Di-dgA-RFB4 immunotoxin

An immunotoxin of monoclonal antibody (MoAb) RFB4 covalently linked to two deglycosylated ricin toxin A-chain (Di-dgA). This agent can be extracted from castor beans. MoAb RFB4 recognizes CD22 antigen, a B-cell adhesion protein expressed on malignant cells in about 70 percent of non-Hodgkin lymphoma and chronic lymphocytic leukemia. Ricin toxin A-chain, a potent protein synthesis inhibitor, was deglycosylated and was used in this immunoconjugate to avoid hepatic entrapment. This Di-dgA conjugated MoAb RFB4 delivers 7 fold more cytotoxicity than the single dgA immunotoxin against CD22-positive malignant cells.