Targeted Cancer Therapy: History and Development of Immunotoxins

Abstract

Though a number of new drugs have been and are being formulated to treat cancer, newer therapeutic approaches are needed due to increased instances of drug resistance and toxic side effects. One relatively new approach for treatment is immunotherapy, using antibodies or ligands to cell surface molecules as vehicles to deliver toxins to specific cells, thus increasing the efficacy of the treatment by several folds. Such conjugates, of antibodies and toxins termed 'immunotoxins' are generated either as chemical conjugates using hetero-bifunctional cross-linkers that link the antibody to the toxin, or as 'fusion proteins', wherein, the gene for the antibody and the gene for the toxin are cloned together as one construct into bacterial expression systems and expressed as recombinant proteins. Several toxins, mainly the inhibitors of translation, are being explored for preparing immunotoxins. This chapter provides an overview of the treatment modalities adopted to date for the cancer management and introduces the field of immunotherapy. The chapter also focuses on the different toxins used in generating immunotoxins and on those that have made it to clinical trials.