Immunotoxins: a review of their use in cancer treatment

Antibody therapies have become an important component in the management of malignant disease. Antibodies can block tumour growth factors or their receptors, activate immunological attack on the tumour, and are used to deliver payloads such as radioisotopes, cytotoxic drugs or toxins. Immunotoxins are a new class of antitumour agents consisting of tumour- selective ligands (generally monoclonal antibodies [MoAbs]) linked to highly toxic protein molecules and take the advantage of the exquisite specificity of antibodies to selectively target drug delivery and the potency of toxins to kill the target cells. Toxins are modified to remove their normal tissue-binding domains by genetic engineering. Analysis of the aminoacid sequence of the region specific for immunogenecity and the signal transduction mechanisms involved in the interaction of immunotoxins with tumour cells will give the clue for the development of most efficient immunotoxins.