Therapeutic use of immunotoxins.

: Much progress has been made in the therapeutic use of immunotoxins since the first clinical trials, especially in the prevention and treatment of AGVHD. This is also further discussed in this symposium by Champlin. Research in immunotoxin use has gone beyond cancer and into the treatment of immunologic disorders, such as rheumatoid arthritis and HIV infection. Before further advances can take place several problems must be overcome, including the rapid clearance of immunotoxin by the liver, the generation of anti-immunotoxin antibodies, and poor penetration by the immunotoxin in solid tumors. Other obstacles to the wide use of immunotoxins are the heterogeneity of tumor cells, the shedding of tumor antigens into the circulation, and the inability to identify neoplastic renewal cell specific antigens that are not cross-reactive with normal tissues. Despite these obstacles, the early success of immunotoxins, especially in hematologic malignancies, reinforces the feasibility of designing rational targeting reagents in cancer therapy.