title: Carrier-free 131I-meta-iodobenzylguanidine: comparison of production from meta-diazobenzylguanidine and from meta-trimethylsilylbenzylguanidine.
abstract: Meta-iodobenzylguanidine (MIBG) is a drug which is selectively accumulated by the uptake-1 process in adrenergic tissues. When labelled with 131I, it may be used for the targetted radiotherapy of tumours such as phaeochromocytoma and neuroblastoma. This paper describes the preparation of carrier-free 131I-MIBG by radioiodination of meta-diazobenzylguanidine, and compares this process with one involving iododesilylation of meta-trimethylsilylbenzylguanidine. Both processes result in the formation of carrier-free 131I-MIBG whose specific activity at greater than 3 x 10(16) Bq mol-1 is at least 100 times higher than that of commercially available 131I-MIBG for therapeutic use. The therapeutic use of 131I-MIBG with a higher than usual specific activity is predicted to result in a greater target-to-nontarget ratio, and therefore enhanced efficacy because of an increased therapeutic index. As the radiochemical yield of the process involving the metadiazobenzylguanidine intermediate is only 13%, compared with 98% for the iododesilylation reaction, the latter is the preferred synthetic route.
authors.affiliation: University of Glasgow Department of Radiation Oncology, Cancer Research Campaign Beatson Laboratories, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Mairs
authors.forename: M N
authors.initials: MN
authors.lastname: Gaze
authors.forename: D G
authors.initials: DG
authors.lastname: Watson
authors.forename: G G
authors.initials: GG
authors.lastname: Skellern
authors.forename: P
authors.initials: P
authors.lastname: Constable
authors.forename: K
authors.initials: K
authors.lastname: McKellar
authors.forename: J
authors.initials: J
authors.lastname: Owens
authors.forename: G
authors.initials: G
authors.lastname: Vaidyanathan
authors.forename: M R
authors.initials: MR
authors.lastname: Zalutsky
mesh_terms: D019797:3-Iodobenzylguanidine; D001596:Benzylamines / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid; D003979:Diazonium Compounds / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D019791:Guanidine; D006146:Guanidines / Q000737:chemistry*; D007457:Iodine Radioisotopes / Q000737:chemistry*; D007462:Iodobenzenes / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011854:Radiochemistry; D014297:Trimethylsilyl Compounds / Q000737:chemistry*
chemical_list: C089014:3-diazobenzylguanidine; D001596:Benzylamines; D003979:Diazonium Compounds; D006146:Guanidines; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D014297:Trimethylsilyl Compounds; C089015:3-trimethylsilylbenzylguanidine; D019797:3-Iodobenzylguanidine; C089016:3-nitrobenzylamine; C089018:3-aminobenzylguanidine; C089017:3-nitrobenzylguanidine; D019791:Guanidine