title: Site-specific chemical modification with polyethylene glycol of recombinant immunotoxin anti-Tac(Fv)-PE38 (LMB-2) improves antitumor activity and reduces animal toxicity and immunogenicity.
abstract: Chemical modification of proteins with polyethylene glycol (PEGylation) can increase plasma half-lives, stability, and therapeutic potency. To make a PEGylated recombinant immunotoxin with improved therapeutic properties, we prepared a mutant of anti-Tac(Fv)-PE38 (LMB-2), a recombinant immunotoxin composed of a single-chain Fv fragment of the anti-human Tac monoclonal antibody to the IL-2 receptor alpha subunit fused to a 38-kDa fragment of Pseudomonas exotoxin. For site-specific PEGylation of LMB-2, one cysteine residue was introduced into the peptide connector (ASGCGPE) between the Fv and the toxin. This mutant LMB-2 (cys1-LMB-2), which retained full cytotoxic activity, was then site-specifically conjugated with 5 or 20 kDa of polyethylene glycol-maleimide. When compared with unmodified LMB-2, both PEGylated immunotoxins showed similar cytotoxic activities in vitro but superior stability at 37 degrees C in mouse serum, a 5- to 8-fold increase in plasma half-lives in mice, and a 3- to 4-fold increase in antitumor activity. This was accompanied by a substantial decrease in animal toxicity and immunogenicity. Site-specific PEGylation of recombinant immunotoxins may increase their therapeutic potency in humans.
authors.affiliation: Laboratory of Molecular Biology, Division of Basic Science, National Cancer Institute, National Institutes of Health, Building 37, Room 4E16, 37 Convent Drive MSC 4255, Bethesda, MD 20892-4255, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsutsumi
authors.forename: M
authors.initials: M
authors.lastname: Onda
authors.forename: S
authors.initials: S
authors.lastname: Nagata
authors.forename: B
authors.initials: B
authors.lastname: Lee
authors.forename: R J
authors.initials: RJ
authors.lastname: Kreitman
authors.forename: I
authors.initials: I
authors.lastname: Pastan
mesh_terms: D000818:Animals; D000906:Antibodies; D000970:Antineoplastic Agents / Q000276:immunology / Q000494:pharmacology* / Q000633:toxicity; D002460:Cell Line; D005260:Female; D006801:Humans; D000922:Immunotoxins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology* / Q000633:toxicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016297:Mutagenesis, Site-Directed; D009374:Neoplasms, Experimental / Q000188:drug therapy; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011994:Recombinant Proteins
chemical_list: D000906:Antibodies; D000970:Antineoplastic Agents; D000922:Immunotoxins; D011994:Recombinant Proteins; C407312:antitac(FV)-PE38 recombinant immunotoxin; D011092:Polyethylene Glycols