Focused on improving macrophage-directed immunotherapy, Xu and Zhou et al. found that blocking CD47-SIRPα upregulated tumor-expressed, secreted PCSK9, resulting in macrophage MHC-1 degradation, impaired antigen presentation, and reduced CD8+T cell activation. To overcome this resistance, a bispecific SIRPαD1–anti-PCSK9 Ab fusion co-targeting CD47 and PCSK9 enhanced phagocytosis, preserved antigen cross-presentation to CD8+ T cells, reprogrammed TIME macrophages to an M1 state, and achieved potent tumor control in preclinical models. The fusion protein exhibited superior tumor targeting (via SIRPα) and had a favorable safety profile.
Contributed by Katherine Turner
(1) Xu C (2) Zhou K (3) Hu X (4) Nan Y (5) Sun Y (6) Dou Z (7) Zhou R (8) Xue W (9) Hu Q (10) Huang X (11) Hua X (12) Ju D (13) Zhang X
Focused on improving macrophage-directed immunotherapy, Xu and Zhou et al. found that blocking CD47-SIRPα upregulated tumor-expressed, secreted PCSK9, resulting in macrophage MHC-1 degradation, impaired antigen presentation, and reduced CD8+T cell activation. To overcome this resistance, a bispecific SIRPαD1–anti-PCSK9 Ab fusion co-targeting CD47 and PCSK9 enhanced phagocytosis, preserved antigen cross-presentation to CD8+ T cells, reprogrammed TIME macrophages to an M1 state, and achieved potent tumor control in preclinical models. The fusion protein exhibited superior tumor targeting (via SIRPα) and had a favorable safety profile.
Contributed by Katherine Turner
ABSTRACT: Macrophage-directed immunotherapy, exemplified by blocking the CD47-signal regulatory protein α (SIRPα) axis, can eliminate tumors by unleashing phagocytosis. However, such approaches often fail to generate durable antitumor immunity, revealing a disconnect between innate activation and effective T cell responses. Here, we identify proprotein convertase subtilisin/kexin type 9 (PCSK9) as an adaptive resistance factor induced by macrophage checkpoint blockade. Tumor-derived PCSK9 promotes lysosomal degradation of major histocompatibility complex class I (MHC-I) in macrophages, impairing antigen cross-presentation and CD8+ T cell priming-thus showing how phagocytosis-targeted therapies can paradoxically suppress adaptive immunity. To overcome this, we engineer bispecific fusion proteins co-targeting the CD47-SIRPα checkpoint and the PCSK9-MHC-I axis, among which SIRPαD1-αPCSK9 is optimal. Dual targeting synergistically enhances phagocytosis, preserves antigen cross-presentation, and reprograms tumor microenvironment toward an immunostimulatory state. Consequently, SIRPαD1-αPCSK9 activates innate and adaptive antitumor immunity, achieving potent tumor control with improved safety. These findings uncover a resistance mechanism to macrophage-centered cancer immunotherapy and establish a dual-targeting strategy bridging phagocytosis and T cell activation.
Author Info:
(1) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China; Quzhou Fudan Institute, 108 Minjiang Avenue,
Kecheng District Quzhou, Zhejiang, China. (2) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China; Quzhou Fudan Institute, 108 Minjiang Avenue, Kecheng District Quzhou, Zhejiang, China. (3) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (4) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (5) Department of Research and Development, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai, China. (6) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (7) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (8) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (9) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (10) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China. (11) Department of Cancer Biology, Abramson Family Cancer Research Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA. Electronic address: huax@pennmedicine.upenn.edu. (12) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China; Quzhou Fudan Institute, 108 Minjiang Avenue, Kecheng District Quzhou, Zhejiang, China. Electronic address: dianwenju@fudan.edu.cn. (13) School of Pharmaceutical Sciences & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University, Shanghai, China; Quzhou Fudan Institute, 108 Minjiang Avenue, Kecheng District Quzhou, Zhejiang, China. Electronic address: xuyaozhang@fudan.edu.cn.
Citation: Cell Rep Med 2026 Oct 5 103087 Epub10/05/2026
