Synthesis, radiolabelling, and biodistribution studies of triazole derivatives for targeting melanoma

Molecular probes that target specific markers expressed in solid tumours are in demand for cancer imaging and radionuclide therapy applications. The synthesis, characterization, and in vivo evaluation of radioiodinated triazoles designed as probes to target melanoma are described here. Compounds were prepared using a thermal click reaction between ethynylstannane and methyl 2-azidoacetate, resulting in preferential formation of the corresponding 1,4-tin triazole. The primary amine of various targeting vectors was then coupled to the resulting tin triazole methyl ester. These precursors were labelled with no carrier added 123 I or 125 I and purified by high performance liquid chromatography to give isolated radiochemical yields between 6% and 51% and radiochemical purities of >95% in all cases. Among the evaluated compounds, N-(2-diethylamino-ethyl)-2-(4-iodo-[1,2,3]triazol-1-yl)acetamide (7a) and N-(1-benzylpiperidin-4-yl)-2-(4-iodo-1H-1,2,3-triazol-1-yl)acetamide (7d) showed the most promising in vivo data, and their 123 I-labelled forms were used in single photon emission computed tomography computed tomography (SPECT–CT) imaging studies. The imaging data showed excellent tumour visualization with a very high signal to noise ratio.