Co-activating the intrinsic FcRγ/TLR4 signaling axis enhances the antitumor activity of NKG2D CAR-macrophages against prostate cancer.

Despite recent advances in T cell immunotherapy for the treatment of human cancer, metastatic solid tumors remain an intractable challenge. Macrophages are usually the most abundant immune cell in the tumor microenvironment (TME) where, as immunosuppressive tumor-associated macrophages (TAMs), they participate in disease progression. The current goals of macrophage-based immunotherapies are to reduce TAM infiltration or enhance TAM phagocytosis. In contrast, we have developed a new paradigm based on the adoptive transfer of genetically engineered chimeric antigen receptor (CAR) macrophages (CAR-M) for the treatment of human cancer. CAR-M can only be produced using a unique adenoviral vector, since human macrophages are highly resistant to other methods of gene transfer. We have previously shown that the primary mechanism of action of CAR-M is phagocytosis, and that a single dose of primary human anti-HER2 CAR-M led to significantly improved overall survival in multiple xenograft models. We now establish that Ad5f35-transduced anti-HER2 CAR-M (CT-0508) adopt a unique proinflammatory and antitumor M1 phenotype. Functional evaluation and RNA sequencing revealed that CT-0508 maintain a proinflammatory M1 phenotype despite challenge with immunosuppressive environments in vitro, highlighting their resistance to subversion. By engrafting immunodeficient mice with human hematopoietic cells and human cancer cells, we established a novel xenografted human TME model. We demonstrate with single-cell resolution that CT-0508 maintain their phenotype within the human TME. Additionally, CT-0508 activated the human TME and generated an activated human dendritic cell signature. To further investigate the potential of CT-0508 for TME activation, we modeled the interaction of CT-0508 with immunosuppressive macrophages, dendritic cells, and T cells. CT-0508 shifted bystander macrophages toward a proinflammatory phenotype, induced activation and maturation markers on DCs, and recruited resting as well as activated T cells in chemotaxis assays. Lastly, CT-0508 demonstrated enhanced antigen presentation when compared to control human macrophages. These results show that in addition to direct antitumor activity, the anti-HER2 CAR macrophage cell product CT-0508 is capable of activating the solid cancer TME and promoting a proinflammatory phenotype. The safety of CT-0508 will be evaluated in an upcoming first-in-human phase I clinical trial. Citation Format: Konrad Gabrusiewicz, Nicholas Anderson, Xueqing Lu, Xinhe Shan, Olga Shestova, Nicholas Petty, Feng Shen, Maggie Schmierer, Andrew Best, Martha Zeeman, Yumi Ohtani, Katherine Cummins, Saar Gill, Michael Klichinsky. CT-0508, a novel CAR macrophage product directed against HER2, promotes a proinflammatory tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B65.

Despite the remarkable efficacy achieved by CAR-T cell therapy in hematologic malignancies, translating these results in solid tumors remains challenging. We previously developed human CAR-M and demonstrated that adoptive cell transfer of CAR-M into xenograft models of human cancer controls tumor progression and improves overall survival1. Herein, we established a fully immunocompetent syngeneic mouse model and evaluated the interaction of CAR-M with the tumor microenvironment (TME) and the endogenous adaptive immune system. Murine bone marrow-derived CAR-expressing macrophages (muCAR-M) were efficiently engineered to express an anti-huHER2 CAR using the chimeric adenoviral vector Ad5f35. MuCAR-M, but not control untransduced (UTD) macrophages, specifically phagocytosed HER2+ target cancer cell lines and killed HER2-expressing murine CT26 colorectal and human AU-565 (HER2+) breast cancer cells in a dose-dependent manner. Moreover, CAR-M induced MHC-I and MHC-II expression on tumor cells and cross-presented tumor-associated antigens (TAA) resulting in CD8 T cell activation. To evaluate muCAR-M in an immunocompetent in vivo setting, BALB/c mice were engrafted with subcutaneous CT26-HER2+ tumors and treated with HER2-CAR or UTD macrophages. CAR-M treated mice showed significant tumor control and improved survival compared to control groups. Analysis of the TME showed increased intratumoral immune infiltration - as well as an increase in T cells reactive to the CT26 MHC-I antigen gp70, indicating enhanced epitope spreading. Mice that achieved complete responses (CRs) after CAR-M therapy were protected against antigen-negative relapse in a HER2- CT26 rechallenge model, indicating the induction of long-term T cell memory against TAA. To evaluate the systemic anti-tumor immune response, we simultaneously engrafted BALB/c mice with CT26-HER2+ and CT26-Wt tumors on opposite flanks and treated mice with local administration of CAR-M restricted to the HER2+ tumors. After CAR-M treatment, 75% of mice cleared their CT26-HER2+ tumors and the growth rate of the contralateral CT26-Wt tumors was significantly reduced, demonstrating an abscopal effect. Given the impact of CAR-M on the endogenous adaptive immune system, we evaluated the combination of CAR-M with PD1 checkpoint inhibitor therapy in the CT26-HER2 model, which is resistant to anti-PD1 monotherapy, and found that the combination further improved tumor control and overall survival. These results demonstrate that CAR-M reprogram the TME, induce epitope spreading, and orchestrate a systemic immune response against solid tumors. Moreover, our findings provide rationale for the combination of CAR-M with immune checkpoint inhibitors. The anti-HER2 CAR-M, CT-0508, is under evaluation in a phase I clinical trial for patients with HER2 overexpressing solid tumors. Citation Format: Stefano Pierini, Rashid Gabbasov, Linara Gabitova, Yumi Ohtani, Olga Shestova, Saar Gill, Sascha Abramson, Thomas Condamine, Michael Klichinsky. Chimeric antigen receptor macrophages (CAR-M) induce anti-tumor immunity and synergize with T cell checkpoint inhibitors in pre-clinical solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 63.

BackgroundDespite the remarkable efficacy achieved by CAR-T therapy in hematologic malignancies, application in solid tumors has been challenging. We previously developed human CAR-M and demonstrated that adoptive transfer of CAR-M...

Despite recent advances in T cell immunotherapy for the treatment of human cancer, metastatic solid tumors remain an intractable challenge. Macrophages are often the most abundant immune cell in the tumor microenvironment (TME) where, as immunosuppressive tumor associated macrophages (TAMs), they participate in disease progression. Currently, most macrophage based immunotherapeutic approaches are focused on the depletion, repolarization, or phagocytic disinhibition of TAMs. We have developed a new paradigm based on the adoptive transfer of genetically engineered CAR macrophages (CAR-M) for the treatment of human cancer. CAR-M can be efficiently produced using the chimeric adenoviral vector Ad5f35. We have previously shown that the primary mechanism of action of CAR-M is antigen dependent phagocytosis, and that a single dose of primary human anti-HER2 CAR-M leads to significantly improved overall survival in multiple solid tumor xenograft models. Given that Ad5f35-transduced anti-HER2 CAR-M (CT-0508) adopt a unique pro-inflammatory M1-like phenotype, we hypothesized that CT-0508 may have the capacity to reprogram the TME toward an activated state. Functional evaluation and transcriptome-wide characterization revealed that CT-0508 maintain a pro-inflammatory phenotype despite challenge with immunosuppressive environments in vitro. By engrafting immunodeficient mice with human hematopoietic cells and human cancer cells we established a novel xenografted human TME model. We demonstrate with single cell resolution that CT-0508 maintain their M1 phenotype within the human TME. Additionally, CT-0508 augmented the human TME by inducing a pro-inflammatory signature in surrounding immune cells, characterized by induction of MHC-II and TNFα. To further investigate the potential of CT-0508 for TME activation, we modeled the interaction of CT-0508 with primary human M2 macrophages, dendritic cells, and T cells in vitro. CT-0508 repolarized bystander M2 macrophages toward a pro-inflammatory phenotype, induced activation and maturation markers on immature dendritic cells, and recruited resting as well as activated T cells in chemotaxis assays. CT-0508 demonstrated enhanced antigen presentation when compared to control human macrophages and cross-presented tumor derived intracellular antigens to CD8 T cells after tumor phagocytosis. Our results show that in addition to direct anti-tumor activity, the anti-HER2 CAR macrophage cell product CT-0508 is capable of promoting a pro-inflammatory tumor microenvironment and has the potential to induce epitope spreading via T cell recruitment and antigen presentation. Citation Format: Michael Klichinsky, Konrad Gabrusiewicz, Nicholas Anderson, Maggie Schmierer, Andrew Best, Martha Zeeman, Sotheavy Chhum, Yumi Ohtani, Olga Shestova, Xueqing Lu, Nicholas Petty, Xinhe Shan, Feng Shen, Saar Gill. CT-0508 is an anti-HER2 chimeric antigen receptor (CAR) macrophage with targeted anti-tumor activity that promotes a pro-inflammatory solid tumor microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3242.

Chimeric antigen receptor (CAR) macrophages (CAR-Ms) mediate antitumor immunity via phagocytosis, cytokine release, activation of the tumor microenvironment and antigen presentation. We report results from a non-prespecified interim analysis of a first-in-human, phase 1 clinical trial of CT-0508, an anti-human epidermal growth factor receptor 2 (HER2) CAR-M in patients with advanced HER2-overexpressing tumors. Fourteen patients were treated across two different regimens. Patients with breast cancer and gastroesophageal cancer were primarily enrolled and had to have demonstrated overexpression of HER2 according to the American Society of Clinical Oncology/College of American Pathologists guidelines (HER2 immunohistochemistry 3+ or immunohistochemistry 2+/in situ hybridization-amplified). No lymphodepletion chemotherapy was used before infusion. The primary endpoints were safety and CAR-M manufacturability. Secondary endpoints included cellular kinetics and efficacy using objective response rate, overall survival, progression-free survival and duration of response. No dose-limiting toxicities, severe cytokine release syndrome (≥grade 3) or immune effector cell-associated neurotoxicity syndrome were observed; 44% (n = 4 of 9, 95% confidence interval = 14-79%) of HER2 3+ tumors achieved stable disease as best overall response 8 weeks after treatment. No meaningful activity was observed in the HER2 2+ population (n = 5). Correlative analyses of serial biopsies confirmed that CT-0508 traffics to and remodels the tumor microenvironment, resulting in expansion of CD8+ T cells. These findings demonstrate the preliminary safety, tolerability and manufacturing feasibility of CT-0508 for HER2+ tumors. ClinicalTrials.gov registration: NCT04660929 .

Despite the remarkable efficacy achieved by CAR-T cell therapy in hematologic malignancies, achieving efficacy against solid tumors has been challenging. We previously developed human CAR-M and demonstrated that adoptive cell transfer of CAR-M into xenograft models of human cancer controls tumor progression and improves overall survival1. Given that CAR-M are M1-polarized macrophages with the potential to remodel the tumor microenvironment (TME) and act as professional antigen presenting cells, we developed an immunocompetent animal model to evaluate the interaction of CAR-M with the endogenous immune system and to study the combinatorial approach of CAR-M with blockade of the PD1/PDL1 T cell checkpoint axis. Murine bone marrow-derived macrophages were engineered to express an anti-HER2 CAR using the chimeric adenoviral vector Ad5f35. In addition to efficient gene delivery, Ad5f35 transduction promoted a pro-inflammatory (M1) phenotype in murine macrophages. Anti-HER2 CAR-M, but not control macrophages, phagocytosed and killed HER2-overexpressing tumor cell lines. CAR-M induced MHC-I expression on tumor cells and enhanced the cytotoxicity of CD8+ T cells. To evaluate the safety and efficacy of CAR-M therapy, immunocompetent mice were engrafted with HER2+ tumors and treated with syngeneic HER2-CAR or untransduced (UTD) macrophages. CAR-M treated mice showed significant tumor control and improved survival compared to control groups. Analysis of the TME showed increased intratumoral immune infiltration - as well as an increase in T cell responsiveness to tumor-associated antigens, indicating enhanced epitope spreading. Given the impact of CAR-M on the endogenous adaptive immune system, we evaluated the combination of CAR-M with anti-PD1 in tumors resistant to anti-PD1 monotherapy and found that the combination further reprogrammed the TME, significantly enhanced tumor control, and improved overall survival compared to monotherapy with either agent. Mice that achieved complete responses (CRs) after CAR-M therapy were protected against antigen-negative relapse in a HER2-negative rechallenge model, indicating long-term anti-tumor immunity. Finally, the combination of CAR-M with anti-PD1 did not trigger sustained elevations of serum analytes associated with cytokine release syndrome (CRS) and was well tolerated across numerous safety assessments. These results demonstrate that CAR-M reprogram the TME, induce epitope spreading, and orchestrate a systemic immune response against solid tumors. Moreover, our findings provide rationale for the combination of CAR-M with immune checkpoint inhibitors. The anti-HER2 CAR-M, CT-0508, is under evaluation in a phase I clinical trial for patients with HER2 overexpressing solid tumors. Citation Format: Stefano Pierini, Rashid Gabbasov, Alison Worth, Ilyssa Ramos, Daniel Blumenthal, Yumi Ohtani, Linara Gabitova, Michael Ball, Sascha Abramson, Thomas Condamine, Michael Klichinsky. Chimeric antigen receptor macrophages (CAR-M) sensitize solid tumors to anti-PD1 immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2112.

Therapeutic strategies for peritoneal metastasis in solid tumors are urgently needed in the clinic. Programming chimeric antigen receptor macrophages (CAR-Ms) in situ offers opportunities for an unmet demand. However, potential intracellular domains (ICDs) for CAR design and their antitumor mechanisms for macrophage empowerment remain to be explored systematically. By developing a targeted mRNA-LNP delivery system for macrophages, we have investigated 36 CAR combinations to determine the impact of CAR-Ms on immune regulation in vitro and in vivo. In two solid tumor mouse models, intraperitoneal programming of CAR-Ms was shown to elicit robust adaptive immune activation and significantly synergize with PD-1/L1 therapy. Single-cell RNA sequencing (scRNA-seq) analysis revealed that CAR-Ms could reshape the immunosuppressive tumor microenvironment (TME) and boost the TCF1+PD-1+ progenitor-exhausted CD8+ T cells (Tpex) population. Meanwhile, we found that tailored CAR-M with CD3ζ/TLR4 ICDs could favorably maintain proinflammatory phenotype and simultaneously upregulate MHC I and PD-L1 expression by perturbing NF-κB pathways. Moreover, the synergism between macrophage PD-L1 knockdown and CAR-M therapy highlighted the need to block the PD-1/L1 axis in antigen cross-presentation. In short, we developed an mRNA-LNP delivery system for intraperitoneal programming of tailored CAR-Ms in vivo and broadened understanding of both regulatory and feedback mechanisms for CAR-M therapies against solid tumors.

Mass spectrometry-based tissue profiling and imaging are technologies that allow identification and visualization of protein signals directly on thin sections cut from fresh frozen tissue specimens. These technologies were utilized to evaluate protein expression profiles in the normal mouse prostate during development (1-5 weeks of age), at sexual maturation (6 weeks of age), and in adult prostate (at 10, 15, or 40 weeks of age). The evolution of protein expression during normal prostate development and maturation were subsequently compared with 15-week prostate tumors derived from genetically engineered mice carrying the Large T antigen gene under regulation of the prostate-specific probasin promoter (LPB-Tag mouse model for prostate cancer). This approach identified proteins differentially expressed at specific time points during prostate development. Furthermore expression of some of these proteins, for example probasin and spermine-binding protein, were associated with prostate maturation, and prostate tumor formation resulted in their loss of expression. Cyclophilin A, a protein found in other cancers, was differentially alpha-acetylated on the N terminus, and both isoforms appeared during normal prostate and prostate tumor development. Imaging mass spectrometry localized the protein signals to specific prostatic lobes or regions. Thus, tissue profiling and imaging can be utilized to analyze the ontogeny of protein expression during prostate morphogenesis and tumorigenesis and identify proteins that could potentially serve as biomarkers for prostate cancer.

Novel Radiation-Guided Nanoparticle Drug Delivery System for Prostate Cancer

Despite recent landmark advances in T-cell immunotherapy for the treatment of human cancer, metastatic solid tumors remain an intractable challenge. Macrophages are often the most abundant immune cell in the tumor microenvironment (TME), where they may convert into immunosuppressive (M2) tumor-associated macrophages (TAMs) and participate in disease progression. Currently, macrophage-orientated immunotherapeutic approaches under clinical development in oncology seek to reduce TAM infiltration (CSF-1 antagonists) or enhance TAM phagocytosis (CD47 antagonists). Transfer of autologous, activated, but nontargeted macrophages failed to demonstrate antitumor efficacy in past clinical trials. We hypothesized that genetically engineering human macrophages with CARs against tumor-associated antigens could redirect their phagocytic activity and lead to therapeutic efficacy with the potential for the induction of an antitumor T-cell response. We first demonstrate that CD3-zeta-based CARs are capable of inducing phagocytosis in human THP-1 macrophages, while truncated intracellular-domain deficient CARs were not. Targeted phagocytosis and clearance of CD19+, mesothelin +, and HER2+ cells by CARs targeted against each respective antigen was significantly superior to that by control untransduced (UTD) macrophages. We demonstrate that primary human macrophages, which are resistant to most viral vectors, are efficiently transduced by the chimeric fiber adenoviral vector Ad5f35 (~70% in 10 normal donors). Using Ad5f35, we engineered primary human macrophages with a CD3-zeta-based CAR against HER2. Anti-HER2 primary human CAR macrophages demonstrated targeted phagocytosis against HER2+ but not HER2- cell lines, with phagocytic activity dependent on both the CAR and antigen densities. Furthermore, CAR, but not UTD, macrophages led to potent dose-dependent killing of three distinct HER2-high cell lines in vitro. We sought to test the efficacy of anti-HER2 primary human macrophages in xenograft models of human HER2+ ovarian cancer. A single dose of CAR, but not UTD macrophages, led to tumor regression and improved overall survival in both intraperitoneal and disseminated models of disease. We show that macrophage transduction with Ad5f35, a double-stranded DNA virus, leads to a broad gene expression change, an interferon signaling signature, and phenotypic clustering toward classically activated M1 macrophages. CAR macrophages upregulated co-stimulatory ligand and antigen processing/presentation genes and led to enhanced T-cell stimulation in vitro and in vivo. Lastly, CAR, but not UTD, macrophages showed a broad resistance for M2 conversion in response to immunosuppressive cytokines. In conclusion, we show that primary human CAR macrophages are capable of targeted tumor phagocytosis, lead to improved overall survival in xenograft models, and demonstrate enhanced T-cell stimulation. CAR macrophages are a novel cell therapy platform for the treatment of human cancer. This abstract is also being presented as Poster B29. Citation Format: Michael Klichinsky, Marco Ruella, Olga Shestova, Andrew Best, Kristin Blouch, Xueqing M. Lu, Saad S. Kenderian, Miriam Y. Kim, Roddy O'Connor, Stephen Wallace, Miroslaw Kozlowski, Dylan M. Marchione, Maksim Shestov, Benjamin A. Garcia, Carl June, Saar Gill. Human chimeric antigen receptor (CAR) macrophages for cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr PR07.

Chimeric antigen receptor T (CAR-T) cell therapy achieves remarkable success in hematological cancers, but its efficacy is severely limited in solid tumors by formidable obstacles including physical barriers, the highly immunosuppressive tumor microenvironment (TME), and antigen escape. To address these persistent challenges, chimeric antigen receptor-macrophage (CAR-M) therapy emerges as a promising alternative, leveraging intrinsic advantages of macrophages like unparalleled tumor infiltration, powerful phagocytosis, and high plasticity. The evolution of CAR-M is primarily defined by the intracellular signaling domain. CAR-M exerts its anti-tumor effects through multifaceted mechanisms, including direct enhanced phagocytosis and tumor cell killing, TME remodeling by repolarizing to a pro-inflammatory M1-like phenotype, releasing anti-tumor effectors, and degrading the extracellular matrix (ECM), and the activation of adaptive immunity via efficient antigen presentation. Despite its promise, CAR-M faces hurdles such as TME physical barriers and the potential for M2-like re-education. Current optimization strategies focus on enhancing tumor infiltration, overcoming immunosuppression with "armored" CAR-Ms, and improving safety with suicide switches. Encouraging pre-clinical data accelerates CAR-M into early-phase clinical trials for solid tumors, and the platform's utility is also being explored beyond oncology in infectious, autoimmune, and neurodegenerative diseases.

Therapeutic strategies for peritoneal metastasis in solid tumors are urgently needed. Programming chimeric antigen receptor macrophages (CAR-Ms) in situ offers opportunities for an unmet demand. However, potential intracellular domains (ICDs) for CAR design and their antitumor mechanisms for macrophage empowerment remain to be explored systematically. By developing a macrophage-targeted mRNA lipid nanoparticle (mRNA-LNP) system, we evaluate 36 CAR formats in CAR-Ms. Tailored CAR-Ms with CD3ζ TLR4 ICDs elicit robust adaptive immune activation and significantly synergize with PD-1/L1 therapy. Single-cell RNA sequencing (scRNA-seq) reveals that CAR-Ms reshape the immunosuppressive tumor microenvironment (TME) and boost the TCF1+PD-1+ progenitor-exhausted CD8+ T cells (Tpex) population. Mechanistically, CAR-Ms maintain a proinflammatory phenotype and simultaneously upregulate MHC-I and PD-L1 by perturbing NF-κB pathways. Collectively, this approach enables intraperitoneal programming of tailored CAR-Ms and broadens understanding of both regulatory and feedback mechanisms for CAR-M therapies against solid tumors.

Breaking the immunosuppressive barrier: an armored CAR-M biotechnology with the original M1 phenotype dominance rescues antitumor immunity.

Chimeric antigen receptor-T (CAR-T) adoptive transfer therapy has shown remarkable efficacy in hematologic malignancies. However, the therapeutic efficacy of CAR-T in treating solid tumors, particularly "cold tumors" such as prostate cancer, is significantly restricted by the cumbersome ex vivo manufacturing, impaired T cell fitness, and an immunosuppressive tumor microenvironment that blunts T cell function. Here, we successfully constructed a nanodelivery system based on zeolitic imidazolate framework-8 (ZIF-8). This system exhibited high CAR-gene encapsulation efficiency, reduced nonspecific hepatic accumulation, targeted delivery to tumor-associated macrophages (TAMs), and efficient intracellular gene transfection efficiency, enabling in situ construction of chimeric antigen receptor macrophage (CAR-M). Co-delivery of IFN-γ and CAR genes not only maintained the specific tumor-killing and phagocytic activity of CAR-Ms against tumor cells but also activated adaptive immunity, inducing excellent antitumor efficacy, as evidenced by the observed 95.54% inhibition of tumor growth in a prostate cancer mouse model. This strategy provides a promising approach for systematic in vivo editing of CAR-Ms.

Advancing immunotherapy with innovations in CAR-M engineering for cancer treatment.