OPTIMIZATION OF RADIOIODINATION AND BIOTINYLATION OF MONOCLONAL-ANTIBODY CHIMERIC BR96 - AN INDIRECT LABELING USING N-SUCCINIMIDYL-3-(TRI-N-BUTYLSTANNYL)BENZOATE CONJUGATE

Chimeric BR96 (chiBR96) is an oxidant sensitive, highly tumor-reactive and internalizing monoclonal antibody. Radioiodination of chiBR96 wit h direct labeling methods has a high risk of damaging the antibody's i mmunoreactivity. Combination of iodination and biotinylation of chiBR9 6 has been particularly difficult. In present studies, indirect radioi odine labeling by use of a conjugate of N-succinimidyl 3-(tri-n-butyls tannyl)benzoate (ATE) war introduced for chiBR96 radioiodination and f or combination of iodination and biotinylation of chiBR96. ATE was syn thesised, radioiodinated with a modified and simplified method by omit ting one step of separation. A same or slightly higher labeling effici ency was obtained comparing to earlier reports. Simultaneous biotinyla tion of the chiBR96 was performed by use of biotin reagent of N-hydrox ysuccinimido-biotin. In a comparative study of biotinylated and unbiot inylated I-125-chiBR96 iodinated with ATE conjugate, it was found that I-125-chiBR96 with or without biotinylation had the same stability, i mmunoreactivity and biodistribution with a high tumor targeting capaci ty. Hence, the ATE conjugate radioiodination method enables the combin ation of iodination and simultaneous biotinylation of chiBR96.