CD47 antibody-armed oncolytic adenovirus promotes chimeric antigen receptor macrophage phagocytosis and antitumor immunity.

Background: Chimeric antigen receptor (CAR)-T cell therapy has shown success in hematologic malignancies but has encountered challenges in solid tumors. Macrophages, being a potentially effective therapeutic target, have led to the development of several therapeutic strategies due to their unique phagocytic function. This study aimed to develop an effective solid tumor immunotherapy strategy by combining CAR macrophages (CAR-Ms) targeting PD-L1 with CD47 antibody-armed oncolytic adenovirus (oAd-CD47).

Methods: In this study, an adenoviral vector was employed to construct CAR-Ms that target PD-L1 and express IFN-γ. The phagocytic capacity and phenotype of CAR-Ms were tested in vitro. Two mouse tumor models with different immunogenicity were utilized to investigate the anti-tumor efficacy of CAR-Ms in vivo. Subsequently, the synergistic anti-tumor effects of CAR-M and oAd-CD47 and their underlying mechanisms were explored.

Results: CAR-Ms exhibited enhanced phagocytic capacity and proinflammatory (M1) phenotype. These CAR-Ms significantly reduced tumor burden and extended overall survival in mice bearing CT26 colon cancer, a model characterized by high immunogenicity. Compared with CAR-Ms and oAd-CD47 monotherapy, this combination therapy (C + o) achieved superior antitumor efficacy in the CT26 and B16 melanoma mouse models, as well as in the ID8 peritoneal metastasis model. Notably, C + o treatment enhanced tumor-associated macrophage (TAM) phagocytosis and reduced the population of inhibitory immune cell subsets, thereby resulting in enhanced adaptive antitumor T-cell and neoantigen-specific T-cell immunity. Additionally, the synergistic antitumor effect of C + o was dependent on CD8⁺ T cells.

Conclusion: The treatment strategy of CAR-Ms combined with oAd-CD47 provides a promising, novel and effective treatment method for individualized targeted therapy of solid tumors.