The detection of prostate cancer lesions by PET imaging of the prostate-specific membrane antigen (PSMA) has gained highest clinical impact during the last years. 68Ga-labelled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]Ga-PSMA-HBED-CC) represents a successful novel PSMA inhibitor radiotracer which has recently demonstrated its suitability in individual first-in-man studies. The radiometal chelator HBED-CC used in this molecule represents a rather rarely used acyclic complexing agent with chemical characteristics favourably influencing the biological functionality of the PSMA inhibitor. The simple replacement of HBED-CC by the prominent radiometal chelator DOTA was shown to dramatically reduce the in vivo imaging quality of the respective 68Ga-labelled PSMA-targeted tracer proving that HBED-CC contributes intrinsically to the PSMA binding of the Glu-urea-Lys(Ahx) pharmacophore. Owing to the obvious growing clinical impact, this work aims to reflect the properties of HBED-CC as acyclic radiometal chelator and presents novel preclinical data and relevant aspects of the radiopharmaceutical production process of [68Ga]Ga-PSMA-HBED-CC.

As the first radiopharmaceutical for Peptide Receptor Radionuclide Therapy (PRRT), Lutathera® was approved by the EMA in 2017 and the FDA in 2018 for the treatment of somatostatin receptor (SSTR) positive gastroenteropancreatic neuroendocrine tumors. Using the concept of PRRT, Lutathera® combines the radionuclide 177Lu with the somatostatin analogue DOTA-TATE, thus delivering ionizing radiation specifically to tumor cells expressing somatostatin receptors. As a result, DNA single- and double-strand breaks are provoked, in case of double-strand breaks leading to cell death of the tumor and its SSTR-positive lesions.

In the United States, [68Ga]Ga-DOTA-TOC has been approved by the Food and Drug Administration (FDA) in 2019 as the first 68Ga-radiopharmaceutical for imaging of somatostatin receptor (SSTR) positive gastroenteropancreatic neuroendocrine tumors while employing positron emission tomography (PET). In Europe (Austria, Germany, France), [68Ga]Ga-DOTA-TOC was already approved back in 2016. This radiopharmaceutical combines the radionuclide 68Ga with the somatostatin analogue DOTA-TOC for specific imaging of tumor cells expressing SSTRs. Such a targeting approach can also be used for therapy planning in the case of both localized as well as disseminated disease and potentially for the evaluation of treatment response.