title: Radiobromination of humanized anti-HER2 monoclonal antibody trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate, a potential label for immunoPET.
abstract: Combining the specificity of radioimmunoscintigraphy and the high sensitivity of PET in an in vivo detection technique could improve the quality of nuclear diagnostics. Positron-emitting nuclide (76)Br (T(1/2)=16.2 h) might be a possible candidate for labeling monoclonal antibodies (mAbs) and their fragments, provided that the appropriate labeling chemistry has been established. For internalizing antibodies, such as the humanized anti-HER2 monoclonal antibody, trastuzumab, radiobromine label should be residualizing, i.e., ensuring that radiocatabolites are trapped intracellularly after the proteolytic degradation of antibody. This study evaluated the chemistry of indirect radiobromination of trastuzumab using N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate. Literature data indicated that the use of this method provided residualizing properties for iodine and astatine labels on some antibodies. An optimized "one-pot" procedure produced an overall labeling efficiency of 45.5+/-1.2% over 15 min. The bromine label was stable under physiological and denaturing conditions. The labeled trastuzumab retained its capacity to bind specifically to HER2-expressing SKOV-3 ovarian carcinoma cells in vitro (immunoreactivity more than 75%). However, in vitro cell test did not demonstrate that the radiobromination of trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate improves cellular retention of radioactivity in comparison with the use of N-succinimidyl 4-bromobenzoate.
authors: Organic Chemistry, Department of Chemistry, Uppsala University, S-751 24 Uppsala, Sweden.
authors: Eskender
authors: E
authors: Mume
authors: Anna
authors: A
authors: Orlova
authors: Per-Uno
authors: PU
authors: Malmström
authors: Hans
authors: H
authors: Lundqvist
authors: Stefan
authors: S
authors: Sjöberg
authors: Vladimir
authors: V
authors: Tolmachev
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D061067:Antibodies, Monoclonal, Humanized; D001967:Bromine Radioisotopes / Q000737:chemistry*; D045744:Cell Line, Tumor; D004355:Drug Stability; D005260:Female; D006801:Humans; D007553:Isotope Labeling; D009525:Niacin / Q000031:analogs & derivatives* / Q000737:chemistry; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism; D016719:Radioimmunodetection / Q000379:methods; D019275:Radiopharmaceuticals / Q000737:chemistry*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D013388:Succinimides / Q000737:chemistry*; D014055:Tomography, Emission-Computed; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D001967:Bromine Radioisotopes; D009525:Niacin; D019275:Radiopharmaceuticals; D018719:Erb-b2 Receptor Tyrosine Kinases; D013388:Succinimides; D000068878:Trastuzumab; C112927:5-bromonicotinic acid N-hydroxysuccinimide ester