Misri Ripen, Saatchi Katayoun, Häfeli Urs O
Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
Nucl Med Commun. 2011 Apr;32(4):324-9. doi: 10.1097/MNM.0b013e328343dee5.
The objective of this study was to design and evaluate a new histidine-modified tridentate chelator for labeling antimesothelin fab and f(ab')2 antibody fragments with the Tc(I) tricarbonyl ([Tc(CO)3]) core. N-(ortho-phenol)-histidine chelator was synthesized by modifying the single amino acid L-histidine, a natural amino acid, with an additional phenol group to obtain the bifunctional tridentate ligand after reductive amination. Bioconjugation was based on the carbodiimide activation of the carboxylate of chelator and on further reaction with the amine groups present on the antibody fragments. Radiolabeling was accomplished by replacing the three aqua ligands of the complex precursor [Tc(CO)3(H2O)3] with the tridentate chelator. The antibody fragments radiolabeled with [Tc(CO)3] core were tested for stability by the cysteine challenge test. The immunoreactivity and binding affinity of the radiolabeled fragments were studied using in-vitro cell-binding assays. Radiochemical yields achieved for [Tc(CO)3] core labeling of fab and f(ab')2 were 91.6±9.1% and 80.7±8.5%, respectively. Stability studies of radiolabeled antibody fragments showed that the Tc label was stable to transchelation by cysteine. Both Tc-fab and Tc-f(ab')2 retained their reactivity and affinity to the mesothelin antigen. From our studies, it can be concluded that the newly synthesized N-(ortho-phenol)-histidine chelator is a promising candidate for [Tc(CO)3] labeling of biomolecules and for developing other novel Tc radiopharmaceuticals.
本研究的目的是设计并评估一种新型的组氨酸修饰三齿螯合剂，用于用三羰基锝（I）（[Tc(CO)3]）核心标记抗间皮素Fab和F(ab')2抗体片段。通过用额外的酚基团修饰天然氨基酸L-组氨酸这种单一氨基酸，经还原胺化反应获得双功能三齿配体，从而合成N-（邻苯酚）-组氨酸螯合剂。生物偶联基于螯合剂羧酸盐的碳二亚胺活化以及与抗体片段上存在的胺基的进一步反应。通过用三齿螯合剂取代络合物前体[Tc(CO)3(H2O)3]的三个水配体来完成放射性标记。用半胱氨酸激发试验测试了用[Tc(CO)3]核心放射性标记的抗体片段的稳定性。使用体外细胞结合试验研究了放射性标记片段的免疫反应性和结合亲和力。Fab和F(ab')2的[Tc(CO)3]核心标记的放射化学产率分别为91.6±9.1%和80.7±8.5%。放射性标记抗体片段的稳定性研究表明，锝标记对半胱氨酸的转螯合作用稳定。Tc-Fab和Tc-F(ab')2均保留了对间皮素抗原的反应性和亲和力。从我们的研究可以得出结论，新合成的N-（邻苯酚）-组氨酸螯合剂是用于生物分子的[Tc(CO)3]标记以及开发其他新型锝放射性药物的有前途的候选物。
