Design,Synthesis and in Vitro Biological Evaluation of Reference Compounds of 123I and ~(99)Tc~m Labeled Indole Radiotracers for σ_2 Receptor Imaging

Novel indole radiotracers for 123Ⅰ and 99Tcm labeling were designed.The corresponding reference compounds(Indole-Ⅰ and Indole-MAMA-Re) and the precursor(Indole-MAMA) for 99Tcm labeling were synthesized.Competition binding assays in vitro show that the Ki values of Indole-Ⅰ for σ1 and σ2 receptors are(0.574±0.355)μmol/L and(0.162±0.030)μmol/L(n=3),respectively.The Ki values of Indole-MAMA-Re for σ1 and σ2 receptors are(3.75±2.22)μmol/L and(7.83±4.87)μmol/L(n=3),respectively.Furthermore,99Tcm-Indole-MAMA was successfully prepared.The radio-chemical purity(RCP) of 99Tcm-Indole-MAMA after purification was higher than 90% by HPLC analysis.The compounds reported in this paper may be used as lead compounds for further structural modification to develop indole SPECT tumor imaging agents with high affinity and selectivity for σ2 receptors.