A Gallium-Labeled DOTA--Melanocyte– Stimulating Hormone Analog for PET Imaging of Melanoma Metastases

Although 18F-FDG PET is widely used for metastatic melanoma diagnosis, it is less accurate than desirable, particularly for small foci. Since both melanotic and amelanotic melanomas overex-press receptors for -melanocyte–stimulating hormone (-MSH; receptor name, melanocortin type 1 receptor [MC1R]), radiolabeled -MSH analogs are potential candidates for mel-anoma diagnosis. The aim of this study was to develop a positron emitter–labeled -MSH analog suitable for PET imag-ing of melanoma metastases. Methods: A short linear -MSH analog, [Nle4,Asp5,D-Phe7]--MSH4–11 (NAPamide), was newly designed and conjugated to the metal chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) to enable ra-diometal incorporation. Compared with our previously reported DOTA--MSH analog, DOTA-MSHoct ([DOTA-Ala3,Nle4,Asp5,D-Phe7,Lys10]--MSH3–10), the major modification lies in the con