An iodine-123 labeled bicyclic nucleoside analogue ([(123)I]-4) has been synthesized and evaluated as a potential single photon emission tomography (SPECT) reporter probe for the non-invasive imaging of expression of the varicella zoster virus thymidine kinase (VZV-tk) reporter gene. In vitro enzymatic assays revealed that the non-radioactive mono-iodo derivative 4 has good affinity for VZV-TK (IC(50): 4.2 microM). Biodistribution of [(123)I]-4 was examined in normal mice. Evaluation of [(123)I]-4 in HEK-293T cells showed 1.74-fold higher accumulation in VZV-TK-expressing cells compared to control cells.
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