Definition

An agent blocking the interaction between the leukocyte surface antigen CD47 and the signal regulatory protein alpha (SIRPalpha; SIRPa), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, CD47/SIRPa blocking agent TQB2928 blocks the interaction between CD47, which is expressed on tumor cells, and SIRPa, which is expressed on phagocytic cells. This prevents CD47/SIRPa-mediated signaling and abrogates the CD47/SIRPa-mediated inhibition of macrophage activation and phagocytosis of cancer cells. This induces pro-phagocytic signaling mediated by the binding of calreticulin (CRT), which is specifically expressed on the surface of tumor cells, to low-density lipoprotein (LDL) receptor-related protein-1 (LRP-1), which is expressed on macrophages, and results in macrophage activation and the specific phagocytosis of tumor cells. CD47, also called integrin-associated protein (IAP), is a tumor-associated antigen (TAA) expressed on normal, healthy hematopoietic stem cells (HSCs) and overexpressed on the surface of a variety of cancer cells. Expression of CD47, and its interaction with SIRPa, leads to the inhibition of macrophage activation and protects cancer cells from phagocytosis, thereby allowing cancer cells to proliferate.