title: Antitumor activity of the single-chain immunotoxin BR96 sFv-PE40 against established breast and lung tumor xenografts.
abstract: We have constructed a single-chain immunotoxin consisting of the variable H and L chains of the carcinoma-reactive mAb BR96, fused to the binding defective protein toxin, PE40. This molecule, BR96 sFv-PE40, has been shown to be extremely cytotoxic toward a variety of BR96 Ag-expressing tumor cell lines. When administered i.v. into athymic mice carrying L2987 tumor xenografts, BR96 sFv-PE40 was cleared rapidly from the blood with a half-life of approximately 30 min. This is in comparison to a chemical conjugate, chiBR96-LysPE40, that remained in the blood for almost 2 h. In addition, the smaller single-chain immunotoxin (67 kDa) penetrates the tumor faster than the larger chemical conjugate (190 kDa). Using a variety of administration schedules and doses, we treated established human tumor xenografts in athymic mice with both the single-chain immunotoxin BR96 sFv-PE40 and the chemical conjugate chiBR96-LysPE40. In both L2987 lung carcinoma and MCF-7 breast carcinoma models, we found that BR96 sFv-PE40 completely regressed the tumor xenografts. With an administration schedule of q4dx5, the tumors were totally regressed and did not reappear. The chiBR96-LysPE40 conjugate produced partial tumor regressions, although at near maximum tolerated dose. These results show that the single-chain immunotoxin, BR96 sFv-PE40, is a potent antitumor agent.
authors.affiliation: Bristol-Myers Squibb, Pharmaceutical Research Institute, Wallingford, CT 06492.
authors.forename: P N
authors.initials: PN
authors.lastname: Friedman
authors.forename: D F
authors.initials: DF
authors.lastname: Chace
authors.forename: P A
authors.initials: PA
authors.lastname: Trail
authors.forename: C B
authors.initials: CB
authors.lastname: Siegall
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use* / Q000633:toxicity; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000633:toxicity; D001427:Bacterial Toxins; D005098:Exotoxins / Q000627:therapeutic use* / Q000633:toxicity; D005260:Female; D006801:Humans; D000922:Immunotoxins / Q000627:therapeutic use* / Q000633:toxicity; D008175:Lung Neoplasms / Q000628:therapy*; D008325:Mammary Neoplasms, Experimental / Q000628:therapy*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use* / Q000633:toxicity; D013329:Structure-Activity Relationship; D014018:Tissue Distribution; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D001427:Bacterial Toxins; D005098:Exotoxins; D000922:Immunotoxins; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C089583:BR96 sFv-PE40