title: Immunotoxins of Pseudomonas exotoxin A (PE): effect of linkage on conjugate yield, potency, selectivity and toxicity.
abstract: Conjugates of monoclonal antibodies and Pseudomonas exotoxin A (PE) were formed with disulfide or thioether bonds. Thioether conjugates which formed with succinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SMCC) modified PE and reduced antibody formed with an 80% yield of equimolar conjugate within 30 min with an offering of one to one (toxin:antibody). The efficiency and kinetics of thioether formation were much higher with SMCC than with other maleimide reagents as well as more efficient than disulfide linkers. Thioether linkage resulted in immunotoxin consistently more potent and more selective in vitro than disulfide bonded conjugate. Thioether bonded conjugates also proved to have other favorable in vivo properties compared to disulfide conjugates: (1) a longer half-life in serum; (2) increased tumor localization; and (3) reduced toxicity. Toxicity of thioether linked holotoxin conjugates was directed at the liver hepatocyte but was easily monitored by serum liver enzymes. The conjugates are currently undergoing clinical evaluation for treatment of ovarian cancer with intraperitoneal administration. Research is ongoing to further decrease residual toxicity without reducing the potency of the conjugate.
authors.affiliation: NeoRx Corporation, Seattle, Washington 98119.
authors.forename: A C
authors.initials: AC
authors.lastname: Morgan
authors.forename: G
authors.initials: G
authors.lastname: Sivam
authors.forename: P
authors.initials: P
authors.lastname: Beaumier
authors.forename: R
authors.initials: R
authors.lastname: McIntyre
authors.forename: M
authors.initials: M
authors.lastname: Bjorn
authors.forename: P G
authors.initials: PG
authors.lastname: Abrams
mesh_terms: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001427:Bacterial Toxins; D002460:Cell Line; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005098:Exotoxins / Q000378:metabolism* / Q000633:toxicity; D006801:Humans; D000922:Immunotoxins / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000473:pathology; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D005098:Exotoxins; D000922:Immunotoxins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A