Synthesis and in Vivo Evaluation of [I-123]Melanin-Targeted Agents

study reports the synthesis, [I-123]radiolabeling, and biological profile of a new series of iodinated compounds for potential translation to the corresponding [I-131]radiolabeled compounds for radionuclide therapy of melanoma. Radiolabeling was achieved via standard electrophilic iododestannylation in 60-90% radiochemical yield. Preliminary SPECT imaging demonstrated high and distinct tumor uptake of all compounds, as well as high tumor-to-background ratios compared to the literature compound [I-123]4 (ICF01012). The most favorable compounds ([I-123]20, [I-123]23, [I-123] 41, and [I-123]53) were selected for further biological investigation. Biodistribution studies indicated that all four compounds bound to melanin containing tissue with low in vivo deiodination; [I-123]20 and [I-123]53 in particular displayed high and prolonged tumor uptake (13% ID/g at 48 h). [I-123]53 had the most favorable overall profile of the cumulative uptake over time of radiosensitive organs. Metabolite analysis of the four radiotracers found [I-123]41 and [I-123]53 to be the most favorable, displaying high and prolonged amounts of intact tracer in melanin containing tissues, suggesting melanin specific binding. Results herein suggest that compound [I-123]53 displays favorable in vivo pharrnacokinetics and stability and hence is an ideal candidate to proceed with further preclinical [I-131] therapeutic evaluation.