An anti-CD47 antibody binds to a distinct epitope in a novel metal ion-dependent manner to minimize cross-linking of red blood cells

作者：Xiaoxia Lü, Ziyue Chen, Chunyan Yi, Zhiyang Ling, Jing Ye, Kaijian Chen, Yao Cong, Sonam Wangmo, Shipeng Cheng, Ran Wang, Danyan Zhang, Jiefang Xu, Jichao Yang, Liyan Ma, Qing Duan, Xiaoyu Sun, Jianping Ding, Bing Sun · 发表于：Journal of Biological Chemistry · 年份：2025 · DOI：10.1016/j.jbc.2025.110420 · 被引用次数：2 · 研究领域：Phagocytosis and Immune Regulation、Erythrocyte Function and Pathophysiology、Cell death mechanisms and regulation

Cluster of differentiation 47 (CD47) is a widely expressed transmembrane protein that plays a crucial role in immune self-recognition. Cancer cells upregulate CD47 expression to promote immune escape through activating the "don't eat me" signal via interactions with signal regulatory protein α (SIRPα) on macrophages. The effectiveness of anti-CD47 antibodies has been demonstrated in multiple tumour models. However, since CD47 is also expressed in human red blood cells (RBCs) and platelets, the clinical application of anti-CD47 antibodies requires careful consideration of blood toxicity. One major obstacle to the clinical application of CD47 antibodies is the haemagglutination caused by RBCs cross-linking. In this study, we generated Hu1C8, a humanized anti-CD47 monoclonal antibody that demonstrated increased selectivity for binding to CD47 on cancer cells and lacked haemagglutination activity. Epitope mapping and the crystal structure of the Hu1C8 Fab-CD47 extracellular domain (ECD) complex revealed that Hu1C8 binds to a distinct epitope of CD47 in a Ca 2+ -dependent manner. The unique recognition and binding mode allowed Hu1C8 to bind CD47 on RBCs with reduced haemagglutination activity while still maintaining effective antitumour activity. These findings demonstrate a feasible strategy for developing CD47 antibodies with high antitumor activity but low RBC haemagglutination activity. Our study elucidates how epitope-specific antibody influences antibody-induced cell cross-l...