Copper-64 Radiopharmaceuticals for PET Imaging of Cancer: Advances in Preclinical and Clinical Research

Copper-64 (T(1/2) = 12.7 hours; beta(+), 0.653 MeV [17.8%]; beta(-), 0.579 MeV [38.4%]) has decay characteristics that allow for positron emission tomography (PET) imaging and targeted radiotherapy of cancer. The well-established coordination chemistry of copper allows for its reaction with a wide variety of chelator systems that can potentially be linked to peptides and other biologically relevant small molecules, antibodies, proteins, and nanoparticles. The 12.7-hours half-life of (64)Cu provides the flexibility to image both smaller molecules and larger, slower clearing proteins and nanoparticles. In a practical sense, the radionuclide or the (64)Cu-radiopharmaceuticals can be easily shipped for PET imaging studies at sites remote to the production facility. Due to the versatility of (64)Cu, there has been an abundance of novel research in this area over the past 20 years, primarily in the area of PET imaging, but also for the targeted radiotherapy of cancer. The biologic activity of the hypoxia imaging agent, (60/64)Cu-ATSM, has been described in great detail in animal models and in clinical PET studies. An investigational new drug application for (64)Cu-ATSM was recently approved by the U. S. Food and Drug Administration (FDA) in the United States, paving the way for a multicenter trial to validate the utility of this agent, with the hopeful result being FDA approval for routine clinical use. This article discusses state-of-the-art cancer imaging with (64)Cu radiopharmaceuticals, including (64)Cu-ATSM for imaging hypoxia, (64)Cu-labeled peptides for tumor-receptor targeting, (64)Cu-labeled monoclonal antibodies for targeting tumor antigens, and (64)Cu-labeled nanoparticles for cancer targeting. The emphasis of this article will be on the new scientific discoveries involving (64)Cu radiopharmaceuticals, as well as the translation of these into human studies.