Immunotoxins: properties, applications and current limitations

Delivery systems for DNA-binding drugs as gene expression modulators

Despite the large number of publications describing the synthesis and physicocharacterization of the binding between drugs and DNA, relatively few examine drug delivery systems (DDSs) for these molecules. The aim to find DDSs for DNA-binding drugs (DBDs) was prompted mainly to reduce the toxicity and/or enhance the tumor specificity of systemically administered drugs. With this in mind, we have reviewed the biological effects of some DBDs that are currently used as antitumor drugs and describe a brief selection of DDSs currently in clinical trials or on the market.

Immunotoxins: an update

The use of immunotoxins (ITs) in the therapy of cancer, graft-vs-host disease (GvHD), autoimmune diseases, and AIDS has been ongoing for the past two decades. ITs contain a targeting moiety for delivery and a toxic moiety for cytotoxicity. Theoretically, one molecule of a toxin, routed to the appropriate cellular compartment, will be lethal to a cell. Newly developed MoAbs, toxins, and molecular biological technologies have enabled researchers to construct ITs that can effectively kill many different cell types. In fact, phase I/II clinical trials have given promising results. Although nonspecific toxicity and immunogenicity still limit the use of IT therapy, these agents hold enormous promise in an optimal setting to treat minimal disease.

Production and in vitro evaluation of gelatin microspheres containing an antitumour tetra-amidine

The preparation and characterization of gelatin microspheres (GMs) containing the antitumour aromatic tetra-amidine TAPP-Br and its release characteristics from microspheres are described. Spherical gelatin microspheres, showing a high percentage of drug encapsulation (over 95 per cent) and an average diameter of 16 microns were obtained by a coacervation method. In addition, the effects of various reaction parameters on the production and chemical hardening of GMs have been investigated. In order to compare the TAPP-Br release profiles from GMs prepared with different procedures, in vitro studies were carried out. The biological effect of TAPP-Br released from gelatin microspheres was determined on 'in vitro' cultured tumour cell lines, showing that, after encapsulation, TAPP-Br still retains antiproliferative activity comparable with that exhibited by the free drug. Taken together, the results obtained suggest that gelatin-based microspheres offer excellent potential as carriers for the controlled release of polyamidines in anticancer chemotherapy.

Purification and properties of immunotoxins containing one vs. two deglycosylated ricin A chains

A method for the preparation of immunotoxins (ITs) containing one and two molecules of deglycosylated ricin A chain (dgA) bound to each molecule of anti-human CD22 mouse IgG1 monoclonal antibody is described. The cross-linking of antibody and dgA molecules was accomplished with N-succinimidyl-oxycarbonyl-alpha-methyl-(2-pyridyldithio) toluene. The two ITs were purified by successive chromatographies on Blue-Sepharose, Sephacryl S-200, Blue-Sepharose with NaCl gradient and Sephacryl S-300. The IT with two dgAs was seven-fold more cytotoxic to CD22+ Daudi cells than that containing one molecule of dgA.