Research & Industry Reports

111In-Labeled Lactam Bridge-Cyclized Alpha-Melanocyte-Stimulating Hormone Peptide for Melanoma Imaging.

By Yubin Miao, Ph.D., University of New Mexico

Skin cancer is the most commonly diagnosed cancer in the United States. Malignant melanoma is the most lethal form of skin cancer and the most commonly diagnosed malignancy among young adults with an increasing incidence. It is predicted that there will be 62,940 cases of malignant melanoma newly reported and 8,420 fatalities in 2008. Unfortunately, no curative treatment exists for metastatic melanoma. Th ere is a great need to develop novel eff ective imaging probes to detect primary, metastatic and recurrent melanoma since early diagnosis and prompt surgical removal are a patient’s best opportunity for a cure.

Despite the clinical use of [18F] FDG in melanoma staging and melanoma metastases identification, [18F]FDG is not a melanoma-
specific imaging agent and is also not eff ective in imaging small melanoma metastases (< 5 mm) and melanomas that have primary energy sources other than glucose. Alternatively, G protein-coupled melanocortin-1 (MC1) receptor is a distinct molecular target due to its over-expression on human and mouse melanoma cells. Alpha-melanocyte-stimulating hormone (a-MSH) peptide can selectively deliver the diagnostic and therapeutic radionuclides to the melanoma cells for melanoma imaging and therapy through its specifi c binding with MC1 receptor.

Novel 111In-labeled DOTA-conjugated lactam bridge-cyclized a MSH peptide (111In-DOTA-GlyGlu-CycMSH) was developed to target MC1 receptors for primary and metastatic melanoma imaging. 111In-DOTA-GlyGlu-CycMSH exhibited high receptor mediated tumor uptakes in primary and metastatic melanoma lesions and appeared to be an eff ective imaging probe for primary and metastatic melanoma detection.