stimulation of proliferation of a network of blood vessels. A large number of studies have provided clear evidence that the emerging HER2-directed treatments could be the outcome of patients suffering from HER2 positive breast and also gastric/gastroesophageal cancers. Thanks to its great anti-tumor competence, immunotherapy using HER2-specific chimeric antigen receptor (CAR) expressing immune cell has recently attracted increasing attention. Human T cells and also natural killer (NK) cells can largely be found in the tumor microenvironment, mainly contributing to the tumor immune surveillance. Such properties make them perfect candidate for genetically modification to express constructed CARs. Herein, we will describe the potential targets of the HER2 signaling in tumor cells to clarify HER2-mediated tumorigenesis and also discuss recent findings respecting the HER2-specific CAR-expressing immune cells (CAR T and CAR NK cell) for the treatment of HER2-expressing tumors.

Adoptive Cellular Therapy for Multiple Myeloma Using CAR- and TCR-Transgenic T Cells: Response and Resistance

Despite the substantial improvement of therapeutic approaches, multiple myeloma (MM) remains mostly incurable. However, immunotherapeutic and especially T cell-based approaches pioneered the therapeutic landscape for relapsed and refractory disease recently. Targeting B-cell maturation antigen (BCMA) on myeloma cells has been demonstrated to be highly effective not only by antibody-derived constructs but also by adoptive cellular therapies. Chimeric antigen receptor (CAR)-transgenic T cells lead to deep, albeit mostly not durable responses with manageable side-effects in intensively pretreated patients. The spectrum of adoptive T cell-transfer covers synthetic CARs with diverse specificities as well as currently less well-established T cell receptor (TCR)-based personalized strategies. In this review, we want to focus on treatment characteristics including efficacy and safety of CAR- and TCR-transgenic T cells in MM as well as the future potential these novel therapies may have. ACT with transgenic T cells has only entered clinical trials and various engineering strategies for optimization of T cell responses are necessary to overcome therapy resistance mechanisms. We want to outline the current success in engineering CAR- and TCR-T cells, but also discuss challenges including resistance mechanisms of MM for evading T cell therapy and point out possible novel strategies.

CAR-NK Cells: From Natural Basis to Design for Kill

Chimeric antigen receptors (CARs) are fusion proteins with an extracellular antigen recognition domain and numerous intracellular signaling domains that have been genetically modified. CAR-engineered T lymphocyte-based therapies have shown great success against blood cancers; however, potential fatal toxicity, such as in cytokine release syndrome, and high costs are some shortcomings that limit the clinical application of CAR-engineered T lymphocytes and remain to overcome. Natural killer (NK) cells are the focal point of current immunological research owing to their receptors that prove to be promising immunotherapeutic candidates for treating cancer. However, to date, manipulation of NK cells to treat malignancies has been moderately successful. Recent progress in the biology of NK cell receptors has greatly transformed our understanding of how NK cells recognize and kill tumor and infected cells. CAR-NK cells may serve as an alternative candidate for retargeting cancer because of their unique recognition mechanisms, powerful cytotoxic effects especially on cancer cells in both CAR-dependent and CAR-independent manners and clinical safety. Moreover, NK cells can serve as an ‘off-the-shelf product’ because NK cells from allogeneic sources can also be used in immunotherapies owing to their reduced risk of alloreactivity. Although ongoing fundamental research is in the beginning stages, this review provides an overview of recent developments implemented to design CAR constructs to stimulate NK activation and manipulate NK receptors for improving the efficiency of immunotherapy against cancer, summarizes the preclinical and clinical advances of CAR-NK cells against both hematological malignancies and solid tumors and confronts current challenges and obstacles of their applications. In addition, this review provides insights into prospective novel approaches that further enhance the efficiency of CAR-NK therapies and highlights potential questions that require to be addressed in the future.

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.

Synergistic T cell signaling by 41BB and CD28 is optimally achieved by membrane proximal positioning within parallel chimeric antigen receptors

Second generation (2G) chimeric antigen receptors (CARs) contain a CD28 or 41BB co-stimulatory endodomain and elicit remarkable efficacy in hematological malignancies. Third generation (3G) CARs extend this linear blueprint by fusing both co-stimulatory units in series. However, clinical impact has been muted despite compelling evidence that co-signaling by CD28 and 41BB can powerfully amplify natural immune responses. We postulate that effective dual co-stimulation requires juxta-membrane positioning of endodomain components within separate synthetic receptors. Consequently, we designed parallel (p)CARs in which a 2G (CD28+CD3ζ) CAR is co-expressed with a 41BB-containing chimeric co-stimulatory receptor. We demonstrate that the pCAR platform optimally harnesses synergistic and tumor-dependent co-stimulation to resist T cell exhaustion and senescence, sustaining proliferation, cytokine release, cytokine signaling, and metabolic fitness upon repeated stimulation. When engineered using targeting moieties of diverse composition, affinity, and specificity, pCAR T cells consistently elicit superior anti-tumor activity compared with T cells that express traditional linear CARs.

NK cell upraise in the dark world of cancer stem cells

One of the obstacles in treating different cancers, especially solid tumors, is cancer stem cells (CSCs) with their ability in resistance to chemo/radio therapy. The efforts for finding advanced treatments to overcome these cells have led to the emergence of advanced immune cell-based therapy (AICBT). Today, NK cells have become the center of attention since they have been proved to show an appropriate cytotoxicity against different cancer types as well as the capability of detecting and killing CSCs. Attempts for reaching an off-the-shelf source of NK cells have been made and resulted in the emergence of chimeric antigen receptor natural killer cells (CAR-NK cells). The CAR technology has then been used for generating more cytotoxic and efficient NK cells, which has increased the hope for cancer treatment. Since utilizing this advanced technology to target CSCs have been published in few studies, the present study has focused on discussing the characteristics of CSCs, which are detected and targeted by NK cells, the advantages and restrictions of using CAR-NK cells in CSCs treatment and the probable challenges in this process.

4-1BB and optimized CD28 co-stimulation enhances function of human mono-specific and bi-specific third-generation CAR T cells

Background

Co-stimulatory signals regulate the expansion, persistence, and function of chimeric antigen receptor (CAR) T cells. Most studies have focused on the co-stimulatory domains CD28 or 4-1BB. CAR T cell persistence is enhanced by 4-1BB co-stimulation leading to nuclear factor kappa B (NF-κB) signaling, while resistance to exhaustion is enhanced by mutations of the CD28 co-stimulatory domain.

Methods

We hypothesized that a third-generation CAR containing 4-1BB and CD28 with only PYAP signaling motif (mut06) would provide beneficial aspects of both. We designed CD19-specific CAR T cells with either 4-1BB or mut06 together with the combination of both and evaluated their immune-phenotype, cytokine secretion, real-time cytotoxic ability and polyfunctionality against CD19-expressing cells. We analyzed lymphocyte-specific protein tyrosine kinase (LCK) recruitment by the different constructs by immunoblotting. We further determined their ability to control growth of Raji cells in NOD scid gamma (NSG) mice. We also engineered bi-specific CARs against CD20/CD19 combining 4-1BB and mut06 and performed repeated in vitro antigenic stimulation experiments to evaluate their expansion, memory phenotype and phenotypic (PD1⁺CD39⁺) and functional exhaustion. Bi-specific CAR T cells were transferred into Raji or Nalm6-bearing mice to study their ability to eradicate CD20/CD19-expressing tumors.

Results

Co-stimulatory domains combining 4-1BB and mut06 confers CAR T cells with an increased central memory phenotype, expansion, and LCK recruitment to the CAR. This enhanced function was dependent on the positioning of the two co-stimulatory domains. A bi-specific CAR targeting CD20/CD19, incorporating 4-1BB and mut06 co-stimulation, showed enhanced antigen-dependent in vitro expansion with lower exhaustion-associated markers. Bi-specific CAR T cells exhibited improved in vivo antitumor activity with increased persistence and decreased exhaustion.

Conclusion

These results demonstrate that co-stimulation combining 4-1BB with an optimized form of CD28 is a valid approach to optimize CAR T cell function. Cells with both mono-specific and bi-specific versions of this design showed enhanced in vitro and in vivo features such as expansion, persistence and resistance to exhaustion. Our observations validate the approach and justify clinical studies to test the efficacy and safety of this CAR in patients.

The Current and Future Role of Radiation Therapy in the Era of CAR T-cell Salvage

Radiation therapy has the potential to modulate the immune system in a variety of ways, and given the critical role of the immune system in cancer elimination, it is becoming increasingly important to understand how radiation can be strategically implemented in conjunction with approved immunotherapies to improve the cancer patient's chance of cure and/or quality of life. Current successful, approved cancer immunotherapies fall into two broad classes: antibodies and cellular therapies. Approved cellular therapies thus far consist of Chimeric Antigen Receptor (CAR) T-cells targeting CD19 for refractory non-Hodgkin lymphoma and relapsed or refractory acute lymphoblastic leukemia. Part of the ardor surrounding CAR T-cells stems from the fact that the survival curve of treated patients has a clear plateau, meaning that a number of patients with aggressive, disseminated disease who would have otherwise died rather rapidly appear to now be cured, commonly after just one dose. Despite an encouraging number of these durable remissions, the majority do still relapse. In this review, we discuss the potential for strategically utilizing radiation to further improve CAR T-cell patient outcomes. Given that there are currently over 750 cellular therapies in development, half of which are now in clinical trial, CAR T-cell usage will inevitably expand; as the field grows in importance and effectiveness, radiation oncology has the opportunity to coevolve symbiotically and steer these novel, exciting live therapies to new depths.

CAR-engineered NK cells; a promising therapeutic option for treatment of hematological malignancies

Adoptive cell therapy has received a great deal of interest in the treatment of advanced cancers that are resistant to traditional therapy. The tremendous success of chimeric antigen receptor (CAR)-engineered T (CAR-T) cells in the treatment of cancer, especially hematological cancers, has exposed CAR's potential. However, the toxicity and significant limitations of CAR-T cell immunotherapy prompted research into other immune cells as potential candidates for CAR engineering. NK cells are a major component of the innate immune system, especially for tumor immunosurveillance. They have a higher propensity for immunotherapy in hematologic malignancies because they can detect and eliminate cancerous cells more effectively. In comparison to CAR-T cells, CAR-NK cells can be prepared from allogeneic donors and are safer with a lower chance of cytokine release syndrome and graft-versus-host disease, as well as being a more efficient antitumor activity with high efficiency for off-the-shelf production. Moreover, CAR-NK cells may be modified to target various antigens while also increasing their expansion and survival in vivo. Extensive preclinical research has shown that NK cells can be effectively engineered to express CARs with substantial cytotoxic activity against both hematological and solid tumors, establishing evidence for potential clinical trials of CAR-NK cells. In this review, we discuss recent advances in CAR-NK cell engineering in a variety of hematological malignancies, as well as the main challenges that influence the outcomes of CAR-NK cell-based tumor immunotherapies.

Making Potent CAR T Cells Using Genetic Engineering and Synergistic Agents

Immunotherapies are emerging as powerful weapons for the treatment of malignancies. Chimeric antigen receptor (CAR)-engineered T cells have shown dramatic clinical results in patients with hematological malignancies. However, it is still challenging for CAR T cell therapy to be successful in several types of blood cancer and most solid tumors. Many attempts have been made to enhance the efficacy of CAR T cell therapy by modifying the CAR construct using combination agents, such as compounds, antibodies, or radiation. At present, technology to improve CAR T cell therapy is rapidly developing. In this review, we particularly emphasize the most recent studies utilizing genetic engineering and synergistic agents to improve CAR T cell therapy.

CAR T-Cells for CNS Lymphoma: Driving into New Terrain?

Primary CNS lymphomas (PCNSL) represent a group of extranodal non-Hodgkin lymphomas and secondary CNS lymphomas refer to secondary involvement of the neuroaxis by systemic disease. CNS lymphomas are associated with limited prognosis even after aggressive multimodal therapy. Chimeric antigen receptor (CAR) T-cells have proven as a promising therapeutic avenue in hematological B-cell malignancies including diffuse large B-cell lymphoma, B-cell acute lymphoblastic leukemia, and mantle-cell lymphoma. CARs endow an autologous T-cell population with MHC-unrestricted effectivity against tumor target antigens such as the pan B-cell marker CD19. In PCNSL, compelling and long-lasting anti-tumor effects of such therapy have been shown in murine immunocompromised models. In clinical studies on CAR T-cells for CNS lymphoma, only limited data are available and often include both patients with PCNSL but also patients with secondary CNS lymphoma. Several clinical trials on CAR T-cell therapy for primary and secondary CNS lymphoma are currently ongoing. Extrapolated from the available preliminary data, an overall acceptable safety profile with considerable anti-tumor effects might be expected. Whether these beneficial anti-tumor effects are as long-lasting as in animal models is currently in doubt; and the immunosuppressive tumor microenvironment of the brain may be among the most pivotal factors limiting efficacy of CAR T-cell therapy in CNS lymphoma. Based on an increasing understanding of CAR T-cell interactions with the tumor cells as well as the cerebral tissue, modifications of CAR design or the combination of CAR T-cell therapy with other therapeutic approaches may aid to release the full therapeutic efficiency of CAR T-cells. CAR T-cells may therefore emerge as a novel treatment strategy in primary and secondary CNS lymphoma.

How Can We Engineer CAR T Cells to Overcome Resistance?

Chimeric antigen receptor (CAR) T cell therapy has achieved unrivalled success in the treatment of B cell and plasma cell malignancies, with five CAR T cell products now approved by the US Food and Drug Administration (FDA). However, CAR T cell therapies for solid tumours have not been nearly as successful, owing to several additional challenges. Here, we discuss mechanisms of tumour resistance in CAR T cell therapy and the emerging strategies that are under development to engineer CAR T cells to overcome resistance.

Natural Killer Cell Interactions With Myeloid Derived Suppressor Cells in the Tumor Microenvironment and Implications for Cancer Immunotherapy

The tumor microenvironment (TME) is a complex and heterogeneous environment composed of cancer cells, tumor stroma, a mixture of tissue-resident and infiltrating immune cells, secreted factors, and extracellular matrix proteins. Natural killer (NK) cells play a vital role in fighting tumors, but chronic stimulation and immunosuppression in the TME lead to NK cell exhaustion and limited antitumor functions. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid cells with potent immunosuppressive activity that gradually accumulate in tumor tissues. MDSCs interact with innate and adaptive immune cells and play a crucial role in negatively regulating the immune response to tumors. This review discusses MDSC-mediated NK cell regulation within the TME, focusing on critical cellular and molecular interactions. We review current strategies that target MDSC-mediated immunosuppression to enhance NK cell cytotoxic antitumor activity. We also speculate on how NK cell-based antitumor immunotherapy could be improved.

Chimeric antigen receptor-engineered natural killer cells: a promising cancer immunotherapy

Introduction:Widespread success of CD19 chimeric antigen receptor (CAR) T cells for the treatment of hematological malignancies have shifted the focus from conventional cancer treatments toward adoptive immunotherapy. There are major efforts to improve CAR constructs and to identify new target antigens. Even though the Food and Drug Administration has approved commercialization of some CD19 CART cell therapies, there are still some limitations that restrict their widespread clinical use. The manufacture of autologous products for individual patients is logistically cumbersome and expensive and allogeneic T cell products may pose an appreciable risk of graft-versus-host disease (GVHD).Areas covered:Natural killer (NK) cells are an attractive alternative for CART-based immunotherapies. They have the innate ability to detect and eliminate malignant cells and are safer in the 'off-the-shelf' setting. This review discusses the current progress within the CAR NK cell field, including the challenges, and future prospects. Gene engineered NK cells was used as the search term in PubMed and Google Scholar through to December 2020.Expert opinion:CAR NK cell therapies hold promise as an 'off-the-shelf' cell therapy for cancer. It is hoped that an enhanced understanding of their immunobiology and molecular mechanisms of action will improve their in vivo potency.

Chimeric Antigen Receptor Design Today and Tomorrow

ABSTRACT

The US Food and Drug Administration has approved 3 chimeric antigen receptor (CAR) T-cell therapies. For continued breakthroughs, novel CAR designs are needed. This includes different antigen-binding domains such as antigen-ligand binding partners and variable lymphocyte receptors. Another recent advancement in CAR design is Boolean logic gates that can minimize on-target, off-tumor toxicities. Recent studies on the optimization of costimulatory signaling have also shown how CAR design can impact function. By using specific signaling pathways and transcription factors, CARs can impact T-cell gene expression to enhance function. By using these techniques, the promise of CAR T-cell therapies for solid tumors can be fulfilled.

How do CARs work?: Early insights from recent clinical studies targeting CD19

Second-generation chimeric antigen receptors (CARs) are powerful tools to redirect antigen-specific T cells independently of HLA-restriction. Recent clinical studies evaluating CD19-targeted T cells in patients with B-cell malignancies demonstrate the potency of CAR-engineered T cells. With results from 28 subjects enrolled by five centers conducting studies in patients with chronic lymphocytic leukemia (CLL) or lymphoma, some insights into the parameters that determine T-cell function and clinical outcome of CAR-based approaches are emerging. These parameters involve CAR design, T-cell production methods, conditioning chemotherapy as well as patient selection. Here, we discuss the potential relevance of these findings and in particular the interplay between the adoptive transfer of T cells and pre-transfer patient conditioning.

CAR T cells in solid tumors: challenges and opportunities

BACKGROUND

CARs are simulated receptors containing an extracellular single-chain variable fragment (scFv), a transmembrane domain, as well as an intracellular region of immunoreceptor tyrosine-based activation motifs (ITAMs) in association with a co-stimulatory signal.

MAIN BODY

Chimeric antigen receptor (CAR) T cells are genetically engineered T cells to express a receptor for the recognition of the particular surface marker that has given rise to advances in the treatment of blood disorders. The CAR T cells obtain supra-physiological properties and conduct as "living drugs" presenting both immediate and steady effects after expression in T cells surface. But, their efficacy in solid tumor treatment has not yet been supported. The pivotal challenges in the field of solid tumor CAR T cell therapy can be summarized in three major parts: recognition, trafficking, and surviving in the tumor. On the other hand, the immunosuppressive tumor microenvironment (TME) interferes with T cell activity in terms of differentiation and exhaustion, and as a result of the combined use of CARs and checkpoint blockade, as well as the suppression of other inhibitor factors in the microenvironment, very promising results were obtained from the reduction of T cell exhaustion.

CONCLUSION

Nowadays, identifying and defeating the mechanisms associated with CAR T cell dysfunction is crucial to establish CAR T cells that can proliferate and lyse tumor cells severely. In this review, we discuss the CAR signaling and efficacy T in solid tumors and evaluate the most significant barriers in this process and describe the most novel therapeutic methods aiming to the acquirement of the promising therapeutic outcome in non-hematologic malignancies.

Preclinical Chimeric Antibody Chimeric Antigen Receptor T Cell Progress in Digestive System Cancers

Digestive system cancers, including hepatocellular carcinoma, colorectal and gastric tumors, are characterized by high rates of incidence and mortality. Digestive cancers are difficult to diagnose during the early stages, and the side effects of chemotherapy are often severe and may outweigh the therapeutic benefits. Chimeric antibody chimeric antigen receptor T cell (CAR-T) therapy, a novel immunotherapy, has achieved excellent results for the treatment of hematological tumors. However, CAR-T treatment of solid tumors has struggled due to a lack of target specificity, a difficult tumor microenvironment, and T cell homing. Despite the challenges, CAR-T treatment of digestive cancers is progressing. Combining CAR-T with other targets and/or modifying the CAR may represent the most promising approaches for future treatment of digestive cancers.

Chimeric antigen receptor T-cell therapy for the treatment of lymphoid malignancies: is there an excess risk for infection?

Therapy with genetically engineered chimeric antigen receptor (CAR) T cells targeting the CD19 antigen is promising for a number of refractory or relapsed B-cell malignancies. Information on the infectious complications of this immunotherapeutic strategy is scarce and difficult to interpret, as many factors influence infection incidence and outcomes. CAR T-cell therapy is usually given to patients with haematological cancers who have been heavily pretreated and are severely immunosuppressed. Moreover, the risk of infection is increased by the administration of lymphodepleting chemotherapy before CAR T-cell infusion, and by the development of complications such as cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome, which are managed with anti-interleukin-6 antibodies, or corticosteroids, or both. On-target, off-tumour toxicities, such as B-cell aplasia, hypogammaglobulinaemia, and persistent or biphasic cytopenia, are common. In this Review, we evaluate the reported infectious complications of CAR T-cell therapy and associated risk factors and offer perspectives on its infection risk.

Chimeric Antigen Receptor (CAR) T Cell Therapy for B-Acute Lymphoblastic Leukemia (B-ALL)

With the exploitation of adoptive immunotherapies, the outcomes of patients with relapsed and refractory B cell hematologic malignancies have seen drastic improvements. To this end, a paradigm shift away from toxic and ineffective chemotherapies has been visible with the FDA approval of genetically modified autologous T cell products designed to express chimeric antigen receptors able to specifically recognize the CD19 cell surface marker. To date, CAR-T cells have two FDA-approved indications including relapsed or refractory acute lymphoblastic leukemia in children and young adults as well as large B cell lymphoma that is relapsed and/or refractory to two prior therapies. This chapter will discuss the utility of this therapy in B-ALL, common toxicities and their management, relationship to other therapies such as stem cell transplantation, and future directions.

A giant step forward: chimeric antigen receptor T-cell therapy for lymphoma

The combination of the immunotherapy (i.e., the use of monoclonal antibodies) and the conventional chemotherapy increases the long-term survival of patients with lymphoma. However, for patients with relapsed or treatment-resistant lymphoma, a novel treatment approach is urgently needed. Chimeric antigen receptor T (CAR-T) cells were introduced as a treatment for these patients. Based on recent clinical data, approximately 50% of patients with relapsed or refractory B-cell lymphoma achieved complete remission after receiving the CD19 CAR-T cell therapy. Moreover, clinical data revealed that some patients remained in remission for more than two years after the CAR-T cell therapy. Other than the CD19-targeted CAR-T, the novel target antigens, such as CD20, CD22, CD30, and CD37, which were greatly expressed on lymphoma cells, were studied under preclinical and clinical evaluations for use in the treatment of lymphoma. Nonetheless, the CAR-T therapy was usually associated with potentially lethal adverse effects, such as the cytokine release syndrome and the neurotoxicity. Therefore, optimizing the structure of CAR, creating new drugs, and combining CAR-T cell therapy with stem cell transplantation are potential solutions to increase the effectiveness of treatment and reduce the toxicity in patients with lymphoma after the CAR-T cell therapy.

Engineering precision therapies: lessons and motivations from the clinic

In the past decade, gene- and cell-based therapies have been at the forefront of the biomedical revolution. Synthetic biology, the engineering discipline of building sophisticated 'genetic software' to enable precise regulation of gene activities in living cells, has been a decisive success factor of these new therapies. Here, we discuss the core technologies and treatment strategies that have already gained approval for therapeutic applications in humans. We also review promising preclinical work that could either enhance the efficacy of existing treatment strategies or pave the way for new precision medicines to treat currently intractable human conditions.

4-1BB Signaling Boosts the Anti-Tumor Activity of CD28-Incorporated 2nd Generation Chimeric Antigen Receptor-Modified T Cells

While chimeric antigen receptor-modified T (CAR-T) cells have shown great success for the treatment of B cell leukemia, their efficacy appears to be compromised in B cell derived lymphoma and solid tumors. Optimization of the CAR design to improve persistence and cytotoxicity is a focus of the current CAR-T study. Herein, we established a novel CAR structure by adding a full length 4-1BB co-stimulatory receptor to a 28Z-based second generation CAR that targets CD20. Our data indicated that this new 2028Z-4-1BB CAR-T cell showed improved proliferation and cytotoxic ability. To further understand the mechanism of action, we found that constitutive 4-1BB sensing significantly reduced the apoptosis of CAR-T cells, enhanced proliferation, and increased NF-κB pathway activation. Consistent with the enhanced proliferation and cytotoxicity in vitro, this new structure of CAR-T cells exhibited robust persistence and anti-tumor activity in a mouse xenograft lymphoma model. This work provides evidence for a new strategy to optimize the function of CAR-T against lymphoma.

Potential strategies against resistance to CAR T-cell therapy in haematological malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a rapidly developing method for adoptive immunotherapy of tumours in recent years. CAR T-cell therapies have demonstrated unprecedented efficacy in the treatment of patients with haematological malignancies. A 90% complete response (CR) rate has been reported in patients with advanced relapse or refractory acute lymphoblastic leukaemia, while >50% CR rates have been reported in cases of chronic lymphocytic leukaemia and partial B-cell lymphoma. Despite the high CR rates, a subset of the patients with complete remission still relapse. The mechanism of development of resistance is not clearly understood. Some patients have been reported to demonstrate antigen-positive relapse, whereas others show antigen-negative relapses. Patients who relapse following CAR T-cell therapy, have very poor prognosis and novel approaches to overcome resistance are required urgently. Herein, we have reviewed current literature and research that have investigated the strategies to overcome resistance to CAR T-cell therapy.

Efficacy and Safety of CD28- or 4-1BB-Based CD19 CAR-T Cells in B Cell Acute Lymphoblastic Leukemia

CD19-directed chimeric antigen receptor-T (CAR-T) cells with a 4-1BB or CD28 co-stimulatory domain have shown impressive antitumor activity against relapsed or refractory B cell acute lymphoblastic leukemia (r/r B-ALL). However, a parallel comparison of their performances in r/r B-ALL therapy has not been sufficiently reported. Here, we manufactured 4-1BB- and CD28-based CD19 CAR-T cells using the same process technology and evaluated their efficacy and safety in r/r B-ALL therapy based on pre-clinical and exploratory clinical investigations. In B-ALL-bearing mice, a similar antitumor effect and CAR-T kinetics in peripheral blood were observed at the CAR-T dose of 1 × 10⁷/mouse. However, when the dose was decreased to 1 × 10⁶/mouse, 4-1BB CAR-T cells were more potent in eradicating tumor cells and showed longer persistence than CD28 CAR-T cells. Retrospective analysis of an exploratory clinical study that used 4-1BB- or CD28-based CAR-T cells to treat r/r B-ALL was performed. Compared with CD28 CAR-T cells, 4-1BB CAR-T cells resulted in higher antitumor efficacy and less severe adverse events. This study demonstrated that the performance of 4-1BB CAR-T cells was superior to that of CD28 CAR-T cells in suppressing CD19⁺ B-ALL, at least under our manufacturing process.

Pre-clinical assessment of chimeric antigen receptor t cell therapy targeting CD19+ B cell malignancy

Background

Autologous chimeric antigen receptor (CAR) T cell therapy is a promising therapeutic strategy for treating hematologic malignancies. A spectrum of serious complications caused by CAR-T cells has caught great attention. We developed a novel CAR against CD19 namely UWC19, consisting anti-CD19 single-chain variable fragment (scFv) hinged with 4-1BB and CD3z signaling domains. In this study, preclinical assessments of UWC19 were conducted to evaluate the safety and efficacy in vitro and in vivo.

Methods

To evaluate the binding activity of UWC19 cells to CD19, we measured the saturation degree of CAR with human CD19 molecules using flow cytometry in vitro. The antitumor efficacy of UWC19 cells was determined by in vitro cytotoxicity assay against CD19 positive cells and in vivo using a xenograft mouse model. Cross tissue reactivity of UWC19 cells was examined by co-culturing with cell lines from difference human tissues. Tumorigenicity was determined by subcutaneously injecting UWC19 in immunodeficient mice. Persistence was analyzed using quantitative PCR.

Results

We showed that UWC19 CAR T cells exerted highly specific binding affinity and cytotoxicity against CD19+ cells in vitro. In vivo, UWC19 CAR T cells are able to fully control disease progression in a Raji-xenografted immunodeficient mouse model. UWC19 exerted no obvious effects on the mean body mass and graft versus host disease were observed in surviving mice. We showed that UWC19 cells specifically recognized and eliminated CD19 positive cells, whereas CD19 negative cells were much less affected. No tumorigenicity of UWC19 in immunodeficient mice was observed.

Conclusions

UWC19 treatment effectively eliminated CD19 positive tumor cells with favorable toxicity profile. The findings suggest encouraging clinical prospects for its use in patients with CD19 positive B cell malignancies. Our study presented an alternative evaluation strategy for CAR-T cell products.

Targeting Cancer Stem Cells by Genetically Engineered Chimeric Antigen Receptor T Cells

The term cancer stem cell (CSC) starts 25 years ago with the evidence that CSC is a subpopulation of tumor cells that have renewal ability and can differentiate into several distinct linages. Therefore, CSCs play crucial role in the initiation and the maintenance of cancer. Moreover, it has been proposed throughout several studies that CSCs are behind the failure of the conventional chemo-/radiotherapy as well as cancer recurrence due to their ability to resist the therapy and their ability to re-regenerate. Thus, the need for targeted therapy to eliminate CSCs is crucial; for that reason, chimeric antigen receptor (CAR) T cells has currently been in use with high rate of success in leukemia and, to some degree, in patients with solid tumors. This review outlines the most common CSC populations and their common markers, in particular CD133, CD90, EpCAM, CD44, ALDH, and EGFRVIII, the interaction between CSCs and the immune system, CAR T cell genetic engineering and signaling, CAR T cells in targeting CSCs, and the barriers in using CAR T cells as immunotherapy to treat solid cancers.

NK Cell-Based Immunotherapies in Cancer

With the development of technologies that can transform immune cells into therapeutic modalities, immunotherapy has remarkably changed the current paradigm of cancer treatment in recent years. NK cells are components of the innate immune system that act as key regulators and exhibit a potent tumor cytolytic function. Unlike T cells, NK cells exhibit tumor cytotoxicity by recognizing non-self, without deliberate immunization or activation. Currently, researchers have developed various approaches to improve the number and anti-tumor function of NK cells. These approaches include the use of cytokines and Abs to stimulate the efficacy of NK cell function, adoptive transfer of autologous or allogeneic ex vivo expanded NK cells, establishment of homogeneous NK cell lines using the NK cells of patients with cancer or healthy donors, derivation of NK cells from induced pluripotent stem cells (iPSCs), and modification of NK cells with cutting-edge genetic engineering technologies to generate chimeric Ag receptor (CAR)-NK cells. Such NK cell-based immunotherapies are currently reported as being promising anti-tumor strategies that have shown enhanced functional specificity in several clinical trials investigating malignant tumors. Here, we summarize the recent advances in NK cell-based cancer immunotherapies that have focused on providing improved function through the use of the latest genetic engineering technologies. We also discuss the different types of NK cells developed for cancer immunotherapy and present the clinical trials being conducted to test their safety and efficacy.

CD28/4-1BB CD123 CAR T cells in blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is associated with a remarkably poor prognosis and with no treatment consensus. The identification of relevant therapeutic targets is challenging. Here, we investigated the immune functions, antileukemia efficacy and safety of CD28/4-1BB CAR T cells targeting CD123 the interleukin (IL)-3 receptor alpha chain which is overexpressed on BPDCN. We demonstrated that both retroviral and lentiviral engineering CD28/4-1BB CD123 CAR T cells exhibit effector functions against BPDCN cells through CD123 antigen recognition and that they efficiently kill BPDCN cell lines and BPDCN-derived PDX cells. In vivo, CD28/4-1BB CD123 CAR T-cell therapy displayed strong efficacy by promoting a decrease of BPDCN blast burden. Furthermore we showed that T cells from BPDCN patient transduced with CD28/4-1BB CD123 CAR successfully eliminate autologous BPDCN blasts in vitro. Finally, we demonstrated in humanized mouse models that these effector CAR T cells exert low or no cytotoxicity against various subsets of normal cells with low CD123 expression, indicating a potentially low on-target/off-tumor toxicity effect. Collectively, our data support the further evaluation for clinical assessment of CD28/4-1BB CD123 CAR T cells in BPDCN neoplasm.

CAR-NK for tumor immunotherapy: Clinical transformation and future prospects

Recently, the use of chimeric antigen receptor-modified T (CAR-T)-cells in the treatment of hematological tumors has been successful and has become a clinical hotspot in tumor immunotherapy. However, their wide application is limited by inherent risks such as graft-versus-host disease (GvHD) and the amount of time it takes to produce CAR-T cells. Natural killer (NK) cells can be xenografted and have the potential to become off-the-shelf products, making CAR-NK cell therapies universal products. These products may be safer than CAR-T cell therapy. Considering that the fundamental researche is still in its infancy, this review focuses on clinical achievements and new strategies for improving the safety and efficacy of CAR-NK cell therapy, as well as the corresponding challenges.

CAR T Cells Beyond Cancer: Hope for Immunomodulatory Therapy of Infectious Diseases

Infectious diseases are still a significant cause of morbidity and mortality worldwide. Despite the progress in drug development, the occurrence of microbial resistance is still a significant concern. Alternative therapeutic strategies are required for non-responding or relapsing patients. Chimeric antigen receptor (CAR) T cells has revolutionized cancer immunotherapy, providing a potential therapeutic option for patients who are unresponsive to standard treatments. Recently two CAR T cell therapies, Yescarta® (Kite Pharma/Gilead) and Kymriah® (Novartis) were approved by the FDA for the treatments of certain types of non-Hodgkin lymphoma and B-cell precursor acute lymphoblastic leukemia, respectively. The success of adoptive CAR T cell therapy for cancer has inspired researchers to develop CARs for the treatment of infectious diseases. Here, we review the main achievements in CAR T cell therapy targeting viral infections, including Human Immunodeficiency Virus, Hepatitis C Virus, Hepatitis B Virus, Human Cytomegalovirus, and opportunistic fungal infections such as invasive aspergillosis.