Synthesis, radioiodination and in vivo screening of novel potent iodinated and fluorinated radiotracers as melanoma imaging and therapeutic probes

• Seven new iodinated and fluorinated matched-pair radiotracers were synthesized.
• [125I]-Labelled analogues were screened in vivo using planar scintigraphic imaging.
• High and specific uptake of radioactivity in melanoma tumours was observed generally.
• Promising dosimetry parameters were calculated for the [131I]-labelled analogues.
• These compounds hold potential for PET imaging and targeted radiotherapy of melanoma.

In order to develop new iodinated and fluorinated matched-pair radiotracers for Single-Photon Emission Computed Tomography (SPECT)/Positron Emission Tomography (PET) imaging and targeted radionuclide therapy of melanoma, we successfully synthesized and radiolabelled with iodine-125 seven new derivatives, starting from our previously described lead structure 3. The relevance of these radiotracers for gamma scintigraphic imaging of melanoma in rodent was assessed. The tumoural radioactivity uptake was most often high and specific even at early time points (12.1–18.3% ID/g at 3 h p.i. for [125I]39–42) and a fast clearance from the non-target organs was observed. Also, calculated effective doses that could be delivered to tumours when using corresponding [131I]-labelled analogues were generally higher than 100 cGy/MBq injected (98.9–150.5 cGy/MBq for [131I]39–42). These results make compounds 39–42 suitable candidates for (i) PET imaging of melanoma after labelling with fluorine-18 and (ii) targeted radionuclide therapy of disseminated melanoma after labelling with iodine-131.

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