Abstract
Background[18F]PSMA-1007, a positron emission tomography (PET) tracer, specifically targets prostate-specific membrane antigen (PSMA), which is highly expressed in prostate cancer. PSMA-PET is effective especially for regional detection of biochemical recurrence, which significantly affects patient management. Herein, we established and optimized a one-step radiolabeling protocol to separate and purify [18F]PSMA-1007 with a CFN-MPS200 synthesizer for clinical application.ResultsA dedicated single use cassette and synthesis program for [18F]PSMA-1007 was generated using a single-step method for direct precursor radiolabeling. In the cassette, three tube types (fluoro-elastomer, PharMed® BPT, silicone) and two different precursor salts (trifluoroacetic acid or acetic acid) were compared for optimization. Furthermore, three-lot tests were performed under optimized conditions for quality confirmation. Activity yields and mean radiochemical purity of [18F]PSMA-1007 were > 5000 MBq and 95%, respectively, at the end of synthesis, and the decay-corrected mean radiochemical yield from all three cassettes was approximately 40% using a trifluoroacetic acid salt precursor. Fluoro-elastomer tubings significantly increased the amount of non-radioactive PSMA-1007 (8.5 ± 3.1 μg/mL) compared to those with other tubings (0.3 μg/mL). This reduced the molar activity of [18F]PSMA-1007 synthesized in the cassette assembled by fluoro-elastomer tubings (46 GBq/μmol) compared to that with PharMed® BPT and silicone tubings (1184 and 1411 GBq/μmol, respectively). Residual tetrabutylammonium, acetonitrile, and dimethyl sulfoxide levels were < 2.6 μg/mL, < 8 ppm, and < 11 ppm, respectively, and ethanol content was 8.0–8.1% in all three cassettes and two different salts. Higher activity yields, radiochemical purities, and decay-corrected radiochemical yields were obtained using an acetic acid salt precursor rather than a trifluoroacetic acid salt precursor (7906 ± 1216 MBq, 97% ± 0%, and 56% ± 4%). In the three-lot tests under conditions optimized with silicone cassettes and acetic acid salt precursor, all quality items passed the specifications required for human use.ConclusionsWe successfully automated the production of [18F]PSMA-1007 for clinical use and optimized synthesis procedures with a CFN-MPS200 synthesizer using a silicone cassette and acetic acid salt precursor. Cassette availability will facilitate a wide spread use of [18F]PSMA-1007-PET, leading to an effective prostate cancer management.
Highlights
The prostate-specific membrane antigen (PSMA) is a major target for theranostics in prostate cancer (Israeli et al 1994; Herrmann et al 2015; Ferdinandus et al 2018)
Positron emission tomography (PET) tracers labeled with 68Ga such as [68Ga]Ga-PSMA-11 have been used for diagnosis (Eder et al 2012; Afshar-Oromieh et al 2012; Rowe et al 2016). 68Ge/68Ga generators enable PET examination at remote facilities; they are associated with logistical limitations such as a long delivery duration due to shortage of commercially available approved generators; high activity yields cannot be obtained due to capacity limitations of the available generators
The production of [18F]PSMA-1007 injection solution was completed within 62 min on average including the trapping of [18F] fluoride from the V-vial to the QMA column on the synthesizer (Fig. 5)
Summary
The prostate-specific membrane antigen (PSMA) is a major target for theranostics in prostate cancer (Israeli et al 1994; Herrmann et al 2015; Ferdinandus et al 2018). Radiosynthesis of [18F]PSMA-1007 via a two-step radiolabeling method using 6[18F]fluoropyridine-3-carboxylic acid ([18F]F-Py-TFP) has previously been conducted (Cardinale et al 2017a) This method was unsuitable for routine clinical examination since the synthesis procedure was complicated and resulted in rather poor radiochemical yields (the radiochemical yield was 1.5–6.0%). PSMA-PET is effective especially for the regional detection of biochemical recurrence and has a significant influence on patient management (Giesel et al 2019; Koerber et al 2018) For this reason, [18F]PSMA-1007 PET examination is expected to be performed on more patients for the precise evaluation of prostate cancer, making its stable and reproducible production to be essential. We verified its quality and application for clinical examination with three-lot tests
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