title: Lysine-directed conjugation of ethidium homodimer to B72.3 antibody: retention of immunoreactivity but altered tumor targeting.
abstract: Ethidium homodimer (EHD) was conjugated to B72.3 monoclonal antibody using a method whereby 85-90% of the conjugated EHD remains available for DNA intercalation. Antibody was thiopropionylated by reaction with N-succinimidyl 3-(2-pyridyldithio)propionate and reduction of pyridyldithio groups with dithiothreitol. EHD was maleimido-functionalized with succinimidyl-4-(N-maleimidoethyl)cyclohexane-1-carboxylate and treated with thiopropionylated antibody to obtain a conjugate containing approximately 3.4 EHD per antibody molecule. For biologic studies, 14C-labeled EHD was synthesized by reductive amination and conjugated as above. In vitro the conjugate maintained chemical integrity and immunoreactivity, while in vivo its targeting of LS174T tumors was reduced compared with that of iodinated antibody. A decrease in isoelectric point of the immunoconjugate was also observed.
authors.affiliation: Department of Radiology (Nuclear Medicine), Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Harapanhalli
authors.forename: K Z
authors.initials: KZ
authors.lastname: Matalka
authors.forename: P L
authors.initials: PL
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Mahmood
authors.forename: S J
authors.initials: SJ
authors.lastname: Adelstein
authors.forename: A I
authors.initials: AI
authors.lastname: Kassis
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000912:Antibodies, Neoplasm / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics*; D003110:Colonic Neoplasms / Q000378:metabolism*; D019281:Dimerization; D004996:Ethidium / Q000031:analogs & derivatives*; D006801:Humans; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008239:Lysine; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D014018:Tissue Distribution
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; C091202:B72.3 antibody; D002250:Carbon Radioisotopes; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes; C018533:ethidium homodimer; D004996:Ethidium; D008239:Lysine