Besilesomab

Nonspecific cross-reacting antigens (NCA) is the name of a collection of highly glycosylated bacterial binding receptors expressed on human granulocytes and other tissues. In particular, these glycoprotein receptors are members of the immunoglobulin supergene family and are related structurally to carcinoembryonic antigen (CEA). CEA is found naturally in the human body and its expression may be increased in both cancer and non-cancerous (benign) circumstances.

Besilesomab is subsequently a murine immunoglobulin monoclonal antibody of IgG1 isotype designed to recognise and bind specifically to NCA-95, or nonspecific cross-reacting antigen 95, an epitope found expressed on the cell membranes of granulocytes and granulocyte precursors.

When radiolabelled with sodium pertechnetate (Tc99m) solution to develop technetium (Tc99m) besilesomab solution, this radiolabelled medicine is injected into patients where the monoclonal antibody carries it to target CEA on target granulocytes. When large numbers of CEA expressing granulocytes gather to the site of an infection, the radioactive monoclonal antibodies will also accumulate at such sites, where it can be detected by diagnostic scanning. The resultant images show where the radioactive besilesomab has accumulated, locating areas affected by osteomyelitis, infection, or inflammation.

Furthermore, it is believed that the besilesomab accumulation is predominantly passive (via increased vascular permeability) and only partially active (via migration of human granulocytes carrying besilesomab to the infection/inflammation location) since only 10% to 20% of the injected radio-diagnostic agent binds in vivo to human circulating granulocytes. Specific binding of besilesomab to activated granulocytes that have already migrated to sites of infection/inflammation might be the primary part of the detection signal.