PET Radiopharmaceuticals for Imaging Integrin Expression: Tracers in Clinical Studies and Recent Developments

Abstract

Noninvasive determination of integrin expression has become an interesting approach in nuclear medicine. Since the discovery of the first18F-labeled cyclic RGD peptide as radiotracer for imaging integrinαvβ3expression in vivo, there have been carried out enormous efforts to develop RGD peptides for PET imaging. Moreover, in recent years, additional integrins, includingα5β1andαvβ6, came into the focus of pharmaceutical radiochemistry. This review will discuss the tracers already evaluated in clinical trials and summarize the preliminary outcome. It will also give an overview on recent developments to further optimize the first-generation compounds such as [18F]Galacto-RGD. This includes recently developed18F-labeling strategies and also new approaches in68Ga-complex chemistry. Furthermore, the approaches to develop radiopharmaceuticals targeting integrinα5β1andαvβ6will be summarized and discussed.