A combination preparation of 1:1 mixture of the immunotoxins HD37-dgA and RFB4-dgA with potential antineoplastic activity. Anti-CD19 IgG monoclonal antibody HD37 and anti-CD22 IgG monoclonal antibody RFB4 are attached individually to a deglycosylated ricin A chain (dgA) via N-succinimidyl-oxycarbonyl-alpha-methyl-alpha-(2-pyridyldithio) toluene (SMPT) linker. Deglycosylated ricin A chain-conjugated anti-CD19/anti-CD22 immunotoxins bind to CD19- and CD22-expressing tumor cells, specifically delivering cytotoxic ricin A chain to leukemia cells expressing these antigens. Ricin A chain is toxic to ribosomal activity and protein synthesis, and inhibits cell growth. CD19 and CD22 molecules are cell surface antigens present on the majority of B acute lymphoblastic leukemia (ALL) cells.
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