title: Anti-Tac(Fab)-PE40, a recombinant double-chain immunotoxin which kills interleukin-2-receptor-bearing cells and induces complete remission in an in vivo tumor model.
abstract: We have produced a single plasmid encoding both the heavy chain Fd domain (VH + CH1) of the anti-interleukin-2 receptor (IL2R) monoclonal antibody anti-Tac, and the anti-Tac light chain fused to PE40, a truncated derivative of Pseudomonas exotoxin. The active immunotoxin anti-Tac(Fab)-PE40 could be recovered from E. coli from either periplasm or renatured inclusion bodies. The double-chain immunotoxin was very cytotoxic toward IL2R-bearing cell lines, human activated T cells and fresh adult-T-cell-leukemia cells. The cytotoxicity was similar to that of anti-Tac(Fv)-PE40, the single-chain recombinant toxin containing only the variable domains of anti-Tac. IL2R-binding affinity was also equivalent to that of anti-Tac(Fv)-PE40, which is one-third that of anti-Tac. The serum half-life in mice was significantly prolonged as compared with anti-Tac(Fv)-PE40, with a beta phase of 430 vs. 57 minutes, but the LD50s were equivalent when the immunotoxins were administered in 3 daily doses. Anti-Tac(Fab)-PE40 was very cytotoxic in vitro toward transfected ATAC-4 carcinoma cells which express IL2Rs. In mice bearing ATAC-4 tumors, anti-Tac(Fab)-PE40 showed significant anti-tumor activity, inducing complete remissions in 80 and 100% of treated animals at approximately 7 and 14% respectively of the LD50. Anti-Tac(Fab)-PE40 was much more effective in vitro and in vivo than chemical conjugates between anti-Tac and truncated PE molecules. The recombinant Fab toxin should be studied further as potential treatment for IL2R-related malignancies, particularly if smaller recombinant immunotoxins have insufficient half-life in humans.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: R J
authors.initials: RJ
authors.lastname: Kreitman
authors.forename: C N
authors.initials: CN
authors.lastname: Chang
authors.forename: D V
authors.initials: DV
authors.lastname: Hudson
authors.forename: C
authors.initials: C
authors.lastname: Queen
authors.forename: P
authors.initials: P
authors.lastname: Bailon
authors.forename: I
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D001427:Bacterial Toxins; D001483:Base Sequence; D005098:Exotoxins / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity; D006801:Humans; D000922:Immunotoxins / Q000737:chemistry* / Q000633:toxicity; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000493:pharmacokinetics; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured / Q000187:drug effects; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D005098:Exotoxins; D000922:Immunotoxins; D009838:Oligodeoxyribonucleotides; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A