Teaching an old dog new tricks: next-generation CAR T cells

Nanotechnology-based chimeric antigen receptor T-cell therapy in treating solid tumor

Chimeric Antigen Receptor (CAR) T cells have changed the therapeutic landscape of hematological malignancies with overwhelming success. The clinical success of CAR T-cell therapy in hematologic malignancies has fueled interest in exploring the technology in solid tumors. However, the treatment of solid tumors presents a unique set of challenges compared to hematological tumors. The biggest impediments to the success of CAR T cell treatment are the paucity of tumor-specific antigens that are produced selectively and uniformly and the immunosuppressive tumor microenvironment. To overcome these significant challenges, nanotechnology has been involved to improve the efficacy of CAR-T cells. In this review, we systematically introduced the components of different generations of CARs and summarized recent innovations in nano-based CAR-T cell therapy to conquer therapeutically resistant non-hematologic malignancies, including mRNA and hydrogel-based CAR T cells delivery, photothermal-remodeling, and tumor microenvironment-based CAR T cell therapy. These nanotechnologies remarkably facilitate in vivo generation of CAR T cells and hold promise as a therapeutic platform to treat solid tumors and even other diseases.

The Proteoglycan Glypican-1 as a Possible Candidate for Innovative Targeted Therapeutic Strategies for Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) accounts for 90% of all pancreatic cancers, with a 5-year survival rate of 7% and 80% of patients diagnosed with advanced or metastatic malignancies. Despite recent advances in diagnostic testing, surgical techniques, and systemic therapies, there remain limited options for the effective treatment of PDAC. There is an urgent need to develop targeted therapies that are able to differentiate between cancerous and non-cancerous cells to reduce side effects and better inhibit tumor growth. Antibody-targeted strategies are a potentially effective option for introducing innovative therapies. Antibody-based immunotherapies and antibody-conjugated nanoparticle-based targeted therapies with antibodies targeting specific tumor-associated antigens (TAA) can be proposed. In this context, glypican-1 (GPC1), which is highly expressed in PDAC and not expressed or expressed at very low levels in non-malignant lesions and healthy pancreatic tissues, is a useful TAA that can be achieved by a specific antibody-based immunotherapy and antibody-conjugated nanoparticle-based targeted therapy. In this review, we describe the main clinical features of PDAC. We propose the proteoglycan GPC1 as a useful TAA for PDAC-targeted therapies. We also provide a digression on the main developed approaches of antibody-based immunotherapy and antibody-conjugated nanoparticle-based targeted therapy, which can be used to target GPC1.

Production and characterization of virus-free, CRISPR-CAR T cells capable of inducing solid tumor regression

BACKGROUND

Chimeric antigen receptor (CAR) T cells have demonstrated high clinical response rates against hematological malignancies (e.g., CD19+ cancers) but have shown limited activity in patients with solid tumors. Recent work showed that precise insertion of a CAR at a defined locus improves treatment outcomes in the context of a CD19 CAR; however, it is unclear if such a strategy could also affect outcomes in solid tumors. Furthermore, CAR manufacturing generally relies on viral vectors for gene delivery, which comprise a complex and resource-intensive part of the manufacturing supply chain.

METHODS

Anti-GD2 CAR T cells were generated using CRISPR/Cas9 within 9 days using recombinant Cas9 protein and nucleic acids, without any viral vectors. The CAR was specifically targeted to the T cell receptor alpha constant gene (TRAC). T cell products were characterized at the level of the genome, transcriptome, proteome, and secretome using CHANGE-seq, targeted next-generation sequencing, scRNA-seq, spectral cytometry, and ELISA assays, respectively. Functionality was evaluated in vivo in an NSG™ xenograft neuroblastoma model.

RESULTS

In comparison to retroviral CAR T cells, virus-free CRISPR CAR (VFC-CAR) T cells exhibit TRAC-targeted genomic integration of the CAR transgene, elevation of transcriptional and protein characteristics associated with a memory-like phenotype, and low tonic signaling prior to infusion arising in part from the knockout of the T cell receptor. On exposure to the GD2 target antigen, anti-GD2 VFC-CAR T cells exhibit specific cytotoxicity against GD2+ cells in vitro and induce solid tumor regression in vivo. VFC-CAR T cells demonstrate robust homing and persistence and decreased exhaustion relative to retroviral CAR T cells against a human neuroblastoma xenograft model.

CONCLUSIONS

This study leverages virus-free genome editing technology to generate CAR T cells featuring a TRAC-targeted CAR, which could inform manufacturing of CAR T cells to treat cancers, including solid tumors.

Recent advances and clinical pharmacology aspects of Chimeric Antigen Receptor (CAR) T-cellular therapy development

Advances in immuno-oncology have provided a variety of novel therapeutics that harness the innate immune system to identify and destroy neoplastic cells. It is noteworthy that acceptable safety profiles accompany the development of these targeted therapies, which result in efficacious cancer treatment with higher survival rates and lower toxicities. Adoptive cellular therapy (ACT) has shown promising results in inducing sustainable remissions in patients suffering from refractory diseases. Two main types of ACT include engineered Chimeric Antigen Receptor (CAR) T cells and T cell receptor (TCR) T cells. The application of these immuno-therapies in the last few years has been successful and has demonstrated a safe and rapid treatment regimen for solid and non-solid tumors. The current review presents an insight into the clinical pharmacology aspects of immuno-therapies, especially CAR-T cells. Here, we summarize the current knowledge of TCR and CAR-T cell immunotherapy with particular focus on the structure of CAR-T cells, the effects and toxicities associated with these therapies in clinical trials, risk mitigation strategies, dose selection approaches, and cellular kinetics. Finally, the quantitative approaches and modeling techniques used in the development of CAR-T cell therapies are described.

Advances in modular control of CAR-T therapy with adapter-mediated CARs

Protein engineering has contributed to successes in the field of T cell-based immunotherapy, including chimeric antigen receptor (CAR) T cell therapy. CAR T cell therapy has become a pillar of cancer immunotherapy, demonstrating clinical effectiveness against B cell malignancies by targeting the B cell antigen CD19. Current gene editing techniques have limited safety controls over CAR T cell activity, which presents a hurdle for control of CAR T cells in patients. Alternatively, CAR T cell activity can be controlled by engineering CARs to bind soluble adapter molecules that direct the interaction between the CAR T cell and target cell. The flexibility in this adapter-mediated approach overcomes the rigid specificity of traditional CAR T cells to allow targeting of multiple cell types. Here we describe adapter CAR T technologies and how these methods emphasize the growing role of protein engineering in the design of programmable tools for T cell therapies.

Developing ROR1 Targeting CAR-T Cells against Solid Tumors in Preclinical Studies

Chimeric antigen receptor (CAR)-modified T-cells (CAR-T) have demonstrated promising clinical benefits against B-cell malignancies. Yet, its application for solid tumors is still facing challenges. Unlike haematological cancers, solid tumors often lack good targets, which are ideally expressed on the tumor cells, but not by the normal healthy cells. Fortunately, receptor tyrosine kinase-like orphan receptor 1 (ROR1) is among a few good cancer targets that is aberrantly expressed on various tumors but has a low expression on normal tissue, suggesting it as a good candidate for CAR-T therapy. Here, we constructed two ROR1 CARs with the same antigen recognition domain that was derived from Zilovertamab but differing in hinge regions. Both CARs target ROR1⁺ cancer cells specifically, but CAR with a shorter IgG4 hinge exhibits a higher surface expression and better in vitro functionality. We further tested the ROR1 CAR-T in three human solid tumor xenografted mouse models. Our ROR1 CAR-T cells controlled the solid tumor growth without causing any severe toxicity. Our results demonstrated that ROR1 CAR-T derived from Zilovertamab is efficacious and safe to suppress ROR1⁺ solid tumors in vitro and in vivo, providing a promising therapeutic option for future clinical application.

Clinical Investigations of CAR-T Cell Therapy for Solid Tumors

Cell therapy is a distinguished targeted immunotherapy with great potential to treat solid tumors in the new era of cancer treatment. Cell therapy products include genetically engineered cell products and non-genetically engineered cell products. Several recent cell therapies, especially chimeric antigen receptor (CAR)-T cell therapies, have been approved as novel treatment strategies for cancer. Many clinical trials on cell therapies, in the form of cell therapy alone or in combination with other treatments, in solid tumors, have been conducted or ongoing. However, there are still challenges since adverse events and the limited efficacy of cell therapies have also been observed. Here, we concisely summarize the clinical milestones of the conducted and ongoing clinical trials of cell therapy, introduce the evolution of CARs, discuss the challenges and limitations of these therapeutic modalities taking CAR-T as the main focus, and analyze the disparities in the regulatory policies in different countries.

Advances and challenges of CAR T therapy and suitability of animal models (Review)

Chimeric antigen receptors (CARs) recently gained momentum in cancer treatment due to their ability to promote T-cell mediated responses to a specific tumor-associated antigen. CARs are part of the adoptive cell transfer (ACT) strategies that utilize patients' T lymphocytes, genetically engineered to kill cancer cells. However, despite the therapy's success against blood-related malignancies, treating solid tumors has not reached its fullest potential yet. The reasons include the complex suppressive tumor microenvironment, mutations on cancer cells' target receptors, lethal side-effects, restricted trafficking into the tumor, suboptimal persistence in vivo and the lack of animal models that faithfully resemble human tumor's immunological responses. Currently, rodent models are used to investigate the safety and efficacy of CAR therapies. However, these models are limited in representing the human disease faithfully, fail to predict the adverse treatment events and overestimate the efficacy of the therapy. On the other hand, spontaneously developed tumors in dogs are more suited in CAR research and their efficacy has been demonstrated in a number of diseases, including lymphoma, osteosarcoma and mammary tumors. The present review discusses the design and evolution of CARs, challenges of CAR in solid tumors, human and canine clinical trials and advantages of the canine model.

Current State of Cell Therapies for Gastrointestinal Cancers

ABSTRACT

Adoptive cell therapies include multiple cell-based therapies to harness the immune system's power to mount a robust anticancer effect. Early successes in solid tumors with checkpoint inhibition have increased the research and development of immunotherapy. The utilization of cell-based therapy for gastrointestinal malignancies is still in its infancy because of challenges of antigen specificity and access to the tumor microenvironment. In this review, we discuss the current state of adoptive cell therapies in terms of challenges and early successes in preclinical and clinical studies.

Gene therapy clinical trials, where do we go? An overview

There have been many ups and downs since the introduction of gene therapy as a therapeutic modality for diseases. However, the journey of gene therapy has reached a fundamental milestone, as evidenced by the increasing number of gene therapy products on the market. Looking at the currently approved and under-approval products, as well as the numerous clinical trials in this field, gene therapy has a promising future. Trend of changes in gene therapy strategies, vectors, and targets could be insightful for pharmaceutical companies, policymakers, and researchers. In this paper, following a brief history of gene therapy, we reviewed current gene therapy products as well as gene therapies that may be approved in the near future. We also looked at ten-year changes in gene therapy clinical trials strategies, such as the use of vectors, target cells, transferred genes, and ex-vivo/in-vivo methods, as well as the major fields that gene therapy has entered. Although gene therapy was initially used to treat genetic diseases, cancer now has the greatest number of gene therapy clinical trials. Changes in gene therapy strategies, particularly in pioneering countries in this field, may point to the direction of future clinical products.

Utility and Drawbacks of Chimeric Antigen Receptor T Cell (CAR-T) Therapy in Lung Cancer

The present treatments for lung cancer include surgical resection, radiation, chemotherapy, targeted therapy, and immunotherapy. Despite advances in therapies, the prognosis of lung cancer has not been substantially improved in recent years. Chimeric antigen receptor (CAR)-T cell immunotherapy has attracted growing interest in the treatment of various malignancies. Despite CAR-T cell therapy emerging as a novel potential therapeutic option with promising results in refractory and relapsed leukemia, many challenges limit its therapeutic efficacy in solid tumors including lung cancer. In this landscape, studies have identified several obstacles to the effective use of CAR-T cell therapy including antigen heterogeneity, the immunosuppressive tumor microenvironment, and tumor penetration by CAR-T cells. Here, we review CAR-T cell design; present the results of CAR-T cell therapies in preclinical and clinical studies in lung cancer; describe existing challenges and toxicities; and discuss strategies to improve therapeutic efficacy of CAR-T cells.

CAR T Cell Therapy in Hematological Malignancies: Implications of the Tumor Microenvironment and Biomarkers on Efficacy and Toxicity

Chimeric antigen receptor (CAR) T cell therapy has ushered in a new era in cancer treatment. Remarkable outcomes have been demonstrated in patients with previously untreatable relapsed/refractory hematological malignancies. However, optimizing efficacy and reducing the risk of toxicities have posed major challenges, limiting the success of this therapy. The tumor microenvironment (TME) plays an important role in CAR T cell therapy’s effectiveness and the risk of toxicities. Increasing research studies have also identified various biomarkers that can predict its effectiveness and risk of toxicities. In this review, we discuss the various aspects of the TME and biomarkers that have been implicated thus far and discuss the role of creating scoring systems that can aid in further refining clinical applications of CAR T cell therapy and establishing a safe and efficacious personalised medicine for individuals.

CAR T Cells Targeting Membrane-Bound Hsp70 on Tumor Cells Mimic Hsp70-Primed NK Cells

Strategies to boost anti-tumor immunity are urgently needed to treat therapy-resistant late-stage cancers, including colorectal cancers (CRCs). Cytokine stimulation and genetic modifications with chimeric antigen receptors (CAR) represent promising strategies to more specifically redirect anti-tumor activities of effector cells like natural killer (NK) and T cells. However, these approaches are critically dependent on tumor-specific antigens while circumventing the suppressive power of the solid tumor microenvironment and avoiding off-tumor toxicities. Previously, we have shown that the stress-inducible heat shock protein 70 (Hsp70) is frequently and specifically expressed on the cell surface of many different, highly aggressive tumors but not normal tissues. We could take advantage of tumors expressing Hsp70 on their membrane (‘mHsp70’) to attract and engage NK cells after in vitro stimulation with the 14-mer Hsp70 peptide TKDNNLLGRFELSG (TKD) plus low dose interleukin (IL)-2. However, a potential limitation of activated primary NK cells after adoptive transfer is their comparably short life span. T cells are typically long-lived but do not recognize mHsp70 on tumor cells, even after stimulation with TKD/IL-2. To combine the advantages of mHsp70-specificity with longevity, we constructed a CAR having specificity for mHsp70 and retrovirally transduced it into primary T cells. Co-culture of anti-Hsp70 CAR-transduced T cells with mHsp70-positive tumor cells stimulates their functional responsiveness. Herein, we demonstrated that human CRCs with a high mHsp70 expression similarly attract TKD/IL-2 stimulated NK cells and anti-Hsp70 CAR T cells, triggering the release of their lytic effector protein granzyme B (GrB) and the pro-inflammatory cytokine interferon (IFN)-γ, after 4 and 24 hours, respectively. In sum, stimulated NK cells and anti-Hsp70 CAR T cells demonstrated comparable anti-tumor effects, albeit with somewhat differing kinetics. These findings, together with the fact that mHsp70 is expressed on a large variety of different cancer entities, highlight the potential of TKD/IL-2 pre-stimulated NK, as well as anti-Hsp70 CAR T cells to provide a promising direction in the field of targeted, cell-based immunotherapies which can address significant unmet clinical needs in a wide range of cancer settings.

Chimeric Antigen Receptor T-Cells: An Overview of Concepts, Applications, Limitations, and Proposed Solutions

Adaptive immunity, orchestrated by B-cells and T-cells, plays a crucial role in protecting the body from pathogenic invaders and can be used as tools to enhance the body's defense mechanisms against cancer by genetically engineering these immune cells. Several strategies have been identified for cancer treatment and evaluated for their efficacy against other diseases such as autoimmune and infectious diseases. One of the most advanced technologies is chimeric antigen receptor (CAR) T-cell therapy, a pioneering therapy in the oncology field. Successful clinical trials have resulted in the approval of six CAR-T cell products by the Food and Drug Administration for the treatment of hematological malignancies. However, there have been various obstacles that limit the use of CAR T-cell therapy as the first line of defense mechanism against cancer. Various innovative CAR-T cell therapeutic designs have been evaluated in preclinical and clinical trial settings and have demonstrated much potential for development. Such trials testing the suitability of CARs against solid tumors and HIV are showing promising results. In addition, new solutions have been proposed to overcome the limitations of this therapy. This review provides an overview of the current knowledge regarding this novel technology, including CAR T-cell structure, different applications, limitations, and proposed solutions.

Optogenetic technologies in translational cancer research

Gene and cell therapies are widely recognized as future cancer therapeutics but poor controllability limits their clinical applications. Optogenetics, the use of light-controlled proteins to precisely spatiotemporally regulate the activity of genes and cells, opens up new possibilities for cancer treatment. Light of specific wavelength can activate the immune response, oncolytic activity and modulate cell signaling in tumor cells non-invasively, in dosed manner, with tissue confined action and without side effects of conventional therapies. Here, we review optogenetic approaches in cancer research, their clinical potential and challenges of incorporating optogenetics in cancer therapy. We critically discuss beneficial combinations of optogenetic technologies with therapeutic nanobodies, T-cell activation and CAR-T cell approaches, genome editors and oncolytic viruses. We consider viral vectors and nanoparticles for delivering optogenetic payloads and activating light to tumors. Finally, we highlight herein the prospects for integrating optogenetics into immunotherapy as a novel, fast, reversible and safe approach to cancer treatment.

Recent Advances in Solid Tumor CAR-T Cell Therapy: Driving Tumor Cells From Hero to Zero?

Chimeric antigen receptor T-cells (CAR-Ts) are known as revolutionary living drugs that have turned the tables of conventional cancer treatments in certain hematologic malignancies such as B-cell acute lymphoblastic leukemia (B-ALL) and diffuse large B-cell lymphoma (DLBCL) by achieving US Food and Drug Administration (FDA) approval based on their successful clinical outcomes. However, this type of therapy has not seen the light of victory in the fight against solid tumors because of various restricting caveats including heterogeneous tumor antigen expression and the immunosuppressive tumor microenvironments (TME) that negatively affect the tumor-site accessibility, infiltration, stimulation, activation, and persistence of CAR-Ts. In this review, we explore strategic twists including boosting vaccines and designing implementations that can support CAR-T expansion, proliferation, and tumoricidal capacity. We also step further by underscoring novel strategies for triggering endogenous antitumor responses and overcoming the limitation of poor CAR-T tumor-tissue infiltration and the lack of definitive tumor-specific antigens. Ultimately, we highlight how these approaches can address the mentioned arduous hurdles.

CAR-T Cells Shoot for New Targets: Novel Approaches to Boost Adoptive Cell Therapy for B Cell-Derived Malignancies

Chimeric antigen receptor (CAR)-T cell therapy is undeniably a promising tool in combating various types of hematological malignancies. However, it is not yet optimal and a significant number of patients experience a lack of response or relapse after the treatment. Therapy improvement requires careful analysis of the occurring problems and a deeper understanding of the reasons that stand behind them. In this review, we summarize the recent knowledge about CAR-T products' clinical performance and discuss diversified approaches taken to improve the major shortcomings of this therapy. Especially, we prioritize the challenges faced by CD19 CAR-T cell-based treatment of B cell-derived malignancies and revise the latest insights about mechanisms mediating therapy resistance. Since the loss of CD19 is one of the major obstacles to the success of CAR-T cell therapy, we present antigens that could be alternatively used for the treatment of various types of B cell-derived cancers.

The translational challenges of precision oncology

The translational challenges in the field of precision oncology are in part related to the biological complexity and diversity of this disease. Technological advances in genomics have facilitated large sequencing efforts and discoveries that have further supported this notion. In this review, we reflect on the impact of these discoveries on our understanding of several concepts: cancer initiation, cancer prevention, early detection, adjuvant therapy and minimal residual disease monitoring, cancer drug resistance, and cancer evolution in metastasis. We discuss key areas of focus for improving cancer outcomes, from biological insights to clinical application, and suggest where the development of these technologies will lead us. Finally, we discuss practical challenges to the wider adoption of molecular profiling in the clinic and the need for robust translational infrastructure.

CAR-T Cell Performance: How to Improve Their Persistence?

Adoptive cell therapy with T cells reprogrammed to express chimeric antigen receptors (CAR-T cells) has been highly successful in patients with hematological neoplasms. However, its therapeutic benefits have been limited in solid tumor cases. Even those patients who respond to this immunotherapy remain at risk of relapse due to the short-term persistence or non-expansion of CAR-T cells; moreover, the hostile tumor microenvironment (TME) leads to the dysfunction of these cells after reinfusion. Some research has shown that, in adoptive T-cell therapies, the presence of less differentiated T-cell subsets within the infusion product is associated with better clinical outcomes. Naive and memory T cells persist longer and exhibit greater antitumor activity than effector T cells. Therefore, new methods are being studied to overcome the limitations of this therapy to generate CAR-T cells with these ideal phenotypes. In this paper, we review the characteristics of T-cell subsets and their implications in the clinical outcomes of adoptive therapy with CAR-T cells. In addition, we describe some strategies developed to overcome the reduced persistence of CAR T-cells and alternatives to improve this therapy by increasing the expansion ability and longevity of modified T cells. These methods include cell culture optimization, incorporating homeostatic cytokines during the expansion phase of manufacturing, modulation of CAR-T cell metabolism, manipulating signaling pathways involved in T-cell differentiation, and strategies related to CAR construct designs.

Design and Evaluation of TIM-3-CD28 Checkpoint Fusion Proteins to Improve Anti-CD19 CAR T-Cell Function

Therapeutic targeting of inhibitory checkpoint molecules in combination with chimeric antigen receptor (CAR) T cells is currently investigated in a variety of clinical studies for treatment of hematologic and solid malignancies. However, the impact of co-inhibitory axes and their therapeutic implication remains understudied for the majority of acute leukemias due to their low immunogenicity/mutational load. The inhibitory exhaustion molecule TIM-3 is an important marker for the interaction of T cells with leukemic cells. Moreover, inhibitory signals from malignant cells could be transformed into stimulatory signals by synthetic fusion molecules with extracellular inhibitory receptors fused to an intracellular stimulatory domain. Here, we designed a variety of different TIM-3-CD28 fusion proteins to turn inhibitory signals derived by TIM-3 engagement into T-cell activation through CD28. In the absence of anti-CD19 CAR, two TIM-3-CD28 fusion receptors with large parts of CD28 showed strongest responses in terms of cytokine secretion and proliferation upon stimulation with anti-CD3 antibodies compared to controls. We then combined these two novel TIM-3-CD28 fusion proteins with first- and second-generation anti-CD19 CAR T cells and found that the fusion receptor can increase proliferation, activation, and cytotoxic capacity of conventional anti-CD19 CAR T cells. These additionally armed CAR T cells showed excellent effector function. In terms of safety considerations, the fusion receptors showed exclusively increased cytokine release, when the CAR target CD19 was present. We conclude that combining checkpoint fusion proteins with anti-CD19 CARs has the potential to increase T-cell proliferation capacity with the intention to overcome inhibitory signals during the response against malignant cells.

An Overview of Conventional Drugs and Nanotherapeutic Options for the Treatment and Management of Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a common form of pediatric cancer affecting the lymphoblast, a type of white blood cell found in the bone marrow. In this disease, the normal lymphoblast cells transform into leukemic cells and subsequently enter the bloodstream. Leukemic cells found in patients with ALL have shown differences in cholesterol uptake and utilization. Current treatment consists of chemotherapy, chimeric antigen receptor (CAR) therapy, and hematopoietic stem cell transplantation (HSCT). In addition, minimal residual disease (MRD) has become an effective tool for measuring treatment efficacy and the potential for relapse. Chemotherapy resistance remains a significant barrier in the treatment of ALL. Biomarkers such as an upregulated Akt signaling pathway and an overexpressed VLA-4 integrin-protein have been associated with drug resistance. Nanoparticles have been used to favorably alter the pharmacokinetic profile of conventional drug agents. These drug-delivery systems are designed to selectively deliver their drug payloads to desired targets. Therefore, nanoparticles offer advantages such as improved efficacy and reduced toxicity. This review highlights conventional treatment options, distinctive characteristics of pediatric ALL, therapeutic challenges encountered during therapy, and the key role that nanotherapeutics play in the treatment of ALL.

Nanobody-based CAR-T cells for cancer immunotherapy

Chimeric antigen receptor T-cell (CAR-T) therapy is the result of combining genetic engineering-based cancer immunotherapy with adoptive cell therapy (ACT). CAR-T therapy has been successful in treating various types of hematological cancers. CARs are receptors made of an extracellular domain, a membrane-spanning domain, and an intracellular domain. The extracellular domain of CARs harbors an antigen-targeting domain responsible for recognizing and binding cell surface-expressed target antigens. Conventionally, the single-chain fragment variable (scFv) of a monoclonal antibody (mAb) is used as the antigen-targeting domain of CARs. However, of late, researchers have exploited nanobodies for this aim based on numerous rationales including the small size of nanobodies, their stability, specificity, and high affinity, and their easy and feasible development process. Many findings have confirmed that nanobody-based CAR-Ts can be as functional as scFv-based CAR-Ts in preclinical and clinical settings. In this review, we discuss the advantages and disadvantages of scFvs and nanobodies in regards to their application as the targeting domain of CARs. Ultimately, we discuss various CAR target antigens which have been targeted using nanobody-based CAR-T cells for the treatment of different types of malignancies.

GMP-Compliant Manufacturing of TRUCKs: CAR T Cells targeting GD2 and Releasing Inducible IL-18

Chimeric antigen receptor (CAR)-engineered T cells can be highly effective in the treatment of hematological malignancies, but mostly fail in the treatment of solid tumors. Thus, approaches using 4^th advanced CAR T cells secreting immunomodulatory cytokines upon CAR signaling, known as TRUCKs (“T cells redirected for universal cytokine-mediated killing”), are currently under investigation. Based on our previous development and validation of automated and closed processing for GMP-compliant manufacturing of CAR T cells, we here present the proof of feasibility for translation of this method to TRUCKs. We generated IL-18-secreting TRUCKs targeting the tumor antigen GD₂ using the CliniMACS Prodigy^® system using a recently described “all-in-one” lentiviral vector combining constitutive anti-GD₂ CAR expression and inducible IL-18. Starting with 0.84 x 10⁸ and 0.91 x 10⁸ T cells after enrichment of CD4⁺ and CD8⁺ we reached 68.3-fold and 71.4-fold T cell expansion rates, respectively, in two independent runs. Transduction efficiencies of 77.7% and 55.1% was obtained, and yields of 4.5 x 10⁹ and 3.6 x 10⁹ engineered T cells from the two donors, respectively, within 12 days. Preclinical characterization demonstrated antigen-specific GD₂-CAR mediated activation after co-cultivation with GD₂-expressing target cells. The functional capacities of the clinical-scale manufactured TRUCKs were similar to TRUCKs generated in laboratory-scale and were not impeded by cryopreservation. IL-18 TRUCKs were activated in an antigen-specific manner by co-cultivation with GD₂-expressing target cells indicated by an increased expression of activation markers (e.g. CD25, CD69) on both CD4⁺ and CD8⁺ T cells and an enhanced release of pro-inflammatory cytokines and cytolytic mediators (e.g. IL-2, granzyme B, IFN-γ, perforin, TNF-α). Manufactured TRUCKs showed a specific cytotoxicity towards GD₂-expressing target cells indicated by lactate dehydrogenase (LDH) release, a decrease of target cell numbers, microscopic detection of cytotoxic clusters and detachment of target cells in real-time impedance measurements (xCELLigence). Following antigen-specific CAR activation of TRUCKs, CAR-triggered release IL-18 was induced, and the cytokine was biologically active, as demonstrated in migration assays revealing specific attraction of monocytes and NK cells by supernatants of TRUCKs co-cultured with GD₂-expressing target cells. In conclusion, GMP-compliant manufacturing of TRUCKs is feasible and delivers high quality T cell products.

In-Vivo Induced CAR-T Cell for the Potential Breakthrough to Overcome the Barriers of Current CAR-T Cell Therapy

Chimeric antigen receptor T cell (CAR-T cell) therapy has shown impressive success in the treatment of hematological malignancies, but the systemic toxicity and complex manufacturing process of current autologous CAR-T cell therapy hinder its broader applications. Universal CAR-T cells have been developed to simplify the production process through isolation and editing of allogeneic T cells from healthy persons, but the allogeneic CAR-T cells have recently encountered safety concerns, and clinical trials have been halted by the FDA. Thus, there is an urgent need to seek new ways to overcome the barriers of current CAR-T cell therapy. In-vivo CAR-T cells induced by nanocarriers loaded with CAR-genes and gene-editing tools have shown efficiency for regressing leukemia and reducing systemic toxicity in a mouse model. The in-situ programming of autologous T-cells avoids the safety concerns of allogeneic T cells, and the manufacture of nanocarriers can be easily standardized. Therefore, the in-vivo induced CAR-T cells can potentially overcome the abovementioned limitations of current CAR-T cell therapy. Here, we provide a review on CAR structures, gene-editing tools, and gene delivery techniques applied in immunotherapy to help design and develop new in-vivo induced CAR-T cells.

Targeting gastrointestinal cancers with chimeric antigen receptor (CAR)-T cell therapy

The immune system is capable of remarkably potent and specific efficacy against infectious diseases. For decades, investigators sought to leverage those characteristics to create immune-based therapies (immunotherapy) that might be far more effective and less toxic than conventional chemotherapy and radiation therapy for cancer. Those studies revealed many factors and mechanisms underlying the success or failure of cancer immunotherapy, leading to synthetic biology approaches, including CAR-T cell therapy. In this approach, patient T cells are genetically modified to express a chimeric antigen receptor (CAR) that converts T cells of any specificity into tumor-specific T cells that can be expanded to large numbers and readministered to the patient to eliminate cancer cells, including bulky metastatic disease. This approach has been most successful against hematologic cancers, resulting in five FDA approvals to date. Here, we discuss some of the most promising attempts to apply this technology to cancers of the gastrointestinal tract.

Therapeutic potential of CAR T cell in malignancies: A scoping review

Although tremendous advancements in cancer therapy over the last several years, cancer still is a complex illness to cure. Traditional cancer treatments, including chemotherapy, radiotherapy, and surgery, have a poor therapeutic effect, emphasizing the significance of employing innovative treatments like activated cell therapy. Chimeric antigen receptor T cell is one of the most prevalent types of activated cell therapy have been developed to direct T lymphocytes toward cancers (CAR-T cells). CAR-T cells therapy has illustrated poor impact versus solid tumors despite the remarkable success in patients suffering from hematological malignancies. CAR-T cells must overcome various hurdles to obtain full responses to solid tumors, including growth, stability, trafficking, and destiny inside tumors. As a result, novel treatment methods will entail overcoming the challenges that CAR-T cells face in solid tumors. The use of CAR-T cells in combination with other therapeutic approaches such as chemotherapy, radiotherapy, immuno-checkpoint inhibitors, and oncolytic viruses can promote the effectiveness of CAR-T cell therapy for the treatment of solid tumors. However, more research is needed to determine the safety and effectiveness of these therapies. CAR-T cell treatment success rates vary by type of disease, but are predicted to reach up to 90% in patients with leukemia. However, since this kind of immunotherapy is still in its infancy, there is much to learn about its efficacy. This review provided an in-depth examination of CAR-T cell therapy and its success and failure as a cancer treatment approach. We also discuss combination therapies with CAR-T Cell.

CAR-based therapies: opportunities for immuno-medicine beyond cancer

One of the most exciting new therapies for cancer involves the use of autologous T cells that are engineered to recognize and destroy cancerous cells. Patients with previously untreatable B cell leukaemias and lymphomas have been cured, and efforts are underway to extend this success to other tumours. Here, we discuss recent studies and emerging research aimed to extend this approach beyond oncology in areas such as cardiometabolic disorders, autoimmunity, fibrosis and senescence. We also summarize new technologies that may help to reduce the cost and increase access to related forms of immunotherapy.

Synthetic Biology in Chimeric Antigen Receptor T (CAR T) Cell Engineering

Synthetic biology is a novel interdisciplinary research area following engineering principles to redesign and construct biological systems for useful purposes. As one of the most notable clinically relevant application of synthetic biology, chimeric antigen receptor (CAR) T cells have demonstrated tremendous success for the treatment of advanced hematological malignancies in recent years. However, various unsolved obstacles limit the widespread application of CAR T cell therapies, including treatment-associated toxicities, antigen heterogeneity, antigen escape, poor CAR T cell persistence and expansion, and particularly inefficient homing, infiltrating into, and surviving within solid tumors. Accordingly, to improve therapeutic efficacy and minimize side effects, innovative CAR design becomes urgently necessary, and researchers are developing numerous methods to overcome the limitations. Here we summarize currently available bioengineering strategies and discuss the future development from a viewpoint of synthetic biology.

The Implementation of TNFRSF Co-Stimulatory Domains in CAR-T Cells for Optimal Functional Activity

The Tumor Necrosis Factor Receptor Superfamily (TNFRSF) is a large and important immunoregulatory family that provides crucial co-stimulatory signals to many if not all immune effector cells. Each co-stimulatory TNFRSF member has a distinct expression profile and a unique functional impact on various types of cells and at different stages of the immune response. Correspondingly, exploiting TNFRSF-mediated signaling for cancer immunotherapy has been a major field of interest, with various therapeutic TNFRSF-exploiting anti-cancer approaches such as 4-1BB and CD27 agonistic antibodies being evaluated (pre)clinically. A further application of TNFRSF signaling is the incorporation of the intracellular co-stimulatory domain of a TNFRSF into so-called Chimeric Antigen Receptor (CAR) constructs for CAR-T cell therapy, the most prominent example of which is the 4-1BB co-stimulatory domain included in the clinically approved product Kymriah. In fact, CAR-T cell function can be clearly influenced by the unique co-stimulatory features of members of the TNFRSF. Here, we review a select group of TNFRSF members (4-1BB, OX40, CD27, CD40, HVEM, and GITR) that have gained prominence as co-stimulatory domains in CAR-T cell therapy and illustrate the unique features that each confers to CAR-T cells.

CAR-Ts: new perspectives in cancer therapy

Chimeric antigen receptor (CAR)-T-cell therapy is a promising anticancer treatment that exploits the host's immune system to fight cancer. CAR-T cell therapy relies on immune cells being modified to express an artificial receptor targeting cancer-specific markers, and infused into the patients where they will recognize and eliminate the tumour. Although CAR-T cell therapy has produced encouraging outcomes in patients with haematologic malignancies, solid tumours remain challenging to treat, mainly due to the lack of cancer-specific molecular targets and the hostile, often immunosuppressive, tumour microenvironment. CAR-T cell therapy also depends on the quality of the injected product, which is closely connected to CAR design. Here, we explain the technology of CAR-Ts, focusing on the composition of CARs, their application, and limitations in cancer therapy, as well as on the current strategies to overcome the challenges encountered. We also address potential future targets to overcome the flaws of CAR-T cell technology in the treatment of cancer, emphasizing glycan antigens, the aberrant forms of which attain high tumour-specific expression, as promising targets for CAR-T cell therapy.

CAR T Cell Immunotherapy Beyond Haematological Malignancy

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

Immuno-oncology trends: preclinical models, biomarkers, and clinical development

The landscape in immuno-oncology (I-O) has undergone profound changes since its early beginnings up through the rapid advances happening today. The current drug development pipeline consists of thousands of potential I-O therapies and therapy combinations, many of which are being evaluated in clinical trials. The efficient and successful development of these assets requires the investment in and utilization of appropriate tools and technologies that can facilitate the rapid transitions from preclinical evaluation through clinical development. These tools include (i) appropriate preclinical models, (ii) biomarkers of pharmacodynamic, predictive and monitoring utility, and (iii) evolving clinical trial designs that allow rapid and efficient evaluation during the development process. This article provides an overview of how novel discoveries and insights into each of these three areas have the potential to further address the clinical management needs for patients with cancer.

Companion Animal Model in Translational Oncology; Feline Oral Squamous Cell Carcinoma and Canine Oral Melanoma

Simple Summary

Laboratory rodents are the most common animal models used in preclinical cancer research. Companion animals with naturally occurring cancers are an under-utilized natural model for the development of new anti-cancer drugs. Dogs and cats develop several types of cancers that resemble those arising in humans with similar clinical and histopathological features and often with similar molecular and genetic backgrounds. Exposure to environmental carcinogens, including air, food and water are also common between people and their pets. Dogs and cats are a unique model that could be integrated between the preclinical laboratory animal model and human clinical trials.

Abstract

Companion animals with naturally occurring cancers can provide an advantageous model for cancer research and in particular anticancer drug development. Compared to commonly utilized mouse models, companion animals, specifically dogs and cats, share a closer phylogenetical distance, body size, and genome organization. Most importantly, pets develop spontaneous, rather than artificially induced, cancers. The incidence of cancer in people and companion animals is quite similar and cancer is the leading cause of death in dogs over 10 years of age. Many cancer types in dogs and cats have similar pathological, molecular, and clinical features to their human counterparts. Drug toxicity and response to anti-cancer treatment in dogs and cats are also similar to those in people. Companion animals share their lives with their owners, including the environmental and socioeconomic cancer-risk factors. In contrast to humans, pets have a shorter life span and cancer progression is often more rapid. Clinical trials in companion animals are cheaper and less time consuming compared to human trials. Dogs and cats with naturally occurring cancers are an ideal and unique model for human cancer research. Model selection for the specific type of cancer is of pivotal importance. Although companion animal models for translational research have been reviewed previously, this review will try to summarize the most important advantages and disadvantages of this model. Feline oral squamous cell carcinoma as a model for head and neck squamous cell carcinoma and canine oral melanoma as a model for mucosal melanoma and immunotherapy in people will be discussed as examples.

Addressing the obstacles of CAR T cell migration in solid tumors: wishing a heavy traffic

Chimeric antigen receptor T cell (CAR-T) therapy has been recognized as one of the most prosperous treatment options against certain blood-based malignancies. However, the same clinical and commercial success have been out of range in the case of solid tumors. The main contributing factor in this regard is the hostile environment the tumor cells impose that results in the exhaustion of immune effector cells alongside the abrogation of their infiltration capacity. The discovery of the underlying mechanisms and the development of reliable counterstrategies to overcome the inaccessibility of CAR-Ts to their target cells might correlate with encouraging clinical outcomes in advanced solid tumors. Here, we highlight the successive physical and metabolic barriers that systemically administered CAR-Ts face on their journey toward their target cells. Moreover, we propose meticulously-devised countertactics and combination therapies that can be applied to maximize the therapeutic benefits of CAR-T therapies against solid tumors.

Immunotherapy of cancer in single-cell RNA sequencing era: A precision medicine perspective

Immunotherapy has revolutionized cancer treatment and brought new aspects into tumor immunology. Effective immunotherapy will require using the suitable target antigens, optimizing the interaction between the antigenic peptide, the APC, and the T cell, and the simultaneous inhibitor of the negative regulatory process that inhibits immunotherapeutic effects and develop resistance. Tumor heterogeneity and its microenvironment is the leading cause of resistance in patients. Recently by emerging the single-cell RNA sequencing technology and its combination with immunotherapy, now we can specifically evaluate the mechanism of tumors in the face of immunotherapy agents at the single-cell resolution by detecting the transcriptional activity of immune checkpoints, screening neoantigens with high transcription levels, identifying rare cells, and other important processes. This review focuses on scRNA-seq, particularly on its application in cancer immunotherapy.

The safety and efficacy of CAR-T cells in the treatment of prostate cancer: review

OBJECTIVE

A new breakthrough development in cancer treatment is chimeric antigen receptor (CAR)-T cell therapy. In this review, we focussed on its efficacy & safety in prostate cancer, obstacles impeding its clinical use, and some strategies trying to overcome them.

METHODS

Searching for relevant articles was done using the PubMed and Cochrane Library databases. Studies had to be published in full-text in English in order to be considered.

RESULTS

Many factors can limit optimal CAR-T cell outcomes, including the hostile Prostate microenvironment, age, comorbidities, and tumour grade. The adverse effects of the therapy, particularly the cytokine release syndrome, are a major source of worry after treatment administration. Attempts to alter gamma/delta T-cells and NK cells with CAR, on the other hand, have demonstrated higher effectiveness and safety than conventional CAR-T cells.

CONCLUSION

To improve the use of immunotherapies, a greater understanding of the prostate cancer microenvironment is required. Concerning toxicity, more research is needed to find the most specific and highly expressed prostate antigens. Furthermore, discovering predictive biomarkers for toxicities, as well as choosing the correct patient for therapy, might decrease immune-related side effects and achieve a greater response.

NK cell upraise in the dark world of cancer stem cells

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

Advancement of chimeric antigen receptor-natural killer cells targeting hepatocellular carcinoma

With the advance of genome engineering technology, chimeric antigen receptors (CARs)-based immunotherapy has become an emerging therapeutic strategy for tumors. Although initially designed for T cells in tumor immunotherapy, CARs have been exploited to modify the function of natural killer (NK) cells against a variety of tumors, including hepatocellular carcinoma (HCC). CAR-NK cells have the potential to sufficiently kill tumor antigen-expressing HCC cells, independent of major histocompatibility complex matching or prior priming. In this review, we summarize the recent advances in genetic engineering of CAR-NK cells against HCC and discuss the current challenges and prospects of CAR-NK cells as a revolutionary cellular immunotherapy against HCC.

NK Cells Armed with Chimeric Antigen Receptors (CAR): Roadblocks to Successful Development

In recent years, cell-based immunotherapies have demonstrated promising results in the treatment of cancer. Chimeric antigen receptors (CARs) arm effector cells with a weapon for targeting tumor antigens, licensing engineered cells to recognize and kill cancer cells. The quality of the CAR-antigen interaction strongly depends on the selected tumor antigen and its expression density on cancer cells. CD19 CAR-engineered T cells approved by the Food and Drug Administration have been most frequently applied in the treatment of hematological malignancies. Clinical challenges in their application primarily include cytokine release syndrome, neurological symptoms, severe inflammatory responses, and/or other off-target effects most likely mediated by cytotoxic T cells. As a consequence, there remains a significant medical need for more potent technology platforms leveraging cell-based approaches with enhanced safety profiles. A promising population that has been advanced is the natural killer (NK) cell, which can also be engineered with CARs. NK cells which belong to the innate arm of the immune system recognize and kill virally infected cells as well as (stressed) cancer cells in a major histocompatibility complex I independent manner. NK cells play an important role in the host’s immune defense against cancer due to their specialized lytic mechanisms which include death receptor (i.e., Fas)/death receptor ligand (i.e., Fas ligand) and granzyme B/perforin-mediated apoptosis, and antibody-dependent cellular cytotoxicity, as well as their immunoregulatory potential via cytokine/chemokine release. To develop and implement a highly effective CAR NK cell-based therapy with low side effects, the following three principles which are specifically addressed in this review have to be considered: unique target selection, well-designed CAR, and optimized gene delivery.

Chimeric Antigen Receptors Expand the Repertoire of Antigenic Macromolecules for Cellular Immunity

T-cell therapies have made significant improvements in cancer treatment over the last decade. One cellular therapy utilizing T-cells involves the use of a chimeric MHC-independent antigen-recognition receptor, typically referred to as a chimeric antigen receptor (CAR). CAR molecules, while mostly limited to the recognition of antigens on the surface of tumor cells, can also be utilized to exploit the diverse repertoire of macromolecules targetable by antibodies, which are incorporated into the CAR design. Leaning into this expansion of target macromolecules will enhance the diversity of antigens T-cells can target and may improve the tumor-specificity of CAR T-cell therapy. This review explores the types of macromolecules targetable by T-cells through endogenous and synthetic antigen-specific receptors.

Sensitivity and Specificity of CD19.CAR-T Cell Detection by Flow Cytometry and PCR

Chimeric-antigen-receptor-T (CAR-T) cells are currently revolutionizing the field of cancer immunotherapy. Therefore, there is an urgent need for CAR-T cell monitoring by clinicians to assess cell expansion and persistence in patients. CAR-T cell manufacturers and researchers need to evaluate transduction efficiency and vector copy number for quality control. Here, CAR expression was analyzed in peripheral blood samples from patients and healthy donors by flow cytometry with four commercially available detection reagents and on the gene level by quantitative polymerase chain reaction (qPCR). Flow cytometric analysis of CAR expression showed higher mean CAR expression values for CD19 CAR detection reagent and the F(ab')2 antibody than Protein L and CD19 Protein. In addition, the CD19 CAR detection reagent showed a significantly lower median background staining of 0.02% (range 0.007-0.06%) when compared to the F(ab')2 antibody, CD19 protein and Protein L with 0.80% (range 0.47-1.58%), 0.65% (range 0.25-1.35%) and 0.73% (range 0.44-1.23%). Furthermore, flow cytometry-based CAR-T cell frequencies by CD19 CAR detection reagent showed a good correlation with qPCR results. In conclusion, quality control of CAR-T cell products can be performed by FACS and qPCR. For the monitoring of CAR-T cell frequencies by FACS in patients, CAR detection reagents with a low background staining are preferable.

CAR T cell therapy in solid tumors: a short review

Chimeric antigen receptor (CAR) T cell therapy has been established in the treatment of hematological malignancies. However, in solid tumors its efficacy remains limited. The aim of this article is to give an overview of the field of cell therapy itself, to introduce the underlying concepts of CAR T cell-based treatment approaches and to address its limitations in advancing the treatment for solid malignancies.

Optimizing the Clinical Impact of CAR-T Cell Therapy in B-Cell Acute Lymphoblastic Leukemia: Looking Back While Moving Forward

Chimeric antigen receptor T-cell (CAR-T) therapy has been successful in creating extraordinary clinical outcomes in the treatment of hematologic malignancies including relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). With several FDA approvals, CAR-T therapy is recognized as an alternative treatment option for particular patients with certain conditions of B-ALL, diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, or multiple myeloma. However, CAR-T therapy for B-ALL can be surrounded by challenges such as various adverse events including the life-threatening cytokine release syndrome (CRS) and neurotoxicity, B-cell aplasia-associated hypogammaglobulinemia and agammaglobulinemia, and the alloreactivity of allogeneic CAR-Ts. Furthermore, recent advances such as improvements in media design, the reduction of ex vivo culturing duration, and other phenotype-determining factors can still create room for a more effective CAR-T therapy in R/R B-ALL. Herein, we review preclinical and clinical strategies with a focus on novel studies aiming to address the mentioned hurdles and stepping further towards a milestone in CAR-T therapy of B-ALL.

T cells armed with C-X-C chemokine receptor type 6 enhance adoptive cell therapy for pancreatic tumours

The efficacy of adoptive cell therapy for solid tumours is hampered by the poor accumulation of the transferred T cells in tumour tissue. Here, we show that forced expression of C-X-C chemokine receptor type 6 (whose ligand is highly expressed by human and murine pancreatic cancer cells and tumour-infiltrating immune cells) in antigen-specific T cells enhanced the recognition and lysis of pancreatic cancer cells and the efficacy of adoptive cell therapy for pancreatic cancer. In mice with subcutaneous pancreatic tumours treated with T cells with either a transgenic T-cell receptor or a murine chimeric antigen receptor targeting the tumour-associated antigen epithelial cell adhesion molecule, and in mice with orthotopic pancreatic tumours or patient-derived xenografts treated with T cells expressing a chimeric antigen receptor targeting mesothelin, the T cells exhibited enhanced intratumoral accumulation, exerted sustained anti-tumoral activity and prolonged animal survival only when co-expressing C-X-C chemokine receptor type 6. Arming tumour-specific T cells with tumour-specific chemokine receptors may represent a promising strategy for the realization of adoptive cell therapy for solid tumours.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

Improving CAR T-Cell Persistence

Over the last decade remarkable progress has been made in enhancing the efficacy of CAR T therapies. However, the clinical benefits are still limited, especially in solid tumors. Even in hematological settings, patients that respond to CAR T therapies remain at risk of relapsing due to several factors including poor T-cell expansion and lack of long-term persistence after adoptive transfer. This issue is even more evident in solid tumors, as the tumor microenvironment negatively influences the survival, infiltration, and activity of T-cells. Limited persistence remains a significant hindrance to the development of effective CAR T therapies due to several determinants, which are encountered from the cell manufacturing step and onwards. CAR design and ex vivo manipulation, including culture conditions, may play a pivotal role. Moreover, previous chemotherapy and lymphodepleting treatments may play a relevant role. In this review, the main causes for decreased persistence of CAR T-cells in patients will be discussed, focusing on the molecular mechanisms underlying T-cell exhaustion. The approaches taken so far to overcome these limitations and to create exhaustion-resistant T-cells will be described. We will also examine the knowledge gained from several key clinical trials and highlight the molecular mechanisms determining T-cell stemness, as promoting stemness may represent an attractive approach to improve T-cell therapies.