A single-valent long-acting human CD47 antagonist enhances antibody directed phagocytic activities


Many cancer cells express CD47 as a ‘don’t eat me’ signal to mask their presences from immune recognition and destruction. Such a signal is transmitted when CD47 binds to the signal regulatory protein-α (SIRPα) on macrophages to cut the phagocytic reaction. Most recent studies have focused on developing CD47 blocking agents with different affinities and avidities in order to optimize the therapeutic window between efficacy and toxicities involving normal cells expressing CD47. We described in this study a new design to fuse one CD47 binding domain of SIRPα with a pharmacokinetics modifying domain F8. The resulted single valent long-acting CD47 antagonist SIRPα-F8 was able to bind to CD47 and disrupt CD47-SIRPα axis. However, by itself it cannot trigger endocytosis and has no effect on tumor growth. Only when used in combination with the anti-CD20 mAbs, there were greatly improved phagocytic activities towards CD20 positive cancer cells. In vivo the combination also resulted in better tumor growth inhibition comparing to the vehicle control group. In addition, we showed that the F8 fusion bound to hFcRn only inside endosomes at pH 6.0, enabled hFcRn mediated recycling and thus greatly extended the circulation half-life in hFcRn knock-in mice. Taken together, the SIRPα-F8 design may suggest a new option to improve the therapeutic index of antibody treatment in clinical use towards tumors.

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Area under the curve


Neonatal Fc receptor


Intra tumoral


Macrophage colony-stimulating factor


Myelodysplastic syndromes


Mean residence time




Renal cell carcinoma


Size exclusion chromatography


Signal regulatory protein-α


Tumor growth inhibition


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We thank Hongtao Lu and Lei Shi for helpful discussions. We also thank Shou Li and Xu Fang for their help with the CHOEGFP−hCD47 cell line and the phagocytosis assays. We appreciated Xinyan Lu for her help with statistical analysis and Yanbing Ma for his help with the protein structure simulation.


This study was sponsored by the National Natural Science Foundation of China (NSFC) No. 81690262.

Author information




Fenglan Wu designed the experiments, did the experiment and drafted the manuscript. Yangsheng Qiu participated in the experiment design and helped with the FcRn binding study. Yuhong Xu directed the experiment design and wrote the manuscript.

Corresponding author

Correspondence to Yuhong Xu.

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The authors declare no potential conflict of interest.

Ethical approval and ethical standards

The animal study protocol A2016014 was approved by the Experimental Animal Management Committee and Experimental Animal Ethics Committee of Shanghai Jiao Tong University following the recommendations in the Guide for the Care and Use of Laboratory Animals (Eighth Edition) and relevant Chinese laws and regulations.

Animal source

NOD/SCID mice were purchased from Beijing HFK Bioscience. FcRn humanized C57BL/6 mice were purchased from Beijing Biocytogen.

Cell line authentication

HEK293-6E suspension cells expression system was purchased from ThermoFisher. CHO cells, Raji cells and CCRF-CEM cells were purchased from ATCC. PBMCs were purchased from all cells.

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Wu, F., Qiu, Y. & Xu, Y. A single-valent long-acting human CD47 antagonist enhances antibody directed phagocytic activities. Cancer Immunol Immunother (2020). https://doi.org/10.1007/s00262-020-02640-6

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  • Long-acting
  • CD47 antagonist
  • Therapeutic mab
  • FcRn
  • anti-CD20