A simple and improved routine praparation of no-carrier-added meta I-123-and I-131-iodobenzylguanidine (I-123-MIBG and I-131-MIBG) for clinical nuclear medicine applications

Aim: Low specific activity meta-iodobenzylguanidine (I-123/I-131-MIBG) is c urrently used in the assessment of abnormalities in the myocardial neuroadr energic function as well as in the management of neuroendocrine tumors. In recent studies an enhanced cardiac and tumor uptake were reported by the us e of high specific activity radiopharmazeuticals, suggesting a potential cl inical benefit of no-carrier-added (n.c.a.) I-123/I-131-MIBG. in this paper we describe a simple and improved preparation of I-123-MIBG and I-132-MIBG for routine clinical application, feasible In any nuclear medicine departm ent. Methods: N.c.a I-123-MIBG and n.c.a. I-131-MIBG were prepared by Cu(I) -assisted [I-123/1-131]iodo-debromination at 170-175 degrees C with 86 +/- 6% and 80 +/- 10% radiochemical yield respectivelly and high specific activ ity (greater than or equal to 4.3 TBq/mu mol and greater than or equal to 0 .21 TBq/mu mol), starting from meta-bromobenzylguanidine (MBBG). The total dme of synthesis including the HPLC purification and the preparation of the injectable solution was less than 60 min. Results: Neither rechromatograph y by HPLC nor TLC gave any indication of disintegration products in the inj ection solution up to 8 h after preparation. Moreover, biological testings confirmed that the buffered and sterilfiltered n.c.a. I-123-MIBG and n.c.a. I-131-MIBG solutions are isotonic, steril and apyrogenic and thus suitable as injectable solutions for clinical use. Conclusion: High specific activi ty I-123-MIBG and I-131-MIBG could now be prepared by a simple one-step rea ction giving rise to high radiochemical yields and high purity for a widesp read clinical applications. Therefore, this encourages clinical validations on a large scale to answer the question of whether n.c.a. I-123-MIBG and I -131-MIBG could play an important role in the assessment of the myocardial sympathetic nervous dysfunction as well as in the diagnosis and therapy of neuroendocrine tumors.