ABSTRACT
Removal of harmful cells from the organisms is fundamental for the treatment of numerous diseases. While bacterial infections can be suc cessfully treated by antibiotics, parasitic infections and malignant trans formations are harder to deal with due to different reasons, most com mon being similarity of metabolic pathways or absence of specific targets for the drugs. One of the approaches for selective targeting and killing of such cells is the use of immunotoxins (IT), chimeric molecules composed of two parts: a targeting and a toxic one. If at the beginning these were merely explorations of the principle of selective killing, the accumulated knowledge about tumors and tumor cells biology, the understanding of biological activity of toxins at a molecular level and the development of new biochemical, genetic and molecular-biology methods has provided a strong basis for the design and production of such drugs. In fact, some of the last generation ITs have now entered the stage of clinical trials (Pastan 1997, Pai and Pastan 1998).
