Gallium-68-labeled DOTA-rhenium-cyclized α-melanocyte-stimulating hormone analog for imaging of malignant melanoma

IntroductionDiagnosis of malignant melanoma is critical, since a patient's prognosis is poor. Previous studies have shown that 64Cu- and 86Y-DOTA-ReCCMSH(Arg11) have the potential for early detection of malignant melanoma by exploiting the sensitivity and high resolution of positron emission tomography (PET). This encouraged us to investigate DOTA-ReCCMSH(Arg11) labeled with another β+-emitting radionuclide, 68Ga.MethodsDOTA-ReCCMSH(Arg11) was successfully labeled with 68Ga at pH 3.8–4 at 85°C. Acute biodistribution and small-animal PET imaging studies were performed in mice bearing B16/F1 melanoma tumor.ResultsBiodistribution studies showed moderate receptor-mediated tumor uptake, fast nontarget organ clearance and high tumor to nontarget tissue ratios. Preadministration of d-lysine significantly reduced kidney uptake without affecting the uptake of the agent in the tumor. Small-animal PET images showed that the tumor could be clearly visualized at all time points examined (0.5–2 h) with the standardized uptake value analysis following a similar trend as the biodistribution data.ConclusionsThe preliminary data obtained suggest that 68Ga-DOTA-ReCCMSH(Arg11) is a promising PET imaging agent for early detection of malignant melanoma.