MODIFICATION OF [18F]FDG BY THE FORMATION OF A HYDRAZONE BOND

Abstract

Purpose: The [18F]-fluorodeoxyglucose ([18F]-FDG) is known to be one of the most used radio-pharmaceuticals for positron emission tomography. [18F]-FDG allows the assessment of glycolytic activity, which is more enhanced in tumor cells than in normal cells. It is also used in the assessment of heart and neurological diseases. The aim of our work is to follow the possibility of modifying [18F]-fluorodeoxyglucose and to develop an indirect radiofluorination procedure applicable under standard clinical conditions. Material/Methods: In the clinic of nuclear medicine at the University Hospital Sta. Marina-Varna, for routine clinical purposes, [18F]-FDG is produced by the nucleophilic method of fluorination, using mannose triflate as a precursor. In addition to being used as a universal radiopharmaceutical, [18F]-FDG may be involved as a prosthetic group in biorthogonal reactions. [18F]-glycosylation by oxime or hydrazone formation is a chemoselective method for indirect radiofluorination of sensitive molecules. The process can improve the pharmacokinetics and stability of the labeled compounds in the blood. Results: We developed a method for modifying fluorine-deoxyglucose by forming a hydrazone bond with bifunctional tetrazine {3-[4-(6-phenyl-[1,2,4,5]-tetrazine-3-yl)-phenoxy]-propyl}-hydrazine) (Tz). The progress of the process and the product obtained were monitored by radio TLC. The radiolabeled tetrazine product will be used for future biorthogonal click reactions with trans-cyclooctene under physiological conditions.