Cancer patient T cells genetically targeted to prostate-specific membrane antigen specifically lyse prostate cancer cells and release cytokines in response to prostate-specific membrane antigen

Targeting HLA-E-overexpressing cancers with a NKG2A/C switch receptor

BACKGROUND

Human leukocyte antigen (HLA)-E is overexpressed by a large proportion of solid tumors, including malignant glioblastoma, and acts as a major checkpoint for NKG2A+ CD8+ T cells and natural killer (NK) cells in the tumor microenvironment and circulation. This axis operates alongside PD-L1 to inhibit effector responses by T and NK cells.

METHODS

We engineered a chimeric A/C switch receptor, combining the high HLA-E binding affinity of the NKG2A receptor ectodomain with the activating signaling of the NKG2C receptor endodomain. The cytotoxic function of A/C switch-transduced NK and T cells was evaluated against tumor cells with varying levels of HLA-E expression. In vivo efficacy was assessed using a xenograft model of glioblastoma.

FINDINGS

A/C switch-transduced NK and T cells exhibited superior and specific cytotoxicity against tumor cells with medium to high HLA-E expression. A/C switch-expressing human T cells demonstrated enhanced anti-tumor function in a glioblastoma xenograft model. The activity of the modified T cells was governed by an equilibrium between A/C switch levels and HLA-E expression, creating a therapeutic window to minimize on-target, off-tumor toxicities. Normal cells remained insensitive to A/C switch T cells, even after interferon (IFN)-γ pretreatment to induce HLA-E expression.

CONCLUSIONS

The A/C switch receptor effectively targets tumor cells expressing high levels of HLA-E, either alone or in combination with other engineered specificities, to overcome the suppressive NKG2A/HLA-E checkpoint. This approach offers a promising therapeutic strategy with a favorable safety profile for targeting HLA-E-overexpressing tumors.

FUNDING

This work was funded by The Research Council of Norway, the Norwegian Cancer Society, and the National Cancer Institute.

Challenges and future perspectives for high-throughput chimeric antigen receptor T cell discovery

Novel chimeric antigen receptor (CAR) T cell designs are being developed to overcome challenges with tumor recognition, trafficking, on-target but off-tumor binding, cytotoxicity, persistence, and immune suppression within the tumor microenvironment. Whereas traditional CAR engineering is an iterative, hypothesis-driven process in which novel designs are rationally constructed and tested for in vivo efficacy, drawing from the fields of small-molecule and protein-based therapeutic discovery, we consider how high-throughput, functional screening technologies are beginning to be applied for the development of promising CAR candidates. We review how the development of high-throughput screening methods has the potential to streamline the CAR discovery process, ultimately improving efficiency and clinical efficacy.

CD28 co-stimulation: novel insights and applications in cancer immunotherapy

Substantial progress in understanding T cell signalling, particularly with respect to T cell co-receptors such as the co-stimulatory receptor CD28, has been made in recent years. This knowledge has been instrumental in the development of innovative immunotherapies for patients with cancer, including immune checkpoint blockade antibodies, adoptive cell therapies, tumour-targeted immunostimulatory antibodies, and immunostimulatory small-molecule drugs that regulate T cell activation. Following the failed clinical trial of a CD28 superagonist antibody in 2006, targeted CD28 agonism has re-emerged as a technologically viable and clinically promising strategy for cancer immunotherapy. In this Review, we explore recent insights into the molecular functions and regulation of CD28. We describe how CD28 is central to the success of current cancer immunotherapies and examine how new questions arising from studies of CD28 as a clinical target have enhanced our understanding of its biological role and may guide the development of future therapeutic strategies in oncology.

Iodinated PSMA Ligands as XFI Tracers for Targeted Cell Imaging and Characterization of Nanoparticles

Prostate cancer is the second most commonly diagnosed cancer in men worldwide. Despite this, current diagnostic tools are still not satisfactory, lacking sensitivity for early-stage or single-cell diagnosis. This study describes the development of small-molecule tracers for the well-known tumor marker prostate-specific membrane antigen (PSMA). These tracers contain a urea motif for PSMA-targeting and iodinated aromatic moieties to allow detection via X-ray fluorescence imaging (XFI). Tracers with a triiodobenzoyl moiety allowed the specific targeting and successful imaging of PSMA+ cell lines with XFI. The XFI-measured uptake of 7.88 × 10-18 mol iodine (I) per cell is consistent with the uptake of known PSMA tracers measured by other techniques such as inductively coupled plasma mass spectrometry (ICP-MS). This is the first successful application of XFI to tumor cell targeting with a small-molecule tracer. In addition, iodinated tracers were used for the characterization of quantum dots (QDs) conjugated to PSMA-targeting urea motifs. The resulting targeted QD conjugates were shown to selectively bind PSMA+ cell lines via confocal microscopy. The immobilized iodinated targeting vectors allowed the determination of the tracer/QD ratio via XFI and ICP-MS. This ratio is a key property of targeted particles and difficult to measure by other techniques.

[89Zr]ZrCl4 for direct radiolabeling of DOTA-based precursors

INTRODUCTION

Zirconium-89 (89Zr) is a positron emitter with several advantages over other shorter-lived positron emission tomography (PET) compatible radiometals such as gallium-68 or copper-64. These include practically unlimited availability, extremely low cost, greatly facilitated distribution logistics, positron energy fit for medical PET imaging, and sufficiently long physical half-life to enable PET imaging at later time points for patient-specific dosimetry estimations. Despite these apparent benefits, the reception of 89Zr in the nuclear medicine community has been tepid. The driving factor for the absence of broader adaptation is mostly routed in its final formulation - [89Zr]zirconium oxalate. While serving as a suitable precursor solution for the gold standard chelator deferoxamine (DFO), [89Zr]Zr-oxalate is inaccessible for the most commonly used chelators, such as the macrocyclic DOTA, due to its pre-chelated state. Consequently, pioneering work has been conducted by multiple research groups to create oxalate-free forms of [89Zr]Zr4+, either via chemical conversion of oxalate into other counterion forms or via direct radiochemical isolation of [89Zr]ZrCl4, showing that [89Zr]Zr-DOTA complexes are possible and stable. However, this success was accompanied by challenges, including complex and labor-intensive radiochemical processing and radiolabeling procedures as well as the relatively minuscule conversion rates. Here, we report on the direct production of [89Zr]ZrCl4 avoiding oxalate and metal contaminants to enable efficient radiolabeling of DOTA constructs.

METHODS

We based our direct production of [89Zr]ZrCl4 on previously reported methods and further optimized its quality by including an additional iron-removing step using the TK400 Resin. Here, we avoided using oxalic acid and effectively minimized the content of trace metal contaminants. Our two-step purification procedure was automated, and we confirmed excellent radionuclide purity, minimal trace metals content, great reactivity over time, and high specific molar activity. In addition, DOTA-based PSMA-617 and DOTAGA-based PSMA-I&T were radiolabeled to demonstrate the feasibility of direct radiolabeling and to estimate the maximum apparent specific activities. Lastly, the biodistribution of [89Zr]Zr-PSMA-617 was assessed in mice bearing PC3-PIP xenografts, and the results were compared to the previously published data.

RESULTS

A total of 18 batches, ranging from 6.9 to 20 GBq (186 to 541 mCi), were produced. The specific molar activity for [89Zr]ZrCl4 exceeded 0.96 GBq (26 mCi) per nanomole of zirconium. The radionuclidic purity was >99 %, and the trace metals content was in the <1 ppm range. The [89Zr]ZrCl4 remained in its reactive chemical form for at least five days when stored in cyclic olefin polymer (COP) vials. Batches of 11.1 GBq (300 mCi) of [89Zr]Zr-PSMA-617 and 14.4 GBq (390 mCi) of [89Zr]Zr-PSMA-I&T, corresponding to specific activities of 11.1 MBq/μg (0.3 mCi/μg), and 14.4 MBq/μg (0.39 mCi/μg), respectively, were produced. [89Zr]Zr-PSMA-617 animal PET imaging results were in agreement with the previously published data.

CONCLUSION

In this work, we report on a suitable application of TK400 Resin to remove iron during [89Zr]ZrCl4 radiochemical isolation. The breakthrough allows for direct radiolabeling of DOTA-based constructs with [89Zr]ZrCl4, leading to high apparent molar activities and excellent conversion rates.

Treatment Options for Hepatocellular Carcinoma Using Immunotherapy: Present and Future

Hepatocellular carcinoma (HCC) is a common cancer, and the body's immune responses greatly affect its progression and the prognosis of patients. Immunological suppression and the maintenance of self-tolerance in the tumor microenvironment are essential responses, and these form part of the theoretical foundations of immunotherapy. In this review, we first discuss the tumor microenvironment of HCC, describe immunosuppression in HCC, and review the major biomarkers used to track HCC progression and response to treatment. We then examine antibody-based therapies, with a focus on immune checkpoint inhibitors (ICIs), monoclonal antibodies that target key proteins in the immune response (programmed cell death protein 1, anti-cytotoxic T-lymphocyte associated protein 4, and programmed death-ligand 1) which have transformed the treatment of HCC and other cancers. ICIs may be used alone or in conjunction with various targeted therapies for patients with advanced HCC who are receiving first-line treatments or subsequent treatments. We also discuss the use of different cellular immunotherapies, including T cell receptor (TCR) T cell therapy and chimeric antigen receptor (CAR) T cell therapy. We then review the use of HCC vaccines, adjuvant immunotherapy, and oncolytic virotherapy, and describe the goals of future research in the development of treatments for HCC.

Disruption of SUV39H1-Mediated H3K9 Methylation Sustains CAR T-cell Function

Suboptimal functional persistence limits the efficacy of adoptive T-cell therapies. CD28-based chimeric antigen receptors (CAR) impart potent effector function to T cells but with a limited lifespan. We show here that the genetic disruption of SUV39H1, which encodes a histone-3, lysine-9 methyl-transferase, enhances the early expansion, long-term persistence, and overall antitumor efficacy of human CAR T cells in leukemia and prostate cancer models. Persisting SUV39H1-edited CAR T cells demonstrate improved expansion and tumor rejection upon multiple rechallenges. Transcriptional and genome accessibility profiling of repeatedly challenged CAR T cells shows improved expression and accessibility of memory transcription factors in SUV39H1-edited CAR T cells. SUV39H1 editing also reduces expression of inhibitory receptors and limits exhaustion in CAR T cells that have undergone multiple rechallenges. Our findings thus demonstrate the potential of epigenetic programming of CAR T cells to balance their function and persistence for improved adoptive cell therapies.

SIGNIFICANCE

T cells engineered with CD28-based CARs possess robust effector function and antigen sensitivity but are hampered by limited persistence, which may result in tumor relapse. We report an epigenetic strategy involving disruption of the SUV39H1-mediated histone-silencing program that promotes the functional persistence of CD28-based CAR T cells. See related article by López-Cobo et al., p. 120. This article is featured in Selected Articles from This Issue, p. 5.

Chimeric Antigen Receptor T-Cell Therapy for Solid Tumors

We review chimeric antigen receptor (CAR) T-cell therapy for solid tumors. We discuss patient selection factors and aspects of clinical management. We describe challenges including physical and molecular barriers to trafficking CAR-Ts, an immunosuppressive tumor microenvironment, and difficulty finding cell surface target antigens. The application of new approaches in synthetic biology and cellular engineering toward solid tumor CAR-Ts is described. Finally, we summarize reported and ongoing clinical trials of CAR-T therapies for select disease sites such as head and neck (including thyroid cancer), lung, central nervous system (glioblastoma, neuroblastoma, glioma), sarcoma, genitourinary (prostate, renal, bladder, kidney), breast and ovarian cancer.

DIALing-up the preclinical characterization of gene-modified adoptive cellular immunotherapies

The preclinical characterization of gene modified adoptive cellular immunotherapy candidates for clinical development often requires the use of mouse models. Gene-modified lymphocytes (GML) incorporating chimeric antigen receptors (CAR) and T-cell receptors (TCR) into immune effector cells require in vivo characterization of biological activity, mechanism of action, and preclinical safety. Typically, this characterization involves the assessment of dose-dependent, on-target, on-tumor activity in severely immunocompromised mice. While suitable for the purpose of evaluating T cell-expressed transgene function in a living host, this approach falls short in translating cellular therapy efficacy, safety, and persistence from preclinical models to humans. To comprehensively characterize cell therapy products in mice, we have developed a framework called "DIAL". This framework aims to enable an end-to-end understanding of genetically engineered cellular immunotherapies in vivo, from infusion to tumor clearance and long-term immunosurveillance. The acronym DIAL stands for Distribution, Infiltration, Accumulation, and Longevity, compartmentalizing the systemic attributes of gene-modified cellular therapy and providing a platform for optimization with the ultimate goal of improving therapeutic efficacy. This review will discuss both existent and emerging examples of DIAL characterization in mouse models, as well as opportunities for future development and optimization.

Bispecific T-Cell Engagers and Chimeric Antigen Receptor T-Cell Therapies in Glioblastoma: An Update

Glioblastoma is the most common malignant primary brain tumor in adults. The prognosis is extremely poor even with standard treatment of maximal safe resection, radiotherapy, and chemotherapy. Recurrence is inevitable within months, and treatment options are very limited. Chimeric antigen receptor T-cell therapy (CART) and bispecific T-cell engagers (TCEs) are two emerging immunotherapies that can redirect T-cells for tumor-specific killing and have shown remarkable success in hematological malignancies and been under extensive study for application in glioblastoma. While there have been multiple clinical trials showing preliminary evidence of safety and efficacy for CART, bispecific TCEs are still in the early stages of clinical testing, with preclinical studies showing very promising results. However, there are multiple shared challenges that need to be addressed in the future, including the route of delivery, antigen escape, the immunosuppressive tumor microenvironment, and toxicity resulting from the limited choice of tumor-specific antigens. Efforts are underway to optimize the design of both these treatments and find the ideal combination therapy to overcome these challenges. In this review, we describe the work that has been performed as well as novel approaches in glioblastoma and in other solid tumors that may be applicable in the future.

Modulation of Radiation Doses and Chimeric Antigen Receptor T Cells: A Promising New Weapon in Solid Tumors-A Narrative Review

Tumor behavior is determined by its interaction with the tumor microenvironment (TME). Chimeric antigen receptor (CART) cell therapy represents a new form of cellular immunotherapy (IT). Immune cells present a different sensitivity to radiation therapy (RT). RT can affect tumor cells both modifying the TME and inducing DNA damage, with different effects depending on the low and high doses delivered, and can favor the expression of CART cells. CART cells are patients' T cells genetically engineered to recognize surface structure and to eradicate cancer cells. High-dose radiation therapy (HDRT, >10-20 Gy/fractions) converts immunologically "cold" tumors into "hot" ones by inducing necrosis and massive inflammation and death. LDRT (low-dose radiation therapy, >5-10 Gy/fractions) increases the expansion of CART cells and leads to non-immunogenetic death. An innovative approach, defined as the LATTICE technique, combines a high dose in higher FDG- uptake areas and a low dose to the tumor periphery. The association of RT and immune checkpoint inhibitors increases tumor immunogenicity and immune response both in irradiated and non-irradiated sites. The aim of this narrative review is to clarify the knowledge, to date, on CART cell therapy and its possible association with radiation therapy in solid tumors.

c-Kit signaling potentiates CAR T cell efficacy in solid tumors by CD28- and IL-2-independent co-stimulation

The limited efficacy of chimeric antigen receptor (CAR) T cell therapy for solid tumors necessitates engineering strategies that promote functional persistence in an immunosuppressive environment. Herein, we use c-Kit signaling, a physiological pathway associated with stemness in hematopoietic progenitor cells (T cells lose expression of c-Kit during differentiation). CAR T cells with intracellular expression, but no cell-surface receptor expression, of the c-Kit D816V mutation (KITv) have upregulated STAT phosphorylation, antigen activation-dependent proliferation and CD28- and interleukin-2-independent and interferon-γ-mediated co-stimulation, augmenting the cytotoxicity of first-generation CAR T cells. This translates to enhanced survival, including in transforming growth factor-β-rich and low-antigen-expressing solid tumor models. KITv CAR T cells have equivalent or better in vivo efficacy than second-generation CAR T cells and are susceptible to tyrosine kinase inhibitors (safety switch). When combined with CD28 co-stimulation, KITv co-stimulation functions as a third signal, enhancing efficacy and providing a potent approach to treat solid tumors.

Engineering second-generation TCR-T cells by site-specific integration of TRAF-binding motifs into the CD247 locus

BACKGROUND

The incorporation of co-stimulatory signaling domains into second-generation chimeric antigen receptors (CARs) significantly enhances the proliferation and persistence of CAR-T cells in vivo, leading to successful clinical outcomes.

METHODS

To achieve such functional enhancement in transgenic T-cell receptor-engineered T-cell (TCR-T) therapy, we designed a second-generation TCR-T cell in which CD3ζ genes modified to contain the intracellular domain (ICD) of the 4-1BB receptor were selectively inserted into the CD247 locus.

RESULTS

This modification enabled the simultaneous recruitment of key adaptor molecules for signals 1 and 2 on TCR engagement. However, the addition of full-length 4-1BB ICD unexpectedly impaired the expression and signaling of TCRs, leading to suboptimal antitumor activity of the resulting TCR-T cells in vivo. We found that the basic-rich motif (BRM) in the 4-1BB ICD was responsible for the undesirable outcomes, and that fusion of minimal tumor necrosis factor receptor-associated factor (TRAF)-binding motifs at the C-terminus of CD3ζ (zBB^ΔBRM) was sufficient to recruit TRAF2, the key adaptor molecule in 4-1BB signaling, while retaining the expression and proximal signaling of the transgenic TCR. Consequently, TCR-T cells expressing zBB^ΔBRM exhibited improved persistence and expansion in vitro and in vivo, resulting in superior antitumor activity in a mouse xenograft model.

CONCLUSIONS

Our findings offer a promising strategy for improving the intracellular signaling of TCR-T cells and their application in treating solid tumors.

Targeting of chimeric antigen receptor T cell metabolism to improve therapeutic outcomes

Genetically engineered chimeric antigen receptor (CAR) T cells can cure patients with cancers that are refractory to standard therapeutic approaches. To date, adoptive cell therapies have been less effective against solid tumors, largely due to impaired homing and function of immune cells within the immunosuppressive tumor microenvironment (TME). Cellular metabolism plays a key role in T cell function and survival and is amenable to manipulation. This manuscript provides an overview of known aspects of CAR T metabolism and describes potential approaches to manipulate metabolic features of CAR T to yield better anti-tumor responses. Distinct T cell phenotypes that are linked to cellular metabolism profiles are associated with improved anti-tumor responses. Several steps within the CAR T manufacture process are amenable to interventions that can generate and maintain favorable intracellular metabolism phenotypes. For example, co-stimulatory signaling is executed through metabolic rewiring. Use of metabolic regulators during CAR T expansion or systemically in the patient following adoptive transfer are described as potential approaches to generate and maintain metabolic states that can confer improved in vivo T cell function and persistence. Cytokine and nutrient selection during the expansion process can be tailored to yield CAR T products with more favorable metabolic features. In summary, improved understanding of CAR T cellular metabolism and its manipulations have the potential to guide the development of more effective adoptive cell therapies.

TET2 guards against unchecked BATF3-induced CAR T cell expansion

Further advances in cell engineering are needed to increase the efficacy of chimeric antigen receptor (CAR) and other T cell-based therapies1-5. As T cell differentiation and functional states are associated with distinct epigenetic profiles6,7, we hypothesized that epigenetic programming may provide a means to improve CAR T cell performance. Targeting the gene that encodes the epigenetic regulator ten-eleven translocation 2 (TET2)8 presents an interesting opportunity as its loss may enhance T cell memory9,10, albeit not cause malignancy9,11,12. Here we show that disruption of TET2 enhances T cell-mediated tumour rejection in leukaemia and prostate cancer models. However, loss of TET2 also enables antigen-independent CAR T cell clonal expansions that may eventually result in prominent systemic tissue infiltration. These clonal proliferations require biallelic TET2 disruption and sustained expression of the AP-1 factor BATF3 to drive a MYC-dependent proliferative program. This proliferative state is associated with reduced effector function that differs from both canonical T cell memory13,14 and exhaustion15,16 states, and is prone to the acquisition of secondary somatic mutations, establishing TET2 as a guardian against BATF3-induced CAR T cell proliferation and ensuing genomic instability. Our findings illustrate the potential of epigenetic programming to enhance T cell immunity but highlight the risk of unleashing unchecked proliferative responses.

CAR-T Cell Therapy and the Gut Microbiota

Chimeric antigen receptor (CAR) - T cell cancer therapy has yielded promising results in treating hematologic malignancies in clinical studies, and a growing number of CAR-T regimens are approved for clinical usage. While the therapy is considered of great potential in expanding the cancer immunotherapy arsenal, more than half of patients receiving CAR-T infusions do not respond, while others develop significant adverse effects, collectively indicating a need for optimization of CAR-T treatment to the individual. The microbiota is increasingly suggested as a major modulator of immunotherapy responsiveness. Studying causal microbiota roles possibly contributing to CAR-T therapy efficacy, adverse effects reduction, and prediction of patient responsiveness constitutes an exciting area of active research. Herein, we discuss the latest developments implicating human microbiota involvement in CAR-T therapy, while highlighting challenges and promises in harnessing the microbiota as a predictor and modifier of CAR-T treatment towards optimized efficacy and minimization of treatment-related adverse effects.

Generation of T-cell-receptor-negative CD8αβ-positive CAR T cells from T-cell-derived induced pluripotent stem cells

The production of autologous T cells expressing a chimaeric antigen receptor (CAR) is time-consuming, costly and occasionally unsuccessful. T-cell-derived induced pluripotent stem cells (TiPS) are a promising source for the generation of 'off-the-shelf' CAR T cells, but the in vitro differentiation of TiPS often yields T cells with suboptimal features. Here we show that the premature expression of the T-cell receptor (TCR) or a constitutively expressed CAR in TiPS promotes the acquisition of an innate phenotype, which can be averted by disabling the TCR and relying on the CAR to drive differentiation. Delaying CAR expression and calibrating its signalling strength in TiPS enabled the generation of human TCR- CD8αβ+ CAR T cells that perform similarly to CD8αβ+ CAR T cells from peripheral blood, achieving effective tumour control on systemic administration in a mouse model of leukaemia and without causing graft-versus-host disease. Driving T-cell maturation in TiPS in the absence of a TCR by taking advantage of a CAR may facilitate the large-scale development of potent allogeneic CD8αβ+ T cells for a broad range of immunotherapies.

The affinity of antigen-binding domain on the antitumor efficacy of CAR T cells: Moderate is better

The overall efficacy of chimeric antigen receptor modified T cells (CARTs) remain limited in solid tumors despite intensive studies that aim at targeting multiple antigens, enhancing migration, reducing tonic signaling, and improving tumor microenvironment. On the other hand, how the affinity and engaging kinetics of antigen-binding domain (ABD) affects the CART's efficacy has not been carefully investigated. In this article, we first analyzed 38 published solid tumor CART trials and correlated the response rate to their ABD affinity. Not surprisingly, majority (25 trials) of the CARTs utilized high-affinity ABDs, but generated merely 5.7% response rate. In contrast, 35% of the patients treated with the CARTs built from moderate-affinity ABDs had clinical responses. Thus, CARTs with moderate-affinity ABDs not only have less off-target toxicity, but also are more effective. We then reviewed the effects of ABD affinity on the biology and function of CARTs, providing further evidence that moderate-affinity ABDs may be better in CART development. In the end, we propose that a fast-on/fast-off (high Kon and Koff ) kinetics of CART-target engagement in solid tumor allow CARTs to generate sufficient signaling to kill tumor cells without being driven to exhaustion. We believe that studying the ABD affinity and the kinetics of CART-tumor interaction may hold a key to designing effective CARTs for solid tumors.

Co-Stimulatory Receptor Signaling in CAR-T Cells

T cell engineering strategies have emerged as successful immunotherapeutic approaches for the treatment of human cancer. Chimeric Antigen Receptor T (CAR-T) cell therapy represents a prominent synthetic biology approach to re-direct the specificity of a patient's autologous T cells toward a desired tumor antigen. CAR-T therapy is currently FDA approved for the treatment of hematological malignancies, including subsets of B cell lymphoma, acute lymphoblastic leukemia (ALL) and multiple myeloma. Mechanistically, CAR-mediated recognition of a tumor antigen results in propagation of T cell activation signals, including a co-stimulatory signal, resulting in CAR-T cell activation, proliferation, evasion of apoptosis, and acquisition of effector functions. The importance of including a co-stimulatory domain in CARs was recognized following limited success of early iteration CAR-T cell designs lacking co-stimulation. Today, all CAR-T cells in clinical use contain either a CD28 or 4-1BB co-stimulatory domain. Preclinical investigations are exploring utility of including additional co-stimulatory molecules such as ICOS, OX40 and CD27 or various combinations of multiple co-stimulatory domains. Clinical and preclinical evidence implicates the co-stimulatory signal in several aspects of CAR-T cell therapy including response kinetics, persistence and durability, and toxicity profiles each of which impact the safety and anti-tumor efficacy of this immunotherapy. Herein we provide an overview of CAR-T cell co-stimulation by the prototypical receptors and discuss current and emerging strategies to modulate co-stimulatory signals to enhance CAR-T cell function.

Development of CAR T Cell Therapy in Children-A Comprehensive Overview

CAR T cell therapy has revolutionized immunotherapy in the last decade with the successful establishment of chimeric antigen receptor (CAR)-expressing cellular therapies as an alternative treatment in relapsed and refractory CD19-positive leukemias and lymphomas. There are fundamental reasons why CAR T cell therapy has been approved by the Food and Drug administration and the European Medicines Agency for pediatric and young adult patients first. Commonly, novel therapies are developed for adult patients and then adapted for pediatric use, due to regulatory and commercial reasons. Both strategic and biological factors have supported the success of CAR T cell therapy in children. Since there is an urgent need for more potent and specific therapies in childhood malignancies, efforts should also include the development of CAR therapeutics and expand applicability by introducing new technologies. Basic aspects, the evolution and the drawbacks of childhood CAR T cell therapy are discussed as along with the latest clinically relevant information.

iPSC-Derived Natural Killer Cell Therapies - Expansion and Targeting

Treatment of cancer with allogeneic natural killer (NK) cell therapies has seen rapid development, especially use against hematologic malignancies. Clinical trials of NK cell-based adoptive transfer to treat relapsed or refractory malignancies have used peripheral blood, umbilical cord blood and pluripotent stem cell-derived NK cells, with each approach undergoing continued clinical development. Improving the potency of these therapies relies on genetic modifications to improve tumor targeting and to enhance expansion and persistence of the NK cells. Induced pluripotent stem cell (iPSC)-derived NK cells allow for routine targeted introduction of genetic modifications and expansion of the resulting NK cells derived from a clonal starting cell population. In this review, we discuss and summarize recent important advances in the development of new iPSC-derived NK cell therapies, with a focus on improved targeting of cancer. We then discuss improvements in methods to expand iPSC-derived NK cells and how persistence of iPSC-NK cells can be enhanced. Finally, we describe how these advances may combine in future NK cell-based therapy products for the treatment of both hematologic malignancies and solid tumors.

Challenges of CAR T-cell Therapy in CLL: Lessons Learned

Development of chimeric antigen receptor T (CART) cell therapy has led to unprecedented success against B cell leukemia and lymphoma and resulted in FDA-approved treatment protocols. Despite the initial clinical response in B cell-related malignancies, high relapse rates suggest that much work is needed to uncover mechanisms of resistance. In chronic lymphocytic leukemia (CLL), the durable activity of CAR T-cells is limited, and CART cell success is lower than in other malignancies. T cells from these patients are vulnerable to a state of dysfunction due to stresses including chronic infection, rapid cell cycle upon antigen recognition, immunosuppressive tumor microenvironment, and cancer-related treatments. T cells are also introduced to additional stresses when cultured ex vivo during the CART manufacturing process. All these factors contribute to the limited regenerative capacity of T cells, which can lead to CART treatment failure. In this short report, we will review the challenges of CAR T-cell therapy in patients with CLL and discuss potential strategies to overcome these challenges.

Novel Cellular Therapies for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer related death worldwide. Most patients present with advanced disease, and current gold-standard management using tyrosine kinase inhibitors or immune checkpoint inhibitors (ICIs) offers modest clinical benefit. Cellular immune therapies targeting HCC are currently being tested in the laboratory and in clinical trials. Here, we review the landscape of cellular immunotherapy for HCC, defining antigenic targets, outlining the range of cell therapy products being applied in HCC (such as CAR-T and TCR-T), and exploring how advanced engineering solutions may further enhance this therapeutic approach.

Targeting memory T cell metabolism to improve immunity

Vaccination affords protection from disease by activating pathogen-specific immune cells and facilitating the development of persistent immunologic memory toward the vaccine-specific pathogen. Current vaccine regimens are often based on the efficiency of the acute immune response, and not necessarily on the generation of memory cells, in part because the mechanisms underlying the development of efficient immune memory remain incompletely understood. This Review describes recent advances in defining memory T cell metabolism and how metabolism of these cells might be altered in patients affected by mitochondrial diseases or metabolic syndrome, who show higher susceptibility to recurrent infections and higher rates of vaccine failure. It discusses how this new understanding could add to the way we think about immunologic memory, vaccine development, and cancer immunotherapy.

An Update on Immune Based Therapies in Acute Myeloid Leukemia: 2021 and Beyond!

Despite advances in the treatment of acute myeloid leukemia (AML), relapse is still widely observed and represents the major cause of death among patients with AML. Treatment options in the relapse setting are limited, still relying predominantly on allogeneic hematopoietic stem cell transplantation (allo-HSCT) and cytotoxic chemotherapy, with poor outcomes. Novel targeted and venetoclax-based combinations are being investigated and have shown encouraging results. Immune checkpoint inhibitors in combination with low-intensity chemotherapy demonstrated encouraging response rates and survival among patients with relapsed and/or refractory (R/R) AML, especially in the pre- and post-allo-HSCT setting. Blocking the CD47/SIRPα pathway is another strategy that showed robust anti-leukemic activity, with a response rate of around 70% and an encouraging median overall survival in patients with newly diagnosed, higher-risk myelodysplastic syndrome and patients with AML with a TP53 mutation. One approach that was proven to be very effective in the relapsed setting of lymphoid malignancies is chimeric antigen receptor (CAR) T cells. It relies on the infusion of genetically engineered T cells capable of recognizing specific epitopes on the surface of leukemia cells. In AML, different CAR constructs with different target antigens have been evaluated and demonstrated safety and feasibility in the R/R setting. However, the difficulty of potently targeting leukemic blasts in AML while sparing normal cells represents a major limitation to their use, and strategies are being tested to overcome this obstacle. A different approach is based on endogenously redirecting the patient's system cells to target and destroy leukemic cells via bispecific T-cell engagers (BiTEs) or dual antigen receptor targeting (DARTs). Early results have demonstrated the safety and feasibility of these agents, and research is ongoing to develop BiTEs with longer half-life, allowing for less frequent administration schedules and developing them in earlier and lower disease burden settings.

The antigen-binding moiety in the driver's seat of CARs

Immuno-oncology has been at the forefront of cancer treatment in recent decades. In particular immune checkpoint and chimeric antigen receptor (CAR)-T cell therapy have achieved spectacular results. Over the years, CAR-T cell development has followed a steady evolutionary path, focusing on increasing T cell potency and sustainability, which has given rise to different CAR generations. However, there was less focus on the mode of interaction between the CAR-T cell and the cancer cell; more specifically on the targeting moiety used in the CAR and its specific properties. Recently, the importance of optimizing this domain has been recognized and the possibilities have been exploited. Over the last 10 years-in addition to the classical scFv-based CARs-single domain CARs, natural receptor-ligand CARs, universal CARs and CARs targeting more than one antigen have emerged. In addition, the specific parameters of the targeting domain and their influence on T cell activation are being examined. In this review, we concisely present the history of CAR-T cell therapy, and then expand on various developments in the CAR ectodomain. We discuss different formats, each with their own advantages and disadvantages, as well as the developments in affinity tuning, avidity effects, epitope location, and influence of the extracellular spacer.

Generation of Redirected Engineered Human Chimeric Antigen Receptor (CAR) T Cells

Chimeric antigen receptor (CAR) T cell therapy that involves genetic engineering a patient's own immune cells with antigen-specific receptors has shown remarkable efficacy in blood cancer treatment. Numerous clinical studies with CAR T cells targeting the blood cell surface protein CD19 led to the FDA 's first approval of a genetically engineered cell therapy. The process of generating potent CAR T cells involves several carefully performed manufacturing steps. Here, we describe the generation of redirected engineered human CAR T cells for preclinical studies starting with the CAR design, retroviral gene transfer, detection of CAR expression, and expansion of transduced T cells.

Current Limitations and Perspectives of Chimeric Antigen Receptor-T-Cells in Acute Myeloid Leukemia

Simple Summary

Acute myeloid leukemia (AML) is the most frequent type of acute leukemia in adults. Allogeneic hematopoietic cell transplantation (allo-HCT) has been the only potentially curative treatment for the majority of patients. The ability of chimeric antigen receptor (CAR)-modified T-cell therapy directed against the CD19 antigen to induce durable remissions in patients with acute lymphoblastic leukemia (ALL) has provided optimism that this novel treatment paradigm can be extrapolated to AML. In this review, we provide an overview of candidate target antigens for CAR-T-cells in AML, an update on recent progress in preclinical and clinical development of investigational CAR-T-cell products, and discuss challenges for the clinical implementation of CAR-T-cell therapy in AML.

Abstract

Adoptive transfer of gene-engineered chimeric antigen receptor (CAR)-T-cells has emerged as a powerful immunotherapy for combating hematologic cancers. Several target antigens that are prevalently expressed on AML cells have undergone evaluation in preclinical CAR-T-cell testing. Attributes of an ‘ideal’ target antigen for CAR-T-cell therapy in AML include high-level expression on leukemic blasts and leukemic stem cells (LSCs), and absence on healthy tissues, normal hematopoietic stem and progenitor cells (HSPCs). In contrast to other blood cancer types, where CAR-T therapies are being similarly studied, only a rather small number of AML patients has received CAR-T-cell treatment in clinical trials, resulting in limited clinical experience for this therapeutic approach in AML. For curative AML treatment, abrogation of bulk blasts and LSCs is mandatory with the need for hematopoietic recovery after CAR-T administration. Herein, we provide a critical review of the current pipeline of candidate target antigens and corresponding CAR-T-cell products in AML, assess challenges for clinical translation and implementation in routine clinical practice, as well as perspectives for overcoming them.

A comparison of chimeric antigen receptors containing CD28 versus 4-1BB costimulatory domains

Chimeric antigen receptors (CARs) are engineered proteins designed to target T cells to cancer cells. To effectively activate the T cells in which they are expressed, CARs must contain a costimulatory domain. The CAR T cell products approved for the treatment of B cell lymphomas and/or acute lymphoblastic leukaemia or multiple myeloma incorporate either a CD28-derived or a 4-1BB-derived costimulatory domain. Almost all other clinically tested CARs also use costimulatory domains from CD28 or 4-1BB. In preclinical experiments, cytokine release is usually greater with CARs containing CD28 versus 4-1BB costimulatory domains; however, constructs with either domain confer similar anticancer activity in mouse models. T cell products expressing CARs with either CD28 or 4-1BB costimulatory domains have been highly efficacious in patients with relapsed haematological malignancies, with anti-CD19 products having similar activity regardless of the source of the costimulatory domain. In large-cohort clinical trials, the rates of neurological toxicities have been higher with CD28-costimulated CARs, although this finding is probably the result of a combination of factors rather than due to CD28 signalling alone. Future preclinical and clinical research should aim to compare different costimulatory domains while controlling for confounding variables. Herein, we provide an overview of T cell costimulation by CD28 and 4-1BB and, using the available preclinical and clinical data, compare the efficacy and toxicity profiles associated with CARs containing either costimulatory domain.

Ectopic activation of the miR-200c-EpCAM axis enhances antitumor T cell responses in models of adoptive cell therapy

Adoptive T cell therapy (ACT) is a promising strategy for treating cancer, but it often fails because of cell intrinsic regulatory programs that limit the degree or duration of T cell function. In this study, we found that ectopic expression of microRNA-200c (miR-200c) markedly enhanced the antitumor activity of CD8+ cytotoxic T lymphocytes (CTLs) during ACT in multiple mouse models. CTLs transduced with miR-200c exhibited reduced apoptosis during engraftment and enhanced in vivo persistence, accompanied by up-regulation of the transcriptional regulator T cell factor 1 (TCF1) and the inflammatory cytokine tumor necrosis factor (TNF). miR-200c elicited these changes by suppressing the transcription factor Zeb1 and thereby inducing genes characteristic of epithelial cells. Overexpression of one of these genes, Epcam, was sufficient to augment therapeutic T cell responses against both solid and liquid tumors. These results identify the miR-200c–EpCAM axis as an avenue for improving ACT and demonstrate that select genetic perturbations can produce phenotypically distinct T cells with advantageous therapeutic properties.

Building on Synthetic Immunology and T Cell Engineering: A Brief Journey Through the History of Chimeric Antigen Receptors

Advancement in our understanding of immune cell recognition and emerging cellular engineering technologies during the last decades made active manipulation of the T cell response possible. Synthetic immunology is providing us with an expanding set of composite receptor molecules capable to reprogram immune cell function in a predefined fashion. Since the first prototypes in the late 1980s, the design of chimeric antigen receptors (CARs; T-bodies, immunoreceptors), has followed a clear line of stepwise improvements from antigen-redirected targeting to designed "living factories" delivering transgenic products on demand. Building on basic research and creative clinical exploration, CAR T cell therapy has been achieving spectacular success in the treatment of hematologic malignancies, now beginning to improve the outcome of cancer patients. In this study, we briefly review the history of CARs and outline how the progress in the basic understanding of T cell recognition and of cell engineering technologies made novel therapies possible.

CAR T cells: Building on the CD19 paradigm

Spearheaded by the therapeutic use of chimeric antigen receptors (CARs) targeting CD19, synthetic immunology has entered the clinical arena. CARs are recombinant receptors for antigen that engage cell surface molecules through the variable region of an antibody and signal through arrayed T-cell activating and costimulatory domains. CARs allow redirection of T-cell cytotoxicity against any antigen of choice, independent of MHC expression. Patient T cells engineered to express CARs specific for CD19 have yielded remarkable outcomes in subjects with relapsed/refractory B- cell malignancies, setting off unprecedented interest in T-cell engineering and cell-based cancer immunotherapy. In this review, we present the challenges to extend the use of CAR T cells to solid tumors and other pathologies. We further highlight progress in CAR design, cell manufacturing, and genome editing, which in aggregate hold the promise of generating safer and more effective genetically instructed immunity. Novel engineered cell types, including innate T-cell types, natural killer (NK) cells, macrophages, and induced pluripotent stem cell-derived immune cells, are on the horizon, as are applications of CAR T cells to treat autoimmunity, severe infections, and senescence-associated pathologies.

Combination of CRISPR/Cas9 System and CAR-T Cell Therapy: A New Era for Refractory and Relapsed Hematological Malignancies

Chimeric antigen receptor T (CAR-T) cell therapy is the novel treatment strategy for hematological malignancies such as acute lymphoblastic leukemia (ALL), lymphoma and multiple myeloma. However, treatment-related toxicities such as cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) have become significant hurdles to CAR-T treatment. Multiple strategies were established to alter the CAR structure on the genomic level to improve efficacy and reduce toxicities. Recently, the innovative gene-editing technology-clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease9 (Cas9) system, which particularly exhibits preponderance in knock-in and knockout at specific sites, is widely utilized to manufacture CAR-T products. The application of CRISPR/Cas9 to CAR-T cell therapy has shown promising clinical results with minimal toxicity. In this review, we summarized the past achievements of CRISPR/Cas9 in CAR-T therapy and focused on the potential CAR-T targets.

Radiotherapy to Enhance Chimeric Antigen Receptor T-Cell Therapeutic Efficacy in Solid Tumors: A Narrative Review

Importance

Immunotherapy has emerged as a new pillar of cancer therapy over the past decade. Adoptive immunotherapy in particular has become a major area of research interest, with advances seen in the development of T-cell engineering. As a result, chimeric antigen receptor (CAR) T-cell therapy has become a new and highly effective treatment option, especially for patients with refractory or resistant blood cell cancers. However, CAR T-cell therapy has shown limited efficacy for the treatment of solid tumors thus far.

Observations

Combinatorial treatment approaches, such as addition of radiotherapy to CAR T cells, may provide a strategy to prevent resistance to CAR T-cell therapy of solid tumors. These approaches need to overcome obstacles that include abnormal vessels and adhesion molecule expression on tumor vasculature, leading to reduced transmigration of effector immune cells, including CAR T cells, and immunosuppressive cues in the tumor microenvironment, including regional hypoxia.

Conclusions and Relevance

This review provides an overview of the current developments in CAR T-cell therapy and highlights the unique opportunities and challenges in combining CAR T-cell therapy with radiotherapy.

Armored CAR T-Cells: The Next Chapter in T-Cell Cancer Immunotherapy

Chimeric antigen receptor (CAR) T-cell therapy engineers T-cells to express a synthetic receptor which redirects effector function to the tumor, to improve efficacy and reduce toxicities associated with conventional treatments, such as radiotherapy and chemotherapy. This approach has proved effective in treating hematological malignancies; however, the same effects have not been observed in solid tumors. The immunosuppressive tumor microenvironment (TME) creates a significant barrier to solid tumor efficacy and reduces the anti-cancer activity of endogenous tumor-resident immune cells, enabling cancer progression. In recent years, researchers have attempted to enhance CAR T-cell function in the TME by engineering the cells to express various proteins alongside the CAR. Examples of this engineering include inducing CAR T-cells to secrete cytokines or express cytokine receptors to modulate the cytokine milieu of the TME. Alternatively, the CAR T-cell may secrete antibody-like proteins to target a range of tumor antigens. Collectively, these methods are termed armored CAR T-cell therapy, and in this review, we will discuss the range of armored CAR T-cell approaches which have been investigated to date.

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.

Current Trends in Cancer Immunotherapy

The search for an effective drug to treat oncological diseases, which have become the main scourge of mankind, has generated a lot of methods for studying this affliction. It has also become a serious challenge for scientists and clinicians who have needed to invent new ways of overcoming the problems encountered during treatments, and have also made important discoveries pertaining to fundamental issues relating to the emergence and development of malignant neoplasms. Understanding the basics of the human immune system interactions with tumor cells has enabled new cancer immunotherapy strategies. The initial successes observed in immunotherapy led to new methods of treating cancer and attracted the attention of the scientific and clinical communities due to the prospects of these methods. Nevertheless, there are still many problems that prevent immunotherapy from calling itself an effective drug in the fight against malignant neoplasms. This review examines the current state of affairs for each immunotherapy method, the effectiveness of the strategies under study, as well as possible ways to overcome the problems that have arisen and increase their therapeutic potentials.

Function and evolution of the prototypic CD28ζ and 4-1BBζ chimeric antigen receptors

T cells engineered to express chimeric antigen receptors (CARs) specific for CD19 have yielded remarkable clinical outcomes in patients with refractory B-cell malignancies. The first CARs to be approved by the US Food and Drug Administration and the European Medicines Agency are CD19 CARs that comprise either CD28/CD3ζ or 4-1BB/CD3ζ dual-signalling domains. While their efficacy and safety profiles in patients with B-cell malignancies are comparable overall, the functional properties these two CAR designs impart upon engineered T cells differ significantly. Remarkably, alternative costimulatory domains have not, to date, superseded these foundational designs. Rather, recent CAR advances have focused on perfecting the original CD28- and 4-1BB-based CD19 CARs by calibrating strength of activation, pre-empting T-cell exhaustion and increasing the functional persistence of CAR T cells. This article reviews the essential biological properties of these first-in-class prototypes and their recent evolution.

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CD19 chimeric antigen receptor (CAR) therapy has shown remarkable success against B-cell malignancies.

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The prototypic CD19 CARs comprise either CD28/CD3ζ or 4-1BB/CD3ζ signalling domains.

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Both CD19 CARs yield similar efficacy but impart distinct T-cell functionalities.

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Novel CAR designs aim to enhance the persistence or effector potency of T cells.

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Genome editing averts variegated CAR expression and sustains T-cell function.

Chimeric antigen receptor T cell therapy for pediatric and young adult B cell acute lymphoblastic leukemia

INTRODUCTION

Though 85% of children and young adults with acute lymphoblastic leukemia (ALL) are cured, until recently, the prognosis of relapsed or refractory disease has been dismal. The advent of chimeric antigen receptor (CAR) T-cell therapy has transformed the treatment of relapsed/refractory ALL. The most well-studied, successful CARs are autologous, murine-based anti-CD19 CARs, but new constructs are currently under clinical investigation.

AREAS COVERED

This review describes the history and design of CAR T cells, clinical trial outcomes of anti-CD19 and newer CARs, treatment-related toxicities including cytokine release syndrome and neurotoxicity, and issues with resistance and relapse. A search of PubMed and clinicaltrials.gov spanning from 2012-present was used to select original reports investigating the use of CAR T in pediatric patients.

EXPERT OPINION

CD19-targeted CARs have demonstrated remarkable response rates and produced durable remissions in very high-risk pediatric patient populations. The therapies, however, are limited by unique treatment-related toxicities and considerable rates of antigen-positive and antigen-negative relapses. Current research efforts focused on elucidating mechanisms of resistance/relapse and on developing strategies to prevent and treat relapse are critical to optimizing the use of CAR-T. In addition, ongoing trials testing CARs earlier in therapy and for new indications are key to informing their widespread usage.

[Basic principles of immunotherapy]

Immunotherapy for malignant diseases is defined as a systematic therapeutic approach that aims to target the individual's immune system to prevent the development of malignancies or to combat existing tumors. Nowadays, this includes various therapeutic approaches, such as immune checkpoint inhibitors, BiTEs (bispecific T‑cell engagers), CAR T‑cells (CAR: chimeric antigen receptors) and oncolytic viruses, which have not only different mechanisms of action and points of attack, but also have very different efficiencies in the treatment of solid and hematological malignancies. These approaches undoubtedly enrich the therapeutic portfolio in oncology-in palliative systematic therapy and also in the interaction with operative and ablative local therapeutic approaches.

Paving the Way toward Successful Multiple Myeloma Treatment: Chimeric Antigen Receptor T-Cell Therapy

Despite the significant progress of modern anticancer therapies, multiple myeloma (MM) is still incurable for the majority of patients. Following almost three decades of development, chimeric antigen receptor (CAR) T-cell therapy now has the opportunity to revolutionize the treatment landscape and meet the unmet clinical need. However, there are still several major hurdles to overcome. Here we discuss the recent advances of CAR T-cell therapy for MM with an emphasis on future directions and possible risks. Currently, CAR T-cell therapy for MM is at the first stage of clinical studies, and most studies have focused on CAR T cells targeting B cell maturation antigen (BCMA), but other antigens such as cluster of differentiation 138 (CD138, syndecan-1) are also being evaluated. Although this therapy is associated with side effects, such as cytokine release syndrome and neurotoxicity, and relapses have been observed, the benefit–risk balance and huge potential drive the ongoing clinical progress. To fulfill the promise of recent clinical trial success and maximize the potential of CAR T, future efforts should focus on the reduction of side effects, novel targeted antigens, combinatorial uses of different types of CAR T, and development of CAR T cells targeting more than one antigen.

CAR T cells: continuation in a revolution of immunotherapy

The recent clinical successes of immunotherapy, as a result of a broader and more profound understanding of cancer immunobiology, and the leverage of this knowledge to effectively eradicate malignant cells, has revolutionised the field of cancer therapeutics. Immunotherapy is now considered the fifth pillar of cancer care, alongside surgery, chemotherapy, radiotherapy, and targeted therapy. Recently, the success of genetically modified T cells that express chimeric antigen receptors (CAR T cells) has generated considerable excitement. CAR T-cell therapy research and development has built on experience generated by laboratory research and clinical investigation of lymphokine-activated killer cells, tumour-infiltrating lymphocytes, and allogeneic haemopoietic stem-cell transplantation for cancer treatment. This Review aims to provide a background on the field of adoptive T-cell therapy and the development of genetically modified T cells, most notably CAR T-cell therapy. Many challenges exist to optimise efficacy, minimise toxicity, and broaden the application of immunotherapies based on T cells.

The long road to the first FDA-approved gene therapy: chimeric antigen receptor T cells targeting CD19

Thirty years after initial publications of the concept of a chimeric antigen receptor (CAR), the U.S. Food and Drug Administration (FDA) approved the first anti-CD19 CAR T-cell therapy. Unlike other immunotherapies, such as immune checkpoint inhibitors and bispecific antibodies, CAR T cells are unique as they are "living drugs," that is, gene-edited killer cells that can recognize and kill cancer. During these 30 years of development, the CAR construct, T-cell manufacturing process, and clinical patient management have gone through rounds of failures and successes that drove continuous improvement. Tisagenlecleucel was the first gene therapy to receive approval from the FDA for any indication. The initial approval was for relapsed or refractory (r/r) pediatric and young-adult B-cell acute lymphoblastic leukemia in August 2017 and in May 2018 for adult r/r diffuse large B-cell lymphoma. Here we review the preclinical and clinical development of what began as CART19 at the University of Pennsylvania and later developed into tisagenlecleucel.

Implications of T cell receptor biology on the development of new T cell therapies for cancer

Recently, two chimeric antigen receptor (CAR) T cell therapies were approved based on their remarkable efficacy in patients with hematological malignancies. By contrast, CAR-T cell therapies results in solid tumors have been less promising. To develop the next generation of T cell therapies a better understanding of T cell receptor (TCR) biology and its implication for the design of synthetic receptors is critical. Here, we review current and newly developed forms of T cell therapies and how their utilization of different components of the TCR signaling machinery and their requirement for engagement (or not) of human leukocyte antigen impacts their design, efficacy and applicability as cancer drugs. Notably, we highlight the development of human leukocyte antigen-independent T cell platforms that utilize the full TCR complex as having promise to overcome some of the limitations of existing T cell therapies.

CAR T Cell Therapy Progress and Challenges for Solid Tumors

The past two decades have marked the beginning of an unprecedented success story for cancer therapy through redirecting antitumor immunity [1]. While the mechanisms that control the initial and ongoing immune responses against tumors remain a strong research focus, the clinical development of technologies that engage the immune system to target and kill cancer cells has become a translational research priority. Early attempts documented in the late 1800s aimed at sparking immunity with cancer vaccines were difficult to interpret but demonstrated an opportunity that more than 100 years later has blossomed into the current field of cancer immunotherapy. Perhaps the most recent and greatest illustration of this is the widespread appreciation that tumors actively shut down antitumor immunity, which has led to the emergence of checkpoint pathway inhibitors that re-invigorate the body's own immune system to target cancer [2, 3]. This class of drugs, with first FDA approvals in 2011, has demonstrated impressive durable clinical responses in several cancer types, including melanoma, lung cancer, Hodgkin's lymphoma, and renal cell carcinoma, with the ongoing investigation in others. The biology and ultimate therapeutic successes of these drugs led to the 2018 Nobel Prize in Physiology or Medicine, awarded to Dr. James Allison and Dr. Tasuku Honjo for their contributions to cancer therapy [4]. In parallel to the emerging science that aided in unleashing the body's own antitumor immunity with checkpoint pathway inhibitors, researchers were also identifying ways to re-engineer antitumor immunity through adoptive cellular immunotherapy approaches. Chimeric antigen receptor (CAR)-based T cell therapy has achieved an early head start in the field, with two recent FDA approvals in 2017 for the treatment of B-cell malignancies [5]. There is an explosion of preclinical and clinical efforts to expand the therapeutic indications for CAR T cell therapies, with a specific focus on improving their clinical utility, particularly for the treatment of solid tumors. In this chapter, we will highlight the recent progress, challenges, and future perspectives surrounding the development of CAR T cell therapies for solid tumors.

The Role of Checkpoint Inhibitors and Cytokines in Adoptive Cell-Based Cancer Immunotherapy with Genetically Modified T Cells

This review focuses on the structure and molecular action mechanisms of chimeric antigen receptors (CARs) and major aspects of the manufacturing and clinical application of products for the CAR-T (CAR-modified T lymphocyte) therapy of hematological and solid tumors with special emphasis on the strategies for combined use of CAR-T therapy with immuno-oncological monoclonal antibodies (checkpoint inhibitors) and cytokines to boost survival, persistence, and antitumor efficacy of CAR-T therapy. The review also summarizes preclinical and clinical data on the additive effects of the combined use of CAR-T therapy with interleukins and monoclonal antibodies targeting immune checkpoints.

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.

Engineered Jurkat Cells for Targeting Prostate-Specific Membrane Antigen on Prostate Cancer Cells by Nanobody-Based Chimeric Antigen Receptor

Background:

Recently, modification of T cells with CAR has been an attractive approach for adoptive immunotherapy of cancers. Typically, CARs contain a scFv. Most often, scfvs are derived from a monoclonal antibody of murine origin and may be a trigger for host immune system that leads to the T-cell clearance. Nanobody is a specific antigen-binding fragment derived from camelid that has great homology to human VH and low immunogenic potential. Therefore, in this study, nanobody was employed instead of scFv in CAR construct.

Methods:

In this study, a CAR was constructed based on a nanobody against PSMA (NBPII-CAR). At first, Jurkat cells were electroporated with NBPII-CAR, and then flow cytometry was performed for NBPII-CAR expression. For functional analysis, CAR T cells were co-cultured with prostate cancer cells and analyzed for IL-2 secretion, CD25 expression, and cell proliferation.

Results:

Flow cytometry results confirmed the expression of NBPII-CAR on the transfected Jurkat cells. Our data showed the specificity of engineered Jurkat cells against prostate cancer cells by not only increasing the IL-2 cytokine (about 370 pg/ml) but also expressing the T-cell activation marker CD25 (about 30%). In addition, proliferation of engineered Jurkat cells increased nearly 60% when co-cultured with LNCaP (PSMA⁺), as compared with DU145 (PSMA^-).

Conclusion:

Here, we describe the ability of nanobody-based CAR to recognize PSMA that leads to the activation of Jurkat cells. This construct might be used as a promising candidate for clinical applications in prostate cancer therapy.