Abstract PR07: Human chimeric antigen receptor (CAR) macrophages for cancer immunotherapy

Abstract

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.

CAFs Interacting With TAMs in Tumor Microenvironment to Enhance Tumorigenesis and Immune Evasion

“…In line with such strategies, macrophages which express a chimeric antigen receptor (CAR) may prove to be useful in order to target solid tumors (229). In a recent inspiring study, Klichinsky et al reported transducing human macrophages with an adenovirus vector carrying a CAR (230). They showed that a single infusion of human CAR macrophages decreased tumor burden and prolonged overall survival in two solid tumor xenograft mouse models (230).…”

“…In a recent inspiring study, Klichinsky et al reported transducing human macrophages with an adenovirus vector carrying a CAR (230). They showed that a single infusion of human CAR macrophages decreased tumor burden and prolonged overall survival in two solid tumor xenograft mouse models (230). In another exciting study, Mitragotri et al recently reported an engineered particle (called as "backpack") which can adhere to the surfaces of macrophage and regulate cellular phenotypes in vivo.…”

Human Tumor Targeted Cytotoxic Mast Cells for Cancer Immunotherapy

“…One of the most promising cell types being explored for ACT are, like MCs, resident in tissue. Macrophages polarized using CAR T cell strategies to redirect their phenotype to M1 with phagocytic functions target cancer-specific biomarkers and induce an adaptive immune response against tumor cells ( 59 ). In short, most cells being investigated as new platforms for cancer immunotherapy exert both pro- and anti-tumor effects.…”

Progress of research on tumor microenvironment and immunotherapy

“…CAR-T therapy has shown excellent therapeutic effects in the field of hematological tumors, and is still being studied in solid tumors, such as local intratumoral injection or intravenous administration. According to the latest news, US research shows that chimeric antigen receptor macrophages (CAR-M) obtained from genetically engineered macrophages can effectively kill tumors and prolong the survival time in ovarian cancer mouse models, which may become a new solid tumor treatment plan [32].…”