Immunotoxins and Recombinant Immunotoxins in Cancer Therapy

Targeted cancer therapy in general and immunotherapy in particular, combines rational drug design with the progress in understanding cancer biology. This approach takes advantage of our recent knowledge of the mechanisms by which normal cells are transformed into cancer cells, thus, using the special properties of cancer cells to device novel therapeutic strategies. Recombinant immunotoxins are excellent examples for such processes, combining the knowledge of antigen expression by cancer cells with the enormous developments in recombinant DNA technology and antibody engineering. Recombinant immunotoxins are composed of a very potent protein toxin fused to a targeting moiety such as recombinant antibody fragment or growth factor. These molecules bind to surface antigens specific for cancer cells and kill the target cells by catalytic inhibition of protein synthesis. Recombinant immunotoxins are developed for solid tumors and hematological malignancies and have been characterized intensively for their biological activity in vitro on cultured tumor cell lines as well as in vivo in animal models of human tumor xenografts. The excellent in vitro and in vivo activities of recombinant immunotoxins have lead to their preclinical development and to the initiation of clinical trial protocols. Recent trial results have demonstrated potent clinical efficacy in patients with malignant diseases that are refractory to traditional modalities of cancer treatment; surgery, radiation therapy, and chemotherapy. Keywords: Cancer Therapy; Immunotoxins; Recombinant Antibodies; Targeted Therapy