Extracellular NGFR Spacers Allow Efficient Tracking and Enrichment of Fully Functional CAR-T Cells Co-Expressing a Suicide Gene

Magnetic CAR T cell purification using an anti-G4S linker antibody

Chimeric antigen receptor (CAR) redirected T cells are successfully employed in the combat against several hematological malignancies, however, are often compromised by low transduction rates making refinement of the CAR T cell products necessary. Here, we report a broadly applicable enrichment protocol relying on marking CAR T cells with an anti-glycine4-serine (G4S) linker antibody followed by magnetic activated cell sorting (MACS). The protocol is broadly applicable since the G4S peptide is an integral part of the vast majority of CARs as it links the VH and VL recognition domains. We demonstrate the feasibility by using the canonical second generation CARs specific for CEA and Her2, respectively, obtaining highly purified CAR T cell products in a one-step procedure without impairing cell viability. The protocol is also applicable to a dual specific CAR (tandem CAR). Except for CD39, T cell activation/exhaustion markers were not upregulated after separation. Purified CAR T cells retained their functionality with respect to antigen-specific cytokine secretion, cytotoxicity, and the capacity to proliferate and eliminate cognate tumor cells upon repetitive stimulation. Collectively, the one-step protocol for purifying CAR T cells extends the toolbox for preclinical research and specifically for clinical CAR T cell manufacturing.

Current progress of chimeric antigen receptor (CAR) T versus CAR NK cell for immunotherapy of solid tumors

Equipping cancer-fighting immune cells with chimeric antigen receptor (CAR) has gained immense attention for cancer treatment. CAR-engineered T cells (CAR T cells) are the first immune-engineered cells that have achieved brilliant results in anti-cancer therapy. Despite promising anti-cancer features, CAR T cells could also cause fatal side effects and have shown inadequate efficacy in some studies. This has led to the introduction of other candidates for CAR transduction, e.g., Natural killer cells (NK cells). Regarding the better safety profile and anti-cancer properties, CAR-armored NK cells (CAR NK cells) could be a beneficial and suitable alternative to CAR T cells. Since introducing these two cells as anti-cancer structures, several studies have investigated their efficacy and safety, and most of them have focused on hematological malignancies. Solid tumors have unique properties that make them more resistant and less curable cancers than hematological malignancies. In this review article, we conduct a comprehensive review of the structure and properties of CAR NK and CAR T cells, compare the recent experience of immunotherapy with CAR T and CAR NK cells in various solid cancers, and overview current challenges and future solutions to battle solid cancers using CARNK cells.

The persistence and antitumor efficacy of CAR-T cells are modulated by tonic signaling within the CDR

Chimeric antigen receptor (CAR) T cell therapy has demonstrated remarkable clinical efficacy, but challenges related to relapse and CAR-T cell exhaustion persist. One contributing factor to this exhaustion is CAR tonic signaling, where CAR-T cells self-activate without antigen stimulation, leading to reduced persistence and impaired antitumor activity. To address this issue, we conducted a preclinical study evaluating tonic signaling using nanobody-derived CAR-T cells. Our investigation revealed that specific characteristics of the complementary determining regions (CDRs), including low solubility, polarity, positive charge, energy, and area of ionic and positive CDR patches of amino acids, were associated with low antigen-independent tonic signaling. Significantly, we observed that stronger tonic signaling directly impacted CAR-T cell proliferation in vitro, consequently leading to CAR-T cell exhaustion and diminished persistence and effectiveness in vivo. Our findings provide compelling preclinical evidence and lay the foundation for the clinical assessment of CAR-T cells with distinct tonic signaling patterns. Understanding the role of CDRs in modulating tonic signaling holds promise for advancing the development of more efficient and durable CAR-T cell therapies, thereby enhancing the treatment of cancer and addressing the challenges of relapse in CAR-T cell therapy.

Challenges of CRISPR/Cas-Based Cell Therapy for Type 1 Diabetes: How Not to Engineer a "Trojan Horse"

Type 1 diabetes mellitus (T1D) is an autoimmune disease caused by the destruction of insulin-producing β-cells in the pancreas by cytotoxic T-cells. To date, there are no drugs that can prevent the development of T1D. Insulin replacement therapy is the standard care for patients with T1D. This treatment is life-saving, but is expensive, can lead to acute and long-term complications, and results in reduced overall life expectancy. This has stimulated the research and development of alternative treatments for T1D. In this review, we consider potential therapies for T1D using cellular regenerative medicine approaches with a focus on CRISPR/Cas-engineered cellular products. However, CRISPR/Cas as a genome editing tool has several drawbacks that should be considered for safe and efficient cell engineering. In addition, cellular engineering approaches themselves pose a hidden threat. The purpose of this review is to critically discuss novel strategies for the treatment of T1D using genome editing technology. A well-designed approach to β-cell derivation using CRISPR/Cas-based genome editing technology will significantly reduce the risk of incorrectly engineered cell products that could behave as a "Trojan horse".

Advancing CART therapy for acute myeloid leukemia: recent breakthroughs and strategies for future development

Chimeric antigen receptor (CAR) T therapies are being developed for acute myeloid leukemia (AML) on the basis of the results obtained for other haematological malignancies and the need of new treatments for relapsed and refractory AML. The biggest challenge of CART therapy for AML is to identify a specific target antigen, since antigens expressed in AML cells are usually shared with healthy haematopoietic stem cells (HSC). The concomitant expression of the target antigen on both tumour and HSC may lead to on-target/off-tumour toxicity. In this review, we guide researchers to design, develop, and translate to the clinic CART therapies for the treatment of AML. Specifically, we describe what issues have to be considered to design these therapies; what in vitro and in vivo assays can be used to prove their efficacy and safety; and what expertise and facilities are needed to treat and manage patients at the hospital.

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

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

Chimeric antigen receptor T cells march into T cell malignancies

T cell malignancies represent a diverse collection of leukemia/lymphoma conditions in humans arising from aberrant T cells. Such malignancies are often associated with poor clinical prognoses, cancer relapse, as well as progressive resistance to anti-cancer treatments. While chimeric antigen receptor (CAR) T cell immunotherapy has emerged as a revolutionary treatment strategy that is highly effective for treating B cell malignancies, its application as a treatment for T cell malignancies remains to be better explored. Furthermore, the effectiveness of CAR-T treatment in T cell malignancies is significantly influenced by the quality of contamination-free CAR-T cells during the manufacturing process, as well as by multiple characteristics of such malignancies, including the sharing of antigens across normal and malignant T cells, fratricide, and T cell aplasia. In this review, we provide a detailed account of the current developments in the clinical application of CAR-T therapy to treat T cell malignancies, offer strategies for addressing current challenges, and outline a roadmap toward its effective implementation as a broad treatment option for this condition.

Enrichment strategies to enhance genome editing

Genome editing technologies hold great promise for numerous applications including the understanding of cellular and disease mechanisms and the development of gene and cellular therapies. Achieving high editing frequencies is critical to these research areas and to achieve the overall goal of being able to manipulate any target with any desired genetic outcome. However, gene editing technologies sometimes suffer from low editing efficiencies due to several challenges. This is often the case for emerging gene editing technologies, which require assistance for translation into broader applications. Enrichment strategies can support this goal by selecting gene edited cells from non-edited cells. In this review, we elucidate the different enrichment strategies, their many applications in non-clinical and clinical settings, and the remaining need for novel strategies to further improve genome research and gene and cellular therapy studies.

Therapeutic effects of anti-GM2 CAR-T cells expressing IL-7 and CCL19 for GM2-positive solid cancer in xenograft model

BACKGROUND

While chimeric antigen receptor (CAR)-T cell therapy has demonstrated excellent efficacy in hematopoietic malignancies, its clinical application in solid cancers has yet to be achieved. One of the reasons for such hurdle is a lack of suitable CAR targets in solid cancers.

METHODS

GM2 is one of the gangliosides, a group of glycosphingolipids with sialic acid in the glycan, and overexpressed in various types of solid cancers. In this study, by using interleukin (IL)-7 and chemokine (C-C motif) ligand 19 (CCL19)-producing human CAR-T system which we previously developed, a possibility of GM2 as a solid tumor target for CAR-T cell therapy was explored in a mouse model with human small-cell lung cancer.

RESULTS

Treatment with anti-GM2 IL-7/CCL19-producing CAR-T cells induced complete tumor regression along with an abundant T cell infiltration into the solid tumor tissue and long-term memory responses, without any detectable adverse events. In addition, as measures to control cytokine-release syndrome and neurotoxicity which could occur in association with clinical use of CAR-T cells, we incorporated Herpes simplex virus-thymidine kinase (HSV-TK), a suicide system to trigger apoptosis by administration of ganciclovir (GCV). HSV-TK-expressing anti-GM2 IL-7/CCL19-producing human CAR-T cells were efficiently eliminated by GCV administration in vivo.

CONCLUSIONS

Our study revealed the promising therapeutic efficacy of anti-GM2 IL-7/CCL19-producing human CAR-T cells with an enhanced safety for clinical application in the treatment of patients with GM2-positive solid cancers.

Advances in the Pathogenesis and Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a genetically predisposed, female-predominant disease, characterized by multiple organ damage, that in its most severe forms can be life-threatening. The pathogenesis of SLE is complex and involves cells of both innate and adaptive immunity. The distinguishing feature of SLE is the production of autoantibodies, with the formation of immune complexes that precipitate at the vascular level, causing organ damage. Although progress in understanding the pathogenesis of SLE has been slower than in other rheumatic diseases, new knowledge has recently led to the development of effective targeted therapies, that hold out hope for personalized therapy. However, the new drugs available to date are still an adjunct to conventional therapy, which is known to be toxic in the short and long term. The purpose of this review is to summarize recent advances in understanding the pathogenesis of the disease and discuss the results obtained from the use of new targeted drugs, with a look at future therapies that may be used in the absence of the current standard of care or may even cure this serious systemic autoimmune disease.

Challenges of Anti-Mesothelin CAR-T-Cell Therapy

Chimeric antigen receptor (CAR)-T-cell therapy is a kind of adoptive T-cell therapy (ACT) that has developed rapidly in recent years. Mesothelin (MSLN) is a tumor-associated antigen (TAA) that is highly expressed in various solid tumors and is an important target antigen for the development of new immunotherapies for solid tumors. This article reviews the clinical research status, obstacles, advancements and challenges of anti-MSLN CAR-T-cell therapy. Clinical trials on anti-MSLN CAR-T cells show that they have a high safety profile but limited efficacy. At present, local administration and introduction of new modifications are being used to enhance proliferation and persistence and to improve the efficacy and safety of anti-MSLN CAR-T cells. A number of clinical and basic studies have shown that the curative effect of combining this therapy with standard therapy is significantly better than that of monotherapy.

Tocilizumab-coated solid lipid nanoparticles loaded with cannabidiol as a novel drug delivery strategy for treating COVID-19: A review

Commonly used clinical strategies against coronavirus disease 19 (COVID-19), including the potential role of monoclonal antibodies for site-specific targeted drug delivery, are discussed here. Solid lipid nanoparticles (SLN) tailored with tocilizumab (TCZ) and loading cannabidiol (CBD) are proposed for the treatment of COVID-19 by oral route. TCZ, as a humanized IgG1 monoclonal antibody and an interleukin-6 (IL-6) receptor agonist, can attenuate cytokine storm in patients infected with SARS-CoV-2. CBD (an anti-inflammatory cannabinoid and TCZ agonist) alleviates anxiety, schizophrenia, and depression. CBD, obtained from Cannabis sativa L., is known to modulate gene expression and inflammation and also shows anti-cancer and anti-inflammatory properties. It has also been recognized to modulate angiotensin-converting enzyme II (ACE2) expression in SARS-CoV-2 target tissues. It has already been proven that immunosuppressive drugs targeting the IL-6 receptor may ameliorate lethal inflammatory responses in COVID-19 patients. TCZ, as an immunosuppressive drug, is mainly used to treat rheumatoid arthritis, although several attempts have been made to use it in the active hyperinflammatory phase of COVID-19, with promising outcomes. TCZ is currently administered intravenously. It this review, we discuss the potential advances on the use of SLN for oral administration of TCZ-tailored CBD-loaded SLN, as an innovative platform for managing SARS-CoV-2 and related infections.

Generation of Human 293-F Suspension NGFR Knockout Cells Using CRISPR/Cas9 Coupled to Fluorescent Protein Expression

Suspension cells derived from human embryonic kidney cells (HEK 293) are attractive cell lines for retroviral vector production in gene therapeutic development studies and applications. The low-affinity nerve growth factor receptor (NGFR) is a genetic marker frequently used as a reporter gene in transfer vectors to detect and enrich genetically modified cells. However, the HEK 293 cell line and its derivatives endogenously express the NGFR protein. To eradicate the high background NGFR expression in future retroviral vector packaging cells, we here employed the CRISPR/Cas9 system to generate human suspension 293-F NGFR knockout cells. The expression of a fluorescent protein coupled via a 2A peptide motif to the NGFR targeting Cas9 endonuclease enabled the simultaneous depletion of cells expressing Cas9 and remaining NGFR-positive cells. Thus, a pure population of NGFR-negative 293-F cells lacking persistent Cas9 expression was obtained in a simple and easily applicable procedure.

New insights in systemic lupus erythematosus: From regulatory T cells to CAR-T-cell strategies

Systemic lupus erythematous is a heterogeneous autoimmune disease with potentially multiorgan damage. Its complex etiopathogenesis involves genetic, environmental, and hormonal factors, leading to a loss of self-tolerance with autoantibody production and immune complex formation. Given the relevance of autoreactive B lymphocytes, several therapeutic approaches have been made targeting these cells. However, the disease remains incurable, reflecting an unmet need for effective strategies. Novel therapeutic concepts have been investigated to provide more specific and sustainable disease modification compared with continued immunosuppression. Autologous hematopoietic stem cell transplantation has already provided the proof-of-concept that immunodepletion can lead to durable treatment-free remissions, albeit with significant treatment-related toxicity. In the future, chimeric antigen receptor-T-cell therapies, for example, CD19 chimeric antigen receptor-T, may provide a more effective lymphodepletion and with less toxicity than autologous hematopoietic stem cell transplantation. An emerging field is to enhance immune tolerance by exploiting the suppressive capacities of regulatory T cells, which are dysfunctional in patients with systemic lupus erythematous, and thus resemble promising candidates for adoptive cell therapy. Different approaches have been developed in this area, from polyclonal to genetically engineered regulatory T cells. In this article, we discuss the current evidence and future directions of cellular therapies for the treatment of systemic lupus erythematous, including hematopoietic stem cell transplantation and advanced regulatory T-cell-based cellular therapies.

CAR-T cell potency: from structural elements to vector backbone components

Chimeric antigen receptor (CAR) T cell therapy, in which a patient’s own T lymphocytes are engineered to recognize and kill cancer cells, has achieved remarkable success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Once equipped with a CAR construct, T cells act as living drugs and recognize and eliminate the target tumor cells in an MHC-independent manner. In this review, we first described all structural modular of CAR in detail, focusing on more recent findings. We then pointed out behind-the-scene elements contributing to CAR expression and reviewed how CAR expression can be drastically affected by the elements embedded in the viral vector backbone.

Optimized NGFR-derived hinges for rapid and efficient enrichment and detection of CAR T cells in vitro and in vivo

Chimeric antigen receptor (CAR) T cell therapy has demonstrated unprecedented success with high remission rates for heavily pretreated patients with hematological malignancies. The hinge connecting the extracellular antigen recognition unit to the transmembrane domain provides the length and flexibility of the CAR constructs and ensures that the CAR can reach the target antigen and mediate recognition and killing of target cells. The hinge can also include specific amino acid sequences to improve CAR expression, influence T cell proliferation, and facilitate CAR T cell detection, enrichment, and even elimination. Here, we report the generation of two novel hinge domains derived from the low-affinity p75 chain of the human nerve growth factor receptor (NGFR), termed N3 and N4, which, when incorporated into the CAR backbone, allow detection as well as high-grade enrichment of CAR T cells with GMP-compatible immunomagnetic reagents. After optimizing the MACS protocol for excellent CAR T cell purity and yield, we demonstrated that N3- and N4-hinged CAR T cells are as efficacious as their CD8-hinged counterparts in vitro against hematological blasts and also in vivo in the control of acute monocytic leukemia in an immunodeficient mouse xenograft model. Thus, both hinges could potentially be an integral part of future CAR designs and universally applicable in clinical applications.

Application and Design of Switches Used in CAR

Among the many oncology therapies, few have generated as much excitement as CAR-T. The success of CAR therapy would not have been possible without the many discoveries that preceded it, most notably, the Nobel Prize-winning breakthroughs in cellular immunity. However, despite the fact that CAR-T already offers not only hope for development, but measurable results in the treatment of hematological malignancies, CAR-T still cannot be safely applied to solid tumors. The reason for this is, among other things, the lack of tumor-specific antigens which, in therapy, threatens to cause a lethal attack of lymphocytes on healthy cells. In the case of hematological malignancies, dangerous complications such as cytokine release syndrome may occur. Scientists have responded to these clinical challenges with molecular switches. They make it possible to remotely control CAR lymphocytes after they have already been administered to the patient. Moreover, they offer many additional capabilities. For example, they can be used to switch CAR antigenic specificity, create logic gates, or produce local activation under heat or light. They can also be coupled with costimulatory domains, used for the regulation of interleukin secretion, or to prevent CAR exhaustion. More complex modifications will probably require a combination of reprogramming (iPSc) technology with genome editing (CRISPR) and allogenic (off the shelf) CAR-T production.

Engineering Next-Generation CAR-T Cells: Overcoming Tumor Hypoxia and Metabolism

T cells engineered to express chimeric antigen receptors (CARs) have shown remarkable success in treating B-cell malignancies, reflected by multiple US Food and Drug Administration-approved CAR-T cell products currently on the market. However, various obstacles have thus far limited the use of approved products and constrained the efficacy of CAR-T cell therapy against solid tumors. Overcoming these obstacles will necessitate multidimensional CAR-T cell engineering approaches and better understanding of the intricate tumor microenvironment (TME). Key challenges include treatment-related toxicity, antigen escape and heterogeneity, and the highly immunosuppressive profile of the TME. Notably, the hypoxic and nutrient-deprived nature of the TME severely attenuates CAR-T cell fitness and efficacy, highlighting the need for more sophisticated engineering strategies. In this review, we examine recent advances in protein- and cell-engineering strategies to improve CAR-T cell safety and efficacy, with an emphasis on overcoming immunosuppression induced by tumor metabolism and hypoxia.

Development of Cancer Immunotherapies

Cancer immunotherapy, or the utilization of components of the immune system to target and eliminate cancer, has become a highly active area of research in the past several decades and a common treatment strategy for several cancer types. The concept of harnessing the immune system for this purpose originated over 100 years ago when a physician by the name of William Coley successfully treated several of his cancer patients with a combination of live and attenuated bacteria, later known as "Coley's Toxins", after observing a subset of prior patients enter remission following their diagnosis with the common bacterial infection, erysipelas. However, it was not until late in the twentieth century that cancer immunotherapies were developed for widespread use, thereby transforming the treatment landscape of numerous cancer types. Pivotal studies elucidating molecular and cellular functions of immune cells, such as the discovery of IL-2 and production of monoclonal antibodies, fostered the development of novel techniques for studying the immune system and ultimately the development and approval of several cancer immunotherapies by the United States Food and Drug Association in the 1980s and 1990s, including the tuberculosis vaccine-Bacillus Calmette-Guérin, IL-2, and the CD20-targeting monoclonal antibody. Approval of the first therapeutic cancer vaccine, Sipuleucel-T, for the treatment of metastatic castration-resistant prostate cancer and the groundbreaking success and approval of immune checkpoint inhibitors and chimeric antigen receptor T cell therapy in the last decade, have driven an explosion of interest in and pursuit of novel cancer immunotherapy strategies. A broad range of modalities ranging from antibodies to adoptive T cell therapies is under investigation for the generalized treatment of a broad spectrum of cancers as well as personalized medicine. This chapter will focus on the recent advances, current strategies, and future outlook of immunotherapy development for the treatment of cancer.

Advances in CAR-T cell therapy for malignant solid tumors

T cells modified by chimeric antigen receptor (CAR) have the advantage of major histocompatibility complex-independent recognition of tumor-associated antigens, so can achieve efficient response to tumor targets. Chimeric antigen receptor (CAR) T cell therapy has shown a good therapeutic effect in hematological malignancies; however, its efficacy is generally not satisfactory for solid tumors. The reasons include the lack of tumor specific antigen target on solid tumors, the uncertainty of homing ability of engineered T cells and the inhibitory immune microenvironment of tumors. In clinical trials, the targets of CAR-T cell therapy for solid tumors are mainly disialoganglioside (GD2), claudin-18 isoform 2 (CLDN18.2), mesenchymal, B7 homolog 3 (B7H3), glypican (GPC) 3 and epidermal growth factor receptor variant Ш (EGFRvШ)Ⅲ. Combination of CAR-T cells with oncolytic viruses, tyrosine kinase inhibitors, and programmed death ligand-1 monoclonal antibodies may increase its efficacy. The CAR-T cell therapy for solid tumors can be optimized through gene editing to enhance the activity of CAR-T cells, adding corresponding regulatory components to make the activation of CAR-T cells safer and more controllable, and enhancing the persistence of CAR-T cells. In this article, we review the latest advances of CAR-T cell therapy in solid tumors to provide new insights for clinical application.

Immunotherapy in Advanced Prostate Cancer-Light at the End of the Tunnel?

Immunotherapeutic treatment approaches are now an integral part of the treatment of many solid tumors. However, attempts to integrate immunotherapy into the treatment of prostate cancer have been disappointing so far. This is due to a highly immunosuppressive, “cold” tumor microenvironment, which is characterized, for example, by the absence of cytotoxic T cells, an increased number of myeloid-derived suppressor cells or regulatory T cells, a decreased number of tumor antigens, or a defect in antigen presentation. The consequence is a reduced efficacy of many established immunotherapeutic treatments such as checkpoint inhibitors. However, a growing understanding of the underlying mechanisms of tumor–immune system interactions raises hopes that immunotherapeutic strategies can be optimized in the future. The aim of this review is to provide an overview of the current status and future directions of immunotherapy development in prostate cancer. Background information on immune response and tumor microenvironment will help to better understand current therapeutic strategies under preclinical and clinical development.

CARving the Path to Allogeneic CAR T Cell Therapy in Acute Myeloid Leukemia

Despite advances in the understanding of the genetic landscape of acute myeloid leukemia (AML) and the addition of targeted biological and epigenetic therapies to the available armamentarium, achieving long-term disease-free survival remains an unmet need. Building on growing knowledge of the interactions between leukemic cells and their bone marrow microenvironment, strategies to battle AML by immunotherapy are under investigation. In the current review we describe the advances in immunotherapy for AML, with a focus on chimeric antigen receptor (CAR) T cell therapy. CARs constitute powerful immunologic modalities, with proven clinical success in B-Cell malignancies. We discuss the challenges and possible solutions for CAR T cell therapy development in AML, and examine the path currently being paved by preclinical and clinical efforts, from autologous to allogeneic products.

Disrupting N-glycan expression on tumor cells boosts chimeric antigen receptor T cell efficacy against solid malignancies

Immunotherapy with chimeric antigen receptor (CAR)-engineered T cells showed exceptional successes in patients with refractory B cell malignancies. However, first-in-human studies in solid tumors revealed unique hurdles contributing to poor demonstration of efficacy. Understanding the determinants of tumor recognition by CAR T cells should translate into the design of strategies that can overcome resistance. Here, we show that multiple carcinomas express extracellular N-glycans, whose abundance negatively correlates with CAR T cell killing. By knocking out mannoside acetyl-glucosaminyltransferase 5 (MGAT5) in pancreatic adenocarcinoma (PAC), we showed that N-glycans protect tumors from CAR T cell killing by interfering with proper immunological synapse formation and reducing transcriptional activation, cytokine production, and cytotoxicity. To overcome this barrier, we exploited the high metabolic demand of tumors to safely inhibit N-glycans synthesis with the glucose/mannose analog 2-deoxy-d-glucose (2DG). Treatment with 2DG disrupts the N-glycan cover on tumor cells and results in enhanced CAR T cell activity in different xenograft mouse models of PAC. Moreover, 2DG treatment interferes with the PD-1-PD-L1 axis and results in a reduced exhaustion profile of tumor-infiltrating CAR T cells in vivo. The combined 2DG and CAR T cell therapy was successful against multiple carcinomas besides PAC, including those arising from the lung, ovary, and bladder, and with different clinically relevant CAR specificities, such as CD44v6 and CEA. Overall, our results indicate that tumor N-glycosylation regulates the quality and magnitude of CAR T cell responses, paving the way for the rational design of improved therapies against solid malignancies.

A novel CD34-derived hinge for rapid and efficient detection and enrichment of CAR T cells

Immunotherapy including chimeric antigen receptor (CAR) T cell therapy has revolutionized modern cancer therapy and has achieved remarkable remission and survival rates for several malignancies with historically dismal outcomes. The hinge of the CAR connects the antigen binding to the transmembrane domain and can be exploited to confer features to CAR T cells including additional stimulation, targeted elimination or detection and enrichment of the genetically modified cells. For establishing a novel hinge derived from human CD34, we systematically tested CD34 fragments of different lengths, all containing the binding site of the QBend-10 monoclonal antibody, in a FMC63-based CD19 CAR lentiviral construct. A final construct of 99 amino acids called C6 proved to be the best candidate for flow cytometry-based detection of CAR T cells and >95% enrichment of genetically modified T cells on MACS columns. The C6 hinge was functionally indistinguishable from the commonly used CD8α hinge in vitro as well as in in vivo experiments in NSG mice. We also showed that the C6 hinge can be used for a variety of different CARs and mediates high killing efficacy without unspecific activation by target antigen-negative cells, thus making C6 ideally suited as a universal hinge for CARs for clinical applications.

Improving the ability of CAR-T cells to hit solid tumors: Challenges and strategies

Chimeric antigen receptor T cell (CAR-T) therapy is a late-model of immune cell therapy that has been shown to be effective in refractory/recurrent B-cell leukemia and lymphoma. Compared with the traditional anti-tumor methods, CAR-T cell therapy has the advantages of higher specificity, stronger lethality and longer-lasting efficacy. Although CAR-T cells have made significant progress in the treatment of hematologic malignancies, diverse difficulties remain in the treatment of solid tumors, including immune escape due to tumor antigen heterogeneity, preventing entry or limiting the persistence of CAR-T cells by physical or cytokine barriers and along with other immunosuppressive molecule and cells in the tumor microenvironment (TME). Otherwise, the intracellular signaling of CAR also impact on CAR-T cells persistence. Appropriate modification of intracellular costimulatory molecular signal in the structure of CAR or coexpression of CAR and cytokines can provide a way to enhance CAR-T cells activity. Additionally, CAR-T cells dysfunction due to T cell exhaustion is associated with multi-factors, especially transcription factors, such as c-Jun, NR4A. Engineering CAR-T cells to coexpress or knockout transcription factors in favor of T_CM memory CAR-T cells differentiation was proved to prolonged the survival of CAR-T cells. Finally, combination of CAR-T cells with oncolytic viruses, nanoparticles or immune checkpoint inhibitors provides an effective measure to improve CAR-T cells function. Here, we discuss all of these advances and challenges and review promising strategies for treating solid tumors. In particular, we also highlight that CAR-T cells have enormous potential to be used in combination with other immunotherapies.

Promising Antigens for the New Frontier of Targeted Immunotherapy in Multiple Myeloma

Simple Summary

Defining the specificity and biological sequalae induced by receptors differentiated expressed in multiple myeloma cells are critical for the development of effective immunotherapies based on monoclonal antibodies. Ongoing studies continue to discover new antigens with superior tumor selectivity and defined function in regulating the pathophysiology of myeloma cells directly or indirectly in the immunosuppressive bone marrow microenvironment. Meanwhile, it is urgent to identify mechanisms of immune resistance and design more potent immunotherapies, alone and/or with best combination partners to further prolong anti-MM immunity.

Abstract

The incorporation of novel agents in recent treatments in multiple myeloma (MM) has improved the clinical outcome of patients. Specifically, the approval of monoclonal antibody (MoAb) against CD38 (daratumumab) and SLAMF7 (elotuzumab) in relapsed and refractory MM (RRMM) represents an important milestone in the development of targeted immunotherapy in MM. These MoAb-based agents significantly induce cytotoxicity of MM cells via multiple effector-dependent mechanisms and can further induce immunomodulation to repair a dysfunctional tumor immune microenvironment. Recently, targeting B cell maturation antigen (BCMA), an even MM-specific antigen, has shown high therapeutic activities by chimeric antigen receptor T cells (CAR T), antibody-drug conjugate (ADC), bispecific T-cell engager (BiTE), as well as bispecific antibody (BiAb), with some already approved for heavily pretreated RRMM patients. New antigens, such as orphan G protein-coupled receptor class C group 5 member D (GPRC5D) and FcRH5, were identified and rapidly moved to ongoing clinical studies. We here summarized the pathobiological function of key MM antigens and the status of the corresponding immunotherapies. The potential challenges and emerging treatment strategies are also discussed.

Genetically Modified T Cells for Esophageal Cancer Therapy: A Promising Clinical Application

Esophageal cancer is an exceedingly aggressive and malignant cancer that imposes a substantial burden on patients and their families. It is usually treated with surgery, chemotherapy, radiotherapy, and molecular-targeted therapy. Immunotherapy is a novel treatment modality for esophageal cancer wherein genetically engineered adoptive cell therapy is utilized, which modifies immune cells to attack cancer cells. Using chimeric antigen receptor (CAR) or T cell receptor (TCR) modified T cells yielded demonstrably encouraging efficacy in patients. CAR-T cell therapy has shown robust clinical results for malignant hematological diseases, particularly in B cell-derived malignancies. Natural killer (NK) cells could serve as another reliable and safe CAR engineering platform, and CAR-NK cell therapy could be a more generalized approach for cancer immunotherapy because NK cells are histocompatibility-independent. TCR-T cells can detect a broad range of targeted antigens within subcellular compartments and hold great potential for use in cancer therapy. Numerous studies have been conducted to evaluate the efficacy and feasibility of CAR and TCR based adoptive cell therapies (ACT). A comprehensive understanding of genetically-modified T cell technologies can facilitate the clinical translation of these adoptive cell-based immunotherapies. Here, we systematically review the state-of-the-art knowledge on genetically-modified T-cell therapy and provide a summary of preclinical and clinical trials of CAR and TCR-transgenic ACT.

Theranostic cells: emerging clinical applications of synthetic biology

Synthetic biology seeks to redesign biological systems to perform novel functions in a predictable manner. Recent advances in bacterial and mammalian cell engineering include the development of cells that function in biological samples or within the body as minimally invasive diagnostics or theranostics for the real-time regulation of complex diseased states. Ex vivo and in vivo cell-based biosensors and therapeutics have been developed to target a wide range of diseases including cancer, microbiome dysbiosis and autoimmune and metabolic diseases. While probiotic therapies have advanced to clinical trials, chimeric antigen receptor (CAR) T cell therapies have received regulatory approval, exemplifying the clinical potential of cellular therapies. This Review discusses preclinical and clinical applications of bacterial and mammalian sensing and drug delivery platforms as well as the underlying biological designs that could enable new classes of cell diagnostics and therapeutics. Additionally, we describe challenges that must be overcome for more rapid and safer clinical use of engineered systems.

Natural Flt3Lg-Based Chimeric Antigen Receptor (Flt3-CAR) T Cells Successfully Target Flt3 on AML Cell Lines

Relapsed/refractory acute myeloid leukemia (AML) cannot be cured with chemotherapy alone, as the blasts survive the treatment. Chimeric antigen receptor (CAR) approaches for AML are being actively developed. CARs promote immune reactions through recognition of the target molecular epitopes at the surface of cancer cells. The recognition involves the extracellular portion of the CAR protein, which corresponds to either the antibody or the physiological binding partner of the targeted antigen. Here, we design a chimeric receptor with a full-length natural Flt3-ligand recognition module that targets Flt3 tyrosine kinase, known as an adverse marker in AML. We demonstrate specific killing of Flt3-positive THP-1 cells by Flt3-CAR T cells and the lack of cytotoxicity towards Flt3-negative U937 cells. We prove that the inherent cytolytic capacity of T cells is essential for the killing. Finally, we confirm the authenticity of targeting by its competitive dose-dependent inhibition with a soluble Flt3-ligand. The developed system can be viewed as a non-immunogenic functional equivalent of scFv-mediated targeting. The robust in vitro antitumor effects of Flt3-CAR T cells, combined with their low off-target cytotoxicity, hold promise for AML treatment.

Myeloid cell-based delivery of IFN-γ reprograms the leukemia microenvironment and induces anti-tumoral immune responses

The immunosuppressive microenvironment surrounding tumor cells represents a key cause of treatment failure. Therefore, immunotherapies aimed at reprogramming the immune system have largely spread in the past years. We employed gene transfer into hematopoietic stem and progenitor cells to selectively express anti-tumoral cytokines in tumor-infiltrating monocytes/macrophages. We show that interferon-γ (IFN-γ) reduced tumor progression in mouse models of B-cell acute lymphoblastic leukemia (B-ALL) and colorectal carcinoma (MC38). Its activity depended on the immune system's capacity to respond to IFN-γ and drove the counter-selection of leukemia cells expressing surrogate antigens. Gene-based IFN-γ delivery induced antigen presentation in the myeloid compartment and on leukemia cells, leading to a wave of T cell recruitment and activation, with enhanced clonal expansion of cytotoxic CD8+ T lymphocytes. The activity of IFN-γ was further enhanced by either co-delivery of tumor necrosis factor-α (TNF-α) or by drugs blocking immunosuppressive escape pathways, with the potential to obtain durable responses.

Droplet digital PCR allows vector copy number assessment and monitoring of experimental CAR T cells in murine xenograft models or approved CD19 CAR T cell-treated patients

BACKGROUND

Genetically engineered chimeric antigen receptor (CAR) T lymphocytes are promising therapeutic tools for cancer. Four CAR T cell drugs, including tisagenlecleucel (tisa-cel) and axicabtagene-ciloleucel (axi-cel), all targeting CD19, are currently approved for treating B cell malignancies. Flow cytometry (FC) remains the standard for monitoring CAR T cells using a recombinant biotinylated target protein. Nevertheless, there is a need for additional tools, and the challenge is to develop an easy, relevant, highly sensitive, reproducible, and inexpensive detection method. Molecular tools can meet this need to specifically monitor long-term persistent CAR T cells.

METHODS

Based on 2 experimental CAR T cell constructs, IL-1RAP and CS1, we designed 2 quantitative digital droplet (ddPCR) PCR assays. By targeting the 4.1BB/CD3z (28BBz) or 28/CD3z (28z) junction area, we demonstrated that PCR assays can be applied to approved CD19 CAR T drugs. Both 28z and 28BBz ddPCR assays allow determination of the average vector copy number (VCN) per cell. We confirmed that the VCN is dependent on the multiplicity of infection and verified that the VCN of our experimental or GMP-like IL-1RAP CAR T cells met the requirement (< 5 VCN/cell) for delivery to the clinical department, similar to approved axi-cel or tisa-cel drugs.

RESULTS

28BBz and 28z ddPCR assays applied to 2 tumoral (acute myeloid leukemia (AML) or multiple myeloma (MM) xenograft humanized NSG mouse models allowed us to quantify the early expansion (up to day 30) of CAR T cells after injection. Interestingly, following initial expansion, when circulating CAR T cells were challenged with the tumor, we noted a second expansion phase. Investigation of the bone marrow, spleen and lung showed that CAR T cells disseminated more within these tissues in mice previously injected with leukemic cell lines. Finally, circulating CAR T cell ddPCR monitoring of R/R acute lymphoid leukemia or diffuse large B cell lymphoma (n = 10 for tisa-cel and n = 7 for axi-cel) patients treated with both approved CAR T cells allowed detection of early expansion, which was highly correlated with FC, as well as long-term persistence (up to 450 days), while FC failed to detect these events.

CONCLUSION

Overall, we designed and validated 2 ddPCR assays allowing routine or preclinical monitoring of early- and long-term circulating approved or experimental CAR T cells, including our own IL-1RAP CAR T cells, which will be evaluated in an upcoming phase I clinical trial.

Characterization and Functional Analysis of CD44v6.CAR T Cells Endowed with a New Low-Affinity Nerve Growth Factor Receptor-Based Spacer

Effectiveness of adoptively transferred chimeric antigen receptor (CAR) T cells strongly depends on the quality of CAR-mediated interaction of the effector cells with the target antigen on tumor cells. A major role in this interaction is played by the affinity of the single-chain variable fragment (scFv) for the antigen, and by the CAR design. In particular, the spacer domain may impact on the CAR T cell function by affecting the length and flexibility of the resulting CAR. This study addresses the need to improve the manufacturing process and the antitumor activity of CD44v6-specific CAR T cells by defining the optimal structure of a spacer region derived from the extracellular domain of the human low-affinity nerve growth factor receptor (LNGFR). We tailored the LNGFR spacer to modulate CAR length to efficiently recognize distal or proximal epitopes and to allow selection of transduced CAR T cells by the use of clinical-grade validated manufacturing systems. The different LNGFR spacers investigated in this study are responsible for the generation of CAR T cells with a different memory phenotype, which is mainly related to the level of CAR expression and the extent of the associated tonic signaling. In particular, the CD44v6-NWN2.CAR T cells are enriched in central memory cells and show improved in vitro functions in terms of killing capability, and in vivo antitumor activity against hematological and solid tumors. Clinical Trial Registration numbers: clinicaltrial.gov NCT04097301; ClinicalTrials.gov, NCT00423124.

Chimeric antigen receptor natural killer (CAR-NK) cell design and engineering for cancer therapy

Due to their efficient recognition and lysis of malignant cells, natural killer (NK) cells are considered as specialized immune cells that can be genetically modified to obtain capable effector cells for adoptive cellular treatment of cancer patients. However, biological and technical hurdles related to gene delivery into NK cells have dramatically restrained progress. Recent technological advancements, including improved cell expansion techniques, chimeric antigen receptors (CAR), CRISPR/Cas9 gene editing and enhanced viral transduction and electroporation, have endowed comprehensive generation and characterization of genetically modified NK cells. These promising developments assist scientists and physicians to design better applications of NK cells in clinical therapy. Notably, redirecting NK cells using CARs holds important promise for cancer immunotherapy. Various preclinical and a limited number of clinical studies using CAR-NK cells show promising results: efficient elimination of target cells without side effects, such as cytokine release syndrome and neurotoxicity which are seen in CAR-T therapies. In this review, we focus on the details of CAR-NK technology, including the design of efficient and safe CAR constructs and associated NK cell engineering techniques: the vehicles to deliver the CAR-containing transgene, detection methods for CARs, as well as NK cell sources and NK cell expansion. We summarize the current CAR-NK cell literature and include valuable lessons learned from the CAR-T cell field. This review also provides an outlook on how these approaches may transform current clinical products and protocols for cancer treatment.

A SARS-CoV-2 targeted siRNA-nanoparticle therapy for COVID-19

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in humans. Despite several emerging vaccines, there remains no verifiable therapeutic targeted specifically to the virus. Here we present a highly effective siRNA therapeutic against SARS-CoV-2 infection using a novel lipid nanoparticle delivery system. Multiple small-interfering RNAs (siRNAs) targeting highly conserved regions of the SARS-CoV-2 virus were screened and three candidate siRNAs emerged that effectively inhibit virus by greater than 90% either alone or in combination with one another. We simultaneously developed and screened two novel lipid nanoparticle formulations for the delivery of these candidate siRNA therapeutics to the lungs, an organ that incurs immense damage during SARS-CoV-2 infection. Encapsulation of siRNAs in these LNPs followed by in vivo injection demonstrated robust repression of virus in the lungs and a pronounced survival advantage to the treated mice. Our LNP-siRNA approaches are scalable and can be administered upon the first sign of SARS-CoV-2 infection in humans. We suggest that an siRNA-LNP therapeutic approach could prove highly useful in treating COVID-19 disease as an adjunctive therapy to current vaccine strategies.

CAR-T cell persistence in the treatment of leukemia and lymphoma

Chimeric antigen receptor (CAR) T cells have emerged as a powerful therapeutic modality for cancer. Following encouraging clinical results, autologous anti-CD19 CAR-T cells first secured regulatory approval from the U.S. Food and Drug Administration in 2017 for the treatment of pediatric B cell acute lymphoblastic leukemia and for diffuse large B cell lymphoma (DLBCL), followed recently by mantle cell lymphoma. While long-term immunosurveillance is among the most important requirements for durable remissions in leukemia and a major potential benefit of immunotherapy, the exact determinants of CAR-T cell persistence remain elusive. Furthermore, it is less clear that long-term persistence is required for durable remission in lymphoma. In this review, we aim to describe the factors governing CAR-T cell persistence as well as unique approaches to exert control over engineered lymphocyte populations post-infusion. Additionally, we explore potential risks and associated clinical considerations arising from prolonged surveillance by highly reactive cytotoxic T lymphocytes.

Arming Immune Cells for Battle: A Brief Journey through the Advancements of T and NK Cell Immunotherapy

Simple Summary

This review is intended to provide an overview on the history and recent advances of T cell and natural killer (NK) cell-based immunotherapy. While the thymus was discovered as the origin of T cells in the 1960s, and NK cells were first described in 1975, the clinical application of adoptive cell therapies (ACT) only began in the early 1980s with the first lymphokine activated killer (LAK) cell product for the treatment of cancer patients. Over the past decades, further immunotherapies have been developed, including ACT using cytokine-induced killer (CIK) cells, products based on the NK cell line NK-92 as well as specific T and NK cell preparations. Recent advances have successfully improved the effectiveness of T, NK, CIK or NK-92 cells towards tumor-targeting antigens generated by genetic engineering of the immune cells. Herein, we summarize the promising development of ACT over the past decades in the fight against cancer.

Abstract

The promising development of adoptive immunotherapy over the last four decades has revealed numerous therapeutic approaches in which dedicated immune cells are modified and administered to eliminate malignant cells. Starting in the early 1980s, lymphokine activated killer (LAK) cells were the first ex vivo generated NK cell-enriched products utilized for adoptive immunotherapy. Over the past decades, various immunotherapies have been developed, including cytokine-induced killer (CIK) cells, as a peripheral blood mononuclear cells (PBMCs)-based therapeutic product, the adoptive transfer of specific T and NK cell products, and the NK cell line NK-92. In addition to allogeneic NK cells, NK-92 cell products represent a possible “off-the-shelf” therapeutic concept. Recent approaches have successfully enhanced the specificity and cytotoxicity of T, NK, CIK or NK-92 cells towards tumor-specific or associated target antigens generated by genetic engineering of the immune cells, e.g., to express a chimeric antigen receptor (CAR). Here, we will look into the history and recent developments of T and NK cell-based immunotherapy.

Recent advances and discoveries in the mechanisms and functions of CAR T cells

This Review discusses the major advances and changes made over the past 3 years to our understanding of chimeric antigen receptor (CAR) T cell efficacy and safety. Recently, the field has gained insight into how various molecular modules of the CAR influence signalling and function. We report on mechanisms of toxicity and resistance as well as novel engineering and pharmaceutical interventions to overcome these challenges. Looking forward, we discuss new targets and indications for CAR T cell therapy expected to reach the clinic in the next 1-2 years. We also consider some new studies that have implications for the future of CAR T cell therapies, including changes to manufacturing, allogeneic products and drug-regulatable CAR T cells.

Chimeric Antigen Receptor (CAR) T Cell Therapy for Cancer. Challenges and Opportunities: An Overview

The use of immunotherapy as an alternative treatment for cancer patients has become of great interest in the scientific community as it is required to overcome many of the currently unsolved problems such as tumor escape, immunosuppression and unwanted unspecific toxicity. The use of chimeric antigen receptor T cells has been a very successful strategy in some hematologic malignancies. However, the application of CAR T cells has been limited to solid tumors, and this has aimed the development of new generation of CARs with enhanced effectivity and specificity. Here, we review the state of the art of CAR T cell therapy with special emphasis on the current challenges and opportunities.

Current Progress in CAR-T Cell Therapy for Hematological Malignancies

Immunotherapies, such as monoclonal antibody therapy and checkpoint inhibitor therapy, have shown inspiring clinical effects for the treatment of cancer. Chimeric antigen receptor T (CAR-T) cells therapy was an efficacious therapeutic approach treating hematological malignancies and encouraging results have been achieved. Three kinds of CAR-T cell therapies, Kymriah (tisagenlecleucel), Yescarta (axicabtagene ciloleucel), were approved for clinical application in 2017 and Tecartus (brexucabtagene autoleucel) was approved in 2020. Despite some progress have been made in treating multiple hematologic tumors, threats still remain for the application of CAR-T cell therapy considering its toxicities and gaps in knowledge. To further comprehend present research status and trends, the review concentrates on CAR-T technologies, applications, adverse effects and safety measures about CAR-T cell therapy in hematological neoplasms. We believe that CAR-T cell therapy will exhibit superior safety and efficacy in the future and have potential to be a mainstream therapeutic choice for the elimination of hematologic tumor.

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.

Clinical CAR-T Cell and Oncolytic Virotherapy for Cancer Treatment

Immunotherapy has recently garnered success with the induction of clinical responses in tumors, which are traditionally associated with poor outcomes. Chimeric antigen receptor T (CAR-T) cells and oncolytic viruses (OVs) have emerged as promising cancer immunotherapy agents. Herein, we provide an overview of the current clinical status of CAR-T cell and OV therapies. While preclinical studies have demonstrated curative potential, the benefit of CAR-T cells and OVs as single-agent treatments remains limited to a subset of patients. Combinations of different targeted therapies may be required to achieve efficient, durable responses against heterogeneous tumors, as well as the microenvironment. Using a combinatorial approach to take advantage of the unique features of CAR-T cells and OVs with other treatments can produce additive therapeutic effects. This review also discusses ongoing clinical evaluations of these combination strategies for improved outcomes in treatment of resistant malignancies.

Immunotherapy in Hematologic Malignancies: Emerging Therapies and Novel Approaches

Immunotherapy is extensively investigated for almost all types of hematologic tumors, from preleukemic to relapse/refractory malignancies. Due to the emergence of technologies for target cell characterization, antibody design and manufacturing, as well as genome editing, immunotherapies including gene and cell therapies are becoming increasingly elaborate and diversified. Understanding the tumor immune microenvironment of the target disease is critical, as is reducing toxicity. Although there have been many successes and newly FDA-approved immunotherapies for hematologic malignancies, we have learned that insufficient efficacy due to disease relapse following treatment is one of the key obstacles for developing successful therapeutic regimens. Thus, combination therapies are also being explored. In this review, immunotherapies for each type of hematologic malignancy will be introduced, and novel targets that are under investigation will be described.

Chimeric antigen receptor T cell therapy and nephrotoxicity: From diagnosis to treatment strategies

Chimeric antigen receptor T (CAR-T) cell therapy is a breakthrough in cancer treatment. With the widespread use of this therapy, increasing evidence is available that CAR-T cell therapy is associated with acute kidney injury (AKI). Nephrologists need to understand the potential nephrotoxicity arising from CAR-T cell therapy. Determining the cause of AKI is a key factor of clinical management. This review focuses on the clinical use of CAR-T cell therapy and the cause and outcomes of nephrotoxicity with its use. We also provide clinical suggestions for clinicians towards both better diagnosis and management of AKI in those receiving CAR-T cell therapy.

Engineering CAR-T Cells for Next-Generation Cancer Therapy

T cells engineered to express chimeric antigen receptors (CARs) with tumor specificity have shown remarkable success in treating patients with hematologic malignancies and revitalized the field of adoptive cell therapy. However, realizing broader therapeutic applications of CAR-T cells necessitates engineering approaches on multiple levels to enhance efficacy and safety. Particularly, solid tumors present unique challenges due to the biological complexity of the solid-tumor microenvironment (TME). In this review, we highlight recent strategies to improve CAR-T cell therapy by engineering (1) the CAR protein, (2) T cells, and (3) the interaction between T cells and other components in the TME.

Identification of Targets to Redirect CAR T Cells in Glioblastoma and Colorectal Cancer: An Arduous Venture

The chimeric antigen receptor (CAR) is an artificial molecule engineered to induce cytolytic T cell reactions in tumors. Generally, this molecule combines an extracellular single-chain variable fragment (scFv) able to recognize tumor-associated epitopes together with the intracellular signaling domains that are required for T cell activation. When expressed by T cells, the CAR enables the recognition and subsequent destruction of cancer cells expressing the complementary antigen on their surface. Although the clinical application for CAR T cells is currently limited to some hematological malignancies, researchers are trying to develop CAR T cell-based therapies for the treatment of solid tumors. However, while in the case of CD19, or other targets restricted to the hematopoietic compartment, the toxicity is limited and manageable, the scarcity of specific antigens expressed by solid tumors and not by healthy cells from vital organs makes the clinical development of CAR T cells in this context particularly challenging. Here we summarize relevant research and clinical trials conducted to redirect CAR T cells to surface antigens in solid tumors and cancer stem cells with a focus on colorectal cancer and glioblastoma. Finally, we will discuss current knowledge of altered glycosylation of CSCs and cancer cells and how these novel epitopes may help to target CAR T cell-based immunotherapy in the future.

CAR T cell therapies for patients with multiple myeloma

Despite several therapeutic advances over the past decade, multiple myeloma (MM) remains largely incurable, indicating a need for new treatment approaches. Chimeric antigen receptor (CAR) T cell therapy works by mechanisms distinct from those of other MM therapies and involves the modification of patient or donor T cells to target specific cell-surface antigens. B cell maturation antigen (BCMA) is expressed only on plasma cells, a small subset of B cells and MM cells, which makes it a suitable target antigen for such therapies. At the time of writing, data from >20 clinical trials involving anti-BCMA CAR T cells have demonstrated that patients with relapsed and/or refractory MM can achieve objective responses. These early investigations have been instrumental in demonstrating short-term safety and efficacy; however, most patients do not have disease remission lasting >18 months. Attempts to reduce or delay the onset of relapsed disease are underway and include identifying additional CAR T cell target antigens and methods of enhancing BCMA expression on MM cells. Engineering CAR T cells to enhance both the activity and safety of treatment continues to be a promising avenue for improvement. In this Review we summarize data from clinical trials that have been carried out to date, describe novel antigens that could be targeted in the future, and highlight potential future innovations that could enhance the efficacy and/or reduce the toxicities associated with CAR T cell therapies.

Emerging vistas in CAR T-cell therapy: challenges and opportunities in solid tumors

INTRODUCTION

Despite advances in modern evidence-based medicine, cancer remains a major cause of global disease-associated mortality. CAR T-cell therapy is a major histocompatibility complex (MHC)-independent immunotherapy involving adoptive cell transfer. Cancer immunotherapy witnessed a major breakthrough with the US FDA approval of the first chimeric antigen receptor (CAR) T-cell therapy Kymriah^TM (tisagenlecleucel) for relapsed or refractory (R/R) acute lymphoblastic leukemia (ALL) in August 2017 followed by approval of Yescarta® (axicabtagene ciloleucel) for R/R non-Hodgkin's lymphoma (NHL) in October 2017.

AREAS COVERED

We review the potential of CAR T-cell therapy which, despite showing great promise in hematological malignancies, faces significant challenges in targeting solid tumors. We address these challenges and discuss proposed strategies to overcome them in solid tumors. We highlight the potential of CAR T-cell therapy as cancer precision medicine and briefly discuss the 'financial toxicity' of CAR T-cell therapy.

EXPERT OPINION

Taken together, we discuss various strategies to circumvent the limitations of CAR T-cell therapy in solid tumors. Despite the rapid advances in CAR NK-cell therapies, there is immense scope for CAR T-cell therapy in solid tumors. We provide a synthetic review of CAR T-cell therapy that will drive future research and harness its full potential in cancer precision medicine for solid tumors.

Overhauling CAR T Cells to Improve Efficacy, Safety and Cost

Gene therapy is now surpassing 30 years of clinical experience and in that time a variety of approaches has been applied for the treatment of a wide range of pathologies. While the promise of gene therapy was over-stated in the 1990’s, the following decades were met with polar extremes between demonstrable success and devastating setbacks. Currently, the field of gene therapy is enjoying the rewards of overcoming the hurdles that come with turning new ideas into safe and reliable treatments, including for cancer. Among these modalities, the modification of T cells with chimeric antigen receptors (CAR-T cells) has met with clear success and holds great promise for the future treatment of cancer. We detail a series of considerations for the improvement of the CAR-T cell approach, including the design of the CAR, routes of gene transfer, introduction of CARs in natural killer and other cell types, combining the CAR approach with checkpoint blockade or oncolytic viruses, improving pre-clinical models as well as means for reducing cost and, thus, making this technology more widely available. While CAR-T cells serve as a prime example of translating novel ideas into effective treatments, certainly the lessons learned will serve to accelerate the current and future development of gene therapy drugs.