Chimeric Antigen Receptor Research Articles

Loop33 × 123 CAR-T targeting CD33 and CD123 against immune escape in acute myeloid leukemia.

Immunotherapy, such as chimeric antigen receptor T (CAR-T) cells targeting CD33 or CD123, has been well developed over the past decade for the treatment of acute myeloid leukemia (AML). However, the inability to sustain tumor-free survival and the possibility of relapse due to antigen loss have raised concerns. A dual targeting of CD33 and CD123 is needed for better outcomes. Based on our previously constructed CD33 and CD123 monovalent CAR-T, Loop33 × 123 and Loop123 × 33 CAR-T were constructed with molecular cloning techniques. All CAR-T cells were generated by lentivirus transduction of T cells from healthy donors. Phenotype detection was evaluated on day 7 concerning activation, exhaustion, and subtype proportions. Coculture killing assays were conducted using various AML cell lines and primary AML cells. Degranulation and cytokine secretion levels were detected by flow cytometry. Cell-derived xenograft models were established using wild-type Molm 13 cell lines, or a mixture of Molm 13-KO33 and Molm 13-KO123 cells as an ideal model of immune escape. By monitoring body weight and survival of tumor-bearing mice, Loop33 × 123 and Loop123 × 33 CAR-T cells were further assessed for their efficacy in vivo. In vitro study, our results demonstrated that Loop33 × 123 CAR-T cells could efficiently eliminate AML cell lines and primary AML cells with elevated degranulation and cytokine secretion levels. Compared with our previously constructed monovalent CD33 or CD123 CAR-T cells, Loop33 × 123 CAR-T cells showed superior advantages in an immune escape model. In vivo studies further confirmed that Loop33 × 123 CAR-T cells could effectively prolong the survival of mice without significant toxicity. However, Loop123 × 33 CAR-T cells failed to show the same effects. Furthermore, Loop33 × 123 CAR-T cells efficiently circumvented potential immune escape, a challenge where monovalent CAR-T cells failed. Loop33 × 123 CAR-T targeting CD33 and CD123 could efficiently eliminate AML cells and prolong survival of tumor-bearing mice, while addressing the issue of immune escape.

CAR-engineered NK cells versus CAR T cells in treatment of glioblastoma; strength and flaws.

Glioblastoma (GBM) is a highly aggressive primary brain tumor that carries a grim prognosis. Because of the dearth of treatment options available for treatment of GBM, Chimeric Antigen Receptor (CAR)-engineered T cell and Natural Killer (NK) therapy could provide alternative strategies to address the challenges in GBM treatment. In these approaches, CAR T and NK cells are engineered for cancer-specific immunotherapy by recognizing surface antigens independently of major histocompatibility complex (MHC) molecules. However, the efficacy of CAR T cells is hindered by GBM's downregulation of its targeted antigens. CAR NK cells face similar challenges, but, in contrast, they offer advantages as off-the-shelf allogeneic products, devoid of graft-versus-host disease (GVHD) risk as well as anti-cancer activity beyond CAR specificity, potentially reducing the risk of relapse or resistance. Despite CAR T cell therapies being extensively studied in clinical settings, the use of CAR-modified NK cells in GBM treatment remains largely in the preclinical stage. This review aims to discuss recent advancements in NK cell and CAR T cell therapies for GBM, including methods for introducing CARs into both NK cells and T cells, addressing manufacturing challenges, and providing evidence supporting the efficacy of these approaches from preclinical and early-phase clinical studies. The comprehensive evaluation of CAR-engineered NK cells and CAR T cells seeks to identify the optimal therapeutic approach for GBM, contributing to the development of effective immunotherapies for this devastating disease.

Significant Advancements and Evolutions in Chimeric Antigen Receptor Design

Recent times have witnessed remarkable progress in cancer immunotherapy, drastically changing the cancer treatment landscape. Among the various immunotherapeutic approaches, adoptive cell therapy (ACT), particularly chimeric antigen receptor (CAR) T cell therapy, has emerged as a promising strategy to tackle cancer. CAR-T cells are genetically engineered T cells with synthetic receptors capable of recognising and targeting tumour-specific or tumour-associated antigens. By leveraging the intrinsic cytotoxicity of T cells and enhancing their tumour-targeting specificity, CAR-T cell therapy holds immense potential in achieving long-term remission for cancer patients. However, challenges such as antigen escape and cytokine release syndrome underscore the need for the continued optimisation and refinement of CAR-T cell therapy. Here, we report on the challenges of CAR-T cell therapies and on the efforts focused on innovative CAR design, on diverse therapeutic strategies, and on future directions for this emerging and fast-growing field. The review highlights the significant advances and changes in CAR-T cell therapy, focusing on the design and function of CAR constructs, systematically categorising the different CARs based on their structures and concepts to guide researchers interested in ACT through an ever-changing and complex scenario. UNIVERSAL CARs, engineered to recognise multiple tumour antigens simultaneously, DUAL CARs, and SUPRA CARs are some of the most advanced instances. Non-molecular variant categories including CARs capable of secreting enzymes, such as catalase to reduce oxidative stress in situ, and heparanase to promote infiltration by degrading the extracellular matrix, are also explained. Additionally, we report on CARs influenced or activated by external stimuli like light, heat, oxygen, or nanomaterials. Those strategies and improved CAR constructs in combination with further genetic engineering through CRISPR/Cas9- and TALEN-based approaches for genome editing will pave the way for successful clinical applications that today are just starting to scratch the surface. The frontier lies in bringing those approaches into clinical assessment, aiming for more regulated, safer, and effective CAR-T therapies for cancer patients.

In vivo gene editing and in situ generation of chimeric antigen receptor cells for next-generation cancer immunotherapy.

Chimeric antigen receptor (CAR) cell therapy has achieved groundbreaking success in treating hematological malignancies. However, its application to solid tumors remains challenging due to complex manufacturing processes, limited in vivo persistence, and transient therapeutic effects. In vivo CAR-immune cells induced by gene delivery systems loaded with CAR genes and gene-editing tools have shown efficiency for anti-tumor immunotherapy. In situ programming of autologous immune cells avoids the safety concerns of allogeneic immune cells, and the manufacture of gene delivery systems could be standardized. Therefore, the in vivo editing and in situ generation of CAR-immune cells might potentially overcome the abovementioned limitations of current CAR cell therapy. This review mainly focuses on CAR structures, gene-editing tools, and gene delivery techniques applied in anti-tumor immunotherapy to help design and develop in situ CAR-immune cell therapy. The recent applications of in vivo CAR-immune cell therapy in both hematologic malignancies and solid tumors are investigated. To sum up, the in vivo editing and in situ generation of CAR therapy holds promise for offering a practical, cost-effective, efficient, safe, and widely applicable approach to the next-generation anti-tumor immunotherapy.

Preclinical delayed toxicity studies of BCMA CAR T-cell injection in B-NDG mice with multiple myeloma

PurposeBased on the efficacy data from the previous study of B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell injection, we further examined the delayed toxicity for 8 weeks after a single dose of BCMA CAR T-cell injection to observe possible toxic reactions.MethodsB-NDG mice transplanted with multiple myeloma (MM) cells were given a single dose of BCMA CAR T-cell injection at two dosages or human normal T cells and then subjected to examinations including clinical signs, weight and food intake measurements, haematology, blood biochemical analysis, cytokine assay, T-lymphocyte subpopulation quantification and histopathology on days 28 and 56 after dosing. In addition, quantitative polymerase chain reaction (qPCR) was used to quantify DNA fragments in different tissues to assess the tissue distribution of CAR and provide a basis for its preclinical safety evaluation and clinical dosing.ResultsIn the delayed toxicity study, no mortality or significant toxic effects such as reductions in food intake, body weight, relevant biochemical parameters and target organ weights were observed in the BCMA CAR T-cell-treated groups. Compared to the model group, restorative changes in clinical signs and clinicopathology indicating therapeutic effects were seen in the BCMA CAR T-cell-treated groups. Human-derived cytokines interleukin-2 (IL-2), IL-4, IL-6, IL-12, IL-10, tumor necrosis factor α (TNF-α), and interferon-γ (IFN-γ) could be detected in all cancer cell–bearing mice by cytokine level measurement. IFN-γ levels showed a geometric increase due to the graft versus host disease (GVHD) response induced in the mice, while the levels of the other cytokines did not show significant changes. Histopathological examination indicated that the BCMA CAR T-cell treatment groups showed mixed cellular infiltration of human-derived T cells, cancer cells, and inflammatory cells in several target organs including the liver, spleen, lung, and kidney, and some of them showed mild tissue damage, but the number of the animals and the severity of damage were significantly less than those of the T-cell control group as well as the model group. The results of the tissue distribution study showed that BCMA CAR T cells were mainly concentrated in the kidney, lung, bone marrow and the related immune organs/tissues, and the distribution of BCMA CAR T cells was highly consistent with that of MM cells, suggesting that BCMA CAR T cells could follow the cancer cells during metastatic targeting of the tissues.ConclusionsThe present study demonstrated a low toxicity of BCMA CAR T-cell injection, with manageable side effects and good anticancer activity and without observable adverse effects. This study provides data to support future clinical studies of BCMA CAR T-cell injection for MM.

Abstract PR014: Robust disease monitoring using CSF liquid biopsies collected from children undergoing cellular therapy for malignant central nervous system tumors

Abstract Background: Central nervous system (CNS) tumors remain the leading cause of cancer-related mortality in children, necessitating more effective treatment options. Chimeric Antigen Receptor T-cells (CAR-T) have emerged as a promising strategy to treat CNS tumors, with B7H3 (CD276) representing an attractive target due to its high expression across a broad range of entities. B7H3-CAR-T therapy is currently being evaluated in a St. Jude Children’s Research Hospital Phase I clinical trial (NCT05835687) for the treatment of relapse/refractory pediatric CNS tumors. Monitoring disease progression after CAR-T infusion by magnetic resonance imaging (MRI) remains challenging, emphasizing the need for more sensitive biomarkers of treatment response. Detection of circulating tumor DNA (ctDNA) in cerebrospinal fluid (CSF) liquid biopsies holds tremendous potential for minimal residual disease (MRD) monitoring in the clinical setting. Here, we leverage CSF liquid biopsies for longitudinal disease profiling in pediatric CNS tumor patients receiving B7H3-CAR-T immunotherapy. Methods: CSF samples were collected from Ommaya reservoirs of 9 pediatric patients with relapse/refractory CNS tumors undergoing B7H3-CAR-T therapy. CSF was sampled at study enrollment, and weekly intervals pre- and post-infusion. Cell-free DNA (cfDNA) was extracted from 115 longitudinally collected CSF samples and subjected to enzymatic methylation sequencing (EM-seq). Implementation of a custom computational workflow enabled detection of tumor-derived copy number variations (CNVs), estimation of malignant vs. non-malignant fractions, and molecular classification of tumor entity. Results: Tumor-derived CNVs were detected in 7/9 (78%) CSF samples collected at enrollment, prior to immunotherapy. Liquid biopsy-inferred CNV profiles and entity classifications were highly concordant with matched tumor tissue profiles. Chromosomal alterations that were restricted to CSF profiles indicated clonal evolution. Increased ctDNA burden was repeatedly observed after B7H3-CAR-T infusions, suggesting subclinical antitumor activity. Transient subclonal alterations emerging in response to treatment were also identified in a subset of patients. Conclusions: EM-seq is a feasible method for serial tracking of ctDNA burden in patients receiving cellular immunotherapy. CSF liquid biopsies capture the global landscape of tumor heterogeneity and genetic alterations that arise during therapy, providing a sensitive platform for detecting clinical response and disclosing potential mechanisms of treatment resistance. Citation Format: Anna Kostecka, Kyle S Smith, Katie Han, Hong Lin, Deanna Langfitt, Tara Walhart, Stephen Gottschalk, Giedre Krenciute, Christopher DeRenzo, Kelsey Bertrand, Paul A Northcott. Robust disease monitoring using CSF liquid biopsies collected from children undergoing cellular therapy for malignant central nervous system tumors [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr PR014.

Detection of Brain-Derived Cell-Free DNA in Plasma

Background: Neuronal loss is a major pathological feature of neurodegenerative diseases. The analysis of plasma cell-free DNA (cfDNA) is an emerging approach to track cell death events in a minimally invasive way and from inaccessible areas of the body, such as the brain. Previous studies showed that DNA methylation (DNAm) profiles can be used to map the tissue of origin of cfDNA and to identify molecules released from the brain upon cell death. The aim of the present study is to contribute to this research field, presenting the development and validation of an assay for the detection of brain-derived cfDNA (bcfDNA). Methods: To identify CpG sites with brain-specific DNAm, we compared brain and non-brain tissues for their chromatin state profiles and genome-wide DNAm data, available in public datasets. The selected target genomic regions were experimentally validated by bisulfite sequencing on DNA extracted from 44 different autoptic tissues, including multiple brain regions. Sequencing data were analysed to identify brain-specific epihaplotypes. The developed assay was tested in plasma cfDNA from patients with immune effector cell-associated neurotoxicity syndrome (ICANS) following chimeric antigen receptor T (CAR-T) therapy. Results: We validated five genomic regions with brain-specific DNAm (four hypomethylated and one hypermethylated in the brain). DNAm analysis of the selected genomic regions in plasma samples from CAR-T patients revealed higher levels of bcfDNA in participants with ongoing neurotoxicity syndrome. Conclusions: We developed an assay for the analysis of bcfDNA in plasma. The assay is a promising tool for the early detection of neuronal loss in neurodegenerative diseases.

Logic-gated and contextual control of immunotherapy for solid tumors: contrasting multi-specific T cell engagers and CAR-T cell therapies

CAR-T cell and T cell engager therapies have demonstrated transformational efficacy against hematological malignancies, but achieving efficacy in solid tumors has been more challenging, in large part because of on-target/off-tumor toxicities and sub-optimal T cell anti-tumor cytotoxic functions. Here, we discuss engineering solutions that exploit biological properties of solid tumors to overcome these challenges. Using logic gates as a framework, we categorize the numerous approaches that leverage two inputs instead of one to achieve better cancer selectivity or efficacy in solid tumors with dual-input CAR-Ts or multi-specific TCEs. In addition to the “OR gate” and “AND gate” approaches that leverage dual tumor antigen targeting, we also review “contextual AND gate” technologies whereby continuous cancer-selective inputs such a pH, hypoxia, target density, tumor proteases, and immune-suppressive cytokine gradients can be creatively incorporated in therapy designs. We also introduce the notion of “output directionality” to distinguish dual-input strategies that mechanistically impact cancer cell killing or T cell fitness. Finally, we contrast the feasibility and potential benefits of the various approaches using CAR-T and TCE therapeutics and discuss why the promising “IF/THEN” and “NOT” gate types pertain more specifically to CAR-T therapies, but can also succeed by integrating both technologies.

Beyond the blood: expanding CAR T cell therapy to solid tumors.

Chimeric antigen receptor (CAR) T cell therapy stands as a transformative advancement in immunotherapy, triumphing against hematological malignancies and, increasingly, autoimmune disorders. After a decade of relatively modest results for solid tumors, recent clinical trials and patient reports have also started to yield promising outcomes in glioblastoma and other challenging solid tumor entities. This Perspective seeks to explore the reasons behind these latest achievements and discusses how they can be sustained and expanded through different strategies involving CAR engineering and synthetic biology. Furthermore, we critically analyze how these breakthroughs can be leveraged to maintain momentum and broaden the therapeutic impact of CAR T cells across a variety of solid tumor landscapes.

Innovative pan-tumor target strategy for CAR-T therapy: cancer-specific exons as novel targets for pediatric solid and brain tumors.

Chimeric antigen receptor T-cell (CAR-T) immunotherapy has achieved remarkable success in treating chemotherapy-refractory hematological malignancies. However, its efficacy in solid and brain tumors remains limited due to challenges such as insufficient target antigens, poor T-cell adaptability, inefficient tumor site trafficking, and the immunosuppressive tumor microenvironment. To address these challenges, Shaw and colleagues proposed an innovative strategy targeting cancer-specific exons (CSEs) in pediatric solid and brain tumors. Using RNA sequencing data from 16 tumor types, the study identified 157 highly tumor-specific targets, including both known and novel proteins. The researchers validated several targets, including FN1 and COL11A1, demonstrating their therapeutic potential in in vitro and in vivo models. The study's approach of integrating exon-level analysis with a broad search for extracellular matrix proteins offers a new frontier for CAR-T therapy, providing valuable insights for improving immunotherapy in pediatric solid tumors. Although promising, the study also highlights the need for further evaluation of tumor recurrence and CAR-T cell exhaustion. The identification of novel pan-tumor targets may revolutionize CAR-T therapy design and expand its application in pediatric cancer treatment.

Abstract 4114505: Cardiovascular Adverse Events After Anti-BCMA CAR-T (Ide-Cel and Cilta-Cel) for Relapsed/ Refractory Multiple Myeloma

Introduction: Idecabtagene vicleucel (Ide-Cel) and ciltacabtagene autoleucel (Cilta-cel) are novel CAR-T therapies targeting B-cell maturation antigen (BCMA) and approved for relapsed and refractory multiple myeloma (RRMM). While cardiovascular adverse events (CVAE) are relatively common with CD-19 CAR-T, the incidence of CVAE in the real-world setting for anti-BCMA CAR-T in RRMM is largely unknown. This study aims to determine the incidence of CVAE and its associated risk factors in patients treated with ide-cel and cilta-cel. Method: This single-center retrospective cohort study evaluated RRMM patients treated with ide-cel and cilta-cel from May 2021 to December 2023. We assessed baseline cardiac and oncologic characteristics and clinical outcomes post-CAR-T. Cytokine release syndrome (CRS) and immune cell-associated neurologic syndrome (ICANS) grading followed ASTCT consensus guidelines. Result: A total of 164 RRMM patients treated with ide-cel (N=109) or cilta-cel (N=55) with at least 6 months follow-up were included. The average age was 63 years, and 57% were male. Advanced RRMM stage (R-ISS III) was present in 17% with a median of 6 prior lines of therapy. CRS grade equal or greater than 2 occurred in 22%, and ICANS grade equal or greater than 3 in 6.7%. Twenty patients (12.2%) experienced CVAE, including atrial fibrillation (7.9%), non-sustained ventricular arrhythmia (3.0%), heart failure (3.7%), and cardiovascular death (0.6%). R-ISS III was associated with increased CVAE (52.9% vs. 11.5%; P=0.001). Patients with CVAE had higher baseline ferritin and CRP levels and a higher incidence of CRS grade ≥ 2 (60% vs. 16.7%; P<0.001) and ICANS grade ≥ 3 (20% vs 4.9%; P=0.001). Treatment with tocilizumab, steroids, or anakinra was more common in patients with CVAE. Conclusion: CVAE occurred relatively frequently following BCMA CAR-T therapy, with high-grade CRS identified as a consistent risk factor. Most CVAEs were manageable with appropriate supportive care, including careful observation and active treatment of CRS.

CD34+ and CD34- MM cells show different immune-checkpoint molecule expression profiles: high expression of CD112 and CD137 ligand on CD34+ MM cells.

Despite the introduction of new drugs, multiple myeloma (MM) still remains incurable. We previously reported that CD34+ MM cells, which are clonogenic and self-renewing, are therapy-resistant and persist as a major component of minimal residual disease, expanding during relapse. To investigate the effects of immunotherapies such as immune-checkpoint inhibitors, CAR-T therapy, and bispecific antibodies on CD34+ MM cells, we analyzed immune profiles of both MM cells and T cells from MM patients using microarrays and flow cytometry. Ingenuity pathway analysis revealed 14 out of 289 canonical pathways were more active in CD34+ MM cells compared to CD34- cells, many of which were involved in inflammation and immune responses. Notably, PD-1 signaling-related genes were highly expressed in CD34+ MM cells. Among 10 immune-checkpoint molecules, CD34+ cells more frequently expressed CD112, CD137L, CD270, CD275, and GAL9 than CD34- cells in both newly diagnosed and relapsed/resistant patients. In addition, CD4+ and CD8+ T cells more frequently expressed TIGIT and CD137, suggesting that CD112/TIGIT and CD137L/CD137 interactions may suppress T-cell activity against CD34+ MM cells. Furthermore, our finding of higher FcRH5 expression on CD34+ MM cells is encouraging for future research into the efficacy of FcRH5-targeted therapy in MM.

A case of acute macular neuroretinopathy as atipycal ICANS manifestation after CAR-T cell infusion

A case of acute macular neuroretinopathy as atipycal ICANS manifestation after CAR-T cell infusion

IMMU-39. CAR T CELLS TARGETING ICAM-1 SHOW A SURVIVAL BENEFIT IN BOTH SYNGENEIC AND XENOGRAFT GLIOMA MOUSE MODELS

Abstract BACKGROUND Chimeric antigen receptor (CAR) T-cell therapy, while effective against hematological malignancies, has faced significant hurdles in its application to solid tumors. Challenges in CAR T-cell therapy for glioblastoma include the immunosuppressive tumor microenvironment, the limited infiltration of CAR T-cells into the tumor, heterogeneous target expression and antigen escape. In this study, we focused on targeting Intracellular adhesion molecule-1 (ICAM-1), a protein expressed on both glioma cells and tumor-associated cells like macrophages and endothelial cells. METHODS Glioblastoma and normal brain tissue microarray sections (TMA) were immunohistochemically analyzed for ICAM-1 expression. Second-generation human and murine ICAM-1-targeting CAR T cells were generated by lentiviral or retroviral transduction of T cells from healthy human donors or murine splenocytes. Their efficacy was evaluated in co- culture assays with human and murine glioma and endothelial cell lines. Syngeneic and xenograft orthotopic glioma mouse models were used to assess the in vivo activity of CAR T cells. Ex vivo analysis of these tumors included examination of changes in the tumor microenvironment using high-dimensional flow cytometry. RESULTS Immunohistochemical staining of TMA revealed a significant upregulation of ICAM-1 in human glioblastoma tissue compared to normal brain tissue. Single-cell RNA sequencing data from glioblastoma specimens showed a high level of ICAM-1 expression in tumor- associated macrophages. Human and murine ICAM-1-targeting CAR T cells displayed strong lysis of ICAM-1-expressing glioma and endothelial cells in vitro. Intratumoral application of CAR T cells resulted in a survival benefit in both syngeneic and xenograft glioma mouse models. Ex vivo analysis of the tumor microenvironment revealed treatment-induced changes from our CAR T cell therapy and indicates potential for further enhancements. CONCLUSION Our study demonstrates that ICAM-1-targeting CAR T cells improve survival in human and murine glioma mouse models. Flow cytometry of the tumor microenvironment reveals therapy-induced changes, for future improvements of the CAR T cell therapy.

EXTH-03. CAR T-CELLS TARGETED TO B7-H3 OR HER2 FUNCTION INDEPENDENTLY OF ANTIGEN DENSITY IN XENOGRAFT MODELS OF EPENDYMOMA

Abstract BACKGROUND Targeted treatment options are desperately needed for ependymomas (EPN). Chimeric antigen receptor (CAR) T-cells have immense potential to positively transform treatment outcomes; however, little is known regarding antitumor efficacy of CAR T-cells against EPNs. Specifically, antigen density has emerged as a major influencer of CAR T-cell potency. However, the specific high and low antigen density thresholds governing CAR T-cell efficacy for EPN are unknown. The goal of this project is to determine the role of antigen density in CAR T-cell potency against EPN. METHODS Using quantitative flow cytometry, we determined antigen density of B7-H3 and HER2 (the two CAR targets currently in pediatric EPN clinical trials), on EPN patient derived cell lines (1425, ST1, CPITT, ST2, EPI, L46SJ). We generated B7-H3 and HER2-CAR T-cells with CD28z signaling domain and compared long-term cytolytic activity, expansion, and cytokine production against EPNs. RESULTS We found that all EPN cell lines express remarkably high yet variable density of B7-H3 (62,700 – 335,440 molecules/ cell). In contrast, surface density of HER2 was consistently and significantly lower (860 – 24,488 molecules/ cell). In repeated-stimulation assays, B7-H3-CAR T-cells killed 7-10 times and expanded up to 325,360-fold when cultured against EPN. However, we observed no significant difference in total expansion or correlation with antigen density against EPNs. Surprisingly, expansion of HER2-CAR T-cells against EPNs was drastically higher and greatly exceeded that of B7-H3-CAR-T cells against the same EPN cells despite much lower antigen density. CONCLUSIONS Our work shows that both B7-H3 and HER2 are good targets against EPN, despite drastic differences in antigen density. Results suggest that lower antigen density of HER2 may be superior for CAR T-cell activity. Future work will validate whether HER-CAR T-cells have superior antitumor efficacy in vivo to further delineate role of antigen density thresholds in CAR T-cell potency.

EXTH-51. ENHANCING GLIOBLASTOMA TREATMENT: ALLOGENEIC CAR-T CELLS OVERCOMES FUNCTIONAL DEFICITS OF PATIENT-DERIVED AUTOLOGOUS PRODUCTS

Abstract Glioblastoma (GBM) is the most common primary brain malignancy in adults, with a dismal prognosis despite an intensive standard of care. Recently, chimeric antigen receptor T-cell (CAR-T) therapy has shown promising outcomes in treating liquid malignancies. However, clinical trials targeting various tumor antigens in GBM failed to show durable clinical benefit. Though this may stem from various tumor-intrinsic immune evasion strategies typical of GBM, there has been little work investigating whether the problem lies in the quality of the CAR-T products treatment itself. Currently, CAR-T cells for clinical studies are produced in an autologous setting, where T-cells are extracted from patients, engineered ex-vivo, and then re-infused. However, peripheral T-cells taken from GBM patients have shown qualitative and functional deficits, which may contribute to suboptimal treatment outcomes. Thus, we aimed to explore whether CAR-Ts generated from GBM patients had any functional deficits in comparison to healthy donors, utilizing our previously validated CD133 CAR-T. In this study, we show pre-treatment exhaustion, poor tumor control, and reduced survival advantage in autologous, patient-derived CD133-targeting CAR-T cell products using an orthotopic xenograft model of human GBM. To address the functional and logistical considerations of autologous therapy, we also sought to generate an “off-the-shelf” allogeneic CD133 CAR-T. Using CRISPR gene editing technology, we generated TCR-knockout CAR-T cells with comparable pre-clinical efficacy to our healthy donor derived autologous models. Ultimately, this work highlights the need to reevaluate autologous CAR-T therapy for GBM and consider allogeneic approaches as biologically-informed therapeutic alternatives.

CTIM-21. FIRST-IN-HUMAN PHASE I CLINICAL TRIAL USING 8R-70CAR T CELLS FOR NEWLY DIAGNOSED ADULT GLIOBLASTOMA

Abstract BACKGROUND To address the challenges of chimeric antigen receptor (CAR) T cell therapy in GBM, we utilized IL-8 release from tumor cells as a ‘GPS homing signal’ to enhance T-cell trafficking with a novel CD70-specific CAR design (8R-70CAR) that targets GBM. The 8R-70CAR offers several advantages: 1) Improved CAR T-cell trafficking, enhancing antitumor efficacy; 2) Reduced CD70, reshaping the tumor microenvironment (TME) and boosting endogenous immunity; 3) Utilized CD27 as the CAR, a co-stimulatory molecule that enhances T-cell functions; 4) Enabled CAR T cells to act as a sink to neutralize or remove IL-8, a pro-cancer chemokine, from the TME; and 5) Required only 120 ml of whole blood (not leukapheresis) for CAR T cell production. Preclinically, 8R-70CAR significantly enhanced CAR-T cell tumor migration and persistence, leading to complete tumor regression and sustained immune memory in a chemo/radiation/PD-1-blockade-resistant GBM model. These findings led to a phase-I trial (IMPACT trial: FDA-IND#23881, NCT05353530) using 8R-70CAR T cells for CD70 -positive newly diagnosed adult GBM. METHODS We aim to recruit 18 adult patients (3 + 3 dose-escalation design) with CD70-positive (>20%) tumors. The CAR T cells will be given intravenously after completing standard-of-care (SOC) therapy. Primary endpoints: Evaluate safety, tolerability, and dose-limiting toxicities (DLTs) to determine the maximum tolerated dose. Secondary endpoints: Assess preliminary efficacy. Immune monitoring and correlative studies will also be conducted. RESULTS To date, four patients have been enrolled in the IMPACT trial, with 2 eligible patients participating in treatment at dose level 1 (1x10^6/kg). One patient has completed treatment with 8R-70CAR T cells, experienced no DLTs, and is currently in follow-up. The remaining patient is under SOC therapy before receiving CAR T cell treatment. CONCLUSIONS This study aims to address current therapeutic gaps and offers options for implementing a novel CAR design for the development of a more effective therapeutic modality for GBM.

IMMU-01. DE NOVO-DESIGNED BINDER-BASED CAR T CELLS ENABLE EFFECTIVE TARGETING OF GLIOBLASTOMA

Abstract Glioblastoma is a devastating disease with poor responses to all current therapies. Chimeric antigen receptor (CAR) T cell therapy has achieved impressive success against hematological malignancies but produces responses in only a limited number of glioblastoma patients. Here, we developed a novel platform for CAR constructs using de novo designed protein binders to target tumor antigens. We firstly designed a binder CAR targeting epidermal growth factor receptor (EGFR), which is highly expressed in glioblastoma, to validate the feasibility of our platform. Our EGFR binder CAR design promoted CAR T cell proliferation, cytotoxic cytokine secretion and exhaustion resistance, leading to better antitumor performance both in vitro and in vivo. Bulk and single-cell transcriptional profiling of binder CAR T cells revealed an underlying mechanism involving enhanced effector activity and reduced exhaustion responses. Mechanismly, the binder CARs exhibited higher surface expression and greater resistance to degradation triggered by tumor antigens. Moreover, we designed and engineered a novel CD276 binder CAR T cell product and verified its antitumor function, further demonstrating the general applicability of our binder-based CAR platform. Overall, our study provides an alternative avenue for the design of a CAR antigen-binding domain to potentiate CAR T cell antitumor efficacy.

IMMU-29. B7-H3-TARGETED CAR-T AND CAR-NK CELLS AGAINST HUMAN GLIOBLASTOMA

Abstract Glioblastoma multiforme (GBM) is the most lethal primary brain tumor, necessitating novel therapies. Chimeric antigen receptor (CAR) T-cell therapy has recently shown efficacy against GBM. However, this approach is costly and time-consuming due to its personalized nature. Alternatively, CAR-transduced natural killer (NK) cells offer a potential “off-the-shelf” immunotherapy option, as they do not cause graft-versus-host disease. This study aimed to assess the anti-GBM efficacy of CAR T and NK cells targeting B7-H3, a protein highly expressed in GBM. To achieve this, CAR T cells targeting B7-H3 were developed using known anti-B7-H3 scFv sequences. Additionally, cord blood-derived NK cells were transduced with the B7-H3 CAR. Both types of CAR-modified cells were tested for their anti-GBM activity in vitro. Moreover, their anti-tumor effects were evaluated in an in vivo xenograft model using patient-derived GBM cells. The results demonstrated that both B7-H3 CAR T cells and CAR NK cells exhibited significant cytotoxicity against patient-derived GBM cells in vitro. Furthermore, intracranial injection of these CAR-modified cells into the xenograft model significantly reduced tumor growth. In conclusion, B7-H3 targeted CAR T cells and cord blood-derived CAR NK cells both show potential in eliminating GBM cells, suggesting promising avenues for future GBM treatment strategies.

EXTH-13. COMBINED ANTI-ANGIOGENIC TREATMENT TO INCREASE INTRATUMORAL PERSISTENCE OF CAR T-CELLS IN LUNG CANCER BRAIN METASTASES

Abstract BACKGROUND Metastatic lung cancer, especially when it spreads to the brain, shows a devastating prognosis. Immunotherapeutic approaches including CAR T-cells show promise in hematologic malignancies. However, the presence of immunosuppressive factors within the tumor microenvironment and physical barriers like elevated interstitial pressure due to dysfunctional tumor vessels are one of the main obstacles especially in solid tumors. Evaluation of the potential synergy between anti-angiogenetic drugs and CAR T-cells in this context are an ongoing investigation. METHODS Here, we set up an immunocompetent syngeneic orthotopic cerebral metastasis model in mice by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning microscopy (TPLSM). This model allows in vivo characterization of fluorescent tumor cells and CAR T-cells on a single cell level over time. Intraparenchymal injection of red fluorescent EpCAM-transduced Lewis Lung carcinoma cells (EpCAM/tdtLL/2 cells) followed by injection of EpCAM-directed or undirected CAR T-cells into the adjacent brain tissue was performed. Additionally, aVEGF-A combined with aVEGF-R2 and the respective isotype control were injected intraperitoneally. RESULTS Compared to undirected CAR T-cells, mice receiving EpCAM-directed CAR T-cells showed higher intratumoral CAR T-cell densities after intraparenchymal injection. This finding was accompanied with reduced tumor growth and eventually translates into a survival benefit. However, intratumoral CAR T-cell numbers diminish over time indicating insufficient persistence inside of the tumor microenvironment. Additional anti-VEGF-A/VEGF-R2 treatment results in reduced tumor growth after EpCAM/GFPCAR T-cell and GFPT-cell treatment, respectively. Interestingly, in vivo imaging reveals higher intratumoral CAR T-cell numbers after anti-angiogenic treatment compared to isotype controls pointing towards enhanced CAR T-cell persistence resulting in a survival benefit. CONCLUSION Collectively, our findings indicate that locally injected CAR T-cells may safely induce relevant anti-tumor effects in brain metastases from lung cancer. Additional anti-angiogenic treatment provides a mechanism to enhance intratumoral CAR T-cell persistence and reduce tumor growth.