4-1BB is superior to CD28 costimulation for generating CD8+ cytotoxic lymphocytes for adoptive immunotherapy

Bridging the gender gap in autoimmunity with T-cell-targeted biomaterials

Autoimmune diseases are caused by malfunctions of the immune system and generally impact women at twice the frequency of men. Many of the most serious autoimmune diseases are accompanied by a dysregulation of T-cell phenotype, both regarding the ratio of CD4+ to CD8+ T-cells and proinflammatory versus regulatory phenotypes. Biomaterials, in the form of particles and hydrogels, have shown promise in ameliorating this dysregulation both in vivo and ex vivo. In this review, we explore the role of T-cells in autoimmune diseases, particularly those with high incidence rates in women, and evaluate the promise and efficacy of innovative biomaterial-based approaches for targeting T-cells.

Cytotoxicity of fourth-generation anti-Trop2 CAR-T cells against breast cancer

The treatment of breast cancer (BC) remains a formidable challenge due to the emergence of drug resistance, necessitating the exploration of innovative strategies. Chimeric antigen receptor (CAR)-T cell therapy, a groundbreaking approach in hematologic malignancies, is actively under investigation for its potential application in solid tumors, including BC. Trophoblast cell surface antigen 2 (Trop2) has emerged as a promising immunotherapeutic target in various cancers and is notably overexpressed in BC. To enhance therapeutic efficacy in BC, a fourth-generation CAR (CAR4) construct was developed. This CAR4 design incorporates an anti-Trop2 single-chain variable fragment (scFv) fused with three costimulatory domains -CD28/4-1BB/CD27, and CD3ζ. Comparative analysis with the conventional second-generation CAR (CAR2; 28ζ) revealed that anti-Trop2 CAR4 T cells exhibited heightened cytotoxicity and interferon-gamma (IFN-γ) production against Trop2-expressing MCF-7 cells. Notably, anti-Trop2 CAR4-T cells demonstrated superior long-term cytotoxic functionality and proliferative capacity. Crucially, anti-Trop2 CAR4-T cells displayed specific cytotoxicity against Trop2-positive BC cells (MDA-MB-231, HCC70, and MCF-7) in both two-dimensional (2D) and three-dimensional (3D) culture systems. Following antigen-specific killing, these cells markedly secreted interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-α), IFN-γ, and Granzyme B compared to non-transduced T cells. This study highlights the therapeutic potential of anti-Trop2 CAR4-T cells in adoptive T cell therapy for BC, offering significant promise for the advancement of BC treatment strategies.

Preclinical Evaluation of Novel Folate Receptor 1-Directed CAR T Cells for Ovarian Cancer

Treatment options for ovarian cancer patients are limited, and a high unmet clinical need remains for targeted and long-lasting, efficient drugs. Genetically modified T cells expressing chimeric antigen receptors (CAR), are promising new drugs that can be directed towards a defined target and have shown efficient, as well as persisting, anti-tumor responses in many patients. We sought to develop novel CAR T cells targeting ovarian cancer and to assess these candidates preclinically. First, we identified potential CAR targets on ovarian cancer samples. We confirmed high and consistent expressions of the tumor-associated antigen FOLR1 on primary ovarian cancer samples. Subsequently, we designed a series of CAR T cell candidates against the identified target and demonstrated their functionality against ovarian cancer cell lines in vitro and in an in vivo xenograft model. Finally, we performed additional in vitro assays recapitulating immune suppressive mechanisms present in solid tumors and developed a process for the automated manufacturing of our CAR T cell candidate. These findings demonstrate the feasibility of anti-FOLR1 CAR T cells for ovarian cancer and potentially other FOLR1-expressing tumors.

Insights gained from single-cell analysis of chimeric antigen receptor T-cell immunotherapy in cancer

Advances in chimeric antigen receptor (CAR)-T cell therapy have significantly improved clinical outcomes of patients with relapsed or refractory hematologic malignancies. However, progress is still hindered as clinical benefit is only available for a fraction of patients. A lack of understanding of CAR-T cell behaviors in vivo at the single-cell level impedes their more extensive application in clinical practice. Mounting evidence suggests that single-cell sequencing techniques can help perfect the receptor design, guide gene-based T cell modification, and optimize the CAR-T manufacturing conditions, and all of them are essential for long-term immunosurveillance and more favorable clinical outcomes. The information generated by employing these methods also potentially informs our understanding of the numerous complex factors that dictate therapeutic efficacy and toxicities. In this review, we discuss the reasons why CAR-T immunotherapy fails in clinical practice and what this field has learned since the milestone of single-cell sequencing technologies. We further outline recent advances in the application of single-cell analyses in CAR-T immunotherapy. Specifically, we provide an overview of single-cell studies focusing on target antigens, CAR-transgene integration, and preclinical research and clinical applications, and then discuss how it will affect the future of CAR-T cell therapy.

Evolution by innovation as a driving force to improve TCR-T therapies

Adoptive cell therapies continually evolve through science-based innovation. Specialized innovations for TCR-T therapies are described here that are embedded in an End-to-End Platform for TCR-T Therapy Development which aims to provide solutions for key unmet patient needs by addressing challenges of TCR-T therapy, including selection of target antigens and suitable T cell receptors, generation of TCR-T therapies that provide long term, durable efficacy and safety and development of efficient and scalable production of patient-specific (personalized) TCR-T therapy for solid tumors. Multiple, combinable, innovative technologies are used in a systematic and sequential manner in the development of TCR-T therapies. One group of technologies encompasses product enhancements that enable TCR-T therapies to be safer, more specific and more effective. The second group of technologies addresses development optimization that supports discovery and development processes for TCR-T therapies to be performed more quickly, with higher quality and greater efficiency. Each module incorporates innovations layered onto basic technologies common to the field of immunology. An active approach of "evolution by innovation" supports the overall goal to develop best-in-class TCR-T therapies for treatment of patients with solid cancer.

Treatment of adult ALL patients with third-generation CD19-directed CAR T cells: results of a pivotal trial

BACKGROUND

Third-generation chimeric antigen receptor (CAR)-engineered T cells (CARTs) might improve clinical outcome of patients with B cell malignancies. This is the first report on a third-generation CART dose-escalating, phase-1/2 investigator-initiated trial treating adult patients with refractory and/or relapsed (r/r) acute lymphoblastic leukemia (ALL).

METHODS

Thirteen patients were treated with escalating doses of CD19-directed CARTs between 1 × 10⁶ and 50 × 10⁶ CARTs/m². Leukapheresis, manufacturing and administration of CARTs were performed in-house.

RESULTS

For all patients, CART manufacturing was feasible. None of the patients developed any grade of Immune effector cell-associated neurotoxicity syndrome (ICANS) or a higher-grade (≥ grade III) catokine release syndrome (CRS). CART expansion and long-term CART persistence were evident in the peripheral blood (PB) of evaluable patients. At end of study on day 90 after CARTs, ten patients were evaluable for response: Eight patients (80%) achieved a complete remission (CR), including five patients (50%) with minimal residual disease (MRD)-negative CR. Response and outcome were associated with the administered CART dose. At 1-year follow-up, median overall survival was not reached and progression-free survival (PFS) was 38%. Median PFS was reached on day 120. Lack of CD39-expression on memory-like T cells was more frequent in CART products of responders when compared to CART products of non-responders. After CART administration, higher CD8 + and γδ-T cell frequencies, a physiological pattern of immune cells and lower monocyte counts in the PB were associated with response.

CONCLUSION

In conclusion, third-generation CARTs were associated with promising clinical efficacy and remarkably low procedure-specific toxicity, thereby opening new therapeutic perspectives for patients with r/r ALL. Trial registration This trial was registered at www.

CLINICALTRIALS

gov as NCT03676504.

Neurological adverse effects of chimeric antigen receptor T-cell therapy

INTRODUCTION

Chimeric antigen receptor (CAR) T-cell is among the most prevalent approaches that act by directing T-cells toward cancer; however, they need to be optimized to minimize side effects and maximize efficacy before being used as standard treatment for malignancies. Neurotoxicity associated with CAR T-cell therapy has been well-documented in recent works.

AREAS COVERED

In this regard, two established syndromes exist. Immune effector cell-associated neurotoxicity syndrome (ICANS), previously called cytokine release encephalopathy syndrome (CRES), is a neuropsychiatric condition which can occur after therapy by immune effector cells (IEC) and T-lymphocytes utilizing treatments. Another syndrome is cytokine release syndrome (CRS), which may overlap with ICANS.

EXPERT OPINION

ICANS clinical manifestations include cerebral edema, mild lethargy, aphasia, and seizures. Notably, ICANS is associated with changes to EEG and neuroradiological findings. Therefore, it is necessary to make a timely and accurate diagnosis of neurological complications of CAR T-cells by clinical presentations, neuroimaging, and EEG. Since neurological events by different CAR T-cell products are heterogeneous, guides should be developed according to each product. Here, we provide an updated review of general information on CAR T-cell therapies and applications, neurological syndromes associated with their use, and risk factors contributing to ICANS.

CD28 and 41BB Costimulatory Domains Alone or in Combination Differentially Influence Cell Surface Dynamics and Organization of Chimeric Antigen Receptors and Early Activation of CAR T Cells

Chimeric antigen receptor (CAR)-modified T cells brought a paradigm shift in the treatment of chemotherapy-resistant lymphomas. Conversely, clinical experience with CAR T cells targeting solid tumors has been disheartening, indicating the necessity of their molecular-level optimization. While incorporating CD28 or 41BB costimulatory domains into CARs in addition to the CD3z signaling domain improved the long-term efficacy of T cell products, their influence on early tumor engagement has yet to be elucidated. We studied the antigen-independent self-association and membrane diffusion kinetics of first- (.z), second- (CD28.z, 41BB.z), and third- (CD28.41BB.z) generation HER2-specific CARs in the resting T cell membrane using super-resolution AiryScan microscopy and fluorescence correlation spectroscopy, in correlation with RoseTTAFold-based structure prediction and assessment of oligomerization in native Western blot. While .z and CD28.z CARs formed large, high-density submicron clusters of dimers, 41BB-containing CARs formed higher oligomers that assembled into smaller but more numerous membrane clusters. The first-, second-, and third-generation CARs showed progressively increasing lateral diffusion as the distance of their CD3z domain from the membrane plane increased. Confocal microscopy analysis of immunological synapses showed that both small clusters of highly mobile CD28.41BB.z and large clusters of less mobile .z CAR induced more efficient CD3ζ and pLck phosphorylation than CD28.z or 41BB.z CARs of intermediate mobility. However, electric cell-substrate impedance sensing revealed that the CD28.41BB.z CAR performs worst in sequential short-term elimination of adherent tumor cells, while the .z CAR is superior to all others. We conclude that the molecular structure, membrane organization, and mobility of CARs are critical design parameters that can predict the development of an effective immune synapse. Therefore, they need to be taken into account alongside the long-term biological effects of costimulatory domains to achieve an optimal therapeutic effect.

Cytotoxic activity of anti-mucin 1 chimeric antigen receptor T cells expressing PD-1-CD28 switch receptor against cholangiocarcinoma cells

BACKGROUND AIMS

Cholangiocarcinoma (CCA) is a lethal bile-duct cancer that is difficult to treat by current standard procedures. This drawback has prompted us to develop adoptive T-cell therapy for CCA, which requires an appropriate target antigen for binding of chimeric antigen receptor (CAR) T cells. Mucin 1 (MUC1), an overexpressed protein in CCA cells, is a potential target antigen for the CAR T-cell development. However, MUC1 overexpression also is associated with the upregulation of programmed death-ligand 1 (PD-L1), an immune checkpoint protein that prohibits anti-tumor functions of T cells, probably causing poor overall survival of patients with CCA.

METHODS

To overcome this problem, we developed anti-MUC1-CAR T cells containing PD-1-CD28 switch receptor (SR), namely αM.CAR/SR T cells, to target MUC1 and switch on the inhibitory signal of PD-1/PD-L1 interaction to activate CD28 signaling. Our lentiviral construct contains the sequences that encode anti-MUC1-single chain variable fragment, CD137 and CD3ζ, linked with P2A, PD-1 and CD28.

RESULTS

Initially, the upregulations of MUC1 and PD-L1 proteins were confirmed in CCA cell lines. αM.CAR and SR were co-expressed in 53.53 ± 13.89% of transduced T cells, mainly CD8⁺ T cells (85.7 ± 0.75%, P<0.0001) with the effector memory phenotype (59.22 ± 16.31%, P < 0.01). αM.CAR/SR T cells produced high levels of intracellular tumor necrosis factor-α and interferon-γ in response to the activation by CCA cells expressing MUC1, including KKU-055 (27.18 ± 4.38% and 27.33 ± 5.55%, respectively, P < 0.05) and KKU-213A (47.37 ± 12.67% and 54.55 ± 8.66%, respectively, P < 0.01). Remarkably, the cytotoxic function of αM.CAR/SR T cells against KKU-213A cells expressing PD-L1 was significantly enhanced compared with the αM.CAR T cells (70.69 ± 14.38% versus 47.15 ± 8.413%, respectively; P = 0.0301), correlated with increased granzyme B production (60.6 ± 9.89% versus 43.2 ± 8.95%, respectively; P = 0.0402). Moreover, the significantly enhanced disruption of KKU-213A spheroids by αM.CAR/SR T cells (P = 0.0027), compared with αM.CAR T cells, was also observed.

CONCLUSION

Taken together, the cytotoxic function of αM.CAR/SR T cells was enhanced over the αM.CAR T cells, which are potential to be further tested for CCA treatment.

Current and future concepts for the generation and application of genetically engineered CAR-T and TCR-T cells

Adoptive cell therapy (ACT) has seen a steep rise of new therapeutic approaches in its immune-oncology pipeline over the last years. This is in great part due to the recent approvals of chimeric antigen receptor (CAR)-T cell therapies and their remarkable efficacy in certain soluble tumors. A big focus of ACT lies on T cells and how to genetically modify them to target and kill tumor cells. Genetically modified T cells that are currently utilized are either equipped with an engineered CAR or a T cell receptor (TCR) for this purpose. Both strategies have their advantages and limitations. While CAR-T cell therapies are already used in the clinic, these therapies face challenges when it comes to the treatment of solid tumors. New designs of next-generation CAR-T cells might be able to overcome these hurdles. Moreover, CARs are restricted to surface antigens. Genetically engineered TCR-T cells targeting intracellular antigens might provide necessary qualities for the treatment of solid tumors. In this review, we will summarize the major advancements of the CAR-T and TCR-T cell technology. Moreover, we will cover ongoing clinical trials, discuss current challenges, and provide an assessment of future directions within the field.

Current and Future Perspectives for Chimeric Antigen Receptor T Cells Development in Poland

Chimeric antigen receptor T (CAR-T) cells are genetically modified autologous T cells that have revolutionized the treatment of relapsing and refractory haematological malignancies. In this review we present molecular pathways involved in the activation of CAR-T cells, describe in details the structures of receptors and the biological activity of CAR-T cells currently approved for clinical practice in the European Union, and explain the functional differences between them. Finally, we present the potential for the development of CAR-T cells in Poland, as well as indicate the possible directions of future research in this area, including novel modifications and applications of CAR-T cells and CAR-natural killer (NK) cells.

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.

Engineering γδ T Cells: Recognizing and Activating on Their Own Way

Adoptive cell therapy (ACT) with engineered T cells has emerged as a promising strategy for the treatment of malignant tumors. Among them, there is great interest in engineered γδ T cells for ACT. With both adaptive and innate immune characteristics, γδ T cells can be activated by γδ TCRs to recognize antigens in a MHC-independent manner, or by NK receptors to recognize stress-induced molecules. The dual recognition system enables γδ T cells with unique activation and cytotoxicity profiles, which should be considered for the design of engineered γδ T cells. However, the current designs of engineered γδ T cells mostly follow the strategies that used in αβ T cells, but not making good use of the specific characteristics of γδ T cells. Therefore, it is no surprising that current engineered γδ T cells in preclinical or clinical trials have limited efficacy. In this review, we summarized the patterns of antigen recognition of γδ T cells and the features of signaling pathways for the functions of γδ T cells. This review will additionally discuss current progress in engineered γδ T cells and provide insights in the design of engineered γδ T cells based on their specific characteristics.

Remodeling Tumor-Associated Neutrophils to Enhance Dendritic Cell-Based HCC Neoantigen Nano-Vaccine Efficiency

Hepatocellular carcinoma (HCC) commonly emerges in an immunologically "cold" state, thereafter protects it away from cytolytic attack by tumor-infiltrating lymphocytes, resulting in poor response to immunotherapy. Herein, an acidic/photo-sensitive dendritic cell (DCs)-based neoantigen nano-vaccine has been explored to convert tumor immune "cold" state into "hot", and remodel tumor-associated neutrophils to potentiate anticancer immune response for enhancing immunotherapy efficiency. The nano-vaccine is constructed by SiPCCl₂ -hybridized mesoporous silica with coordination of Fe(III)-captopril, and coating with exfoliated membrane of matured DCs by H22-specific neoantigen stimulation. The nano-vaccines actively target H22 tumors and induce immunological cell death to boost tumor-associated antigen release by the generation of excess ¹ O₂ through photodynamic therapy, which act as in situ tumor vaccination to strengthen antitumor T-cell response against primary H22 tumor growth. Interestingly, the nano-vaccines are also home to lymph nodes to directly induce the activation and proliferation of neoantigen-specific T cells to suppress the primary/distal tumor growth. Moreover, the acidic-triggered captopril release in tumor microenvironment can polarize the protumoral N2 phenotype neutrophils to antitumor N1 phenotype for improving the immune effects to achieve complete tumor regression (83%) in H22-bearing mice and prolong the survival time. This work provides an alternative approach for developing novel HCC immunotherapy strategies.

Anti-CAIX BBζ CAR4/8 T cells exhibit superior efficacy in a ccRCC mouse model

Improving CAR-T cell therapy for solid tumors requires a better understanding of CAR design and cellular composition. Here, we compared second-generation (BBζ and 28ζ) with third-generation (28BBζ) carbonic anhydrase IX (CAIX)-targeted CAR constructs and investigated the antitumor effect of CAR-T cells with different CD4/CD8 proportions in vitro and in vivo. The results demonstrated that BBζ exhibited superior efficacy compared with 28ζ and 28BBζ CAR-T cells in a clear-cell renal cell carcinoma (ccRCC) skrc-59 cell bearing NSG-SGM3 mouse model. The mice treated with a single dose of BBζ CD4/CD8 mixture (CAR4/8) showed complete tumor remission and remained tumor-free 72 days after CAR-T cells infusion. In the other CAR-T and control groups, tumor-infiltrating T cells were recovered and profiled. We found that BBζ CAR8 cells upregulated expression of major histocompatibility complex (MHC) class II and cytotoxicity-associated genes, while downregulating inhibitory immune checkpoint receptor genes and diminishing differentiation of regulatory T cells (Treg cells), leading to excellent therapeutic efficacy in vivo. Increased memory phenotype, elevated tumor infiltration, and decreased exhaustion genes were observed in the CD4/8 untransduced T (UNT) cells compared with CD8 alone, indicating that CD4/8 would be the favored cellular composition for CAR-T cell therapy with long-term persistence. In summary, these findings support that BBζ CAR4/8 cells are a highly potent, clinically translatable cell therapy for ccRCC.

Neoantigen Immunotherapeutic-Gel Combined with TIM-3 Blockade Effectively Restrains Orthotopic Hepatocellular Carcinoma Progression

Herein, we integrate the Hepa1-6 liver cancer-specific neoantigen, toll-like receptor 9 agonist and stimulator of interferon genes agonist by silk-hydrogel package, and combine with TIM-3 blockade to elicit robust antitumor immunity for effectively suppressing orthotopic hepatocellular carcinoma (HCC) progression. Unlike intradermal injection of simple mixed components with short-term immune protection, the neoantigen immunotherapeutic-gels evoke long-term immune protection to achieve significant prophylactic and therapeutic activity against HCC through only one-shot administration without any side effects. Notably, the synergized immunotherapy by further combining NGC-gels with TIM-3 antibody significantly reduces regulatory T-cells and increases the IFN-γ and IL-12p70 levels in tumor tissues for promoting the infiltration of IFN-γ+CD8+T-cells and 41BB+CD8+T-cells to achieve complete remission (4/7) and prevent pulmonary metastasis in orthotopic HCC, and establish long-term memory against tumor rechallenge with remarkably longer survival time (180 days). Overall, this study provides an attractive and promising synergistic strategy for HCC immunotherapy with possible clinical translation prospects.

Rapid manufacturing of non-activated potent CAR T cells

Chimaeric antigen receptor (CAR) T cells can generate durable clinical responses in B-cell haematologic malignancies. The manufacturing of these T cells typically involves their activation, followed by viral transduction and expansion ex vivo for at least 6 days. However, the activation and expansion of CAR T cells leads to their progressive differentiation and the associated loss of anti-leukaemic activity. Here we show that functional CAR T cells can be generated within 24 hours from T cells derived from peripheral blood without the need for T-cell activation or ex vivo expansion, and that the efficiency of viral transduction in this process is substantially influenced by the formulation of the medium and the surface area-to-volume ratio of the culture vessel. In mouse xenograft models of human leukaemias, the rapidly generated non-activated CAR T cells exhibited higher anti-leukaemic in vivo activity per cell than the corresponding activated CAR T cells produced using the standard protocol. The rapid manufacturing of CAR T cells may reduce production costs and broaden their applicability.

Leveraging biomaterials for enhancing T cell immunotherapy

The dynamic roles of T cells in the immune system to recognize and destroy the infected or mutated cells render T cell therapy a prospective treatment for a variety of diseases including cancer, autoimmune diseases, and allograft rejection. However, the clinical applications of T cell therapy remain unsatisfactory due to the tedious manufacturing process, off-target cytotoxicity, poor cell persistence, and associated adverse effects. To this end, various biomaterials have been introduced to enhance T cell therapy by facilitating proliferation, enhancing local enrichment, prolonging retention, and alleviating side effects. This review highlights the design strategies of biomaterials developed for T cell expansion, enrichment, and delivery as well as their corresponding therapeutic effects. The prospects of biomaterials for enhancing T cell immunotherapy are also discussed in this review.

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.

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.

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

Background

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

Methods

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

Results

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

Conclusion

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

Improved Immunotherapy Efficacy by Vascular Modulation

Several strategies have been developed to modulate the tumour vasculature for cancer therapy including anti-angiogenesis and vascular normalisation. Vasculature modulation results in changes to the tumour microenvironment including oxygenation and immune cell infiltration, therefore lending itself to combination with cancer therapy. The development of immunotherapies has led to significant improvements in cancer treatment. Particularly promising are immune checkpoint blockade and CAR T cell therapies, which use antibodies against negative regulators of T cell activation and T cells reprogrammed to better target tumour antigens, respectively. However, while immunotherapy is successful in some patients, including those with advanced or metastatic cancers, only a subset of patients respond. Therefore, better predictors of patient response and methods to overcome resistance warrant investigation. Poor, or periphery-limited, T cell infiltration in the tumour is associated with poor responses to immunotherapy. Given that (1) lymphocyte recruitment requires leucocyte-endothelial cell adhesion and (2) the vasculature controls tumour oxygenation and plays a pivotal role in T cell infiltration and activation, vessel targeting strategies including anti-angiogenesis and vascular normalisation in combination with immunotherapy are providing possible new strategies to enhance therapy. Here, we review the progress of vessel modulation in enhancing immunotherapy efficacy.

Chimeric antigen receptor (CAR) immunotherapy: basic principles, current advances, and future prospects in neuro-oncology

With recent advances, chimeric antigen receptor (CAR) immunotherapy has become a promising modality for patients with refractory cancer diseases. The successful results of CAR T cell therapy in relapsed and refractory B-cell malignancies shifted the paradigm of cancer immunotherapy by awakening the scientific, clinical, and commercial interest in translating this technology for the treatment of solid cancers. This review elaborates on fundamental principles of CAR T cell therapy (development of CAR construct, challenges of CAR T cell therapy) and its application on solid tumors as well as CAR T cell therapy potential in the field of neuro-oncology. Glioblastoma (GBM) is identified as one of the most challenging solid tumors with a permissive immunological milieu and dismal prognosis. Standard multimodal treatment using maximal safe resection, radiochemotherapy, and maintenance chemotherapy extends the overall survival beyond a year. Recurrence is, however, inevitable. GBM holds several unique features including its vast intratumoral heterogeneity, immunosuppressive environment, and a partially permissive anatomic blood–brain barrier, which offers a unique opportunity to investigate new treatment approaches. Tremendous efforts have been made in recent years to investigate novel CAR targets and target combinations with standard modalities for solid tumors and GBM to improve treatment efficacy. In this review, we outline the history of CAR immunotherapy development, relevant CAR target antigens validated with CAR T cells as well as preclinical approaches in combination with adjunct approaches via checkpoint inhibition, bispecific antibodies, and second-line systemic therapies that enhance anticancer efficacy of the CAR-based cancer immunotherapy.

CAR-T after Stem Cell Transplantation in B-Cell Lymphoproliferative Disorders: Are They Really Autologous or Allogenic Cell Therapies?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is one of the standard treatments for B-cell lymphoproliferative disorders; however, deep relapses are common after an allo-HSCT, and it is associated with poor prognosis. A successful approach to overcome these relapses is to exploit the body's own immune system with chimeric antigen receptor (CAR) T-cells. These two approaches are potentially combinatorial for treating R/R B-cell lymphoproliferative disorders. Several clinical trials have described different scenarios in which allo-HSCT and CAR-T are successively combined. Further, for all transplanted patients, assessment of chimerism is important to evaluate the engraftment success. Nonetheless, for those patients who previously received an allo-HSCT there is no monitorization of chimerism before manufacturing CAR T-cells. In this review, we focus on allo-HSCT and CAR-T treatments and the different sources of T-cells for manufacturing CAR T-cells.

Novel DNA-based T-Cell Activator Promotes Rapid T-Cell Activation and Expansion

Supplemental Digital Content is available in the text.

Autologous chimeric antigen receptor engineered T-cell therapies are beginning to dramatically change the outlook for patients with several hematological malignancies. Yet methods to activate and expand these cells are limited, often pose challenges to automation, and have biological limitations impacting the output of the injectable dose. This study describes the development of a novel, highly flexible, soluble DNA-based T-cell activation and expansion platform which alleviates the limitations of current technologies and provides rapid T-cell activation and expansion.

Tisagenlecleucel Immunogenicity in Relapsed/Refractory Acute Lymphoblastic Leukemia and Diffuse Large B-Cell Lymphoma

Pre- and posttreatment anti-mCAR19 antibodies did not alter tisagenlecleucel cellular kinetics, efficacy, or safety in r/r B-ALL or r/r DLBCL.

T-cell responses to mCAR19 peptides did not influence patient outcomes or cellular expansion in r/r B-ALL or r/r DLBCL.

Tisagenlecleucel is indicated for pediatric and young adult patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL) and adult patients with r/r diffuse large B-cell lymphoma (DLBCL). The tisagenlecleucel chimeric antigen receptor (CAR) contains a murine single-chain variable fragment domain; we examined the effects of humoral and cellular immune responses to tisagenlecleucel on clinical outcomes using 2 validated assays. Data were pooled from the ELIANA (registered at www.clinicaltrials.gov as #NCT02435849) and ENSIGN (#NCT02228096) trials in r/r B-ALL (N = 143) and the JULIET trial (#NCT02445248) in r/r DLBCL (N = 115). Humoral responses were determined by flow cytometric measurement of anti-murine CAR19 (mCAR19) antibodies in serum. Cellular responses were determined using T-cell production of interferon-γ in response to 2 different pools of mCAR19 peptides. Pretreatment anti-mCAR19 antibodies were detected in 81% of patients with r/r B-ALL and 94% of patients with r/r DLBCL. Posttreatment anti-mCAR19 antibodies were higher than patient-specific baseline in 42% of r/r B-ALL and 9% of r/r DLBCL patients. Pretreatment and posttreatment anti-mCAR19 antibodies did not affect tisagenlecleucel cellular kinetics, including maximum concentration and persistence (r² < 0.05), clinical response (day-28 response, duration of response, and event-free survival), and safety. T-cell responses were consistent over time, with net responses <1% at baseline and posttreatment time points in a majority of patients and no effect on transgene expansion or persistence or outcomes. Presence of baseline and/or posttreatment anti-mCAR19 antibodies or T-cell responses did not alter the activity of tisagenlecleucel in patients with r/r B-ALL or r/r DLBCL.

Lisocabtagene Maraleucel for the treatment of B-cell lymphoma

Introduction: Lisocabtagene Maraleucel (Liso-cel) is a second-generation Chimeric Antigen Receptor T-cell (CAR-T) therapy product targeting CD19. It is currently being evaluated for B-cell lymphomas with pivotal trials conducted in Aggressive B-cell LymphomasAreas covered: To prepare this article reviewing preclinical and clinical data studying Liso-cel, we performed a Pubmed search using the terms 'JCAR017' and 'Lisocabtagene maraleucel'. Pre-clinical work done with Liso-cel demonstrate the synergistic activity of CD4 + T-cells and CD8+ central memory T-cells (TCM) at a predefined ratio of 1:1. The trial, TRANSCEND NHL001 in aggressive B-cell lymphoma, confirms robust antitumor activity while demonstrating manageable toxicity profile.Expert Opinion: There are inherent differences amongst the three CD19 directed CAR-T products. This could explain the differences in efficacy and safety profiles of the products. In the absence of randomized data, it would be scientifically unsound to prioritize one product over another. Nevertheless, when aiming to balance efficacy and safety, current prospective data indicate that Liso-cel is well positioned with impressive response rates.

Objectives, benefits and challenges of bioreactor systems for the clinical-scale expansion of T lymphocyte cells

Cell therapies based on T cell have gathered interest over the last decades for treatment of cancers, becoming recently the most investigated lineage for clinical trials. Although results of adoptive cell therapies are very promising, obtaining large batches of T cell at clinical scale is still challenging nowadays. We propose here a review study focusing on how bioreactor systems could increase expansion rates of T cell culture specifically towards efficient, reliable and reproducible cell therapies. After describing the specificities of T cell culture, in particular activation, phenotypical characterization and cell density considerations, we detail the main objectives of bioreactors in this context, namely scale-up, GMP-compliance and reduced time and costs. Then, we report recent advances on the different classes of bioreactor systems commonly investigated for non-adherent cell expansion, in comparison with the current "gold standard" of T cell culture (flasks and culture bag). Results obtained with hollow fibres, G-Rex® flasks, Wave bioreactor, multiple-step bioreactors, spinner flasks as well as original homemade designs are discussed to highlight advantages and drawbacks in regards to T cells' specificities. Although there is currently no consensus on an optimal bioreactor, overall, most systems reviewed here can improve T cell culture towards faster, easier and/or cheaper protocols. They also offer strong outlooks towards automation, process control and complete closed systems, which could be mandatory developments for a massive clinical breakthrough. However, proper controls are sometimes lacking to conclude clearly on the features leading to the progresses regarding cell expansion, and the field could benefit from process engineering methods, such as quality by design, to perform multi parameters studies and face these challenges.

Anti-mucin 1 chimeric antigen receptor T cells for adoptive T cell therapy of cholangiocarcinoma

Current treatments for cholangiocarcinoma (CCA) are largely unsuccessful due to late diagnosis at advanced stage, leading to high mortality rate. Consequently, improved therapeutic approaches are urgently needed. Chimeric antigen receptor (CAR) T cell therapy is a newly potential therapy that can recognize specific surface antigen without major histocompatibility complex (MHC) restriction. Mucin 1 (MUC1) is an attractive candidate antigen as it is highly expressed and associated with poor prognosis and survival in CCA. We, therefore, set forth to create the fourth-generation CAR (CAR4) construct containing anti-MUC1-single-chain variable fragment (scFv) and three co-stimulatory domains (CD28, CD137, and CD27) linked to CD3ζ and evaluate anti-MUC1-CAR4 T cells in CCA models. Compared to untransduced T cells, anti-MUC1-CAR4 T cells produced increased levels of TNF-α, IFN-γ and granzyme B when exposed to MUC1-expressing KKU-100 and KKU-213A CCA cells (all p < 0.05). Anti-MUC1-CAR4 T cells demonstrated specific killing activity against KKU-100 (45.88 ± 7.45%, p < 0.05) and KKU-213A cells (66.03 ± 3.14%, p < 0.001) at an effector to target ratio of 5:1, but demonstrated negligible cytolytic activity against immortal cholangiocytes. Furthermore, the anti-MUC1-CAR4 T cells could effectively disrupt KKU-213A spheroids. These activities of anti-MUC1-CAR4 T cells supports the development of this approach as an adoptive T cell therapeutic strategy for CCA.

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.

CD19-specific CAR T Cells that Express a PD-1/CD28 Chimeric Switch-Receptor are Effective in Patients with PD-L1-positive B-Cell Lymphoma

PURPOSE

CD19-specific chimeric antigen receptor (CAR) T-cell therapy is effective against refractory or relapsed (R/R) B-cell lymphoma, but the efficacy is hindered by the existence of PD-1/PD-L1 pathway.

PATIENTS AND METHODS

Here, we generated a novel anti-CD19 CAR-expressing PD-1/CD28 chimeric switch-receptor (CD19-PD-1/CD28-CAR). We then conducted a phase Ib study to evaluate safety and efficacy of CD19-PD-1/CD28-CAR T cells in the treatment of PD-L1+ B-cell lymphoma.

RESULTS

We found that CD19-PD-1/CD28-CAR T cells had superior T-cell proliferation, cytokine production, and sequentially capability of killing PD-L1+ B-cell lymphoma cells in vitro and in vivo relative to the prototype, CD19-CAR T cells. Among 17 adult patients with R/R lymphoma who received the CAR T therapy, 10 patients had objective response (58.8%), including seven patients with complete remission (41.2%). At a median follow-up 15 months, median overall survival for all patients was not reached. Remarkably, no severe neurologic toxicity or cytokine release syndrome was observed.

CONCLUSIONS

This first-in-human study demonstrates the tolerability, safety, and encouraging efficacy of CD19-PD-1/CD28-CART in PD-L1+ large B-cell lymphoma.

4-1BB costimulation promotes bystander activation of human CD8 T cells

Costimulatory signals potently promote T‐cell proliferation and effector function. Agonistic antibodies targeting costimulatory receptors of the TNFR family, such as 4‐1BB and CD27, have entered clinical trials in cancer patients. Currently there is limited information how costimulatory signals regulate antigen‐specific but also bystander activation of human CD8 T cells.

Engineered antigen presenting cells (eAPC) efficiently presenting several common viral epitopes on HLA‐A2 in combination with MHC class I tetramer staining were used to investigate the impact of costimulatory signals on human CD8 T‐cell responses. CD28 costimulation potently augmented the percentage and number of antigen‐reactive CD8 T cells, whereas eAPC expressing 4‐1BB‐ligand induced bystander proliferation of CD8 T cells and massive expansion of NK cells. Moreover, the 4‐1BB agonist urelumab similarly induced bystander proliferation of CD8 T cells and NK cells in a dose‐dependent manner. However, the promotion of bystander CD8 T‐cell responses is not a general attribute of costimulatory TNF receptor superfamily (TNFRSF) members, since CD27 signals enhanced antigen‐specific CD8 T cells responses without promoting significant bystander activation.

Thus, the differential effects of costimulatory signals on the activation of human bystander CD8 T cells should be taken into account when costimulatory pathways are harnessed for cancer immunotherapy.

Engineering CAR T Cells to Target the HIV Reservoir

The HIV reservoir remains to be a difficult barrier to overcome in order to achieve a therapeutic cure for HIV. Several strategies have been developed to purge the reservoir, including the “kick and kill” approach, which is based on the notion that reactivating the latent reservoir will allow subsequent elimination by the host anti-HIV immune cells. However, clinical trials testing certain classes of latency reactivating agents (LRAs) have so far revealed the minimal impact on reducing the viral reservoir. A robust immune response to reactivated HIV expressing cells is critical for this strategy to work. A current focus to enhance anti-HIV immunity is through the use of chimeric antigen receptors (CARs). Currently, HIV-specific CARs are being applied to peripheral T cells, NK cells, and stem cells to boost recognition and killing of HIV infected cells. In this review, we summarize current developments in engineering HIV directed CAR-expressing cells to facilitate HIV elimination. We also summarize current LRAs that enhance the “kick” strategy and how new generation and combinations of LRAs with HIV specific CAR T cell therapies could provide an optimal strategy to target the viral reservoir and achieve HIV clearance from the body.

Tisagenlecleucel in Acute Lymphoblastic Leukemia: A Review of the Literature and Practical Considerations

OBJECTIVE

To evaluate the current literature for tisagenlecleucel in the treatment of relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (ALL).

DATA SOURCES

A literature search of PubMed (inception to June 18, 2020) and ClinicalTrials.gov was conducted using the following search terms: CTL019, chimeric antigen receptor, CAR-T, and tisagenlecleucel.

STUDY SELECTION AND DATA EXTRACTION

All trials evaluating the use of tisagenlecleucel in B-cell ALL were reviewed and considered for inclusion.

DATA SYNTHESIS

Tisagenlecleucel displayed overall remission rates ranging from 69% to 93% in patients who historically respond extremely poorly to salvage therapy. Remissions were durable, with 12-month relapse-free survival (RFS) rates of 55% to 59%. These promising results are tempered by the unique adverse effect profile of chimeric antigen receptor (CAR) T-cell therapy. Potentially life-threatening cytokine release syndrome (CRS) occurred in 77% to 100% of patients, and immune effector cell-associated neurotoxicity syndrome (ICANS) developed in 31% to 45% of patients receiving tisagenlecleucel.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The successful utilization of tisagenlecleucel therapy requires meticulous planning, prudent patient selection, multidisciplinary collaboration, and expert training to ensure optimal patient care. The complex interplay of patient- and treatment-related factors creates problematic barriers that must be expertly navigated by the health care team and authorized treatment center.

CONCLUSIONS

As the first US Food and Drug Administration-approved gene therapy, tisagenlecleucel heralds an immunotherapeutic breakthrough for treating pediatric and young adult patients with r/r B-cell ALL. Many questions surrounding patient-specific gene and cellular therapies remain, but their transformative potential in cancer care remains promising.

A Novel Siglec-4 Derived Spacer Improves the Functionality of CAR T Cells Against Membrane-Proximal Epitopes

A domain that is often neglected in the assessment of chimeric antigen receptor (CAR) functionality is the extracellular spacer module. However, several studies have elucidated that membrane proximal epitopes are best targeted through CARs comprising long spacers, while short spacer CARs exhibit highest activity on distal epitopes. This finding can be explained by the requirement to have an optimal distance between the effector T cell and target cell. Commonly used long spacer domains are the CH2-CH3 domains of IgG molecules. However, CARs containing these spacers generally show inferior in vivo efficacy in mouse models compared to their observed in vitro activity, which is linked to unspecific Fcγ-Receptor binding and can be abolished by mutating the respective regions. Here, we first assessed a CAR therapy targeting membrane proximal CD20 using such a modified long IgG1 spacer. However, despite these mutations, this construct failed to unfold its observed in vitro cytotoxic potential in an in vivo model, while a shorter but less structured CD8α spacer CAR showed complete tumor clearance. Given the shortage of well-described long spacer domains with a favorable functionality profile, we designed a novel class of CAR spacers with similar attributes to IgG spacers but without unspecific off-target binding, derived from the Sialic acid-binding immunoglobulin-type lectins (Siglecs). Of five constructs tested, a Siglec-4 derived spacer showed highest cytotoxic potential and similar performance to a CD8α spacer in a CD20 specific CAR setting. In a pancreatic ductal adenocarcinoma model, a Siglec-4 spacer CAR targeting a membrane proximal (TSPAN8) epitope was efficiently engaged in vitro, while a membrane distal (CD66c) epitope did not activate the T cell. Transfer of the TSPAN8 specific Siglec-4 spacer CAR to an in vivo setting maintained the excellent tumor killing characteristics being indistinguishable from a TSPAN8 CD8α spacer CAR while outperforming an IgG4 long spacer CAR and, at the same time, showing an advantageous central memory CAR T cell phenotype with lower release of inflammatory cytokines. In summary, we developed a novel spacer that combines cytotoxic potential with an advantageous T cell and cytokine release phenotype, which make this an interesting candidate for future clinical applications.

HIV-Resistant and HIV-Specific CAR-Modified CD4+ T Cells Mitigate HIV Disease Progression and Confer CD4+ T Cell Help In Vivo

HIV infection preferentially depletes HIV-specific CD4+ T cells, thereby impairing antiviral immunity. In this study, we explored the therapeutic utility of adoptively transferred CD4+ T cells expressing an HIV-specific chimeric antigen receptor (CAR4) to restore CD4+ T cell function to the global HIV-specific immune response. We demonstrated that CAR4 T cells directly suppressed in vitro HIV replication and eliminated virus-infected cells. Notably, CAR4 T cells containing intracellular domains (ICDs) derived from the CD28 receptor family (ICOS and CD28) exhibited superior effector functions compared to the tumor necrosis factor receptor (TNFR) family ICDs (CD27, OX40, and 4-1BB). However, despite demonstrating limited in vitro efficacy, only HIV-resistant CAR4 T cells expressing the 4-1BBζ ICD exhibited profound expansion, concomitant with reduced rebound viremia after antiretroviral therapy (ART) cessation and protection of CD4+ T cells (CAR-) from HIV-induced depletion in humanized mice. Moreover, CAR4 T cells enhanced the in vivo persistence and efficacy of HIV-specific CAR-modified CD8+ T cells expressing the CD28ζ ICD, which alone exhibited poor survival. Collectively, these studies demonstrate that HIV-resistant CAR4 T cells can directly control HIV replication and augment the virus-specific CD8+ T cell response, highlighting the therapeutic potential of engineered CD4+ T cells to engender a functional HIV cure.

Cellular immunotherapies for cancer

Cancer is a major burden on the healthcare system, and new therapies are needed. Recently, the development of immunotherapies, which aim to boost or use the immune system, or its constituents, as a tool to fight malignant cells, has provided a major new tool in the arsenal of clinicians and has revolutionized the treatment of many cancers.

Cellular immunotherapies are based on the administration of living cells to patients and have developed hugely, especially since 2010 when Sipuleucel-T (Provenge), a DC vaccine, was the first cellular immunotherapy to be approved by the FDA. The ensuing years have seen two further cellular immunotherapies gain FDA approval: tisagenlecleucel (Kymriah) and axicabtagene ciloleucel (Yescarta).

This review will give an overview of the principles of immunotherapies before focusing on the major forms of cellular immunotherapies individually, T cell-based, natural killer (NK) cell-based and dendritic cell (DC)-based, as well as detailing some of the clinical trials relevant to each therapy.

CAR-T Cells Hit the Tumor Microenvironment: Strategies to Overcome Tumor Escape

Chimeric antigen receptor (CAR) T cell therapies have demonstrated remarkable efficacy for the treatment of hematological malignancies. However, in patients with solid tumors, objective responses to CAR-T cell therapy remain sporadic and transient. A major obstacle for CAR-T cells is the intrinsic ability of tumors to evade immune responses. Advanced solid tumors are largely composed of desmoplastic stroma and immunosuppressive modulators, and characterized by aberrant cell proliferation and vascularization, resulting in hypoxia and altered nutrient availability. To mount a curative response after infusion, CAR-T cells must infiltrate the tumor, recognize their cognate antigen and perform their effector function in this hostile tumor microenvironment, to then differentiate and persist as memory T cells that confer long-term protection. Fortunately, recent advances in synthetic biology provide a wide set of tools to genetically modify CAR-T cells to overcome some of these obstacles. In this review, we provide a comprehensive overview of the key tumor intrinsic mechanisms that prevent an effective CAR-T cell antitumor response and we discuss the most promising strategies to prevent tumor escape to CAR-T cell therapy.

Signaling from T cell receptors (TCRs) and chimeric antigen receptors (CARs) on T cells

T cells react to foreign or self-antigens through T cell receptor (TCR) signaling. Several decades of research have delineated the mechanism of TCR signal transduction and its impact on T cell performance. This knowledge provides the foundation for chimeric antigen receptor T cell (CAR-T cell) technology, by which T cells are redirected in a major histocompatibility complex-unrestricted manner. TCR and CAR signaling plays a critical role in determining the T cell state, including exhaustion and memory. Given its artificial nature, CARs might affect or rewire signaling differently than TCRs. A better understanding of CAR signal transduction would greatly facilitate improvements to CAR-T cell technology and advance its usefulness in clinical practice. Herein, we systematically review the knowns and unknowns of TCR and CAR signaling, from the contact of receptors and antigens, proximal signaling, immunological synapse formation, and late signaling outcomes. Signaling through different T cell subtypes and how signaling is translated into practice are also discussed.

Adoptive Cell Therapy-Harnessing Antigen-Specific T Cells to Target Solid Tumours

In recent years, much research has been focused on the field of adoptive cell therapies (ACT) that use native or genetically modified T cells as therapeutic tools. Immunotherapy with T cells expressing chimeric antigen receptors (CARs) demonstrated great success in the treatment of haematologic malignancies, whereas adoptive transfer of autologous tumour infiltrating lymphocytes (TILs) proved to be highly effective in metastatic melanoma. These encouraging results initiated many studies where ACT was tested as a treatment for various solid tumours. In this review, we provide an overview of the challenges of T cell-based immunotherapies of solid tumours. We describe alternative approaches for choosing the most efficient T cells for cancer treatment in terms of their tumour-specificity and phenotype. Finally, we present strategies for improvement of anti-tumour potential of T cells, including combination therapies.

Engineering T Cells to Treat Cancer: The Convergence of Immuno-Oncology and Synthetic Biology

T cells engineered to recognize and kill tumor cells have emerged as powerful agents for combating cancer. Nonetheless, our ability to engineer T cells remains relatively primitive. Aside from CAR T cells for treating B cell malignancies, most T cell therapies are risky, toxic, and often ineffective, especially those that target solid cancers. To fulfill the promise of cell-based therapies, we must transform cell engineering into a systematic and predictable science by applying the principles and tools of synthetic biology. Synthetic biology uses a hierarchical approach—assembling sets of modular molecular parts that can be combined into larger circuits and systems that perform defined target tasks. We outline the toolkit of synthetic modules that are needed to overcome the challenges of solid cancers, progress in building these components, and how these modules could be used to reliably engineer more effective and precise T cell therapies.

CAR T‑cell therapy for gastric cancer: Potential and perspective (Review)

Gastric cancer (GC) is one of the most frequently diagnosed digestive malignancies and is the third leading cause of cancer‑associated death worldwide. Delayed diagnosis and poor prognosis indicate the urgent need for new therapeutic strategies. The success of chimeric antigen receptor (CAR) T‑cell therapy for chemotherapy‑refractory hematological malignancies has inspired the development of a similar strategy for GC treatment. Although using CAR T‑cells against GC is not without difficulty, results from preclinical studies remain encouraging. The current review summarizes relevant preclinical studies and ongoing clinical trials for the use of CAR T‑cells for GC treatment and investigates possible toxicities, as well as current clinical experiences and emerging approaches. With a deeper understanding of the tumor microenvironment, novel target epitopes and scientific‑technical progress, the potential of CAR T‑cell therapy for GC is anticipated in the near future.

In situ genetic engineering of tumors for long-lasting and systemic immunotherapy

There is an urgent need for improved cancer immunotherapies. The nanoparticles described here deliver genes to stimulate the immune system to specifically kill tumor cells. This synthetic, biodegradable system avoids the use of common gene delivery materials like viruses that can have safety concerns and manufacturing limitations. Local nanoparticle delivery evades adverse side effects stemming from systemic administration of immune-activating therapeutics. Importantly, this technology causes a tumor-targeting response but does not require prior knowledge of a particular patient’s gene expression profile; thus, it can serve as a platform to combat many different solid cancers. Moreover, local nanoparticle administration causes a systemic cellular immune response, which has the potential to lead to better outcomes in the context of recurrence or metastasis.

Cancer immunotherapy has been the subject of extensive research, but highly effective and broadly applicable methods remain elusive. Moreover, a general approach to engender endogenous patient-specific cellular therapy, without the need for a priori knowledge of tumor antigen, ex vivo cellular manipulation, or cellular manufacture, could dramatically reduce costs and broaden accessibility. Here, we describe a biotechnology based on synthetic, biodegradable nanoparticles that can genetically reprogram cancer cells and their microenvironment in situ so that the cancer cells can act as tumor-associated antigen-presenting cells (tAPCs) by inducing coexpression of a costimulatory molecule (4-1BBL) and immunostimulatory cytokine (IL-12). In B16-F10 melanoma and MC38 colorectal carcinoma mouse models, reprogramming nanoparticles in combination with checkpoint blockade significantly reduced tumor growth over time and, in some cases, cleared the tumor, leading to long-term survivors that were then resistant to the formation of new tumors upon rechallenge at a distant site. In vitro and in vivo analyses confirmed that locally delivered tAPC-reprogramming nanoparticles led to a significant cell-mediated cytotoxic immune response with systemic effects. The systemic tumor-specific and cell-mediated immunotherapy response was achieved without requiring a priori knowledge of tumor-expressed antigens and reflects the translational potential of this nanomedicine.

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

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

Efficacy of adoptive therapy with tumor-infiltrating lymphocytes and recombinant interleukin-2 in advanced cutaneous melanoma: a systematic review and meta-analysis

Adoptive cell therapy (ACT) using autologous tumor-infiltrating lymphocytes (TIL) has been tested in advanced melanoma patients at various centers. We conducted a systematic review and meta-analysis to assess its efficacy on previously treated advanced metastatic cutaneous melanoma. The PubMed electronic database was searched from inception to 17 December 2018 to identify studies administering TIL-ACT and recombinant interleukin-2 (IL-2) following non-myeloablative chemotherapy in previously treated metastatic melanoma patients. Objective response rate (ORR) was the primary end point. Secondary end points were complete response rate (CRR), overall survival (OS), duration of response (DOR) and toxicity. Pooled estimates were derived from fixed or random effect models, depending on the amount of heterogeneity detected. Analysis was carried out separately for high dose (HD) and low dose (LD) IL-2. Sensitivity analyses were carried out. Among 1211 records screened, 13 studies (published 1988 - 2016) were eligible for meta-analysis. Among 410 heavily pretreated patients (some with brain metastasis), 332 received HD-IL-2 and 78 LD-IL-2. The pooled overall ORR estimate was 41% [95% confidence interval (CI) 35% to 48%], and the overall CRR was 12% (95% CI 7% to 16%). For the HD-IL-2 group, the ORR was 43% (95% CI 36% to 50%), while for the LD-IL-2 it was 35% (95% CI 25% to 45%). Corresponding pooled estimates for CRR were 14% (95% CI 7% to 20%) and 7% (95% CI 1% to 12%). The majority of HD-IL-2 complete responders (27/28) remained in remission during the extent of follow-up after CR (median 40 months). Sensitivity analyses yielded similar results. Higher number of infused cells was associated with a favorable response. The ORR for HD-IL-2 compared favorably with the nivolumab/ipilimumab combination following anti-PD-1 failure. TIL-ACT therapy, especially when combined with HD-IL-2, achieves durable clinical benefit and warrants further investigation. We discuss the current position of TIL-ACT in the therapy of advanced melanoma, particularly in the era of immune checkpoint blockade therapy, and review future opportunities for improvement of this approach.

Optimizing CAR-T Cell Manufacturing Processes during Pivotal Clinical Trials

Tisagenlecleucel is a CD19-specific chimeric antigen receptor (CAR)-T cell therapy approved for patients aged ≤25 years with relapsed or refractory B cell precursor acute lymphoblastic leukemia (B-ALL) and adults with relapsed or refractory diffuse large B cell lymphoma (DLBCL). The initial tisagenlecleucel manufacturing process technology was developed at an academic center and was subsequently transferred, optimized, validated, and scaled out to supply large global trials before commercialization. Tisagenlecleucel manufactured in two centralized facilities has been successfully used in global multicenter trials for B-ALL and DLBCL (>50 clinical centers in 12 countries). In this paper, we describe some of the continuous process improvements made to tisagenlecleucel manufacturing over time to meet global demand while maintaining and improving product quality. During early tisagenlecleucel clinical trials, process enhancements were made to address logistical challenges related to manufacturing for multicenter trials and to accommodate the variability observed in patient starting cellular material. These enhancements resulted in improvements in manufacturing capacity, process robustness, manufacturing success rates, and product quality, and reductions in throughput time. In summary, through continuous evaluation and improvements based on experience during global trials, a consistent and robust commercial manufacturing process for tisagenlecleucel has been developed, leading to improvements in manufacturing success when compared to the initial processes.