Preclinical Evaluation of Radioiodinated Quinoxaline Derivative as a Possible Brain Imaging Agent

Abstract

4-{(4-Methylphenyl)glycyl}-3,4-dihydroquinoxalin-2(1H)-one (QIN) was prepared from 4-(2-chloroacetyl)- 3,4-dihydroquinoxalin-1(1H)-one). ¹²⁵I-QIN was prepared by electrophilic substitution using Chloramine- T as an oxidizing agent. The highest labeling yield, 94%, was obtained under the following conditions: pH 7, 15 min, 100 μg of QIN, 50 μg of Chloramine-T, and carrier-free Na¹²⁵I. The labeled compound was stable for up to 12 h post labeling. A biodistribution study of ¹²⁵I-QIN in mice showed that its brain uptake was about 5.1% at 30 min post injection and remained on this level up to 1 h. As compared to commercially used radiopharmaceuticals for brain imaging, ¹²⁵I-QIN is more stable and shows higher brain uptake.