4-1BB costimulation ameliorates T cell exhaustion induced by tonic signaling of chimeric antigen receptors

CD8α Structural Domains Enhance GUCY2C CAR-T Cell Efficacy

Despite success in treating some hematological malignancies, CAR-T cells have not yet produced similar outcomes in solid tumors due, in part, to the tumor microenvironment, poor persistence, and a paucity of suitable target antigens. Importantly, the impact of the CAR components on these challenges remains focused on the intracellular signaling and antigen-binding domains. In contrast, the flexible hinge and transmembrane domains have been commoditized and are the least studied components of the CAR. Here, we compared the hinge and transmembrane domains derived from either the CD8ɑ or CD28 molecule in identical GUCY2C-targeted third-generation designs for colorectal cancer. While these structural domains do not contribute to differences in antigen-independent contexts, such as CAR expression and differentiation and exhaustion phenotypes, the CD8ɑ structural domain CAR has a greater affinity for GUCY2C. This results in increased production of inflammatory cytokines and granzyme B, improved cytolytic effector function with low antigen-expressing tumor cells, and robust anti-tumor efficacy in vivo compared with the CD28 structural domain CAR. This suggests that CD8α structural domains should be considered in the design of all CARs for the generation of high-affinity CARs and optimally effective CAR-T cells in solid tumor immunotherapy.

Advancements in the design and function of bispecific CAR-T cells targeting B Cell-Associated tumor antigens

Single-targeted CAR-T has exhibited notable success in treating B-cell tumors, effectively improving patient outcomes. However, the recurrence rate among patients remains above fifty percent, primarily attributed to antigen escape and the diminished immune persistence of CAR-T cells. Over recent years, there has been a surge of interest in bispecific CAR-T cell therapies, marked by an increasing number of research articles and clinical applications annually. This paper undertakes a comprehensive review of influential studies on the design of bispecific CAR-T in recent years, examining their impact on bispecific CAR-T efficacy concerning disease classification, targeted antigens, and CAR design. Notable distinctions in antigen targeting within B-ALL, NHL, and MM are explored, along with an analysis of how CAR scFv, transmembrane region, hinge region, and co-stimulatory region design influence Bi-CAR-T efficacy across different tumors. The summary provided aims to serve as a reference for designing novel and improved CAR-Ts, facilitating more efficient treatment for B-cell malignant tumors.

Regulatory T cell-based therapy in type 1 diabetes: Latest breakthroughs and evidence

Autoimmune diseases (ADs) are among the most significant health complications, with their incidence rising in recent years. Type 1 diabetes (T1D), an AD, targets the insulin-producing β cells in the pancreas, leading to chronic insulin deficiency in genetically susceptible individuals. Regulatory immune cells, particularly T-cells (Tregs), have been shown to play a crucial role in the pathogenesis of diabetes by modulating immune responses. In diabetic patients, Tregs often exhibit diminished effectiveness due to various factors, such as instability in forkhead box P3 (Foxp3) expression or abnormal production of the proinflammatory cytokine interferon-gamma (IFN-γ) by autoreactive T-cells. Consequently, Tregs represent a potential therapeutic target for diabetes treatment. Building on the successful clinical outcomes of chimeric antigen receptor (CAR) T-cell therapy in cancer treatment, particularly in leukemias, the concept of designing and utilizing CAR Tregs for ADs has emerged. This review summarizes the findings on Treg targeting in T1D and discusses the benefits and limitations of this treatment approach for patients suffering from T1D.

GLUT1 overexpression in CAR-T cells induces metabolic reprogramming and enhances potency

The intensive nutrient requirements needed to sustain T cell activation and proliferation, combined with competition for nutrients within the tumor microenvironment, raise the prospect that glucose availability may limit CAR-T cell function. Here, we seek to test the hypothesis that stable overexpression (OE) of the glucose transporter GLUT1 in primary human CAR-T cells would improve their function and antitumor potency. We observe that GLUT1OE in CAR-T cells increases glucose consumption, glycolysis, glycolytic reserve, and oxidative phosphorylation, and these effects are associated with decreased T cell exhaustion and increased Th17 differentiation. GLUT1OE also induces broad metabolic reprogramming associated with increased glutathione-mediated resistance to reactive oxygen species, and increased inosine accumulation. When challenged with tumors, GLUT1OE CAR-T cells secrete more proinflammatory cytokines and show enhanced cytotoxicity in vitro, and demonstrate superior tumor control and persistence in mouse models. Our collective findings support a paradigm wherein glucose availability is rate limiting for effector CAR-T cell function and demonstrate that enhancing glucose availability via GLUT1OE could augment antitumor immune function.

Antigen-independent activation is critical for the durable antitumor effect of GUCY2C-targeted CAR-T cells

BACKGROUND

Chimeric antigen receptor (CAR)-T cells face many obstacles in solid tumor therapy, including heterogeneous antigen expression and inefficient T cell persistence. Guanylyl cyclase C (GUCY2C) has been identified as a suitable tumor antigen for targeted therapy due to its intestinal-restricted expression pattern in normal tissues and steady overexpression in gastrointestinal tumors, especially colorectal cancer. An antigen-sensitive and long-lasting CAR-T cell targeting GUCY2C was investigated in this study.

METHODS

Using constructed tumor cell lines with various GUCY2C expression densities, we screened out an antigen-sensitive single chain variable fragment (scFv) that enabled CAR-T cells to efficiently eradicate the GUCY2C lowly expressed tumor cells. CAR-T cells with different compositions of the hinge, transmembrane and costimulatory domains were also constructed for selection of the long-lasting CAR-T format with durable antitumor efficacy in vitro and in tumor-bearing mice. The underlying mechanism was further investigated based on mutation of the hinge and transmembrane domains.

RESULTS

We found that the composition of the antigen-sensitive scFv, CD8α hinge, CD8α transmembrane, and CD28 costimulatory domains boosted CAR-T cells to rapidly kill tumors, maintain high expansion capacity, and long-term efficacy in various colorectal cancer models. The durable antitumor function was attributed to the optimal CAR tonic signaling that conferred CAR-T cells with autonomous activation, proliferation, survival and cytokine release in the absence of antigen stimulation. The tonic signaling was associated with the length and the cysteine residues in the CD8α hinge and transmembrane domains.

CONCLUSIONS

This study demonstrated a potent GUCY2C-targeted CAR-T cell for gastrointestinal tumor therapy and highlights the importance of adequate tonic signaling for effective CAR-T cell therapy against solid tumors.

PD-1 blockade does not improve efficacy of EpCAM-directed CAR T-cell in lung cancer brain metastasis

BACKGROUND

Lung cancer brain metastasis has a devastating prognosis, necessitating innovative treatment strategies. While chimeric antigen receptor (CAR) T-cell show promise in hematologic malignancies, their efficacy in solid tumors, including brain metastasis, is limited by the immunosuppressive tumor environment. The PD-L1/PD-1 pathway inhibits CAR T-cell activity in the tumor microenvironment, presenting a potential target to enhance therapeutic efficacy. This study aims to evaluate the impact of anti-PD-1 antibodies on CAR T-cell in treating lung cancer brain metastasis.

METHODS

We utilized a murine immunocompetent, syngeneic orthotopic cerebral metastasis model for repetitive intracerebral two-photon laser scanning microscopy, enabling in vivo characterization of red fluorescent tumor cells and CAR T-cell at a single-cell level over time. Red fluorescent EpCAM-transduced Lewis lung carcinoma cells (EpCAM/tdtLL/2 cells) were implanted intracranially. Following the formation of brain metastasis, EpCAM-directed CAR T-cell were injected into adjacent brain tissue, and animals received either anti-PD-1 or an isotype control.

RESULTS

Compared to controls receiving T-cell lacking a CAR, mice receiving EpCAM-directed CAR T-cell showed higher intratumoral CAR T-cell densities in the beginning after intraparenchymal injection. This finding was accompanied with reduced tumor growth and translated into a survival benefit. Additional anti-PD-1 treatment, however, did not affect intratumoral CAR T-cell persistence nor tumor growth and thereby did not provide an additional therapeutic effect.

CONCLUSION

CAR T-cell therapy for brain malignancies appears promising. However, additional anti-PD-1 treatment did not enhance intratumoral CAR T-cell persistence or effector function, highlighting the need for novel strategies to improve CAR T-cell therapy in solid tumors.

Unlocking Apoptotic Pathways: Overcoming Tumor Resistance in CAR-T-Cell Therapy

BACKGROUND

Chimeric antigen receptor (CAR)-T-cell therapy has transformed cancer treatment, leading to remarkable clinical outcomes. However, resistance continues to be a major obstacle, significantly limiting its efficacy in numerous patients.

OBJECTIVES

This review critically examines the challenges associated with CAR-T-cell therapy, with a particular focus on the role of apoptotic pathways in overcoming resistance.

METHODS

We explore various strategies to sensitize tumor cells to CAR-T-cell-mediated apoptosis, including the use of combination therapies with BH3 mimetics, Mcl-1 inhibitors, IAP inhibitors, and HDAC inhibitors. These agents inhibit anti-apoptotic proteins and activate intrinsic mitochondrial pathways, enhancing the susceptibility of tumor cells to apoptosis. Moreover, targeting the extrinsic pathway can increase the expression of death receptors on tumor cells, further promoting their apoptosis. The review also discusses the development of novel CAR constructs that enhance anti-apoptotic protein expression, such as Bcl-2, which may counteract CAR-T cell exhaustion and improve antitumor efficacy. We assess the impact of the tumor microenvironment (TME) on CAR-T cell function and propose dual-targeting CAR-T cells to simultaneously address both myeloid-derived suppressor cells (MDSCs) and tumor cells. Furthermore, we explore the potential of combining agents like PPAR inhibitors to activate the cGAS-STING pathway, thereby improving CAR-T cell infiltration into the tumor.

CONCLUSIONS

This review highlights that enhancing tumor cell sensitivity to apoptosis and increasing CAR-T cell cytotoxicity through apoptotic pathways could significantly improve therapeutic outcomes. Targeting apoptotic proteins, particularly those involved in the intrinsic mitochondrial pathway, constitutes a novel approach to overcoming resistance. The insights presented herein lay a robust foundation for future research and clinical applications aimed at optimizing CAR-T cell therapies.

Spatiotemporal dynamics of tumor - CAR T-cell interaction following local administration in solid cancers

The success of chimeric antigen receptor (CAR) T-cell therapy in treating hematologic malignancies has generated widespread interest in translating this technology to solid cancers. However, issues like tumor infiltration, the immunosuppressive tumor microenvironment, and tumor heterogeneity limit its efficacy in the solid tumor setting. Recent experimental and clinical studies propose local administration directly into the tumor or at the tumor site to increase CAR T-cell infiltration and improve treatment outcomes. Characteristics of the types of solid tumors that may be the most receptive to this treatment approach remain unclear. In this work, we develop a spatiotemporal model for CAR T-cell treatment of solid tumors, and use numerical simulations to compare the effect of introducing CAR T cells via intratumoral injection versus intracavitary administration in diverse cancer types. We demonstrate that the model can recapitulate tumor and CAR T-cell data from imaging studies of local administration of CAR T cells in mouse models. Our results suggest that locally administered CAR T cells will be most successful against slowly proliferating, highly diffusive tumors, which have the lowest average tumor cell density. These findings affirm the clinical observation that CAR T cells will not perform equally across different types of solid tumors, and suggest that measuring tumor density may be helpful when considering the feasibility of CAR T-cell therapy and planning dosages for a particular patient. We additionally find that local delivery of CAR T cells can result in deep tumor responses, provided that the initial CAR T-cell dose does not contain a significant fraction of exhausted cells.

Engineered CD4 T cells for in vivo delivery of therapeutic proteins

The CD4 T cell, when engineered with a chimeric antigen receptor (CAR) containing specific intracellular domains, has been transformed into a zero-order drug-delivery platform. This introduces the capability of prolonged, disease-specific engineered protein biologics production, at the disease site. Experimental findings demonstrate that CD4 T cells offer a solution when modified with a CAR that includes 4-1BB but excludes CD28 intracellular domain. In this configuration, they achieve ~3X transduction efficiency of CD8 T cells, ~2X expansion rates, generating ~5X more biologic, and exhibit minimal cytolytic activity. Cumulatively, this addresses two main hurdles in the translation of cell-based drug delivery: scaling the production of engineered T cell ex vivo and generating sufficient biologics in vivo. When programmed to induce IFNβ upon engaging the target antigen, the CD4 T cells outperforms CD8 T cells, effectively suppressing cancer cell growth in vitro and in vivo. In summary, this platform enables precise targeting of disease sites with engineered protein-based therapeutics while minimizing healthy tissue exposure. Leveraging CD4 T cells' persistence could enhance disease management by reducing drug administration frequency, addressing critical challenges in cell-based therapy.

Optimization of anti-TIM3 chimeric antigen receptor with CD8α spacer and TNFR-based costimulation for enhanced efficacy in AML therapy

CAR T cell therapy for AML remains limited due to the lack of a proper target without on-target off-tumor toxicity. TIM3 is a promising target due to its high expression on AML cells and absence in most normal hematopoietic cells. Previous reports have shown that each CAR component impacts CAR functionality. Here, we optimized TIM-3 targeting CAR T cells for AML therapy. We generated CARs targeting TIM3 with two different non-signaling domains: an IgG2-CH3 spacer with CD28 transmembrane domain (CH3/CD28) and a CD8α spacer with CD8α transmembrane domain (CD8/CD8), and evaluated their characteristics and function. Incorporating the non-signaling CH3/CD28 domain resulted in unstable CAR expression in anti-TIM3 CAR T cells, leading to lower surface CAR expression over time and reduced cytotoxic function compared to anti-TIM3 CARs with the CD8/CD8 domain. Both types of anti-TIM3 CAR T cells transiently exhibited fratricide, which subsided overtime, and both CAR T cells achieved substantial T cell expansion. To further optimize the design, we explored the effects of different costimulatory domains. Compared with CD28 costimulation, 4-1BB and CD27 combined with a CD8/CD8 non-signaling domain showed higher cytokine secretion, superior antitumor activity, and enhanced T-cell persistence after repeated antigen exposure. These findings emphasize the impact of the optimal design of CAR constructs that provide efficient function. In the context of anti-TIM3 CAR T cells, using a CD8α spacer and transmembrane domain with TNFR-based costimulation is a promising CAR design to improve anti-TIM3 CAR T cell function for AML therapy.

Single-cell CAR T atlas reveals type 2 function in 8-year leukaemia remission

Despite a high response rate in chimeric antigen receptor (CAR) T cell therapy for acute lymphocytic leukaemia (ALL)1-3, approximately 50% of patients relapse within the first year4-6, representing an urgent question to address in the next stage of cellular immunotherapy. Here, to investigate the molecular determinants of ultralong CAR T cell persistence, we obtained a single-cell multi-omics atlas from 695,819 pre-infusion CAR T cells at the basal level or after CAR-specific stimulation from 82 paediatric patients with ALL enrolled in the first two CAR T ALL clinical trials and 6 healthy donors. We identified that elevated type 2 functionality in CAR T infusion products is significantly associated with patients maintaining a median B cell aplasia duration of 8.4 years. Analysis of ligand-receptor interactions revealed that type 2 cells regulate a dysfunctional subset to maintain whole-population homeostasis, and the addition of IL-4 during antigen-specific activation alleviates CAR T cell dysfunction while enhancing fitness at both transcriptomic and epigenomic levels. Serial proteomic profiling of sera after treatment revealed a higher level of circulating type 2 cytokines in 5-year or 8-year relapse-free responders. In a leukaemic mouse model, type 2high CAR T cell products demonstrated superior expansion and antitumour activity, particularly after leukaemia rechallenge. Restoring antitumour efficacy in type 2low CAR T cells was attainable by enhancing their type 2 functionality, either through incorporating IL-4 into the manufacturing process or by priming manufactured CAR T products with IL-4 before infusion. Our findings provide insights into the mediators of durable CAR T therapy response and suggest potential therapeutic strategies to sustain long-term remission by boosting type 2 functionality in CAR T cells.

CAR T cells in solid tumors and metastasis: paving the way forward

CAR T cell therapy, hailed as a breakthrough in cancer treatment due to its remarkable outcomes in hematological malignancies, encounters significant hurdles when applied to solid tumors. While notable responses to CAR T cells remain sporadic in these patients, challenges persist due to issues such as on-target off-tumor toxicity, difficulties in their trafficking and infiltration into the tumor, and the presence of a hostile and immunosuppressive microenvironment. This review aims to explore recent endeavors aimed at overcoming these obstacles in CAR T cell therapy for solid tumors. Specifically, we will delve into promising strategies for enhancing tumor specificity through antigen targeting, addressing tumor heterogeneity, overcoming physical barriers, and counteracting the immune-suppressive microenvironment.

CAR T-cells for pediatric solid tumors: where to go from here?

Despite the great success that chimeric antigen receptor (CAR) T-cells have had in patients with B-cell malignancies and multiple myeloma, they continue to have limited efficacy against most solid tumors. Especially in the pediatric population, pre- and post-treatment biopsies are rarely performed due to ethical reasons, and thus, our understanding is still very limited regarding the mechanisms in the tumor microenvironment by which tumor cells exclude effectors and attract immune-suppressive cells. Nevertheless, based on the principles that are known, current T-cell engineering has leveraged some of these processes and created more potent CAR T-cells. The recent discovery of new oncofetal antigens and progress made in CAR design have expanded the potential pool of candidate antigens for therapeutic development. The most promising approaches to enhance CAR T-cells are novel CAR gating strategies, creative ways of cytokine delivery to the TME without enhancing systemic toxicity, and hijacking the chemokine axis of tumors for migratory purposes. With these new modifications, the next step in the era of CAR T-cell development will be the clinical validation of these promising preclinical findings.

Electrophilic proximity-inducing synthetic adapters enhance universal T cell function by covalently enforcing immune receptor signaling

Proximity-induction of cell-cell interactions via small molecules represents an emerging field in basic and translational sciences. Covalent anchoring of these small molecules represents a useful chemical strategy to enforce proximity; however, it remains largely unexplored for driving cell-cell interactions. In immunotherapeutic applications, bifunctional small molecules are attractive tools for inducing proximity between immune effector cells like T cells and tumor cells to induce tumoricidal function. We describe a two-component system composed of electrophilic bifunctional small molecules and paired synthetic antigen receptors (SARs) that elicit T cell activation. The molecules, termed covalent immune recruiters (CIRs), were designed to affinity label and covalently engage SARs. We evaluated the utility of CIRs to direct anti-tumor function of human T cells engineered with three biologically distinct classes of SAR. Irrespective of the electrophilic chemistry, tumor-targeting moiety, or SAR design, CIRs outperformed equivalent non-covalent bifunctional adapters, establishing a key role for covalency in maximizing functionality. We determined that covalent linkage enforced early T cell activation events in a manner that was dependent upon each SARs biology and signaling threshold. These results provide a platform to optimize universal SAR-T cell functionality and more broadly reveal new insights into how covalent adapters modulate cell-cell proximity-induction.

Targeting the membrane-proximal C2-set domain of CD33 for improved CAR T cell therapy

Current CD33-targeted immunotherapies typically recognize the membrane-distal V-set domain of CD33. Here, we show that decreasing the distance between T cell and leukemia cell membrane increases the efficacy of CD33 chimeric antigen receptor (CAR) T cells. We therefore generated and optimized second-generation CAR constructs containing single-chain variable fragments from antibodies raised against the membrane-proximal C2-set domain, which bind CD33 regardless of whether the V-set domain is present (CD33PAN antibodies). CD33PAN CAR T cells resulted in efficient tumor clearance and improved survival of immunodeficient mice bearing human AML cell xenografts and, in an AML model with limited CD33 expression, forced escape of CD33neg leukemia. Compared to CD33V-set CAR T cells, CD33PAN CAR T cells showed greater in vitro and in vivo efficacy against several human AML cell lines with differing levels of CD33 without increased expression of exhaustion markers. CD33PAN moieties were detected at a higher frequency on human leukemic stem cells, and CD33PAN CAR T cells had greater in vitro efficacy against primary human AML cells. Together, our studies demonstrate improved efficacy with CAR T cells binding CD33 close to the cell membrane, providing the rationale to investigate CD33PAN CAR T cells further toward possible clinical application.

High specificity of engineered T cells with third generation CAR (CD28-4-1BB-CD3-ζ) based on biotin-bound monomeric streptavidin for potential tumor immunotherapy

Introduction

Immunotherapy has revolutionized cancer treatment, and Chimeric Antigen Receptor T cell therapy (CAR-T) is a groundbreaking approach. Traditional second-generation CAR-T therapies have achieved remarkable success in hematological malignancies, but there is still room for improvement, particularly in developing new targeting strategies. To address this limitation, engineering T cells with multi-target universal CARs (UniCARs) based on monomeric streptavidin has emerged as a versatile approach in the field of anti-tumor immunotherapy. However, no studies have been conducted on the importance of the intracellular signaling domains of such CARs and their impact on efficiency and specificity.

Method

Here, we developed second-generation and third-generation UniCARs based on an extracellular domain comprising an affinity-enhanced monomeric streptavidin, in addition to CD28 and 4-1BB co-stimulatory intracellular domains. These UniCAR structures rely on a biotinylated intermediary, such as an antibody, for recognizing target antigens. In co-culture assays, we performed a functional comparison between the third-generation UniCAR construct and two second-generation UniCAR variants, each incorporating either the CD28 or 4-1BB as co-stimulatory domain.

Results

We observed that components in culture media could inhibit the binding of biotinylated antibodies to monomeric streptavidin-CARs, potentially compromising their efficacy. Furthermore, third-generation UniCAR-T cells showed robust cytolytic activity against cancer cell lines upon exposure to specific biotinylated antibodies like anti-CD19 and anti-CD20, underscoring their capability for multi-targeting. Importantly, when assessing engineered UniCAR-T cell activation upon encountering their target cells, third-generation UniCAR-T cells exhibited significantly enhanced specificity compared to second-generation CAR-T cells.

Discussion

First, optimizing culture conditions would be essential before deploying UniCAR-T cells clinically. Moreover, we propose that third-generation UniCAR-T cells are excellent candidates for preclinical research due to their high specificity and multi-target anti-tumor cytotoxicity.

IL-4 drives exhaustion of CD8+ CART cells

Durable response to chimeric antigen receptor T (CART) cell therapy remains limited in part due to CART cell exhaustion. Here, we investigate the regulation of CART cell exhaustion with three independent approaches including: a genome-wide CRISPR knockout screen using an in vitro model for exhaustion, RNA and ATAC sequencing on baseline and exhausted CART cells, and RNA and ATAC sequencing on pre-infusion CART cell products from responders and non-responders in the ZUMA-1 clinical trial. Each of these approaches identify interleukin (IL)-4 as a regulator of CART cell dysfunction. Further, IL-4-treated CD8+ CART cells develop signs of exhaustion independently of the presence of CD4+ CART cells. Conversely, IL-4 pathway editing or the combination of CART cells with an IL-4 monoclonal antibody improves antitumor efficacy and reduces signs of CART cell exhaustion in mantle cell lymphoma xenograft mouse models. Therefore, we identify both a role for IL-4 in inducing CART exhaustion and translatable approaches to improve CART cell therapy.

Chimeric antigen receptor T-cell therapy for haematological malignancies: Insights from fundamental and translational research to bedside practice

Autologous chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of lymphoid malignancies, leading to the approval of CD19-CAR T cells for B-cell lymphomas and acute leukaemia, and more recently, B-cell maturation antigen-CAR T cells for multiple myeloma. The long-term follow-up of patients treated in the early clinical trials demonstrates the possibility for long-term remission, suggesting a cure. This is associated with a low incidence of significant long-term side effects and a rapid improvement in the quality of life for responders. In contrast, other types of immunotherapies require prolonged treatments or carry the risk of long-term side effects impairing the quality of life. Despite impressive results, some patients still experience treatment failure or ultimately relapse, underscoring the imperative to improve CAR T-cell therapies and gain a better understanding of their determinants of efficacy to maximize positive outcomes. While the next-generation of CAR T cells will undoubtingly be more potent, there are already opportunities for optimization when utilizing the currently available CAR T cells. This review article aims to summarize the current evidence from clinical, translational and fundamental research, providing clinicians with insights to enhance their understanding and use of CAR T cells.

TCR/CD3-based synthetic antigen receptors (TCC) convey superior antigen sensitivity combined with high fidelity of activation

Low antigen sensitivity and a gradual loss of effector functions limit the clinical applicability of chimeric antigen receptor (CAR)-modified T cells and call for alternative antigen receptor designs for effective T cell-based cancer immunotherapy. Here, we applied advanced microscopy to demonstrate that TCR/CD3-based synthetic constructs (TCC) outperform second-generation CAR formats with regard to conveyed antigen sensitivities by up to a thousandfold. TCC-based antigen recognition occurred without adverse nonspecific signaling, which is typically observed in CAR-T cells, and did not depend-unlike sensitized peptide/MHC detection by conventional T cells-on CD4 or CD8 coreceptor engagement. TCC-endowed signaling properties may prove critical when targeting antigens in low abundance and aiming for a durable anticancer response.

Radiolabelling and preclinical characterisation of [89Zr]Zr-Df-ATG-101 bispecific to PD-L1/4-1BB

PURPOSE

ATG-101, a bispecific antibody that simultaneously targets the immune checkpoint PD-L1 and the costimulatory receptor 4-1BB, activates exhausted T cells upon PD-L1 crosslinking. Previous studies demonstrated promising anti-tumour efficacy of ATG-101 in preclinical models. Here, we labelled ATG-101 with 89Zr to confirm its tumour targeting effect and tissue biodistribution in a preclinical model. We also evaluated the use of immuno-PET to study tumour uptake of ATG-101 in vivo.

METHODS

ATG-101, anti-PD-L1, and an isotype control were conjugated with p-SCN-Deferoxamine (Df). The Df-conjugated antibodies were radiolabelled with 89Zr, and their radiochemical purity, immunoreactivity, and serum stability were assessed. We conducted PET/MRI and biodistribution studies on [89Zr]Zr-Df-ATG-101 in BALB/c nude mice bearing PD-L1-expressing MDA-MB-231 breast cancer xenografts for up to 10 days after intravenous administration of [89Zr]Zr-labelled antibodies. The specificity of [89Zr]Zr-Df-ATG-101 was evaluated through a competition study with unlabelled ATG-101 and anti-PD-L1 antibodies.

RESULTS

The Df-conjugation and [89Zr]Zr -radiolabelling did not affect the target binding of ATG-101. Biodistribution and imaging studies demonstrated biological similarity of [89Zr]Zr-Df-ATG-101 and [89Zr]Zr-Df-anti-PD-L1. Tumour uptake of [89Zr]Zr-Df-ATG-101 was clearly visualised using small-animal PET imaging up to 7 days post-injection. Competition studies confirmed the specificity of PD-L1 targeting in vivo.

CONCLUSION

[89Zr]Zr-Df-ATG-101 in vivo distribution is dependent on PD-L1 expression in the MDA-MB-231 xenograft model. Immuno-PET with [89Zr]Zr-Df-ATG-101 provides real-time information about ATG-101 distribution and tumour uptake in vivo. Our data support the use of [89Zr]Zr-Df-ATG-101 to assess tumour and tissue uptake of ATG-101.

Synergistic effect of chimeric antigen receptor modified with Bcl-2 on enhanced solid tumour targeting

Engineered T cells expressing chimeric antigen receptors (CARs) have shown remarkable therapeutic effects on haematological malignancies. However, CART cells are less effective on solid tumours mainly due to their weak persistence, which might be caused by activation-induced cell death (AICD). To overcome this limitation, CART cell with the antigen, Epidermal growth factor receptor variant III (EGFRvIII), targeting was modified to carry the anti-apoptotic molecule B cell lymphoma 2 (Bcl-2), and the final construct was named as EGFRvIII·CART-Bcl2 cells. Compared with the EGFRvIII·CART cells, EGFRvIII·CART-Bcl2 cells revealed higher capacities of proliferation, anti-apoptosis and tumour cell killing in vitro. Moreover, EGFRvIII·CART-Bcl2 cells had a longer persistence rate and exerted better anti-tumour effects than EGFRvIII·CART cells in cervical carcinoma xenograft model. Taken together, our findings suggest that incorporating anti-apoptotic molecules into CART cells may enhance its therapeutic effects against solid tumours.

CD28 hinge used in chimeric antigen receptor (CAR) T-cells exhibits local structure and conformational exchange amidst global disorder

T-cell therapies based on chimeric antigen receptor (CAR) targeting of a tumor-specific antigen offer hope for patients with relapsed or refractory cancers. CAR hinge and transmembrane regions link antigen recognition domains to intracellular signal transduction domains. Here, we apply biophysical methods to characterize the structure and dynamic properties of the CD28 CAR hinge (CD28H) used in an FDA-approved CD19 CAR for the treatment of B-lineage leukemia/lymphoma. By using nuclear Overhauser effect spectroscopy (NOESY), which detects even transiently occupied structural motifs, we observed otherwise elusive local structural elements amidst overall disorder in CD28H, including a conformational switch from a native β-strand to a 310-helix and polyproline II helix-like structure. These local structural motifs contribute to an overall loosely formed extended geometry that could be captured by NOESY data. All FDA-approved CARs use prolines in the hinge region, which we find in CD28, and previously in CD8α, isomerize to promote structural plasticity and dynamics. These local structural elements may function in recognition and signaling events and constrain the spacing between the transmembrane and antigen recognition domains. Our study thus demonstrates a method for detecting local and transient structure within intrinsically disordered systems and moreover, our CD28H findings may inform future CAR design.

Functional Activity of Cytokine-Induced Killer Cells Enhanced by CAR-CD19 Modification or by Soluble Bispecific Antibody Blinatumomab

Strategies to increase the anti-tumor efficacy of cytokine-induced killer cells (CIKs) include genetic modification with chimeric antigen receptors (CARs) or the addition of soluble T-cell engaging bispecific antibodies (BsAbs). Here, CIKs were modified using a transposon system integrating two distinct anti-CD19 CARs (CAR-MNZ and CAR-BG2) or combined with soluble CD3xCD19 BsAb blinatumomab (CIK + Blina). CAR-MNZ bearing the CD28-OX40-CD3ζ signaling modules, and CAR-BG2, designed on the Tisagenlecleucel CAR sequence (Kymriah®), carrying the 4-1BB and CD3ζ signaling elements, were employed. After transfection and CIK expansion, cells expressed CAR-CD19 to a similar extent (35.9% CAR-MNZ and 17.7% CAR-BG2). In vitro evaluations demonstrated robust proliferation and cytotoxicity (~50% cytotoxicity) of CARCIK-MNZ, CARCIK-BG2, and CIK + Blina against CD19+ target cells, suggesting similar efficacy. All effectors formed an increased number of synapses, activated NFAT and NFkB, and secreted IL-2 and IFN-ɣ upon encountering targets. CIK + Blina displayed strongest NFAT and IFN-ɣ induction, whereas CARCIK-BG2 demonstrated superior synapse formation. All the effectors have shown therapeutic activity in vivo against the CD19+ Daudi tumor model, with CARCIK cells showing a more durable response compared to CIK + Blina, likely due to the short half-life of Blina in this model.

iSECRETE: Integrating Microfluidics and DNA Proximity Amplification for Synchronous Single-Cell Activation and IFN-γ Secretion Profiling

Cytokines, crucial in immune modulation, impact disease progression when their secretion is dysregulated. Existing methods for profiling cytokine secretion suffer from time-consuming and labor-intensive processes and often fail to capture the dynamic nature of immune responses. Here, iSECRETE, an integrated platform that enables synchronous cell activation, wash-free, and target-responsive protein detection for single-cell IFN-γ cytokine secretion analysis within 30 min at room temperature is presented. By incorporating a DNA proximity assay (DPA) into a multifunctional microfluidic system, one-pot homogenous cytokine signal amplification, with a limit of detection of ≈50 secreted molecules per cell is achieved. iSECRETE can robustly handle various sample types that are shown. Two distinct immune activation assay modalities are demonstrated on iSECRETE. Finally, the detection of single-cell IFN-γ secretion as an activation hallmark of chimeric antigen receptor T cells within 6 h of exposure to cancer targets is shown. iSECRETE represents the fastest single-cell sample-to-result cytokine secretion assay to date, providing a powerful tool for advancing the understanding of biological phenotypes, functions, and pathways under in vivo-like conditions.

Degron-Based bioPROTACs for Controlling Signaling in CAR T Cells

Chimeric antigen receptor (CAR) T cells have made a tremendous impact in the clinic, but potent signaling through the CAR can be detrimental to treatment safety and efficacy. The use of protein degradation to control CAR signaling can address these issues in preclinical models. Existing strategies for regulating CAR stability rely on small molecules to induce systemic degradation. In contrast to small molecule regulation, genetic circuits offer a more precise method to control CAR signaling in an autonomous cell-by-cell fashion. Here, we describe a programmable protein degradation tool that adopts the framework of bioPROTACs, heterobifunctional proteins that are composed of a target recognition domain fused to a domain that recruits the endogenous ubiquitin proteasome system. We develop novel bioPROTACs that utilize a compact four-residue degron and demonstrate degradation of cytosolic and membrane protein targets using either a nanobody or synthetic leucine zipper as a protein binder. Our bioPROTACs exhibit potent degradation of CARs and can inhibit CAR signaling in primary human T cells. We demonstrate the utility of our bioPROTACs by constructing a genetic circuit to degrade the tyrosine kinase ZAP70 in response to recognition of a specific membrane-bound antigen. This circuit can disrupt CAR T cell signaling only in the presence of a specific cell population. These results suggest that bioPROTACs are powerful tools for expanding the CAR T cell engineering toolbox.

Strategies for Improving CAR T Cell Persistence in Solid Tumors

CAR T cells require optimization to be effective in patients with solid tumors. There are many barriers affecting their ability to succeed. One barrier is persistence, as to achieve an optimal antitumor response, infused CAR T cells must engraft and persist. This singular variable is impacted by a multitude of factors-the CAR T cell design, lymphodepletion regimen used, expansion method to generate the T cell product, and more. Additionally, external agents can be utilized to augment CAR T cells, such as the addition of novel cytokines, pharmaceutical drugs that bolster memory formation, or other agents during either the ex vivo expansion process or after CAR T cell infusion to support them in the oppressive tumor microenvironment. This review highlights many strategies being used to optimize T cell persistence as well as future directions for improving the persistence of infused cells.

Targeting GPC2 on Intraocular and CNS Metastatic Retinoblastomas with Local and Systemic Delivery of CAR T Cells

PURPOSE

Retinoblastoma is the most common intraocular malignancy in children. Although new chemotherapeutic approaches have improved ocular salvage rates, novel therapies are required for patients with refractory intraocular and metastatic disease. Chimeric antigen receptor (CAR) T cells targeting glypican-2 (GPC2) are a potential new therapeutic strategy.

EXPERIMENTAL DESIGN

GPC2 expression and its regulation by the E2F1 transcription factor were studied in retinoblastoma patient samples and cellular models. In vitro, we performed functional studies comparing GPC2 CAR T cells with different costimulatory domains (4-1BB and CD28). In vivo, the efficacy of local and systemic administration of GPC2 CAR T cells was evaluated in intraocular and leptomeningeal human retinoblastoma xenograft models.

RESULTS

Retinoblastoma tumors, but not healthy retinal tissues, expressed cell surface GPC2, and this tumor-specific expression was driven by E2F1. GPC2-directed CARs with 4-1BB costimulation (GPC2.BBz) were superior to CARs with CD28 stimulatory domains (GPC2.28z), efficiently inducing retinoblastoma cell cytotoxicity and enhancing T-cell proliferation and polyfunctionality. In vivo, GPC2.BBz CARs had enhanced persistence, which led to significant tumor regression compared with either control CD19 or GPC2.28z CARs. In intraocular models, GPC2.BBz CAR T cells efficiently trafficked to tumor-bearing eyes after intravitreal or systemic infusions, significantly prolonging ocular survival. In central nervous system (CNS) retinoblastoma models, intraventricular or systemically administered GPC2.BBz CAR T cells were activated in retinoblastoma-involved CNS tissues, resulting in robust tumor regression with substantially extended overall mouse survival.

CONCLUSIONS

GPC2-directed CAR T cells are effective against intraocular and CNS metastatic retinoblastomas.

Preclinical Development of CAR T Cells with Antigen-Inducible IL18 Enforcement to Treat GD2-Positive Solid Cancers

PURPOSE

Cytokine-engineering of chimeric antigen receptor-redirected T cells (CAR T cells) is a promising principle to overcome the limited activity of canonical CAR T cells against solid cancers.

EXPERIMENTAL DESIGN

We developed an investigational medicinal product, GD2IL18CART, consisting of CAR T cells directed against ganglioside GD2 with CAR-inducible IL18 to enhance their activation response and cytolytic effector functions in the tumor microenvironment. To allow stratification of patients according to tumor GD2 expression, we established and validated immunofluorescence detection of GD2 on paraffin-embedded tumor tissues.

RESULTS

Lentiviral all-in-one vector engineering of human T cells with the GD2-specific CAR with and without inducible IL18 resulted in cell products with comparable proportions of CAR-expressing central memory T cells. Production of IL18 strictly depends on GD2 antigen engagement. GD2IL18CART respond to interaction with GD2-positive tumor cells with higher IFNγ and TNFα cytokine release and more effective target cytolysis compared with CAR T cells without inducible IL18. GD2IL18CART further have superior in vivo antitumor activity, with eradication of GD2-positive tumor xenografts. Finally, we established GMP-compliant manufacturing of GD2IL18CART and found it to be feasible and efficient at clinical scale.

CONCLUSIONS

These results pave the way for clinical investigation of GD2IL18CART in pediatric and adult patients with neuroblastoma and other GD2-positive cancers (EU CT 2022- 501725-21-00). See related commentary by Locatelli and Quintarelli, p. 3361.

Chimeric Antigen Receptor T Cell Bearing Herpes Virus Entry Mediator Co-Stimulatory Signal Domain Exhibits Exhaustion-Resistant Properties

Improving chimeric antigen receptor (CAR)-T cell therapeutic outcomes and expanding its applicability to solid tumors requires further refinement of CAR-T cells. We previously reported that CAR-T cells bearing a herpes virus entry mediator (HVEM)-derived co-stimulatory signal domain (CSSD) (HVEM-CAR-T cells) exhibit superior functions and characteristics. Here, we conducted comparative analyses to evaluate the impact of different CSSDs on CAR-T cell exhaustion. The results indicated that HVEM-CAR-T cells had significantly lower frequencies of exhausted cells and exhibited the highest proliferation rates upon antigenic stimulation. Furthermore, proliferation inhibition by programmed cell death ligand 1 was stronger in CAR-T cells bearing CD28-derived CSSD (CD28-CAR-T cells) whereas it was weaker in HVEM-CAR-T. Additionally, HVEM-CAR-T cells maintained a low exhaustion level even after antigen-dependent proliferation and exhibited potent killing activities, suggesting that HVEM-CAR-T cells might be less prone to early exhaustion. Analysis of CAR localization on the cell surface revealed that CAR formed clusters in CD28-CAR-T cells whereas uniformly distributed in HVEM-CAR-T cells. Analysis of CD3ζ phosphorylation indicated that CAR-dependent tonic signals were strongly sustained in CD28-CAR-T cells whereas they were significantly weaker in HVEM-CAR-T cells. Collectively, these results suggest that the HVEM-derived CSSD is useful for generating CAR-T cells with exhaustion-resistant properties, which could be effective against solid tumors.

The physical landscape of CAR-T synapse

Chimeric antigen receptor (CAR)-T cells form dynamic immunological synapses with their cancer cell targets. After a CAR-antigen engagement, the CAR-T synapse forms, matures, and finally disassembles, accompanied by substantial remodeling of cell surface proteins, lipids, and glycans. In this review, we provide perspectives for understanding protein distribution, membrane topology, and force transmission across the CAR-T synapse. We highlight the features of CAR-T synapses that differ from T cell receptor synapses, including the disorganized protein pattern, adjustable synapse width, diverse mechano-responding properties, and resulting signaling consequences. Through a range of examples, we illustrate how revealing the biophysical nature of the CAR-T synapse could guide the design of CAR-Ts with improved anti-tumor function.

Beyond CAR-T: The rise of CAR-NK cell therapy in asthma immunotherapy

Asthma poses a major public health burden. While existing asthma drugs manage symptoms for many, some patients remain resistant. The lack of a cure, especially for severe asthma, compels exploration of novel therapies. Cancer immunotherapy successes with CAR-T cells suggest its potential for asthma treatment. Researchers are exploring various approaches for allergic diseases including membrane-bound IgE, IL-5, PD-L2, and CTLA-4 for asthma, and Dectin-1 for fungal asthma. NK cells offer several advantages over T cells for CAR-based immunotherapy. They offer key benefits: (1) HLA compatibility, meaning they can be used in a wider range of patients without the need for matching tissue types. (2) Minimal side effects (CRS and GVHD) due to their limited persistence and cytokine profile. (3) Scalability for "off-the-shelf" production from various sources. Several strategies have been introduced that highlight the superiority and challenges of CAR-NK cell therapy for asthma treatment including IL-10, IFN-γ, ADCC, perforin-granzyme, FASL, KIR, NCRs (NKP46), DAP, DNAM-1, TGF-β, TNF-α, CCL, NKG2A, TF, and EGFR. Furthermore, we advocate for incorporating AI for CAR design optimization and CRISPR-Cas9 gene editing technology for precise gene manipulation to generate highly effective CAR constructs. This review will delve into the evolution and production of CAR designs, explore pre-clinical and clinical studies of CAR-based therapies in asthma, analyze strategies to optimize CAR-NK cell function, conduct a comparative analysis of CAR-T and CAR-NK cell therapy with their respective challenges, and finally present established novel CAR designs with promising potential for asthma treatment.

4-1BB-encoding CAR causes cell death via sequestration of the ubiquitin-modifying enzyme A20

CD28 and 4-1BB costimulatory endodomains included in chimeric antigen receptor (CAR) molecules play a critical role in promoting sustained antitumor activity of CAR-T cells. However, the molecular events associated with the ectopic and constitutive display of either CD28 or 4-1BB in CAR-T cells have been only partially explored. In the current study, we demonstrated that 4-1BB incorporated within the CAR leads to cell cluster formation and cell death in the forms of both apoptosis and necroptosis in the absence of CAR tonic signaling. Mechanistic studies illustrate that 4-1BB sequesters A20 to the cell membrane in a TRAF-dependent manner causing A20 functional deficiency that in turn leads to NF-κB hyperactivity, cell aggregation via ICAM-1 overexpression, and cell death including necroptosis via RIPK1/RIPK3/MLKL pathway. Genetic modulations obtained by either overexpressing A20 or releasing A20 from 4-1BB by deleting the TRAF-binding motifs of 4-1BB rescue cell cluster formation and cell death and enhance the antitumor ability of 4-1BB-costimulated CAR-T cells.

CAR T-cell therapy: a potential treatment strategy for pediatric midline gliomas

Pediatric brain tumors are the primary cause of death in children with cancer. Diffuse midline glioma (DMG) and diffuse intrinsic pontine glioma (DIPG) are frequently unresectable due to their difficult access location, and 5-year survival remains less than 20%. Despite significant advances in tumor biology and genetics, treatment options remain limited and ineffective. Immunotherapy using T cells with a chimeric antigen receptor (CAR) that has been genetically engineered is quickly emerging as a new treatment option for these patients. High levels of expression were detected for both disialoganglioside (GD2) and B7-H3 in pediatric DMG/DIPG. Numerous studies have been conducted in recent years employing various generations of GD2-CAR T cells. The two most prevalent adverse effects found with this therapy are cytokine release syndrome, which varies in severity from mild constitutional symptoms to a high-grade disease associated with potentially fatal multi-organ failure, and neurotoxicity, known as CAR T-cell-related encephalopathy syndrome. During the acute phase of anticancer action, peri-tumoral neuro-inflammation might cause deadly hydrocephalus. The initial results of clinical trials show that the outcomes are not highly encouraging as B cell malignancies and myelomas. In vivo research on CAR T-cell therapy for DIPG has yielded encouraging results, but in human trials, the early results have shown potentially fatal side effects and very modest, but fleeting improvements. Solid tumors present a hindrance to CAR T-cell therapy because of the antigenic dilemma and the strong immune-suppressing tumor microenvironment.

Synthetic biology approaches for enhancing safety and specificity of CAR-T cell therapies for solid cancers

CAR-T cell therapies have been successful in treating numerous hematologic malignancies as the T cell can be engineered to target a specific antigen associated with the disease. However, translating CAR-T cell therapies for solid cancers is proving more challenging due to the lack of truly tumor-associated antigens and the high risk of off-target toxicities. To combat this, numerous synthetic biology mechanisms are being incorporated to create safer and more specific CAR-T cells that can be spatiotemporally controlled with increased precision. Here, we seek to summarize and analyze the advancements for CAR-T cell therapies with respect to clinical implementation, from the perspective of synthetic biology and immunology. This review should serve as a resource for further investigation and growth within the field of personalized cellular therapies.

Arming Vδ2 T Cells with Chimeric Antigen Receptors to Combat Cancer

Immunotherapy has emerged as a promising approach in the field of cancer treatment, with chimeric antigen receptor (CAR) T-cell therapy demonstrating remarkable success. However, challenges such as tumor antigen heterogeneity, immune evasion, and the limited persistence of CAR-T cells have prompted the exploration of alternative cell types for CAR-based strategies. Gamma delta T cells, a unique subset of lymphocytes with inherent tumor recognition capabilities and versatile immune functions, have garnered increasing attention in recent years. In this review, we present how arming Vδ2-T cells might be the basis for next-generation immunotherapies against solid tumors. Following a comprehensive overview of γδ T-cell biology and innovative CAR engineering strategies, we discuss the clinical potential of Vδ2 CAR-T cells in overcoming the current limitations of immunotherapy in solid tumors. Although the applications of Vδ2 CAR-T cells in cancer research are relatively in their infancy and many challenges are yet to be identified, Vδ2 CAR-T cells represent a promising breakthrough in cancer immunotherapy.

Lysine methylation modifications in tumor immunomodulation and immunotherapy: regulatory mechanisms and perspectives

Lysine methylation is a crucial post-translational modification (PTM) that significantly impacts gene expression regulation. This modification not only influences cancer development directly but also has significant implications for the immune system. Lysine methylation modulates immune cell functions and shapes the anti-tumor immune response, highlighting its dual role in both tumor progression and immune regulation. In this review, we provide a comprehensive overview of the intrinsic role of lysine methylation in the activation and function of immune cells, detailing how these modifications affect cellular processes and signaling pathways. We delve into the mechanisms by which lysine methylation contributes to tumor immune evasion, allowing cancer cells to escape immune surveillance and thrive. Furthermore, we discuss the therapeutic potential of targeting lysine methylation in cancer immunotherapy. Emerging strategies, such as immune checkpoint inhibitors (ICIs) and chimeric antigen receptor T-cell (CAR-T) therapy, are being explored for their efficacy in modulating lysine methylation to enhance anti-tumor immune responses. By targeting these modifications, we can potentially improve the effectiveness of existing treatments and develop novel therapeutic approaches to combat cancer more effectively.

CD19 CAR-T treatment shows limited efficacy in r/r DLBCL with double expression and TP53 alterations

OBJECT

Autologous CD19 chimeric antigen receptor T-cell therapy (CAR-T) significantly modifies the natural course of chemorefractory diffuse large B-cell lymphoma (DLBCL). However, 25% to 50% of patients with relapsed/refractory DLBCL still do not achieve remission. Therefore, investigating new molecular prognostic indicators that affect the effectiveness of CAR-T for DLBCL and developing novel combination therapies are crucial.

METHODS

Data from 73 DLBCL patients who received CD19 CAR-T (Axi-cel or Relma-cel) were retrospectively collected from Shanghai Tongji Hospital of Tongji University, The Second Affiliated Hospital Zhejiang University School of Medicine, and The Affiliated People's Hospital of Ningbo University. Prior to CD19 CAR-T-cell transfusions, the patients received fludarabine and cyclophosphamide chemotherapy regimen.

RESULTS

Our study revealed that relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL) patients with both Double-expression (MYC > 40% and BCL2 > 50%) and TP53 alterations tend to have a poorer clinical prognosis after CAR-T therapy, even when CAR-T therapy is used in combination with other therapies. However, CAR-T therapy was found to be effective in patients with only TP53 alterations or DE status, suggesting that their prognosis is in line with that of patients without TP53 alterations or DE status.

CONCLUSIONS

Our study suggests that r/r DLBCL patients with both DE status and TP53 alterations treated with CAR-T therapy are more likely to have a poorer clinical prognosis. However, CAR-T therapy has the potential to improve the prognosis of patients with only TP53 alterations or DE status to be similar to that of patients without these abnormalities.

Generation of antitumor chimeric antigen receptors incorporating T cell signaling motifs

Chimeric antigen receptor (CAR) T cells have been used to successfully treat various blood cancers, but adverse effects have limited their potential. Here, we developed chimeric adaptor proteins (CAPs) and CAR tyrosine kinases (CAR-TKs) in which the intracellular ζ T cell receptor (TCRζ) chain was replaced with intracellular protein domains to stimulate signaling downstream of the TCRζ chain. CAPs contain adaptor domains and the kinase domain of ZAP70, whereas CAR-TKs contain only ZAP70 domains. We hypothesized that CAPs and CAR-TKs would be more potent than CARs because they would bypass both the steps that define the signaling threshold of TCRζ and the inhibitory regulation of upstream molecules. CAPs were too potent and exhibited high tonic signaling in vitro. In contrast, CAR-TKs exhibited high antitumor efficacy and significantly enhanced long-term tumor clearance in leukemia-bearing NSG mice as compared with the conventional CD19-28ζ-CAR-T cells. CAR-TKs were activated in a manner independent of the kinase Lck and displayed slower phosphorylation kinetics and prolonged signaling compared with the 28ζ-CAR. Lck inhibition attenuated CAR-TK cell exhaustion and improved long-term function. The distinct signaling properties of CAR-TKs may therefore be harnessed to improve the in vivo efficacy of T cells engineered to express an antitumor chimeric receptor.

CAR T-cells targeting FGFR4 and CD276 simultaneously show potent antitumor effect against childhood rhabdomyosarcoma

Chimeric antigen receptor (CAR) T-cells targeting Fibroblast Growth Factor Receptor 4 (FGFR4), a highly expressed surface tyrosine receptor in rhabdomyosarcoma (RMS), are already in the clinical phase of development, but tumour heterogeneity and suboptimal activation might hamper their potency. Here we report an optimization strategy of the co-stimulatory and targeting properties of a FGFR4 CAR. We replace the CD8 hinge and transmembrane domain and the 4-1BB co-stimulatory domain with those of CD28. The resulting CARs display enhanced anti-tumor activity in several RMS xenograft models except for an aggressive tumour cell line, RMS559. By searching for a direct target of the RMS core-regulatory transcription factor MYOD1, we identify another surface protein, CD276, as a potential target. Bicistronic CARs (BiCisCAR) targeting both FGFR4 and CD276, containing two distinct co-stimulatory domains, have superior prolonged persistent and invigorated anti-tumor activities compared to the optimized FGFR4-specific CAR and the other BiCisCAR with the same 4-1BB co-stimulatory domain. Our study thus lays down the proof-of-principle for a CAR T-cell therapy targeting both FGFR4 and CD276 in RMS.

C-JUN overexpressing CAR-T cells in acute myeloid leukemia: preclinical characterization and phase I trial

Chimeric antigen receptor (CAR) T cells show suboptimal efficacy in acute myeloid leukemia (AML). We find that CAR T cells exposed to myeloid leukemia show impaired activation and cytolytic function, accompanied by impaired antigen receptor downstream calcium, ZAP70, ERK, and C-JUN signaling, compared to those exposed to B-cell leukemia. These defects are caused in part by the high expression of CD155 by AML. Overexpressing C-JUN, but not other antigen receptor downstream components, maximally restores anti-tumor function. C-JUN overexpression increases costimulatory molecules and cytokines through reinvigoration of ERK or transcriptional activation, independent of anti-exhaustion. We conduct an open-label, non-randomized, single-arm, phase I trial of C-JUN-overexpressing CAR-T in AML (NCT04835519) with safety and efficacy as primary and secondary endpoints, respectively. Of the four patients treated, one has grade 4 (dose-limiting toxicity) and three have grade 1-2 cytokine release syndrome. Two patients have no detectable bone marrow blasts and one patient has blast reduction after treatment. Thus, overexpressing C-JUN endows CAR-T efficacy in AML.

IL-18-secreting multiantigen targeting CAR T cells eliminate antigen-low myeloma in an immunocompetent mouse model

ABSTRACT

Multiple myeloma is a plasma cell malignancy that is currently incurable with conventional therapies. Following the success of CD19-targeted chimeric antigen receptor (CAR) T cells in leukemia and lymphoma, CAR T cells targeting B-cell maturation antigen (BCMA) more recently demonstrated impressive activity in relapsed and refractory myeloma patients. However, BCMA-directed therapy can fail due to weak expression of BCMA on myeloma cells, suggesting that novel approaches to better address this antigen-low disease may improve patient outcomes. We hypothesized that engineered secretion of the proinflammatory cytokine interleukin-18 (IL-18) and multiantigen targeting could improve CAR T-cell activity against BCMA-low myeloma. In a syngeneic murine model of myeloma, CAR T cells targeting the myeloma-associated antigens BCMA and B-cell activating factor receptor (BAFF-R) failed to eliminate myeloma when these antigens were weakly expressed, whereas IL-18-secreting CAR T cells targeting these antigens promoted myeloma clearance. IL-18-secreting CAR T cells developed an effector-like T-cell phenotype, promoted interferon-gamma production, reprogrammed the myeloma bone marrow microenvironment through type-I/II interferon signaling, and activated macrophages to mediate antimyeloma activity. Simultaneous targeting of weakly-expressed BCMA and BAFF-R with dual-CAR T cells enhanced T-cell:target-cell avidity, increased overall CAR signal strength, and stimulated antimyeloma activity. Dual-antigen targeting augmented CAR T-cell secretion of engineered IL-18 and facilitated elimination of larger myeloma burdens in vivo. Our results demonstrate that combination of engineered IL-18 secretion and multiantigen targeting can eliminate myeloma with weak antigen expression through distinct mechanisms.

Fueling CARs: metabolic strategies to enhance CAR T-cell therapy

CAR T cells are widely applied for relapsed hematological cancer patients. With six approved cell therapies, for Multiple Myeloma and other B-cell malignancies, new insights emerge. Profound evidence shows that patients who fail CAR T-cell therapy have, aside from antigen escape, a more glycolytic and weakened metabolism in their CAR T cells, accompanied by a short lifespan. Recent advances show that CAR T cells can be metabolically engineered towards oxidative phosphorylation, which increases their longevity via epigenetic and phenotypical changes. In this review we elucidate various strategies to rewire their metabolism, including the design of the CAR construct, co-stimulus choice, genetic modifications of metabolic genes, and pharmacological interventions. We discuss their potential to enhance CAR T-cell functioning and persistence through memory imprinting, thereby improving outcomes. Furthermore, we link the pharmacological treatments with their anti-cancer properties in hematological malignancies to ultimately suggest novel combination strategies.

Off-the-shelf CAR-NK cells targeting immunogenic cell death marker ERp57 execute robust antitumor activity and have a synergistic effect with ICD inducer oxaliplatin

BACKGROUND

Chimeric antigen receptor natural killer (CAR-NK) therapy holds great promise for treating hematologic tumors, but its efficacy in solid tumors is limited owing to the lack of suitable targets and poor infiltration of engineered NK cells. Here, we explore whether immunogenic cell death (ICD) marker ERp57 translocated from endoplasmic reticulum to cell surface after drug treatment could be used as a target for CAR-NK therapy.

METHODS

To target ERp57, a VHH phage display library was used for screening ERp57-targeted nanobodies (Nbs). A candidate Nb with high binding affinity to both human and mouse ERp57 was used for constructing CAR-NK cells. Various in vitro and in vivo studies were performed to assess the antitumor efficacy of the constructed CAR-NK cells.

RESULTS

We demonstrate that the translocation of ERp57 can not only be induced by low-dose oxaliplatin (OXP) treatment but also is spontaneously expressed on the surface of various types of tumor cell lines. Our results show that G6-CAR-NK92 cells can effectively kill various tumor cell lines in vitro on which ERp57 is induced or intrinsically expressed, and also exhibit potent antitumor effects in cancer cell-derived xenograft and patient-derived xenograft mouse models. Additionally, the antitumor activity of G6-CAR-NK92 cells is synergistically enhanced by the low-dose ICD-inducible drug OXP.

CONCLUSION

Collectively, our findings suggest that ERp57 can be leveraged as a new tumor antigen for CAR-NK targeting, and the resultant CAR-NK cells have the potential to be applied as a broad-spectrum immune cell therapy for various cancers by combining with ICD inducer drugs.

Overview of infectious complications among CAR T- cell therapy recipients

Chimeric antigen receptor-modified T cell (CAR T-cell) therapy has revolutionized the management of hematological malignancies. In addition to impressive malignancy-related outcomes, CAR T-cell therapy has significant toxicity-related adverse events, including cytokine release syndrome (CRS), immune effector cell associated neurotoxicity syndrome (ICANS), immune effector cell-associated hematotoxicity (ICAHT), and opportunistic infections. Different CAR T-cell targets have different epidemiology and risk factors for infection, and these targets result in different long-term immunodeficiency states due to their distinct on-target and off- tumor effects. These effects are exacerbated by the use of multimodal immunosuppression in the management of CRS and ICANS. The most effective course of action for managing infectious complications involves determining screening, prophylactic, and monitoring strategies and understanding the role of immunoglobulin replacement and re-vaccination strategies. This involves considering the nature of prior immunomodulating therapies, underlying malignancy, the CAR T-cell target, and the development and management of related adverse events. In conclusion, we now have an increasing understanding of infection management for CAR T-cell recipients. As additional effector cells and CAR T-cell targets become available, infection management strategies will continue to evolve.

Overcoming the challenges of primary resistance and relapse after CAR-T cell therapy

INTRODUCTION

While CAR T-cell therapy has led to remarkable responses in relapsed B-cell hematologic malignancies, only 50% of patients ultimately have a complete, sustained response. Understanding the mechanisms of resistance and relapse after CAR T-cell therapy is crucial to future development and improving outcomes.

AREAS COVERED

We review reasons for both primary resistance and relapse after CAR T-cell therapies. Reasons for primary failure include CAR T-cell manufacturing problems, suboptimal fitness of autologous T-cells themselves, and intrinsic features of the underlying cancer and tumor microenvironment. Relapse after initial response to CAR T-cell therapy may be antigen-positive, due to CAR T-cell exhaustion or limited persistence, or antigen-negative, due to antigen-modulation on the target cells. Finally, we discuss ongoing efforts to overcome resistance to CAR T-cell therapy with enhanced CAR constructs, manufacturing methods, alternate cell types, combinatorial strategies, and optimization of both pre-infusion conditioning regimens and post-infusion consolidative strategies.

EXPERT OPINION

There is a continued need for novel approaches to CAR T-cell therapy for both hematologic and solid malignancies to obtain sustained remissions. Opportunities for improvement include development of new targets, optimally combining existing CAR T-cell therapies, and defining the role for adjunctive immune modulators and stem cell transplant in enhancing long-term survival.

Altered cancer metabolism and implications for next-generation CAR T-cell therapies

This review critically examines the evolving landscape of chimeric antigen receptor (CAR) T-cell therapy in treating solid tumors, with a particular focus on the metabolic challenges within the tumor microenvironment. CAR T-cell therapy has demonstrated remarkable success in hematologic malignancies, yet its efficacy in solid tumors remains limited. A significant barrier is the hostile milieu of the tumor microenvironment, which impairs CAR T-cell survival and function. This review delves into the metabolic adaptations of cancer cells and their impact on immune cells, highlighting the competition for nutrients and the accumulation of immunosuppressive metabolites. It also explores emerging strategies to enhance CAR T-cell metabolic fitness and persistence, including genetic engineering and metabolic reprogramming. An integrated approach, combining metabolic interventions with CAR T-cell therapy, has the potential to overcome these constraints and improve therapeutic outcomes in solid tumors.

Alternative target recognition elements for chimeric antigen receptor (CAR) T cells: beyond standard antibody fragments

BACKGROUND AIMS

Chimeric antigen receptor T (CAR-T) cells are a remarkably efficacious, highly promising and rapidly evolving strategy in the field of immuno-oncology. The precision of these targeted cellular therapies is driven by the specificity of the antigen recognition element (the "binder") encoded in the CAR. This binder redirects these immune effector cells precisely toward a defined antigen on the surface of cancer cells, leading to T-cell receptor-independent tumor lysis. Currently, for tumor targeting most CAR-T cells are designed using single-chain variable fragments (scFvs) derived from murine or human immunoglobulins. However, there are several emerging alternative binder modalities that are finding increasing utility for improved CAR function beyond scFvs.

METHODS

Here we review the most recent developments in the use of non-canonical protein binding domains in CAR design, including nanobodies, DARPins, natural ligands, and de novo-designed protein elements.

RESULTS

Overall, we describe how new protein binder formats, with their unique structural properties and mechanisms of action, may possess key advantages over traditional scFv CAR designs.

CONCLUSIONS

These alternative binder designs may contribute to enhanced CAR-T therapeutic options and, ultimately, improved outcomes for cancer patients.

T-cell exhaustion in multiple myeloma

INTRODUCTION

Chimeric Antigen Receptor (CAR) T-cells and Bispecific Antibodies (BsAb) are the leading platforms for redirecting the immune system against cells expressing the specific antigen, revolutionizing the treatment of hematological malignancies, including multiple myeloma (MM). In MM, drug-resistant relapses are the main therapy-limiting factor and the leading cause of why the disease is still considered incurable. T-cell-engaging therapies hold promise in improving the treatment of MM. However, the effectiveness of these treatments may be hindered by T-cell fitness. T-cell exhaustion is a condition of a gradual decline in effector function, reduced cytokine secretion, and increased expression of inhibitory receptors due to chronic antigen stimulation.

AREAS COVERED

This review examines findings about T-cell exhaustion in MM in the context of T-cell redirecting BsAbs and CAR-T treatment.

EXPERT OPINION

The fitness of T-cells has become an important factor in the development of T-cell redirecting therapies. The way T-cell exhaustion relates to these therapies could affect the further development of CAR and BsAbs technologies, as well as the strategies used for clinical use. Therefore, this review aims to explore the current understanding of T-cell exhaustion in MM and its relationship to these therapies.

Metabolic dialogues: regulators of chimeric antigen receptor T cell function in the tumor microenvironment

Tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor (CAR) T cells have demonstrated remarkable success in the treatment of relapsed/refractory melanoma and hematological malignancies, respectively. These treatments have marked a pivotal shift in cancer management. However, as "living drugs," their effectiveness is dependent on their ability to proliferate and persist in patients. Recent studies indicate that the mechanisms regulating these crucial functions, as well as the T cell's differentiation state, are conditioned by metabolic shifts and the distinct utilization of metabolic pathways. These metabolic shifts, conditioned by nutrient availability as well as cell surface expression of metabolite transporters, are coupled to signaling pathways and the epigenetic landscape of the cell, modulating transcriptional, translational, and post-translational profiles. In this review, we discuss the processes underlying the metabolic remodeling of activated T cells, the impact of a tumor metabolic environment on T cell function, and potential metabolic-based strategies to enhance T cell immunotherapy.

Unraveling the complexity of drug resistance mechanisms to SINE, T cell-engaging therapies and CELMoDs in multiple myeloma: a comprehensive review

Despite significant advances in the understanding of multiple myeloma (MM) biology and the development of novel treatment strategies in the last two decades, MM is still an incurable disease. Novel drugs with alternative mechanisms of action, such as selective inhibitors of nuclear export (SINE), modulators of the ubiquitin pathway [cereblon E3 ligase modulatory drugs (CELMoDs)], and T cell redirecting (TCR) therapy, have led to significant improvement in patient outcomes. However, resistance still emerges, posing a major problem for the treatment of myeloma patients. This review summarizes current data on treatment with SINE, TCR therapy, and CELMoDs and explores their mechanism of resistance. Understanding these resistance mechanisms is critical for developing strategies to overcome treatment failure and improve therapeutic outcomes.