UCSF

Introduction: The human norepinephrine transporter (hNET) is involved in a number of pathological disorders and is the target of many pharmaceutical drugs. [123I]MIBG is a clinically established radiotracer used in single photon emission computed tomography (SPECT) imaging of hNET expression in tumors and sympathetic innervation. We

evaluated a new method for synthesizing the fluorine-18 analog of MIBG, i.e., [18F]MFBG and sought to optimize its production parameters.

Materials and Methods: A two-step labeling process was developed using an iodonium benzyl guanidine salt precursor created by Ground Flour Pharmaceuticals. The labeling was analyzed with radio TLC in 100% ethyl acetate and the solution is purified using an HLB sep-pak and HPLC. The synthesized [18F]MFBG was then tested for uptake in

NB1691 (control) and NB1691-hNET cell lines after being incubated for 1 hour.

Results: An average labeling yield of 16.0% (±13%) was established after multiple optimization steps, showing inconsistent labeling. Roughly 12.3% (±7.7%) of the recovered 85% activity is isolated for HPLC purification. This leads to an overall radiochemical yield of 6.9% (±4.4%) at the end of the synthetic process. When performing in vitro studies hNET-overexpressing cells (NB1691-hNET) showed a 3.5 fold increase in uptake (21.4% of 1 microCi) compared to control (6.2% of 1 microCi).