Development and characterization of a 99mTc‐labeled Neuropeptide Y short analog with potential application in breast cancer imaging

The aim of this work was to develop and evaluate a ^99mTc‐labeled neuropeptide Y derivative with affinity toward Y1‐receptor. The selected amino acid sequence included nine amino acids derived from the C‐terminal portion of the NPY complemented with the addition of one cysteine‐mercaptoacetic acid moiety to bind the radiometal. Labeling was achieved through the preparation of a 3 + 1 nitrido complex. Physicochemical evaluation, cell uptake, internalization and externalization studies, and competitive assays were performed. Biodistribution experiments were carried out in normal and tumor‐bearing mice. A single product with radiochemical purity >90% and high stability was obtained. In vitro analysis showed specific cellular uptake, IC₅₀ of 73.2 nM, and a high internalization rate (80%). Biodistribution studies showed low blood and renal uptake and combined hepatobiliary and urinary elimination. Preliminary studies in mice bearing induced breast tumors rendered promising uptake values.