**1. Introduction**

In recent years, 68Ga-radiopharmaceuticals gained more and more attention due to their steadily growing clinical application. Facilitated is this development by increasing interest in the application of its "theranostic twin" lutetium-177. Combining both, gallium-68 and lutetium-177, enables diagnostic molecular imaging followed by personalized treatment based on the diagnostic scan [1].

This concept is well established for treatment of neuroendocrine tumors (NETs) using peptide receptor radionuclide therapy (PRRT). This approach allows the targeted treatment of inoperable or metastatic NETs already proven in multiple clinical trials employing radiolabeled somatostatin analogs [2–9]. Based on the data received, the U.S. Food and Drug Administration (FDA) recently approved 177Lu-labeled DOTA-TATE for PRRT treatment. However, not only for NETs, but also for other types of cancer (e.g. prostate cancer (PC)), lutetium-177 is of interest, reflected in numerous clinical trials registered at https://clinicaltrials.gov (keyword: lutetium-177; 87 trials; 12/9/2019). Even more trials are enrolled for its diagnostic counterpart gallium-68 (keyword: gallium-68; 268 trials; 12/9/2019). While only a handful clinical trials were conducted before 2012 for both radionuclides

(gallium-68, 12 trials between 1991 and 2011; lutetium-177, 16 trials between 1996 and 2011) both have increasingly found application in clinical routine reflected in the rapidly increasing amount of enrolled phase 1–3 studies.

Although, gallium-68 was already proposed for medical use by Gleason [10] its way to clinical application was not possible without the advancement of the primary generator design. Providing [68Ga]GaCl3 and containing only trace levels of the long-living mother radionuclide germanium-68 regarding 68Ga-activity, the commercially availability of generator simplified research and motivated developments with a view to a broad routine application. The launch of this new type of 68Ga-generator together with decades of research in chelation chemistry and drug discovery resulted in the design of 68Ga-radiopharmaceuticals of high affinity/selectivity for their biological targets [11–13].

The advantages of the generator availability and the easy one-step chelation chemistry ensured the relatively fast and broad application of the 68Ga-radiopharmaceuticals even in smaller institutions. However, exactly these advantages lead to problems in the supply today and require new developments in order to meet the growing demands.
