Radiopharmaceuticals Labelled with Copper Radionuclides: Clinical Results in Human Beings

Positron emission tomography (PET) is an instrumental diagnostic modality developed around the positron-emitting radioisotopes of biologically important elements such as carbon, oxygen and nitrogen (11C, 15O, 13N). Among longer-lived PET radionuclides, 18F is by far the most commonly used radiotracer, extensively used for tumour imaging with FDG ([18F]-fluorodeoxyglucose) and also frequently investigated in the development of novel radiopharmaceuticals. Many other positron- emitting radionuclides with higher atomic numbers and longer half-lives have been investigated for both imaging and therapeutic purposes, including the halogens (124I, 120I, 76Br) and a number of metal radionuclides. The radio-copper has attracted considerable attention, because they include isotopes which, due to their emission properties, offer themselves as agents of both diagnostic imaging (60Cu, 61Cu, 62Cu, 64Cu) and in vivo targeted radiation therapy (64Cu and 67Cu).

Although the use of this radionuclide has grown exponentially over the last decade, academic institutions have largely been responsible for its production and for the development of the vast majority of radiopharmaceutical based on these nuclides. A number of compounds labelled with Cuisotopes have been proposed, not only for imaging purposes but also for therapy. The aim of the present paper is to provide an overview on the clinical results obtained in human beings with copper radionuclides.

Several preliminary studies and clinical trials evaluated the potential clinical role of copper radioisotopes for diagnostic and therapeutic purposes. 64Cu seems to be the most suitable radioisotope for future clinical applications due to its longer half-life (12.7 h) and its commercial availability. Future clinical applications of copper radioisotopes could be enhanced by the possibility of radioligand therapy with the beta-emitting 67Cu, creating a new "theranostics pair".