Recent developments in 68Ga-radiopharmaceuticals, including a number of regulatory approvals for clinical use, has created a hitherto unprecedented demand for 68Ga. Reliable access to enough 68Ga to meet growing clinical demand using only 68Ge/68Ga generators has been problematic in recent years. To address this challenge, we have optimized the direct production of 68Ga on a cyclotron via the 68Zn(p,n)68Ga reaction using a liquid target. This protocol describes the cyclotron-based production of [68Ga]GaCl3 implemented at the University of Michigan using a liquid target on GE PETtrace instrumentation. The protocol provides 56 ± 4 mCi (n = 3) of [68Ga]GaCl3 that meets the necessary quality control criteria to use for the preparation of 68Ga-radiopharmaceuticals for human use.

[ 68 Ga]Ga-PSMA-11, a urea-based peptidomimetic, is a diagnostic radiopharmaceutical for positron emission tomography (PET) imaging that targets the prostate-specific membrane antigen (PSMA). The recent Food and Drug Administration approval of [ 68 Ga]Ga-PSMA-11 for PET imaging of patients with prostate cancer, expected follow-up approval of companion radiotherapeutics (e.g., [ 177 Lu]Lu-PSMA-617, [ 225 Ac]Ac-PSMA-617) and large prostate cancer patient volumes requiring access are poised to create an unprecedented demand for [ 68 Ga]Ga-PSMA-11 in nuclear medicine clinics around the world. Meeting this global demand is going to require a variety of synthesis methods compatible with 68 Ga eluted from a generator or produced on a cyclotron. To address this urgent need in the PET radiochemistry community, herein we report detailed protocols for the synthesis of [ 68 Ga]Ga-PSMA-11, (also known as HBED-CC, Glu-urea-Lys(Ahx)-HBED-CC and PSMA-HBED-CC) using both generator-eluted and cyclotron-produced 68 Ga and contrast the pros and cons of each method. The radiosyntheses are automated and have been validated for human use at two sites (University of Michigan (UM), United States; Royal Prince Alfred Hospital (RPA), Australia) and used to produce [ 68 Ga]Ga-PSMA-11 for patient use in good activity yields (single generator, 0.52 GBq (14 mCi); dual generators, 1.04–1.57 GBq (28–42 mCi); cyclotron method (single target), 1.47–1.89 GBq (40–51 mCi); cyclotron method (dual target), 3.63 GBq (98 mCi)) and high radiochemical purity (99%) (UM, n = 645; RPA, n > 600). Both methods are appropriate for clinical production but, in the long term, the method employing cyclotron-produced 68 Ga is the most promising for meeting high patient volumes. Quality control testing (visual inspection, pH, radiochemical purity and identity, radionuclidic purity and identity, sterile filter integrity, bacterial endotoxin content, sterility, stability) confirmed doses are suitable for clinical use, and there is no difference in clinical prostate cancer PET imaging using [ 68 Ga]Ga-PSMA-11 prepared using the two production methods.

We prospectively investigated the performance of the prostateing prostate adenocarcinoma in patients with elevated levels of prostate-specific antigen (PSA) after initial therapy. Methods: 68GaPSMA-11 hybrid PET was performed on 2,005 patients at the time of biochemically recurrent prostate cancer after radical prostatectomy (RP) (50.8%), definitive radiation therapy (RT) (19.7%), or RP with postoperative RT (PORT) (29.6%). The presence of prostate cancer was assessed qualitatively (detection rate = positivity rate) and quantitatively on a per-patient and per-region basis, creating a disease burden estimate from the presence or absence of local (prostate/prostate bed), nodal (N1: pelvis), and distant metastatic (M1: distant soft tissue and bone) disease. The primary study endpoint was the positive predictive value (PPV) of 68Ga-PSMA-11 PET/CT confirmed by histopathology. Results: After RP, the scan detection rate increased significantly with rising PSA level (44.8% at PSA 0.25%???96.2% at PSA 10 ng/mL; P<0.001). The detection rate significantly increased with rising PSA level in each individual region, overall disease burden, prior androgen deprivation, clinical T-stage, and Gleason grading from the RP specimen (P < 0.001). After RT, the detection rate for in-gland prostate recurrence was 64.0%, compared with 20.6% prostate bed recurrence after RP and 13.3% after PORT. PSMA-positive pelvic nodal disease was detected in 42.7% after RP, 40.8% after PORT, and 38.8% after RT. In patients with histopathologic validation, the PPV per patient was 0.82 (146/179). The SUVmax of histologically proven true-positive lesions was significantly higher than that of false-positive lesions (median, 11.0 [interquartile range, recurrence and the PSA level as the main predictor of scan positivity.

The European Association of Urology (EAU) prostate cancer guidelines panel recommends risk groups for biochemical recurrence (BCR) of prostate cancer to identify men at high risk of progression or metastatic disease. The rapidly growing availability of PSMA-directed PET imaging will impact prostate cancer staging. We determined the rates of local and metastatic disease in BCR and biochemical persistence (BCP) of prostate cancer stratified by EAU BCR risk groups and BCP. Methods: Patients with BCR or BCP were enrolled under the same prospective clinical trial protocol conducted at 3 sites (n = 1,777 [91%]: UCLA, n = 662 [NCT02940262]; University of California San Francisco, n = 508 [NCT03353740]; University of Michigan, n = 607 [NCT03396874]); 183 patients with BCP from the Universities of Essen, Bologna, and Munich were included retrospectively. Patients with BCR had to have sufficient data to determine the EAU risk score. Multivariate, binomial logistic regression models were applied to assess independent predictors of M1 disease. Results: In total, 1,960 patients were included. Post-radical prostatectomy EAU BCR low-risk, EAU BCR high-risk, and BCP groups yielded distant metastatic (M1) detection in 43 of 176 (24%), 342 of 931 (37%), and 154 of 386 (40%) patients. For postradiotherapy EAU BCR low-risk and EAU BCR high-risk groups, the M1 detection rate was 113 of 309 (37%) and 110 of 158 (70%), respectively. BCP, high-risk BCR, and higher levels of serum prostate-specific antigen were significantly associated with PSMA PET M1 disease in multivariate regression analysis. PSMA PET revealed no disease in 25% and locoregional-only disease in 33% of patients with post-radical prostatectomy or postradiotherapy EAU BCR high risk. Conclusion: Our findings support the new EAU classification; EAU BCR high-risk groups have higher rates of metastatic disease on PSMA PET than do the low-risk groups. Discordant subgroups, including metastatic disease in low-risk patients and no disease in high-risk patients, warrant inclusion of PSMA PET stage to refine risk assessment.

Purpose To optimize the direct production of 68 Ga on a cyclotron, via the 68 Zn(p,n) 68 Ga reaction using a liquid cyclotron target. We Investigated the yield of cyclotron-produced 68 Ga, extraction of [ 68 Ga]GaCl 3 and subsequent [ 68 Ga]Ga-PSMA-11 labeling using an automated synthesis module. Methods Irradiations of a 1.0 M solution of [ 68 Zn]Zn(NO 3 ) 2 in dilute (0.2–0.3 M) HNO 3 were conducted using GE PETtrace cyclotrons and GE 68 Ga liquid targets. The proton beam energy was degraded to a nominal 14.3 MeV to minimize the co-production of 67 Ga through the 68 Zn(p,2n) 67 Ga reaction without unduly compromising 68 Ga yields. We also evaluated the effects of varying beam times (50–75 min) and beam currents (27–40 μA). Crude 68 Ga production was measured. The extraction of [ 68 Ga]GaCl 3 was performed using a 2 column solid phase method on the GE FASTlab Developer platform. Extracted [ 68 Ga]GaCl 3 was used to label [ 68 Ga]Ga-PSMA-11 that was intended for clinical use. Results The decay corrected yield of 68 Ga at EOB was typically > 3.7 GBq (100 mCi) for a 60 min beam, with irradiations of [ 68 Zn]Zn(NO 3 ) 2 at 0.3 M HNO 3. Target/chemistry performance was more consistent when compared with 0.2 M HNO 3 . Radionuclidic purity of 68 Ga was typically > 99.8% at EOB and met the requirements specified in the European Pharmacopoeia (< 2% combined 66/67 Ga) for a practical clinical product shelf-life. The activity yield of [ 68 Ga]GaCl 3 was typically > 50% (~ 1.85 GBq, 50 mCi); yields improved as processes were optimized. Labeling yields for [ 68 Ga]Ga-PSMA-11 were near quantitative (~ 1.67 GBq, 45 mCi) at EOS. Cyclotron produced [ 68 Ga]Ga-PSMA-11 underwent full quality control, stability and sterility testing, and was implemented for human use at the University of Michigan as an Investigational New Drug through the US FDA and also at the Royal Prince Alfred Hospital (RPA). Conclusion Direct cyclotron irradiation of a liquid target provides clinically relevant quantities of [ 68 Ga]Ga-PSMA-11 and is a viable alternative to traditional 68 Ge/ 68 Ga generators.

Naloxone (NLX) is a mu receptor antagonist used to treat acute opioid overdoses. Currently approved doses of naloxone to treat opioid overdoses are 4 mg intranasal (IN) and 2 mg intramuscular (IM). However, higher mu receptor occupancy (RO) may be required to treat overdoses due to more potent synthetic opioids such as fentanyl and carfentanil that have entered the illicit drug market recently. To address this need, a higher dose of NLX has been investigated in a 5 mg IM formulation called ZIMHI but, while the effects of intravenous (IV) and IN administration of NLX on the opioid mu receptor occupancy (RO) have been studied, comparatively little is known about RO for IM administration of NLX. The goal of this study was to examine the effect of IM dosing of NLX on mu RO in rhesus macaques using [11C]carfentanil positron emission tomography (PET) imaging. The lowest dose of NLX (0.06 mg/kg) approximated 51% RO. Higher doses of NLX (0.14 mg/kg, 0.28 mg/kg) resulted in higher mu RO of 70% and 75%, respectively. Plasma levels were 4.6 ng/mL, 16.8 ng/mL, and 43.4 ng/mL for the three IM doses, and a significant correlation between percent RO and plasma NLX level was observed (r = 0.80). These results suggest that higher doses of IM NLX result in higher mu RO and could be useful in combating overdoses resulting from potent synthetic opioids.

BACKGROUND:The recent approval of radiopharmaceuticals for diagnosis and treatment of cancer is ushering nuclear medicine into a new era of theranostics and alpha therapy using radiopharmaceuticals labeled with 225Ac shows remarkable results in clinical trials. As such, reliable methods for the synthesis and quality control of 225Ac-radiopharmaceuticals are needed.OBJECTIVE:225Ac-PSMA-617 is being used for targeted alpha therapy in patients with prostate cancer, and we had cause to synthesize the agent for preclinical use. However, technology transfer proved cumbersome owing to the paucity of information available on synthesizing and analyzing 225Ac-radiotherapeutics. To address this need, we describe a straightforward synthesis of 225Ac-PSMA- 617 as well as suitable approaches for quality control analysis using standard equipment in a modern PET Center.METHODS:PSMA-617 precursor was dissolved in 25 μL metal-free water (0.67 mg/mL) and combined with 500 μL 0.05M Tris buffer, pH 9. Actinium stock solution (~65 μCi in 15 μL) was added and the reaction was heated at 120°C for 40-50 min. The reaction was cooled and 0.6 mL gentisic acid solution (4 mg/mL in 0.2 M NH4OAc) was added. To formulate the dose for injection, sterile saline, USP (8 mL) was added and the pH was adjusted by the addition of 100 μL 0.05 M Tris buffer (pH 9) to give a final pH of ~7.2. The final solution was filtered using a 0.22 μm GV sterile filter into a sterile dose vial. Radiochemical purity was determined by radio-TLC (eluent: 50mM Sodium Citrate, pH 5), and plates were analyzed using an AR2000 scanner.RESULTS:The method provided 225Ac-PSMA-617 in high radiochemical yield (57 ± 3 μCi, >99%) and radiochemical purity (98 ± 1%), formulated for preclinical studies (9 mL, pH = 7.2), n=3.CONCLUSION:A straightforward synthesis of 225Ac-PSMA-617 is described that will facilitate production for (pre)clinical studies. The approach could also be applicable to the synthesis of other alpha radiotherapeutics incorporating 225Ac.

Purpose : To optimize the direct production of 68 Ga on a cyclotron, via the 68 Zn(p,n) 68 Ga reaction using a liquid cyclotron target. We Investigated the yield of cyclotron-produced 68 Ga, extraction of [ 68 Ga]GaCl 3 and subsequent [ 68 Ga]Ga-PSMA-11 labeling using an automated synthesis module. Methods : Irradiations of a 1.0 M solution of [ 68 Zn]Zn(NO 3 ) 2 in dilute (0.2-0.3 M) HNO 3 were conducted using GE PETtrace cyclotrons and GE 68 Ga liquid targets. The proton beam energy was degraded to a nominal 14.3 MeV to minimize the co-production of 67 Ga through the 68 Zn(p,2n) 67 Ga reaction without unduly compromising 68 Ga yields. We also evaluated the effects of varying beam times (50-75 min) and beam currents (27-40 μA). Crude 68 Ga production was measured. The extraction of [ 68 Ga]GaCl 3 was performed using a 2 column solid phase method on the GE FASTlab Developer platform. Extracted [ 68 Ga]GaCl 3 was used to label [ 68 Ga]Ga-PSMA-11 that was intended for clinical use. Results : The decay corrected yield of 68 Ga at EOB was typically >3.7 GBq (100 mCi) for a 60 min beam, with irradiations of [ 68 Zn]Zn(NO 3 ) 2 at 0.3 M HNO 3. Target/chemistry performance was more consistent when compared with 0.2 M HNO 3 . Radionuclidic purity of 68 Ga was typically >99.8% at EOB and met the requirements specified in the European Pharmacopoeia (<2% combined 66/67 Ga) for a practical clinical product shelf-life. The activity yield of [ 68 Ga]GaCl 3 was typically >50% (~1.85 GBq, 50 mCi); yields improved as processes were optimized. Labeling yields for [ 68 Ga]Ga-PSMA-11 were near quantitative (~1.67 GBq, 45mCi) at EOS. Cyclotron produced [ 68 Ga]Ga-PSMA-11 underwent full quality control, stability and sterility testing , and was implemented for human use at the University of Michigan as an Investigational New Drug through the US FDA and also at the Royal Prince Alfred Hospital (RPA). Conclusion: Direct cyclotron irradiation of a liquid target provides clinically relevant quantities of [ 68 Ga]Ga-PSMA-11 and is a viable alternative to traditional 68 Ge/ 68 Ga generators.

BackgroundIn the US, EU and elsewhere, basic clinical research studies with positron emission tomography (PET) radiotracers that are generally recognized as safe and effective (GRASE) can often be conducted under institutional approval. For example, in the United States, such research is conducted under the oversight of a Radioactive Drug Research Committee (RDRC) as long as certain requirements are met. Firstly, the research must be for basic science and cannot be intended for immediate therapeutic or diagnostic purposes, or to determine the safety and effectiveness of the PET radiotracer. Secondly, the PET radiotracer must be generally recognized as safe and effective. Specifically, the mass dose to be administered must not cause any clinically detectable pharmacological effect in humans, and the radiation dose to be administered must be the smallest dose practical to perform the study and not exceed regulatory dose limits within a 1-year period. In our experience, the main barrier to using a PET radiotracer under RDRC approval is accessing the required information about mass and radioactive dosing.ResultsThe University of Michigan (UM) has a long history of using PET radiotracers in clinical research studies. Herein we provide dosing information for 55 radiotracers that will enable other PET Centers to use them under the approval of their own RDRC committees.ConclusionsThe data provided herein will streamline future RDRC approval, and facilitate further basic science investigation of 55 PET radiotracers that target functionally relevant biomarkers in high impact disease states.

Radiolabeled erythrocytes have multiple applications in nuclear medicine, including blood pool imaging.