Therapeutic targeting of CD47 using a tri-specific NK cell engager to inhibit multiple myeloma.

Multiple myeloma (MM), a hematological malignancy, remains an incurable disease due to the development of resistance to the treatment; thus, there is an urgent need for new and effective therapeutic strategies, particularly for patients who do not respond to standard therapies. High levels of Cluster of Differentiation 47 (CD47) expression have been reported in MM and are associated with disease progression. CD47 acts as a cancer immune escape mechanism by binding to SIRPα protein, resulting in inhibiting phagocytosis of macrophages and NK cell activity. Therefore, blocking the CD47 signaling pathway has emerged as a promising strategy for cancer immunotherapy. In this study, we confirmed that MM cells have high CD47 expression. We generated and characterized a tri-specific killer engager targeting CD47, namely TriKE-CD47, that targets both CD47 on MM cells and CD16 on NK cells. Additionally, it incorporates an IL-15 moiety to enhance NK cell proliferation. TriKE-CD47 treatment promoted a remarkable proliferation of NK cells overexpressing CD16 (N6 cells). Co-culturing MM cells with N6 cells, primary NK cells, and monocyte-derived macrophages in the presence of 200 ng of TriKE-CD47 significantly improved NK cytotoxicity and macrophage phagocyte activities against MM cells. Notably, the efficacy of TriKE-CD47 was directly correlated with CD47 expression levels on the target cells reflecting the specificity of TriKE-CD47 to target antigen. Furthermore, TriKE-CD47 effectively suppressed tumor growth in MM xenograft mice models. Taken together, these findings strongly supported that TriKE-CD47 could be a potential therapeutic for MM patients.