Tumor Antigen and Receptor Densities Regulate Efficacy of a Chimeric Antigen Receptor Targeting Anaplastic Lymphoma Kinase

ALK in cancer: from function to therapeutic targeting

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that acts as an oncogenic driver in solid and haematological malignancies in both children and adults. Although ALK-expressing (ALK+) tumours show strong initial responses to the series of ALK inhibitors currently available, many patients will develop resistance. In this Review, we discuss recent advances in ALK oncogenic signalling, together with existing and promising new modalities to treat ALK-driven tumours, including currently approved ALK-directed therapies, namely tyrosine kinase inhibitors, and novel approaches such as ALK-specific immune therapies. Although ALK inhibitors have changed the management and clinical history of ALK+ tumours, they are still insufficient to cure most of the patients. Therefore, more effort is needed to further improve outcomes and prevent the tumour resistance, recurrence and metastatic spread that many patients with ALK+ tumours experience. Here, we outline how a multipronged approach directed against ALK and other essential pathways that sustain the persistence of ALK+ tumours, together with potent or specific immunotherapies, could achieve this goal. We envision that the lessons learned from treating ALK+ tumours in the clinic could ultimately accelerate the implementation of innovative combination therapies to treat tumours driven by other tyrosine kinases or oncogenes with similar properties.

Tailoring CAR surface density and dynamics to improve CAR-T cell therapy

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment landscape for relapsed and/or refractory B-cell neoplasms, garnering Food and Drug Administration/European Medicines Agency approval for six commercial products. Despite this success, challenges persist, including a relapse rate of 30-50% in hematologic tumors, limited clinical efficacy in solid tumors, and severe side effects. This review addresses the critical need for therapeutic enhancement by focusing on the often-overlooked strategy of modulating CAR protein density on the cell membrane. We delve into the key factors influencing CAR surface expression, such as CAR downmodulation following antigen encounter and antigen-related factors. The dynamics of CAR downmodulation remain underexplored; however, recent data point to its modification as a useful tool for improving functionality. Notably, transcriptional control of CAR expression and the incorporation of specific elements into the CAR design have emerged as interesting strategies to tailor CAR expression profiles. Therefore, controlling CAR dynamic density may represent an attractive strategy for achieving optimal therapeutic outcomes.

Strategies to overcome tumour relapse caused by antigen escape after CAR T therapy

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of B cell and plasma cell malignancies, and numerous promising targets against solid tumours are being explored. Despite their initial therapeutic success in hematological cancers, relapse occurs in a significant fraction of patients, highlighting the need for further innovations in advancing CAR T cell therapy. Tumour antigen heterogeneity and acquired tumour resistance leading to antigen escape (antigen loss/downregulation) have emerged as a crucial factor contributing to immune escape and CAR T cell resistance, particularly in the case of solid tumours with only limited success achieved to date. In this review, we discuss mechanisms of tumour relapse in CAR T cell therapy and the promising strategies that are under development to overcome multiple resistance mechanisms, thereby reducing outgrowth of antigen escape variants. Specifically, we emphasize the importance of designing clinical translational strategies to enhance CAR T cell crosstalk with host immune cells, eliciting endogenous antitumour immune responses through antigen/epitope spreading, which offers a genuine solution to the limitations of targeting tumour antigen heterogeneity in solid tumours with monospecific T cell therapies.

RESET: A TCR-coupled antigen receptor with superior targeting sensitivity and reversible drug-regulated anti-tumor activity

Chimeric antigen receptor (CAR) T cells are effective cancer therapies, particularly in indications with high, stable, and tumor-specific antigen expression. Other settings may require improved targeting sensitivity, controllable targeting selectivity, and/or additional potency enhancements to achieve robust efficacy. Here, we describe a novel receptor architecture called RESET (rapamycin-enabled, switchable endogenous T cell receptor) that combines (1) cell surface antigen targeting, (2) small-molecule regulation, and (3) the signaling proficiency and inherent sensitivity of native T cell receptors. RESET-T cells outperformed both constitutive and drug-regulated CAR-T cells and show hallmarks of TCR activation that suggest improved fidelity to native T cell responses. Pharmacological control then increases safety through toggling T cell activation between active and resting states and may mitigate T cell exhaustion caused by continuous antigen exposure. This convergence of drug-regulated targeting and natural immune receptor signal transduction may better replicate the kinetics and physiology of a classical T cell response and potentiate more successful and safer immunotherapies.

Two-Stage CD8+ CAR T-Cell Differentiation in Patients with Large B-Cell Lymphoma

Chimeric antigen receptor (CAR) T-cell therapy has expanded therapeutic options for patients with diffuse large B-cell lymphoma (DLBCL). However, progress in improving clinical outcomes has been limited by an incomplete understanding of CAR T-cell differentiation in patients. To comprehensively investigate CAR T-cell differentiation in vivo, we performed single-cell, multimodal, and longitudinal analyses of CD28-costimulated CAR T cells from infusion product and peripheral blood (day 8-28) of patients with DLBCL who were successfully treated with axicabtagene ciloleucel. Here, we show that CD8+ CAR T cells undergo two distinct waves of clonal expansion. The first wave is dominated by CAR T cells with an exhausted-like effector memory phenotype during the peak expansion period (day 8-14). The second wave is dominated by CAR T cells with a terminal effector phenotype during the post-peak persistence period (day 21-28). Importantly, the two waves have distinct ontogeny and are biologically uncoupled. Furthermore, lineage tracing analysis via each CAR T cell's endogenous TCR clonotype demonstrates that the two waves originate from different effector precursors in the infusion product. Precursors of the first wave exhibit more effector-like signatures, whereas precursors of the second wave exhibit more stem-like signatures. These findings suggest that pre-infusion heterogeneity mediates the two waves of in vivo clonal expansion. Our findings provide evidence against the intuitive idea that the post-peak contraction in CAR abundance is solely apoptosis or extravasation of short-lived CAR T cells from peak expansion. Rather, our findings demonstrate that CAR T-cell expansion and persistence are mediated by clonally, phenotypically, and ontogenically distinct CAR T-cell populations that serve complementary clinical purposes.

Restoration of LAT activity improves CAR T cell sensitivity and persistence in response to antigen-low acute lymphoblastic leukemia

Chimeric antigen receptor (CAR) T cells induce responses in patients with relapsed/refractory leukemia; however, long-term efficacy is frequently limited by relapse. The inability to target antigen-low cells is an intrinsic vulnerability of second-generation CAR T cells and underlies most relapses following CD22BBz CAR T cell therapy. Here, we interrogate CD22BBz CAR signaling in response to low antigen and find inefficient phosphorylation of the linker for activation of T cells (LAT) limiting downstream signaling. To overcome this, we designed the adjunctive LAT-activating CAR T cell (ALA-CART) platform, pairing a second-generation CAR with a LAT-CAR incorporating the intracellular domain of LAT. ALA-CART cells demonstrate reduced differentiation during manufacturing and increased LAT phosphorylation, MAPK signaling, and AP-1 activity. ALA-CART cells show improved cytotoxicity, proliferation, persistence, and efficacy against antigen-low leukemias that were refractory to clinically active CD22BBz CAR T cells. Restoration of LAT signaling through the ALA-CART platform represents a promising strategy for overcoming multiple mechanisms of CAR T cell failure.

Depletion of alloreactive B cells by drug-resistant chimeric alloantigen receptor T cells to prevent transplant rejection

Antibody-mediated rejection (AMR) remains a major complication after solid organ transplantation (SOT). Current treatment options are inefficient and result in drastic impairment of the general immunity. To selectively eliminate responsible alloreactive B cells characterized by anti-donor-HLA B cell receptors (BCRs), we generated T cells overcoming rejection by antibodies (CORA-Ts) engineered with a novel chimeric receptor comprising a truncated donor-HLA molecule as antigen recognition domain. As proof-of-concept, CORA receptors based on HLA-A∗02 were developed. In co-cultures with anti-HLA-A∗02 B cell lines, CORA-Ts were specifically activated, released pro-inflammatory mediators, and exhibited strong cytotoxicity resulting in an effective reduction of anti-HLA-A∗02 antibody release. Significant reduction of growth of an anti-HLA-A∗02 B cell line could be confirmed using an in vivo mouse model. Modification of the CORA receptor effectively abrogated T cell binding, thereby avoiding T cell sensitization. Additionally, using CRISPR-Cas9-mediated knockout of the FKBP12 gene, CORA-Ts were able to resist immunosuppressive treatment with tacrolimus, thereby allowing high efficiency in transplant patients. Our results demonstrate that CORA-Ts are able to specifically eliminate alloreactive, anti-HLA B cells, thus selectively preventing anti-HLA antibody release even under immunosuppressive conditions. This suggests CORA-Ts as potent approach to combat AMR and improve long-term graft survival in SOT patients while preserving their overall B cell immunity.

From TCR fundamental research to innovative chimeric antigen receptor design

Engineered T cells that express chimeric antigen receptors (CARs) have transformed the treatment of haematological cancers. CARs combine the tumour-antigen-binding function of antibodies with the signalling functions of the T cell receptor (TCR) ζ chain and co-stimulatory receptors. The resulting constructs aim to mimic the TCR-based and co-receptor-based activation of T cells. Although these have been successful for some types of cancer, new CAR formats are needed, to limit side effects and broaden their use to solid cancers. Insights into the mechanisms of TCR signalling, including the identification of signalling motifs that are not present in the TCR ζ chain and mechanistic insights in TCR activation, have enabled the development of CAR formats that outcompete the current CARs in preclinical mouse models and clinical trials. In this Perspective, we explore the mechanistic rationale behind new CAR designs.

Bortezomib enhances the efficacy of BCMA CAR-T therapy through up-regulating BCMA expression in myeloma cells

Chimeric antigen receptor T (CAR-T) cell therapy targeting B cell mature antigen (BCMA) has shown remarkable clinical benefits in treating multiple myeloma (MM). Bortezomib, a proteasome inhibitor approved as a first-line agent for MM for two decades, has demonstrated potent antitumor activity. In this study, we found that bortezomib treatment stabilizes the expression of BCMA and conceived the hypothesis that BCMA CAR-T therapy combined with bortezomib would enhance the anti-MM efficacy. The in vitro experiments revealed that pretreatment of both MM tumor cell line MM1.S and tumor cell line NALM-6 forced expression of BCMA with low concentrations of bortezomib up-regulated BCMA expression. When encountered with BCMA CAR-T cells, the cytotoxicity to these bortezomib-treated tumor cells was increased, indicating that the up-regulated BCMA induced by bortezomib contributes to the enhanced activities of the CAR-T cells. Further, in the in vivo experiment, the combined treatment significantly enhanced the anti-MM ability and prolonged the survival rate. Moreover, safety analysis found that there is no tissue damage or loss of weight, suggesting the favorable tolerability of this combination strategy. Our study provided a surety and efficacious strategy for the BCMA-targeted CAR-T cancer immunotherapy enhancement.

Strategies to Overcome Antigen Heterogeneity in CAR-T Cell Therapy

Chimeric antigen receptor (CAR) gene-modified T-cell therapy has achieved significant success in the treatment of hematological malignancies. However, this therapy has not yet made breakthroughs in the treatment of solid tumors and still faces issues of resistance and relapse in hematological cancers. A major reason for these problems is the antigenic heterogeneity of tumor tissues. This review outlines the antigenic heterogeneity encountered in CAR-T cell therapy and the corresponding strategies to address it. These strategies include using combination therapy to increase the abundance of target antigens, optimizing the structure of CARs to enhance sensitivity to low-density antigens, developing multi-targeted CAR-T cells, and reprogramming the TME to activate endogenous immunity. These approaches offer new directions for overcoming tumor antigenic heterogeneity in CAR-T cell therapy.

In Situ Bioconjugation of Synthetic Peptides onto Universal Chimeric Antigen Receptor T Cells for Targeted Cancer Immunotherapies

The recent development of modular universal chimeric antigen receptor (CAR) T-cell platforms that use bifunctional adaptor intermediates to redirect engineered T-cell effector function has greatly expanded the capabilities of adoptive T-cell therapy, enabling safer and more comprehensive cancer treatment. However, universal CAR receptor systems rely on unstable transient recognition of tag-coupled intermediates for T-cell activation, and the array of targeting intermediates has been limited to antibodies and small molecules. Addressing these shortcomings, we engineered universal CAR T-cell receptors that can be covalently modified with synthetic biomaterials in vivo by accelerated SpyCatcher003-SpyTag003 chemistry for cancer-cell targeting. SpyCatcher003-modified CARs, nicknamed DB5 CARs, displayed fast, low-nanomolar reaction kinetics with a synthetic αvβ6-binding peptide that incorporates a SpyTag003 peptide via branched peptide synthesis to comprise a bifunctional intermediate. Prearming DB5 CAR T cells or prelabeling target cells with the bifunctional peptide produced selective CD4+ and CD8+ CAR T-cell responses against αvβ6+ cancer cells in vitro. Furthermore, the synthetic targeting intermediate showed robust DB5 CAR T-cell arming in vivo and selectively reduced αvβ6+ tumor progression in a dual flank xenograft model. We demonstrate the versatility and therapeutic potential of "Cyborg" CAR T-cell therapies that utilize synthetic biomaterials to direct CAR T-cell activity via highly selective bioconjugation that occurs in vivo.

New approach methodologies to assess wanted and unwanted drugs-induced immunostimulation

This review examines various classes of drugs, focusing on their therapeutic and adverse effects, particularly in relation to immunostimulation. We emphasize the potential of new approach methodologies (NAMs) to study both expected and unexpected immunostimulatory effects. By evaluating the modes of action of different immunostimulatory drugs, we aim to provide insights into effectively assessing unwanted immunostimulatory responses. The review begins by exploring drugs that stimulate the immune system-including immunostimulants, monoclonal antibodies, chemotherapeutics, and nucleic acid-based drugs-to outline NAMs that could be employed to evaluate immunostimulation.

Targeting MYCN upregulates L1CAM tumor antigen in MYCN-dysregulated neuroblastoma to increase CAR T cell efficacy

Current treatment protocols have limited success against MYCN-amplified neuroblastoma. Adoptive T cell therapy presents an innovative strategy to improve cure rates. However, L1CAM-targeting CAR T cells achieved only limited response against refractory/relapsed neuroblastoma so far. We investigated how oncogenic MYCN levels influence tumor cell response to CAR T cells, as one possible factor limiting clinical success. A MYCN-inducible neuroblastoma cell model was created. L1CAM-CAR T cell effector function was assessed (activation markers, cytokine release, tumor cytotoxicity) after coculture with the model or MYCN-amplified neuroblastoma cell lines. RNA sequencing datasets characterizing the model were compared to publicly available RNA/proteomic datasets. MYCN-directed L1CAM regulation was explored using public ChIP-sequencing datasets. Synergism between CAR T cells and the indirect MYCN inhibitor, MLN8237, was assessed in vitro using the Bliss model and in vivo in an immunocompromised mouse model. Inducing high MYCN levels in the neuroblastoma cell model reduced L1CAM expression and, consequently, L1CAM-CAR T cell effector function in vitro. Primary neuroblastomas possessing high MYCN levels expressed lower levels of both the L1CAM transcript and L1CAM tumor antigen. MLN8237 treatment restored L1CAM tumor expression and L1CAM-CAR T cell effector function. Combining MLN8237 and L1CAM-CAR T cell treatment synergistically enhanced MYCN-overexpressing tumor cytotoxicity in vitro and in vivo concomitant with severe in vivo toxicity. We identify target antigen downregulation as source of resistance against L1CAM-CAR T cells in MYCN-driven neuroblastoma cells. These data suggest that L1CAM-CAR T cell therapy combined with pharmacological MYCN inhibition may benefit patients with MYCN-amplified neuroblastoma.

Progress in personalized immunotherapy for patients with brain metastasis

Brain metastasis leads to poor outcomes and CNS injury, significantly reducing quality of life and survival rates. Advances in understanding the tumor immune microenvironment have revealed the promise of immunotherapies, which, alongside surgery, chemotherapy, and radiation, offer improved survival for some patients. However, resistance to immunotherapy remains a critical challenge. This review explores the immune landscape of brain metastases, current therapies, clinical trials, and the need for personalized, biomarker-driven approaches to optimize outcomes.

Single-cell analysis of the multiple myeloma microenvironment after γ-secretase inhibition and CAR T-cell therapy

ABSTRACT

Chimeric antigen receptor (CAR) T cells and bispecific antibodies targeting B-cell maturation antigen (BCMA) have significantly advanced the treatment of relapsed and refractory multiple myeloma. Resistance to BCMA-targeting therapies, nonetheless, remains a significant challenge. BCMA shedding by γ-secretase is a known resistance mechanism, and preclinical studies suggest that inhibition may improve anti-BCMA therapy. Leveraging a phase 1 clinical trial of the γ-secretase inhibitor (GSI), crenigacestat, with anti-BCMA CAR T cells (FCARH143), we used single-nuclei RNA sequencing and assay for transposase-accessible chromatin sequencing to characterize the effects of GSI on the tumor microenvironment. The most significant impacts of GSI involved effects on monocytes, which are known to promote tumor growth. In addition to observing a reduction in the frequency of nonclassical monocytes, we also detected significant changes in gene expression, chromatin accessibility, and inferred cell-cell interactions after exposure to GSI. Although many genes with altered expression are associated with γ-secretase-dependent signaling, such as Notch, other pathways were affected, indicating GSI has far-reaching effects. Finally, we detected monoallelic deletion of the BCMA locus in some patients with prior exposure to anti-BCMA therapy, which significantly correlated with reduced progression-free survival (PFS; median PFS, 57 vs 861 days). GSIs are being explored in combination with the full spectrum of BCMA-targeting agents, and our results reveal widespread effects of GSI on both tumor and immune cell populations, providing insight into mechanisms for enhancing BCMA-directed therapies.

XCL1-secreting CEA CAR-T cells enhance endogenous CD8+ T cell responses to tumor neoantigens to confer a long-term antitumor immunity

BACKGROUND

Therapeutic efficacy of carcinoembryonic antigen (CEA)-specific chimeric antigen receptor (CAR) T cells against colorectal cancer (CRC) remains limited due to the unique characteristics and distinct microenvironments of tumor tissues. We modified CEA-specific CAR-T cells, aiming to stimulate endogenous CD8+ T cell responses against neoantigens that were derived from CEA-positive tumors destroyed by the CAR T cells.

METHODS

In a conventional CEA CAR (reg-CAR), we modified it to express lymphotactin XCL1 and interleukin (IL)-7 genes, constructing a modified 7XCL1-CAR. By generating the CEA-specific 7XCL1-CAR T cells, we assessed their antitumor efficacy against CRC cells with varying levels of CEA expression, both in cell-cultures and in two strains of tumor-bearing syngeneic mice.

RESULTS

Following retroviral transduction, 7XCL1-CAR T cells and reg-CAR T cells exhibited similar positive proportions of CEA-CAR and CD4:CD8 ratios. In co-culture system with CEA-negative CT26 cells, no differences in cytotoxicity were observed between 7XCL1-CAR and reg-CAR T cells. However, in co-culture with CT26.CEAhigh and CT26.CEAint cells, 7XCL1-CAR T cells displayed higher cytotoxicity than that reg-CAR T cells after 60 hours. On interaction with CT26.CEA-positive cells, 7XCL1-CAR T cells secreted higher levels of XCL1 and IL-7, effectively recruited the most potent cross-presenting cDC1s (type-I conventional dendritic cells), and sustained the antitumor activity of CAR-T cells. In treating mice that carried tumors derived from universally CEA-positive cells, 7XCL1-CAR T cells exhibited no difference compared with reg-CAR T cells. However, in treating mice with tumors containing both CEA-positive and CEA-negative cells, 7XCL1-CAR T cells displayed greater inhibition than that of reg-CAR-T cells. After treatment of 7XCL1-CAR T cells, tumor-bearing mice exhibited enhanced infiltration of cDC1s, maintained CAR-T activity, and generation of endogenous neoantigen-specific T cells. Consequently, 7XCL1-CAR T cell-treated mice demonstrated resistance to challenge with CEA-negative CT26 cells.

CONCLUSION

Treatment with CEA-specific, XCL1-secreting CAR-T cells for CEA-positive tumors promoted the generation of CD8+ T cells against tumor neoantigens, mediating a long-term antitumor immunity against heterogeneous CRCs.

Advancing Chimeric Antigen Receptor T-Cell Therapy for Acute Myeloid Leukemia: Current Limitations and Emerging Strategies

Chimeric antigen receptor (CAR) T-cell therapy represents one of the most impressive advances in anticancer therapy of the last decade. While CAR T-cells are gaining ground in various B cell malignancies, their use in acute myeloid leukemia (AML) remains limited, and no CAR-T product has yet received approval for AML. The main limitation of CAR-T therapy in AML is the lack of specific antigens that are expressed in leukemic cells but not in their healthy counterparts, such as hematopoietic stem cells (HSCs), as their targeting would result in an on-target/off-tumor toxicity. Moreover, the heterogeneity of AML and the tendency of blasts to modify surface antigens' expression in the course of the disease make identification of suitable targets even more challenging. Lastly, AML's immunosuppressive microenvironment dampens CAR-T therapeutic activities. In this review, we focus on the actual pitfalls of CAR T-cell therapy in AML, and we discuss promising approaches to overcome them.

Ectopic expression of NKG7 enhances CAR-T function and improves the therapeutic efficacy in liquid and solid tumors

Lack of biopsies after treatment, especially in solid tumors, restricts the understanding of chimeric antigen receptor (CAR)-T cells -related characteristic in vivo, thus hindering the development of strategies to improve CAR-T cells efficacy. Here, we applied nineteen individual single-cell RNA sequencing (scRNA-seq) data from clinical samples of digestive cancers to explore the characteristics of tumor-infiltrating T cells (TILs) to identify effective targets which might be benefit for enhancing the function of CAR-T cells. The data showed that natural killer cell granule protein 7 (NKG7) was overexpressed in TILs and positively associated with anti-PD1 or anti-CTLA4 therapy in digestive cancers. Subsequently, we found that ectopic expression of NKG7 significantly improved the cytotoxicity of B7H3-targeting CAR-T cells to B7H3-positive digestive cancer cells (MKN45, Huh7, HuCCT-1, SW620 and PANC-1 cells), as well as promoted the TNF-α and IL-2 expression. Furthermore, in a CD19-targeting CAR-T model, the therapeutic efficacy was also found increased after NKG7 overexpression. Mechanically, NKG7 preserved surface CAR expression and promoted CAR-T cell proliferation after exposing to relative tumor antigen. These results indicated that it may be feasible to explore single-cell sequencing data of clinical tumor samples to find strategies to improve CAR-T function, and that ectopic expression of NKG7 is an effective strategy to improve the therapeutic efficacy of CAR-T cells against tumors.

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.

Targeting overexpressed antigens in glioblastoma via CAR T cells with computationally designed high-affinity protein binders

Chimeric antigen receptor (CAR) T cells targeting receptors on tumour cells have had limited success in patients with glioblastoma. Here we report the development and therapeutic performance of CAR constructs leveraging protein binders computationally designed de novo to have high affinity for the epidermal growth factor receptor (EGFR) or the tumour-associated antigen CD276, which are overexpressed in glioblastoma. With respect to T cells with a CAR using an antibody-derived single-chain variable fragment as antigen-binding domain, the designed binders on CAR T cells promoted the proliferation of the cells, the secretion of cytotoxic cytokines and their resistance to cell exhaustion, and improved antitumour performance in vitro and in vivo. Moreover, CARs with the binders exhibited higher surface expression and greater resistance to degradation, as indicated by bulk and single-cell transcriptional profiling of the cells. The de novo design of binding domains for specific tumour antigens may potentiate the antitumour efficacy of CAR T cell therapies for other solid cancers.

Identification and Characterization of Fully Human FOLR1-Targeting CAR T Cells for the Treatment of Ovarian Cancer

CAR T cell therapy has been an effective treatment option for hematological malignancies. However, the therapeutic potential of CAR T cells can be reduced by several constraints, partly due to immunogenicity and toxicities. The lack of established workflows enabling thorough evaluation of new candidates, limits comprehensive CAR assessment. To improve the selection of lead CAR candidates, we established a stringent, multistep workflow based on specificity assessments, employing multiple assays and technologies. Moreover, we characterized a human FOLR1-directed CAR binding domain. Selection of binding domains was based on extensive specificity assessment by flow cytometry and imaging, to determine on-/off-target and off-tumor reactivity. CAR T cell functionality and specificity were assessed by high-throughput screening and advanced in vitro assays. Our validation strategy highlights that assays comprehensively characterizing CAR functionality and binding specificity complement each other. Thereby, critical specificity considerations can be addressed early in the development process to overcome current limitations for future CAR T cell therapies.

Comparison of seven CD19 CAR designs in engineering NK cells for enhancing anti-tumour activity

Chimeric antigen receptor-natural killer (CAR-NK) cell therapy is emerging as a promising cancer treatment, with notable safety and source diversity benefits over CAR-T cells. This study focused on optimizing CAR constructs for NK cells to maximize their therapeutic potential. We designed seven CD19 CAR constructs and expressed them in NK cells using a retroviral system, assessing their tumour-killing efficacy and persistence. Results showed all constructs enhanced tumour-killing and prolonged survival in tumour-bearing mice. In particular, CAR1 (CD8 TMD-CD3ζ SD)-NK cells showed superior efficacy in treating tumour-bearing animals and exhibited enhanced persistence when combined with OX40 co-stimulatory domain. Of note, CAR1-NK cells were most effective at lower effector-to-target ratios, while CAR4 (CD8 TMD-OX40 CD- FcεRIγ SD) compromised NK cell expansion ability. Superior survival rates were noted in mice treated with CAR1-, CAR2 (CD8 TMD- FcεRIγ SD)-, CAR3 (CD8 TMD-OX40 CD- CD3ζ SD)- and CAR4-NK cells over those treated with CAR5 (CD28 TMD- FcεRIγ SD)-, CAR6 (CD8 TMD-4-1BB CD-CD3ζ 1-ITAM SD)- and CAR7 (CD8 TMD-OX40 CD-CD3ζ 1-ITAM SD)-NK cells, with CAR5-NK cells showing the weakest anti-tumour activity. Increased expression of exhaustion markers, especially in CAR7-NK cells, suggests that combining CAR-NK cells with immune checkpoint inhibitors might improve anti-tumour outcomes. These findings provide crucial insights for developing CAR-NK cell products for clinical applications.

Yeast-based screening platforms to understand and improve human health

Detailed molecular understanding of the human organism is essential to develop effective therapies. Saccharomyces cerevisiae has been used extensively for acquiring insights into important aspects of human health, such as studying genetics and cell-cell communication, elucidating protein-protein interaction (PPI) networks, and investigating human G protein-coupled receptor (hGPCR) signaling. We highlight recent advances and opportunities of yeast-based technologies for cost-efficient chemical library screening on hGPCRs, accelerated deciphering of PPI networks with mating-based screening and selection, and accurate cell-cell communication with human immune cells. Overall, yeast-based technologies constitute an important platform to support basic understanding and innovative applications towards improving human health.

The peptide-based bispecific CAR T cells target EGFR and tumor stroma for effective cancer therapy

BACKGROUND AND PURPOSE

The efficacy of chimeric antigen receptor (CAR)-T cell for solid tumors is limited partially because of the lack of tumor-specific antigens and off-target effects. Low molecular weight peptides allowed CAR T cell to display several antigen receptors to reduce off-target effects. Here, we develop a peptide-based bispecific CAR for EGFR and tumor stroma, which are expressed in a variety of tumor types.

EXPERIMENTAL APPROACH AND KEY RESULTS

The peptide-based CAR T cells show excellent proliferation, cytotoxicity activity and are only activated by tumor cells overexpressing EGFR instead of normal cells with low EGFR expressing. In mouse xenograft models, the peptide bispecific CAR T cells can be delivered into the inner of tumor masses and thus are effective in inhibiting tumor growth. Meanwhile, they show strong expansion capacity and the property of maintaining long-term function in vivo. During treatment, no off-tumor toxicity is observed on healthy organs expressing lower levels of EGFR.

CONCLUSIONS & IMPLICATIONS

Our findings demonstrate that peptide-based bispecific CAR T holds great potential in solid tumor therapy due to an excellent targeting ability towards tumors and tumor microenvironment.

Fast on-rates of chimeric antigen receptors enhance the sensitivity to peptide MHC via antigen rebinding

Chimeric antigen receptor (CAR) is a synthetic receptor that induces T cell-mediated lysis of abnormal cells. As cancer driver proteins are present at low levels on the cell surface, they can cause weak CAR reactivity, resulting in antigen sensitivity defects and consequently limited therapeutic efficacy. Although affinity maturation enhances the efficacy of CAR-T cell therapy, it causes off-target cross-reactions resulting in adverse effects. Preferentially expressed antigen in melanoma (PRAME) is an intracellular oncoprotein that is overexpressed in various tumors and restricted in normal tissues, except the testis. Therefore, PRAME could be an ideal target for cancer immunotherapy. In this study, we developed an experimental CAR system comprising six single-chain variable fragments that specifically recognizes the PRAMEp301/HLA-A∗24:02 complex. Cell-mediated cytotoxicity was demonstrated using a panel of CARs with a wide range of affinities (KD = 10-10-10-7 M) and affinity modulation. CAR-T cells with fast on-rates enhance antigen sensitivity by accelerating the killing rates of these cells. Alanine scanning data demonstrated the potential of genetically engineered CARs to reduce the risk of cross-reactivity, even among CARs with high affinities. Given the correlation between on-rates and dwell time that occurs in rebinding and cell-mediated cytotoxicity, it is proposed that CAR-binding characteristics, including on-rate, play a pivotal role in the lytic capacity of peptide-major histocompatibility complex-targeting CAR-T cells, thus facilitating the development of strategies whereby genetically engineered CARs target intracellular antigens in cancer cells to lyse the cells.

Influencing factors and solution strategies of chimeric antigen receptor T-cell therapy (CAR-T) cell immunotherapy

Chimeric antigen receptor T-cesll therapy (CAR-T) has achieved groundbreaking advancements in clinical application, ushering in a new era for innovative cancer treatment. However, the challenges associated with implementing this novel targeted cell therapy are increasingly significant. Particularly in the clinical management of solid tumors, obstacles such as the immunosuppressive effects of the tumor microenvironment, limited local tumor infiltration capability of CAR-T cells, heterogeneity of tumor targeting antigens, uncertainties surrounding CAR-T quality, control, and clinical adverse reactions have contributed to increased drug resistance and decreased compliance in tumor therapy. These factors have significantly impeded the widespread adoption and utilization of this therapeutic approach. In this paper, we comprehensively analyze recent preclinical and clinical reports on CAR-T therapy while summarizing crucial factors influencing its efficacy. Furthermore, we aim to identify existing solution strategies and explore their current research status. Through this review article, our objective is to broaden perspectives for further exploration into CAR-T therapy strategies and their clinical applications.

Current Knowledge and Perspectives of Immunotherapies for Neuroblastoma

Neuroblastoma (NBL) cells highly express disialoganglioside GD2, which is restricted and weakly expressed in selected healthy cells, making it a desirable target of immunotherapy. Over the past two decades, application of dinutuximab, an anti-GD2 monoclonal antibody (mAb), has been one of the few new therapies to substantially improve outcomes to current levels. Given the persistent challenge of relapse and therapeutic resistance, there is an urgent need for new effective and tolerable treatment options for high-risk NBL. Recent breakthroughs in immune checkpoint inhibitor (ICI) therapeutics have not translated into high-risk NBL, like many other major pediatric solid tumors. Given the suppressed tumor microenvironment (TME), single ICIs like anti-CTLA4 and anti-PD1 have not demonstrated significant antitumor response rates. Meanwhile, emerging studies are reporting novel advancements in GD2-based therapies, targeted therapies, nanomedicines, and other immunotherapies such as adoptive transfer of natural killer (NK) cells and chimeric antigen receptors (CARs), and these hold interesting promise for the future of high-risk NBL patient care. Herein, we summarize the current state of the art in NBL therapeutic options and highlight the unique challenges posed by NBL that have limited the successful adoption of immune-modifying therapies. Through this review, we aim to direct the field's attention to opportunities that may benefit from a combination immunotherapy strategy.

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.

Analysis of polyfunctionality for enhanced BAFF-R CAR T-cell therapy for hematologic malignancies

ABSTRACT

Chimeric antigen receptor (CAR) T-cell therapy has emerged as a promising immunotherapeutic strategy for eradicating human cancers. Their therapeutic success and durability of clinical responses hinges, in large part, on their functional capacity, including the ability of these engineered cells to simultaneously expand and persist after infusion into patients. CD19 CAR T-cell polyfunctionality, assessing the simultaneous functions of cytokine production, proliferation, and cytotoxicity has been reported to correlate with clinical outcomes. Assay optimization is potentially limited by the heterogeneous nature of CAR T-cell infusion products and target specificity. We optimized a single-cell platform for polyfunctionality using CAR T-cell products manufactured from healthy donors, engineered against a novel target, B-cell-activating factor receptor (BAFF-R) and validated the protocol using CD19 CAR T cells. We observed distinct qualitative differences between BAFF-R and CD19 CAR T cells relative to the proportions of stimulatory vs effector cytokines, based on target antigen density, and, generally, CD19 CAR T cells exhibited lower indices of polyfunctionality. Finally, we applied our assay to the autologous BAFF-R CAR T-cell product generated from the first patient with non-Hodgkin lymphoma treated in an ongoing clinical trial who had progressed after prior CD19 CAR T-cell therapy. We observed robust indicators of polyfunctionality, which correlated with successful CAR T-cell expansion after infusion and achievement of durable complete remission ongoing after 18 months. The precise identification of factors determining the role of BAFF-R CAR T-cell fitness in toxicity and clinical outcome will require the application of this robust assay in the analysis of additional treated patients. This trial was registered at www.ClinicalTrials.gov as #NCT05370430.

Rab5 Overcomes CAR T Cell Dysfunction Induced by Tumor-Mediated CAR Capture

Continuous interaction between chimeric antigen receptor (CAR) T cell (CART) and tumors often result in CART dysfunction and tumor escape. We observed that tumors can take up CAR molecules, leaving CARTs without surface-expressed CARs and thus unable to kill tumors after prolonged exposure. Overexpression of Rab5 resulted in augmented clathrin-independent endocytosis, preventing loss of surface-expressed CARs, and enhanced CART activity. Interestingly, we observed membrane protrusions on the CART cell surface which disappeared after multiple tumor challenges. Rab5 maintained these protrusions after repeated tumor engagements and their presence correlated with effective tumor clearance, suggesting a link between endocytosis, membrane protrusions, and cytolytic activity. In vivo , Rab5-expressing CARTs demonstrated improved activity and were able to clear an otherwise refractory mesothelin-expressing solid cancer in humanized mice by maintaining CAR surface expression within the tumor. Thus, pairing Rab5 with CAR expression could improve the clinical efficacy of CART therapy. Highlights "CAR-jacking" occurs when surface CAR is internalized by target tumor cells.Rab5 overexpression prevents "CAR-jacking" and enhances CART function.Rab5 promotes CAR endocytic recycling and maintains membrane protrusions.Rab5-expressing CARTs exhibit enhanced therapeutic efficacy against solid tumors.

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.

Chimeric antigen receptor-induced antigen loss protects CD5.CART cells from fratricide without compromising on-target cytotoxicity

Chimeric antigen receptor T cells (CART) targeting lymphocyte antigens can induce T cell fratricide and require additional engineering to mitigate self-damage. We demonstrate that the expression of a chimeric antigen receptor (CAR) targeting CD5, a prominent pan-T cell antigen, induces rapid internalization and complete loss of the CD5 protein on T cells, protecting them from self-targeting. Notably, exposure of healthy and malignant T cells to CD5.CART cells induces similar internalization of CD5 on target cells, transiently shielding them from cytotoxicity. However, this protection is short-lived, as sustained activity of CD5.CART cells in patients with T cell malignancies results in full ablation of CD5+ T cells while sparing healthy T cells naturally lacking CD5. These results indicate that continuous downmodulation of the target antigen in CD5.CART cells produces effective fratricide resistance without undermining their on-target cytotoxicity.

Lineage-dependence of the neuroblastoma surfaceome defines tumor cell state-dependent and independent immunotherapeutic targets

Background

Neuroblastoma is a heterogeneous disease with adrenergic (ADRN)- and therapy resistant mesenchymal (MES)-like cells driven by distinct transcription factor networks. Here, we investigate the expression of immunotherapeutic targets in each neuroblastoma subtype and propose pan-neuroblastoma and cell state specific targetable cell-surface proteins.

Methods

We characterized cell lines, patient-derived xenografts, and patient samples as ADRN-dominant or MES- dominant to define subtype-specific and pan-neuroblastoma gene sets. Targets were validated with ChIP- sequencing, immunoblotting, and flow cytometry in neuroblastoma cell lines and isogenic ADRN-to-MES transition cell line models. Finally, we evaluated the activity of MES-specific agents in vivo and in vitro .

Results

Most immunotherapeutic targets being developed for neuroblastoma showed significantly higher expression in the ADRN subtype with limited expression in MES-like tumor cells. In contrast, CD276 (B7-H3) and L1CAM maintained expression across both ADRN and MES states. We identified several receptor tyrosine kinases (RTKs) enriched in MES-dominant samples and showed that AXL targeting with ADCT-601 was potently cytotoxic in MES-dominant cell lines and showed specific anti-tumor activity in a MES cell line-derived xenograft.

Conclusions

Immunotherapeutic strategies for neuroblastoma must address the potential of epigenetic downregulation of antigen density as a mechanism for immune evasion. We identified several RTKs as candidate MES-specific immunotherapeutic target proteins for the elimination of therapy-resistant cells. We hypothesize that the phenomena of immune escape will be less likely when targeting pan-neuroblastoma cell surface proteins such as B7-H3 and L1CAM, and/or dual targeting strategies that consider both the ADRN- and MES-cell states.

Key Points

Cellular plasticity influences the abundance of immunotherapeutic targets.Subtype-specific targets may be susceptible to epigenetically-mediated downregulation.Immunotherapeutic targets in development, B7-H3 and L1CAM, show "pan-subtype" expression.

Importance of Study

Neuroblastoma is a lethal childhood malignancy that shows cellular plasticity in response to anti-cancer therapies. Several plasma membrane proteins are being developed as immunotherapeutic targets in this disease. Here we define which cell surface proteins are susceptible to epigenetically regulated downregulation during an adrenergic to mesenchymal cell state switch and propose immunotherapeutic strategies to anticipate and circumvent acquired immunotherapeutic resistance.

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.

Anaplastic Large-cell Lymphoma in Children: State of the Art in 2023

Anaplastic large-cell lymphoma is a rare disease and account for approximately 10% to 15% of pediatric non-Hodgkin lymphomas. They are characterized by extended stages, a high frequency of B signs and extra nodal involvement. Multiagent chemotherapy cures ∽60% to 75% of patients and relapse occurs in 35% of cases. For relapsed patients, various treatments ranging from vinblastine monotherapy to therapeutic intensification with hematopoietic stem cell transplantation have been evaluated, but there is currently no consensus on the optimal therapeutic strategy. New therapeutic perspectives are being evaluated for relapses and refractory forms as well as high-risk forms including monoclonal antibodies (Anti CD30), ALK inhibitors, and CART cells.

CXCR4 has a dual role in improving the efficacy of BCMA-redirected CAR-NK cells in multiple myeloma

Multiple myeloma (MM) is a plasma cell disease with a preferential bone marrow (BM) tropism. Enforced expression of tissue-specific chemokine receptors has been shown to successfully guide adoptively-transferred CAR NK cells towards the malignant milieu in solid cancers, but also to BM-resident AML and MM. For redirection towards BM-associated chemokine CXCL12, we armored BCMA CAR-NK-92 as well as primary NK cells with ectopic expression of either wildtype CXCR4 or a gain-of-function mutant CXCR4R334X. Our data showed that BCMA CAR-NK-92 and -primary NK cells equipped with CXCR4 gained an improved ability to migrate towards CXCL12 in vitro. Beyond its classical role coordinating chemotaxis, CXCR4 has been shown to participate in T cell co-stimulation, which prompted us to examine the functionality of CXCR4-cotransduced BCMA-CAR NK cells. Ectopic CXCR4 expression enhanced the cytotoxic capacity of BCMA CAR-NK cells, as evidenced by the ability to eliminate BCMA-expressing target cell lines and primary MM cells in vitro and through accelerated cytolytic granule release. We show that CXCR4 co-modification prolonged BCMA CAR surface deposition, augmented ZAP-70 recruitment following CAR-engagement, and accelerated distal signal transduction kinetics. BCMA CAR sensitivity towards antigen was enhanced by virtue of an enhanced ZAP-70 recruitment to the immunological synapse, revealing an increased propensity of CARs to become triggered upon CXCR4 overexpression. Unexpectedly, co-stimulation via CXCR4 occurred in the absence of CXCL12 ligand-stimulation. Collectively, our findings imply that co-modification of CAR-NK cells with tissue-relevant chemokine receptors affect adoptive NK cell therapy beyond improved trafficking and retention within tumor sites.

Antigen Presenting Cell Mimetic Lipid Nanoparticles for Rapid mRNA CAR T Cell Cancer Immunotherapy

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable clinical success in the treatment of hematological malignancies. However, producing these bespoke cancer-killing cells is a complicated ex vivo process involving leukapheresis, artificial T cell activation, and CAR construct introduction. The activation step requires the engagement of CD3/TCR and CD28 and is vital for T cell transfection and differentiation. Though antigen-presenting cells (APCs) facilitate activation in vivo, ex vivo activation relies on antibodies against CD3 and CD28 conjugated to magnetic beads. While effective, this artificial activation adds to the complexity of CAR T cell production as the beads must be removed prior to clinical implementation. To overcome this challenge, this work develops activating lipid nanoparticles (aLNPs) that mimic APCs to combine the activation of magnetic beads and the transfection capabilities of LNPs. It is shown that aLNPs enable one-step activation and transfection of primary human T cells with the resulting mRNA CAR T cells reducing tumor burden in a murine xenograft model, validating aLNPs as a promising platform for the rapid production of mRNA CAR T cells.

Immunotherapy-related cognitive impairment after CAR T cell therapy in mice

Persistent central nervous system (CNS) immune dysregulation and consequent dysfunction of multiple neural cell types is central to the neurobiological underpinnings of a cognitive impairment syndrome that can occur following traditional cancer therapies or certain infections. Immunotherapies have revolutionized cancer care for many tumor types, but the potential long-term cognitive sequelae are incompletely understood. Here, we demonstrate in mouse models that chimeric antigen receptor (CAR) T cell therapy for both CNS and non-CNS cancers can impair cognitive function and induce a persistent CNS immune response characterized by white matter microglial reactivity and elevated cerebrospinal fluid (CSF) cytokines and chemokines. Consequently, oligodendroglial homeostasis and hippocampal neurogenesis are disrupted. Microglial depletion rescues oligodendroglial deficits and cognitive performance in a behavioral test of attention and short-term memory function. Taken together, these findings illustrate similar mechanisms underlying immunotherapy-related cognitive impairment (IRCI) and cognitive impairment following traditional cancer therapies and other immune challenges.

Identification of a Fully Human Antibody VH Domain Targeting Anaplastic Lymphoma Kinase (ALK) with Applications in ALK-Positive Solid Tumor Immunotherapy

The anaplastic lymphoma kinase (ALK, CD247) is a potential target for antibody-based therapy. However, no antibody-based therapeutics targeting ALK have entered clinical trials, necessitating the development of novel antibodies with unique therapeutic merits. Single-domain antibodies (sdAb) bear therapeutic advantages compared to the full-length antibody including deeper tumor penetration, cost-effective production and fast washout from normal tissues. In this study, we identified a human immunoglobulin heavy chain variable domain (VH domain) (VH20) from an in-house phage library. VH20 exhibits good developability and high specificity with no off-target binding to ~6000 human membrane proteins. VH20 efficiently bound to the glycine-rich region of ALK with an EC50 of 0.4 nM and a KD of 6.54 nM. Both VH20-based bispecific T cell engager (TCE) and chimeric antigen receptor T cells (CAR Ts) exhibited potent cytolytic activity to ALK-expressing tumor cells in an ALK-dependent manner. VH20 CAR Ts specifically secreted proinflammatory cytokines including IL-2, TNFα and IFNγ after incubation with ALK-positive cells. To our knowledge, this is the first reported human single-domain antibody against ALK. Our in vitro characterization data indicate that VH20 could be a promising ALK-targeting sdAb with potential applications in ALK-expressing tumors, including neuroblastoma (NBL) and non-small cell lung cancer.

Armored TGFβRIIDN ROR1-CAR T cells reject solid tumors and resist suppression by constitutively-expressed and treatment-induced TGFβ1

BACKGROUND

Chimeric antigen receptor (CAR) T-cell therapy target receptor tyrosine kinase-like orphan receptor 1 (ROR1) is broadly expressed in hematologic and solid tumors, however clinically-characterized ROR1-CAR T cells with single chain variable fragment (scFv)-R12 targeting domain failed to induce durable remissions, in part due to the immunosuppressive tumor microenvironment (TME). Herein, we describe the development of an improved ROR1-CAR with a novel, fully human scFv9 targeting domain, and augmented with TGFβRIIDN armor protective against a major TME factor, transforming growth factor beta (TGFβ).

METHODS

CAR T cells were generated by lentiviral transduction of enriched CD4+ and CD8+ T cells, and the novel scFv9-based ROR1-CAR-1 was compared with the clinically-characterized ROR1-R12-scFv-based CAR-2 in vitro and in vivo.

RESULTS

CAR-1 T cells exhibited greater CAR surface density than CAR-2 when normalized for %CAR+, and produced more interferon (IFN)-γ tumor necrosis factor (TNF)-α and interleukin (IL)-2 in response to hematologic (Jeko-1, RPMI-8226) and solid (OVCAR-3, Capan-2, NCI-H226) tumor cell lines in vitro. In vivo, CAR-1 and CAR-2 both cleared hematologic Jeko-1 lymphoma xenografts, however only CAR-1 fully rejected ovarian solid OVCAR-3 tumors, concordantly with greater expansion of CD8+ and CD4+CAR T cells, and enrichment for central and effector memory phenotype. When equipped with TGFβ-protective armor TGFβRIIDN, CAR-1 T cells resisted TGFβ-mediated pSmad2/3 phosphorylation, as compared with CAR-1 alone. When co-cultured with ROR-1+ AsPC-1 pancreatic cancer line in the presence of TGFβ1, armored CAR-1 demonstrated improved recovery of killing function, IFN-γ, TNF-α and IL-2 secretion. In mouse AsPC-1 pancreatic tumor xenografts overexpressing TGFβ1, armored CAR-1, in contrast to CAR-1 alone, achieved complete tumor remissions, and yielded accelerated expansion of CAR+ T cells, diminished circulating active TGFβ1, and no apparent toxicity or weight loss. Unexpectedly, in AsPC-1 xenografts without TGFβ overexpression, TGFβ1 production was specifically induced by ROR-1-CAR T cells interaction with ROR-1 positive tumor cells, and the TGFβRIIDN armor conferred accelerated tumor clearance.

CONCLUSIONS

The novel fully human TGFßRIIDN-armored ROR1-CAR-1 T cells are highly potent against ROR1-positive tumors, and withstand the inhibitory effects of TGFß in solid TME. Moreover, TGFβ1 induction represents a novel, CAR-induced checkpoint in the solid TME, which can be circumvented by co-expressing the TGβRIIDN armor on T cells.

CRISPR-Cas9 applications in T cells and adoptive T cell therapies

T cell immunity is central to contemporary cancer and autoimmune therapies, encompassing immune checkpoint blockade and adoptive T cell therapies. Their diverse characteristics can be reprogrammed by different immune challenges dependent on antigen stimulation levels, metabolic conditions, and the degree of inflammation. T cell-based therapeutic strategies are gaining widespread adoption in oncology and treating inflammatory conditions. Emerging researches reveal that clustered regularly interspaced palindromic repeats-associated protein 9 (CRISPR-Cas9) genome editing has enabled T cells to be more adaptable to specific microenvironments, opening the door to advanced T cell therapies in preclinical and clinical trials. CRISPR-Cas9 can edit both primary T cells and engineered T cells, including CAR-T and TCR-T, in vivo and in vitro to regulate T cell differentiation and activation states. This review first provides a comprehensive summary of the role of CRISPR-Cas9 in T cells and its applications in preclinical and clinical studies for T cell-based therapies. We also explore the application of CRISPR screen high-throughput technology in editing T cells and anticipate the current limitations of CRISPR-Cas9, including off-target effects and delivery challenges, and envisioned improvements in related technologies for disease screening, diagnosis, and treatment.

Cellular strategies to induce immune tolerance after liver transplantation: Clinical perspectives

Liver transplantation (LT) has become the most efficient treatment for pediatric and adult end-stage liver disease and the survival time after transplantation is becoming longer due to the development of surgical techniques and perioperative management. However, long-term side-effects of immunosuppressants, like infection, metabolic disorders and malignant tumor are gaining more attention. Immune tolerance is the status in which LT recipients no longer need to take any immunosuppressants, but the liver function and intrahepatic histology maintain normal. The approaches to achieve immune tolerance after transplantation include spontaneous, operational and induced tolerance. The first two means require no specific intervention but withdrawing immunosuppressant gradually during follow-up. No clinical factors or biomarkers so far could accurately predict who are suitable for immunosuppressant withdraw after transplantation. With the understanding to the underlying mechanisms of immune tolerance, many strategies have been developed to induce tolerance in LT recipients. Cellular strategy is one of the most promising methods for immune tolerance induction, including chimerism induced by hematopoietic stem cells and adoptive transfer of regulatory immune cells. The safety and efficacy of various cell products have been evaluated by prospective preclinical and clinical trials, while obstacles still exist before translating into clinical practice. Here, we will summarize the latest perspectives and concerns on the clinical application of cellular strategies in LT recipients.

Engineered Treg cells: The heir to the throne of immunotherapy

Recently, increased interest in the use of Tregs as adoptive cell therapy for the treatment of autoimmune diseases and transplant rejection had led to several advances in the field. However, Treg cell therapies, while constantly advancing, indiscriminately suppress the immune system without the permanent stabilization of certain diseases. Genetically modified Tregs hold great promise towards solving these problems, but, challenges in identifying the most potent Treg subtype, accompanied by the ambiguity involved in identifying the optimal Treg source, along with its expansion and engineering in a clinical-grade setting remain paramount. This review highlights the recent advances in methodologies for the development of genetically engineered Treg cell-based treatments for autoimmune, inflammatory diseases, and organ rejection. Additionally, it provides a systematized guide to all the recent progress in the field and informs the readers of the feasibility and safety of engineered adoptive Treg cell therapy, with the aim to provide a framework for researchers involved in the development of engineered Tregs.

Mesothelin antigen density influences anti-mesothelin chimeric antigen receptor T cell cytotoxicity

BACKGROUND AIMS

Several anti-mesothelin (MSLN) chimeric antigen receptor (CAR) T cells are in phase 1/2 clinical trials to treat solid-organ malignancies. The effect of MSLN antigen density on MSLN CAR cytotoxicity against tumor cells has not been examined previously, nor are there data regarding the effect of agents that increase MSLN antigen density on anti-MSLN CAR T cell efficacy.

METHODS

MSLN antigen density was measured on a panel of pancreatic cancer and mesothelioma cell lines by flow cytometry. In parallel, the cytotoxicity and specificity of two anti-MSLN CAR T cells (m912 and SS1) were compared against these cell lines using a real-time impedance-based assay. The effect of two MSLN 'sheddase' inhibitors (lanabecestat and TMI-1) that increase MSLN surface expression was also tested in combination with CAR T cells.

RESULTS

SS1 CAR T cells were more cytotoxic compared with m912 CAR T cells against cell lines that expressed fewer than ∼170 000 MSLN molecules/cell. A comparison of the m912 and amatuximab (humanized SS1) antibodies identified that amatuximab could detect and bind to lower levels of MSLN on pancreatic cancer and mesothelioma cell lines, suggesting that superior antibody/scFv affinity was the reason for the SS1 CAR's superior cytotoxicity. The cytotoxicity of m912 CAR T cells was improved in the presence of sheddase inhibitors, which increased MSLN antigen density.

CONCLUSIONS

These data highlight the value of assessing CAR constructs against a panel of cells expressing varying degrees of target tumor antigen as occurs in human tumors. Furthermore, the problem of low antigen density may be overcome by concomitant administration of drugs that inhibit enzymatic shedding of MSLN.

Targeting solid tumor antigens with chimeric receptors: cancer biology meets synthetic immunology

Chimeric antigen receptor (CAR) T cell therapy is a medical breakthrough in the treatment of B cell malignancies. There is intensive focus on developing solid tumor-targeted CAR-T cell therapies. Although clinically approved CAR-T cell therapies target B cell lineage antigens, solid tumor targets include neoantigens and tumor-associated antigens (TAAs) with diverse roles in tumor biology. Multiple early-stage clinical trials now report encouraging signs of efficacy for CAR-T cell therapies that target solid tumors. We review the landscape of solid tumor target antigens from the perspective of cancer biology and gene regulation, together with emerging clinical data for CAR-T cells targeting these antigens. We then discuss emerging synthetic biology strategies and their application in the clinical development of novel cellular immunotherapies.

Emerging Strategies to Overcome Current CAR-T Therapy Dilemmas - Exosomes Derived from CAR-T Cells

Adoptive T cells immunotherapy, specifically chimeric antigen receptor T cells (CAR-T), has shown promising therapeutic efficacy in the treatment of hematologic malignancies. As extensive research on CAR-T therapies has been conducted, various challenges have emerged that significantly hampered their clinical application, including tumor recurrence, CAR-T cell exhaustion, and cytokine release syndrome (CRS). To overcome the hurdles of CAR-T therapy in clinical treatment, cell-free emerging therapies based on exosomes derived from CAR-T cells have been developed as an effective and promising alternative approach. In this review, we present CAR-T cell-based therapies for the treatment of tumors, including the features and benefits of CAR-T therapies, the limitations that exist in this field, and the measures taken to overcome them. Furthermore, we discuss the notable benefits of utilizing exosomes released from CAR-T cells in tumor treatment and anticipate potential issues in clinical trials. Lastly, drawing from previous research on exosomes from CAR-T cells and the characteristics of exosomes, we propose strategies to overcome these restrictions. Additionally, the review discusses the plight in large-scale preparation of exosome and provides potential solutions for future clinical applications.

Low-dose targeted radionuclide therapy synergizes with CAR T cells and enhances tumor response

Ionizing radiation has garnered considerable attention as a combination partner for immunotherapy due to its potential immunostimulatory effects. In contrast to the more commonly used external beam radiation, we explored the feasibility of combining chimeric antigen receptor (CAR) T cell therapy with targeted radionuclide therapy (TRT), which is achieved by delivering β-emitting 177Lu-DOTATATE to tumor via tumor-infiltrating CAR T cells that express somatostatin receptor 2 (SSTR2). We hypothesized that the delivery of radiation to tumors could synergize with CAR T therapy, resulting in enhanced antitumor immunity and tumor response. To determine the optimal dosage and timing of 177Lu-DOTATATE treatment, we measured CAR T cell infiltration and expansion in tumors longitudinally through positron emission tomography (PET) using a SSTR2-specific positron-emitting radiotracer,18F-NOTA-Octreotide. In animals receiving CAR T cells and a low-dose (2.5 Gy) of TRT following the administration of 177Lu-DOTATATE, we observed a rapid regression of large subcutaneous tumors, which coincided with a dramatic increase in serum proinflammatory cytokines. Tumor burden was also reduced when a higher radiation dose (6 Gy) was delivered to the tumor. However, this higher dose led to cell death in both the tumor and CAR T cells. Our study suggests that there may exist an optimum range of TRT dosage that can enhance T cell activity and sensitize tumor cells to T cell killing, which may result in more durable tumor control compared to a higher radiation dose.

Chemical genetic control of cytokine signaling in CAR-T cells using lenalidomide-controlled membrane-bound degradable IL-7

CAR-T cell therapy has emerged as a breakthrough therapy for the treatment of relapsed and refractory hematologic malignancies. However, insufficient CAR-T cell expansion and persistence is a leading cause of treatment failure. Exogenous or transgenic cytokines have great potential to enhance CAR-T cell potency but pose the risk of exacerbating toxicities. Here we present a chemical-genetic system for spatiotemporal control of cytokine function gated by the off-patent anti-cancer molecular glue degrader drug lenalidomide and its analogs. When co-delivered with a CAR, a membrane-bound, lenalidomide-degradable IL-7 fusion protein enforced a clinically favorable T cell phenotype, enhanced antigen-dependent proliferative capacity, and enhanced in vivo tumor control. Furthermore, cyclical pharmacologic combined control of CAR and cytokine abundance enabled the deployment of highly active, IL-7-augmented CAR-T cells in a dual model of antitumor potency and T cell hyperproliferation.