Blocking [211At]astatide accumulation in normal tissues: preliminary evaluation of seven potential compounds.

Normal tissue accumulation of 211At must be minimized during targeted radiotherapy with 211At-labeled compounds. Therefore, we investigated the ability of seven compounds to block normal organ uptake of [211At]astatide in mice: potassium iodide, sodium thiocyanate, sodium perchlorate, sodium periodate, cysteine, 2,3-dimercapto-1-propanesulfonic acid, and meso-2,3-dimercaptosuccinic acid. The monovalent anions I-, SCN-, and ClO4- reduced 211At uptake in stomach and thyroid, while thiocyanate and cysteine were the only compounds to significantly reduce activity levels in lungs and spleen. This study suggests that blocking agents may help reduce normal organ radiation doses in endoradiotherapeutic procedures with 211At-labeled radiopharmaceuticals.