Human CD47 Stable Cell Line-CHO-K1

CD47 is a ligand for the signal regulatory protein (SIRP)-α receptor on these innate immune cells, which in turn inhibits phagocytosis. Here, researchers developed a CD47 blocking antibody, called IBI188, that specifically blocks the CD47-SIRP-α axis that transmits the "don't eat me" signal to macrophages. In vitro phagocytosis assays demonstrated the pro-phagocytic ability of IBI188. In addition, researchers selected several in vivo models to evaluate the anti-tumor efficacy of IBI188. IBI188 treatment upregulated the expression of cell motility and inflammation-related genes in macrophages. Synergistic effects were observed when combined with an anti-CD20 therapeutic antibody, whose action relied on antibody-dependent cellular cytotoxicity/phagocytosis (ADCC/ADCP). CD47 expression was evaluated after treatment with azacytidine (AZA), a standard treatment for multiple myeloma. In an AML xenograft model, enhanced anti-tumor efficacy was observed in the combination treatment group. Notably, IBI188 treatment increased vascular endothelial growth factor A (VEGF-A) levels in solid tumor models, and anti-VEGF-A antibody combined with IBI188 enhanced anti-tumor efficacy. These data suggest that IBI188 is a therapeutic anti-CD47 antibody with anti-tumor potency that can be enhanced when combined with standard therapeutic agents for cancer treatment.

Using the yeast display platform, therapeutic antibodies targeting CD47 were discovered from a synthetic fully human antibody library. After three rounds of screening, 25 anti-human CD47 candidate antibodies were obtained. The final lead molecule IBI188 was selected based on its suitable affinity level (nM) and its ability to block ligands and receptors. The affinity of IBI188 and Hu5F9 was measured by biomembrane interferometry (BLI) (Figure 1a). The KD of IBI188 and Hu5F9 for human CD47 was 5.3 and 4 nM, respectively. The binding ability of IBI188 to hCD47 was measured using a CD47-overexpressing CHO cell line (CHO-hCD47) and primary tumor cells (Raji and MDA-MB-231). As shown in Figure 1b, IBI188 was able to effectively bind to cell surface hCD47, similar to Hu5F9. IBI188 promotes phagocytosis by blocking CD47-SIRP-α. High CD47 expression is found in tumor cells, thereby escaping macrophage surveillance through CD47/SIRP-α interaction. Next, the researchers tested the ability of IBI188 to block CD47/SIRP-α interaction. The blocking efficacy of IBI188 was confirmed in both CHO-hCD47 and primary tumor cell lines (Raji and MDA-MB-231) (Figure 1c).

Figure 1. IBI188 potently blocks the CD47/SIRP-α interaction. (Ni H, et al., 2022)