title: Toward antibody-directed "abzyme" prodrug therapy, ADAPT: carbamate prodrug activation by a catalytic antibody and its in vitro application to human tumor cell killing.
abstract: Antibody-directed enzyme prodrug therapy, ADEPT, is a recent approach to targeted cancer chemotherapy intended to diminish the nonspecific toxicity associated with many commonly used chemotherapeutic agents. Most ADEPT systems incorporate a bacterial enzyme, and thus their potential is reduced because of the immunogenicity of that component of the conjugate. This limitation can be circumvented by the use of a catalytic antibody, which can be "humanized," in place of the bacterial enzyme catalyst. We have explored the scope of such antibody-directed "abzyme" prodrug therapy, ADAPT, to evaluate the potential for a repeatable targeted cancer chemotherapy. We report the production of a catalytic antibody that can hydrolyze the carbamate prodrug 4-[N,N-bis(2-chloroethyl)]aminophenyl-N-[(1S)-(1,3- dicarboxy)propyl]carbamate (1) to generate the corresponding cytotoxic nitrogen mustard (Km = 201 microM, kcat = 1.88 min-1). In vitro studies with this abzyme, EA11-D7, and prodrug 1 lead to a marked reduction in viability of cultured human colonic carcinoma (LoVo) cells relative to appropriate controls. In addition, we have found a good correlation between antibody catalysis as determined by this cytotoxicity assay in vitro and competitive binding studies of candidate abzymes to the truncated transition-state analogue ethyl 4-nitrophenylmethylphosphonate. This cell-kill assay heralds a general approach to direct and rapid screening of antibody libraries for catalysts.
authors.affiliation: Department of Chemistry, Krebs Institute for Biomolecular Research, University of Sheffied, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Wentworth
authors.forename: A
authors.initials: A
authors.lastname: Datta
authors.forename: D
authors.initials: D
authors.lastname: Blakey
authors.forename: T
authors.initials: T
authors.lastname: Boyle
authors.forename: L J
authors.initials: LJ
authors.lastname: Partridge
authors.forename: G M
authors.initials: GM
authors.lastname: Blackburn
mesh_terms: D000816:Aniline Mustard / Q000031:analogs & derivatives* / Q000494:pharmacology; D017151:Antibodies, Catalytic / Q000378:metabolism / Q000494:pharmacology*; D000915:Antibody Affinity; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D002277:Carcinoma; D003110:Colonic Neoplasms; D006241:Haptens; D006801:Humans; D006868:Hydrolysis; D009588:Nitrogen Mustard Compounds / Q000378:metabolism / Q000494:pharmacology*; D011355:Prodrugs / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: C097876:4-(N,N-bis(2-chloroethyl))aminophenyl-N-((1,3-dicarboxy)propyl)carbamate; D017151:Antibodies, Catalytic; D018906:Antineoplastic Agents, Alkylating; D006241:Haptens; D009588:Nitrogen Mustard Compounds; D011355:Prodrugs; C000929:hydroxyaniline mustard; D000816:Aniline Mustard