Synthesis and evaluation of 99mTc-analogues of [123/131I]mIBG prepared via [99mTc][Tc(CO)3(H2O)3]+ synthon for targeting norepinephrine transporter

Novel [18F]-Labeled Meta-Bromobenzylguanidine Derivatives: Potential Positron Emission Tomography Imaging Probes for the Norepinephrine Transporter

“…Similar to MIBG, these NET-targeting radiotracers were mainly derived from a NE-like benzylguanidine core structure, sharing two key pharmacophore characteristics: an aromatic ring and a positively charged guanidine group (Figure ). Over the past few years, extensive research has focused on the meta substituent on the aromatic ring. − It has been found that a halogen substituent in this position may be essential for the NET-targeting bioactivity of benzylguanidine analogues. For example, compared with 3-[ 18 F]­fluorobenzylguanidine ([ 18 F]­MFBG) and 4- 18 F-fluoro-3-iodobenzylguanidine ([ 18 F]­FIBG), 4- 18 F-fluorobenzylguanidine ([ 18 F]­PFBG, without a halogen substituent in the meta position) displays a lower affinity for the NET. − Notably, the meta - Br-substituted derivatives [ 76 Br]­MBBG and [ 18 F]­LMI1195 have demonstrated excellent NET-specific affinity both in vitro and in vivo. ,, However, the biological properties of 4- 18 F-fluoropropoxy-3-iodobenzylguanidine ([ 18 F]­FPOIBG), an analogue containing iodine instead of bromine, are inferior to those of [ 18 F]­LMI1195 …”