A single chain chimeric protein consisting of a monoclonal antibody fragment attached to a portion of the Pseudomonas exotoxin A. LMB-7 immunotoxin attaches to B3, a Lewis Y-related carbohydrate epitope on some solid tumor cells. The antibody attaches to the cell and the exotoxin inhibits protein synthesis by inactivating elongation factor 2. Check foractive clinical trials using this agent. or A toxic substance linked to an antibody that attaches to tumor cells and kills them.