Journal
BLOOD
Volume 134, Issue 17, Pages 1430-1440Publisher
AMER SOC HEMATOLOGY
DOI: 10.1182/blood.2019001744
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Funding
- Leukemia and Lymphoma Society Specialized Center of Research [7011-16]
- Surface Oncology
- National Institutes of Health [R01 HL125780]
- T-cell Leukemia Lymphoma Foundation Young Investigator Grant
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Antibodies that bind CD47 on tumor cells and prevent interaction with SIRP alpha on phagocytes are active against multiple cancer types including T-cell lymphoma (TCL). Here we demonstrate that surface CD47 is heterogeneously expressed across primary TCLs, whereas major histocompatibility complex (MHC) class I, which can also suppress phagocytosis, is ubiquitous. Multiple monoclonal antibodies (mAbs) that block CD47-SIRP alpha interaction promoted phagocytosis of TCL cells, which was enhanced by cotreatment with antibodies targeting MHC class I. Expression levels of surface CD47 and genes that modulate CD47 pyroglutamation did not correlate with the extent of phagocytosis induced by CD47 blockade in TCL lines. In vivo treatment of multiple human TCL patient-derived xenografts or an immunocompetent murine TCL model with a short course of anti-CD47 mAb markedly reduced lymphoma burden and extended survival. Depletion of macrophages reduced efficacy in vivo, whereas depletion of neutrophils had no effect. F(ab')2-only fragments of anti-CD47 antibodies failed to induce phagocytosis by human macrophages, indicating a requirement for Fc-Fc gamma receptor interactions. In contrast, F(ab')2-only fragments increased phagocytosis by murine macrophages independent of SLAMF7-Mac-1 interaction. Full-length anti-CD47 mAbs also induced phagocytosis by Fc gamma receptor-deficient murine macrophages. An immunoglobulin G1 anti-CD47 mAb induced phagocytosis and natural killer cell-mediated cytotoxicity of TCL cells that was augmented by cotreatment with mogamulizumab, an anti-CCR4 mAb, or a mAb blocking MHC class I. These studies help explain the disparate activity of monotherapy with agents that block CD47 inmurine models compared with patients. They also have direct translational implications for the deployment of anti-CD47 mAbs alone or in combination.
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