On site production of [ 18 F]PSMA-1007 using different [ 18 F]fluoride activities: practical, technical and economical impact

Background Prostate-specific membrane antigen is overexpressed in prostate cancer and it is considered a good target for positron emission tomography/computed tomography imaging of primary cancer and recurrent/metastatic disease, as well as for radioligand therapy. Different PSMA-analogues labeled with [ 68 Ga]gallium have been investigated, showing excellent imaging properties; however, only small amounts can be produced for each radiolabeling. Recently, a [ 18 F]fluoride labeled PSMA-inhibitor, [ 18 F]PSMA-1007, has been introduced, and it has ensured large-scale productions, overcoming this limitation of [ 68 Ga]PSMAs. In this study, PSMA-1007 has been labeled with low (A), medium (B) and high (C) starting activities of [ 18 F]fluoride, in order to verify if radiochemical yield, radiochemical purity and stability of [ 18 F]PSMA-1007 were affected. These parameters have been measured in sixty-five consecutive batches. In addition, the estimation of [ 18 F]PSMA-1007 production costs is provided. Results The radiochemical yield for low and medium activities of [ 18 F]fluoride was 52%, while for the high one it decreased to 40%. The radiochemical purity was 99% for all three activities. [ 18 F]PSMA-1007 did not show radiolysis up to 8 h after the end of synthesis, confirming that the radiopharmaceutical is stable and suitable to perform diagnostic studies in humans for a long period of time after the end of radiolabeling. Furthermore, radiochemical stability was demonstrated in fetal bovine serum at 4 °C and 37 °C for 120′ . Conclusions A starting activity of [ 18 F]fluoride of 90 GBq (B) seems to be the best option enabling a final amount of about of 50 GBq of [ 18 F]PSMA-1007, which is promising as it allows to: (a) perform a large number of scans, and/or (b) supply the radiopharmaceutical to any peripheral diagnostic centers in need.