Meta-[211At]astatobenzylguanidine: further evaluation of a potential therapeutic agent

Meta-[211At]astatobenzylguanidine ([211At]MABG) is an astatinated analogue of meta-iodobenzylguanidine (MIBG) that could be of value for therapeutic applications. The initial goal of this study was to determine whether [211At]MABG is taken up, like MIBG, by a specific uptake-I mechanism. Norepinephrine and desipramine (DMI) decreased [211At]MABG uptake in SK-N-SH human neuroblastoma cells. This uptake was found to be energy-dependent: In mice, pre-treatment with DMI reduced uptake of [211At]MABG at 1 hr post-injection in the adrenal and in the heart. Tetrabenazine at a dose of 40 mg/kg reduced uptake of [211At]MABG in the mouse heart in vivo (69% of control) whereas up to 100 microM of tetrabenazine did not affect the in vitro uptake of [211At]MABG in SK-N-SH cells. In SK-N-SH cells, 53% and 38%, respectively, of the initial uptake of [211At]MABG was retained at 4 hr and 6 hr. For no-carrier-added (n.c.a.) [131I]MIBG these values were similar, 60% and 48%. The ability of SK-N-SH cells to incorporate [3H]thymidine was reduced to less than 50% of control values when treated with as little as 3.2 nCi of [211At]MABG. In contrast, no significant reduction in the thymidine uptake was observed, even with 80 nCi of n.c.a. MIBG.