Optimization of a convenient route to produce N-succinimidyl 4-radiodobenzoate for radioiodination of proteins.

The preparation of N-succinimidyl-4-[131I]iodobenzoate (SIB) has been optimized using an alternative technique employing Cu(I)-assisted radioiododebromination that produces p-[131I]iodobenzoic acid. The reaction conditions were optimized and radiochemical purity of more than 90% was obtained when using 160 degrees C, 60 min reaction time and a [CuCl]/[p-bromobenzoic acid] relation of about 10(-2). After purification, the p-[131I]iodobenzoic acid reacted with TSTU to produce the SIB in a radiochemical yield greater than 98%. Protein conjugation using SIB resulted in a relatively low radiochemical yield. Biological distribution studies evidenced the in vivo stability of the labeled protein.