title: Preparation and characterization of a beta-lactamase-Fab' conjugate for the site-specific activation of oncolytic agents.
abstract: Antibody-directed catalysis (ADC) is a two-step method for the targeted delivery of chemotherapeutic agents in which enzyme-antibody conjugates, prelocalized to antigen-bearing cells, activate prodrugs designed to be substrates for the enzyme. An enzyme-Fab' conjugate exhibiting both native beta-lactamase activity and immunoreactivity toward carcinoembryonic antigen (CEA) was constructed. Treatment of CEA-expressing LS174T cells with this conjugate imparted beta-lactamase activity to the cells; beta-lactamase activity was not imparted by treatment with unconjugated beta-lactamase and not to CEA negative cells treated with conjugate. Cephalosporin-based prodrugs, and other substrates synthesized as model compounds, were found to have wide variations in their kinetic parameters toward the conjugate, with kcat values ranging from 16 to 3300 s-1 and KM values ranging from 5 to 160 microM. The prodrug derived from desacetylvinblastine-3-carboxylic acid hydrazide (DAVLBHYD) was studied in vitro and found to be 5-fold less cytotoxic to LS174T cells than the parent DAVLBHYD. For antigen-positive cells preincubated with conjugate, however, the prodrug showed the same potency as the parent drug. Thus, the combination of conjugate and prodrug appears to provide antigen-dependent toxicity to tumor cells.
authors.affiliation: Hybritech Incorporated, San Diego, California 92196-9006.
authors.forename: D L
authors.initials: DL
authors.lastname: Meyer
authors.forename: L N
authors.initials: LN
authors.lastname: Jungheim
authors.forename: S D
authors.initials: SD
authors.lastname: Mikolajczyk
authors.forename: T A
authors.initials: TA
authors.lastname: Shepherd
authors.forename: J J
authors.initials: JJ
authors.lastname: Starling
authors.forename: C N
authors.initials: CN
authors.lastname: Ahlem
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000378:metabolism / Q000633:toxicity; D002272:Carcinoembryonic Antigen / Q000276:immunology; D002511:Cephalosporins / Q000008:administration & dosage* / Q000378:metabolism / Q000633:toxicity; D016503:Drug Delivery Systems; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D011355:Prodrugs / Q000008:administration & dosage* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D002272:Carcinoembryonic Antigen; D002511:Cephalosporins; D007140:Immunoglobulin Fab Fragments; D011355:Prodrugs; C075479:LY 266070; C055170:4-desacetylvinblastine hydrazide; D014747:Vinblastine; D001618:beta-Lactamases