Definition

A radiopharmaceutical composed of the sialic acid binding Ig-like lectin 9 (siglec-9) linked by the macrocyclic chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to the positron-emitting radionuclide gallium Ga 68, with potential use in diagnostic imaging upon positron emission tomography (PET). Upon administration of gallium Ga 68-DOTA-siglec-9, the siglec-9 moiety binds to the ligand vascular adhesion protein-1 (VAP-1; amine oxidase, copper containing 3; AOC3) in vasculature. VAP-1 is a homodimeric sialylated glycoprotein with enzymatic activity that is expressed on the endothelium of human tissues such as skin, brain, lung, liver and heart in both normal and inflammatory conditions; it mediates leukocyte migration from the bloodstream to sites of inflammation and can also be found in certain cancers. Siglec-9 is primarily expressed on neutrophils, monocytes, macrophages, and dendritic cells. Detection of siglec-9 binding to VAP-1 using PET may serve as a surrogate marker for inflammation and the presence of cancer cells.