Anti-CD47 Antibody Synergizes with Rituximab to Promote Phagocytosis and Eradicate Non-Hodgkin Lymphoma

Abstract

Summary Monoclonal antibodies are standard therapeutics for several cancers including the anti-CD20 antibody rituximab for B cell non-Hodgkin lymphoma (NHL). Rituximab and other antibodies are not curative, and must be combined with cytotoxic chemotherapy for clinical benefit. Here we report the eradication of human NHL solely with a monoclonal antibody therapy combining rituximab with a blocking anti-CD47 antibody. We identified increased expression of CD47 on human NHL cells, and determined that higher CD47 expression independently predicted adverse clinical outcomes in multiple NHL subtypes. Blocking anti-CD47 antibodies preferentially enabled phagocytosis of NHL cells and synergized with rituximab. Treatment of human NHL-engrafted mice with anti-CD47 antibody reduced lymphoma burden and improved survival, while combination treatment with rituximab led to elimination of lymphoma and cure. These antibodies synergized through a mechanism combining Fc receptor (FcR)-dependent and FcR-independent stimulation of phagocytosis that might be applicable to many other cancers.

Anti-CD47 antibodies promote phagocytosis and inhibit the growth of human myeloma cells

“…Consistent with previous reports, 12,13,15,25 B6H12 induced the phagocytosis of myeloma cells but a non-blocking anti-CD47 antibody, clone 2D3, showed minimal increase of the phagocytosis (Supplementary Figure S2). Previously, it was reported that bivalent single-chain antibodies targeting CD47 induced the apoptosis of leukemia, 31 myeloma, 26 monocytes and dendritic cells.…”

“…12,13,[15][16][17]25 In some instances, CD47 expression levels were highly correlated with a worse prognosis. 12,13,15,16,25 Here we have shown that in most cases (65%) CD47 expression on patient CD38 high myeloma cells is at least twofold higher than in patient-matched healthy bone marrow cells. Consistent with our observation, Zhan et al 18 demonstrated that CD47 mRNA expression levels are highly upregulated in myeloma cells compared with healthy plasma cells.…”

“…23,24 Anti-CD47 antibody, B6H12 promotes the phagocytosis of myeloma cells Blocking CD47 with anti-CD47 monoclonal antibodies has enabled the phagocytosis of leukemia and lymphoma cells. 12,13,15 We investigated whether an anti-CD47 monoclonal antibody (B6H12) promotes the phagocytosis of myeloma cells. Macrophages derived from mouse bone marrow cells phagocytosed human myeloma cells at a low frequency when treated with PBS or a control mouse IgG.…”

“…Anti-CD47 monoclonal antibodies inhibiting the interaction of CD47 and SIRPa promote the phagocytosis of tumor cells by macrophages, and also by monocytes and neutrophils. [9][10][11] Cancer cells including acute myelogenous leukemias, 11,12 lymphomas, 13,14 and various solid cancers [15][16][17] express CD47 at a high level, and can be phagocytosed by macrophages in the presence of blocking antibodies to CD47. [11][12][13][14][15][16][17] In those cases where the tumor-initiating cells (or cancer stem cells) are known, for example, from acute myelogenous leukemias and bladder cancers, the tumor-initiating cells also upregulate CD47 expression, possibly to avoid phagocytosis.…”

“…12,15,16 Blocking the CD47-SIRPa interaction with anti-CD47 monoclonal antibodies has proven effective in inducing the phagocytosis of tumor cells in vitro and inhibiting the growth of the various hematological and solid tumors in vivo. 12,13,15,16 A previous microarray analysis indicated that CD47 is among the highly expressed genes by malignant myeloma cells compared with healthy plasma cells. 18 Here, we examined the expression of CD47 on the surface of patient myeloma cells, the therapeutic potential of an anti-CD47 monoclonal antibody (B6H12) in vitro and in xenotransplantation models.…”