Monoclonal antibody therapy immunotoxins

Ricin is a type II toxin. The A chain (ricin A) contains 267 amino acid residues, and the B chain (ricin B) 262 residues. Ricin A is exceptionally toxic, and it has been estimated that a single molecule is sufficient to kill an individual cell. This peptide can be prepared by genetic engineering using Escherichia coli. The potent action of this material on eukaryotic cells has been investigated in anticancer therapy. Ricin A has been coupled to monoclonal antibodies and successfully delivered specifically to the tumour cells. However, in vitro toxicity of ricin A-based immunotoxins is enhanced significantly if ricin B is also present. 

Immunotoxins composed of ricin A chain coupled to a cell-specific monoclonal antibody have continued to show promise as a new class of antitumor agents. Gnt tin and Raso investigated the use of the carboxylic ionophor monensin formulated in an O/W emulsion for the in vitro and in vivo potentiation of immu-notoxin.s. Monensin in this pharmacologically available form significantly improved the in vivo efficacy of both anti-human transferrin receptor immunotoxin and anticarcinoembryonic antigen immunotoxin when used as regional therapy. 

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