Rapid and automated production of [68Ga]gallium chloride and [68Ga]Ga-DOTA-TATE on a medical cyclotron

Improved purification of cyclotron [68Ga]GaCl3 for the production of 68Ga radiopharmaceuticals

INTRODUCTION

Increased demand for NetSpot and Illuccix as requirement to receive the respective Lutathera and Pluvicto radiotherapies, and monitor subsequent response to treatment, have reinforced the need to develop alternative ways of producing gallium-68 (68Ga). Building on our efforts to produce 68Ga in a liquid target on a GE PETtrace, the goal of this work is to modify the current GE Gallium Chloride cassette using the FASTLab 2 synthesis module to produce [68Ga]GaCl3 equivalent to a 1.85 GBq generator and demonstrate compatibility with FDA-approved kits for production of 68Ga-labeled radiopharmaceuticals.

METHODS

68Ga was produced in a liquid target via the 68Zn(p,n)68Ga reaction. 68Ga was loaded onto various sizes of ZR resins (ZR Load, 0.3 mL, 1 mL, or 2 mL). The loading efficiency was determined using a dose calibrator. After washing with HNO3, 1.75 M HCl was used to elute the ZR Load resin through various sizes of a second ZR resin (ZR CG, 0 mL, 2 mL, 4 mL). Using 0.5 mL fractions, the elution profile was determined. Compatibility of the [68Ga]GaCl3 with NetSpot and Illuccix kits was investigated. Radiochemical purity (RCP) and 4 h stability were determined using radioTLC and radioHPLC. Using a modified [68Ga]GaCl3 cassette and new FASTLab program, 6 validation preparations were conducted using NetSpot and Illuccix kits for which RCP, stability, sterility and suitability were determined. Dual irradiation of 2 liquid targets was also performed, which was used to simultaneously prepare 1 NetSpot and 2 Illuccix kits by diluting the required activity with 0.1 M HCl.

RESULTS

The commercially available GE Cassette gave low RCP using commercial FDA kits. To optimize this, the loading efficiency onto ZR Load and the ratio of ZR resin used to load the initial activity and subsequent elution were explored. When using a 2:4 ratio of ZR Load to ZR CG, 97.89 % RCP was observed when a 3.8 mL [68Ga]GaCl3 solution was used. For Dotatate validation, 0.55 mL of buffer was added to 4.2 mL of [68Ga]GaCl3 which gave 1.35 GBq of formulated product. For Illuccix validation, [68Ga]GaCl3 was added to 2.5 mL of buffer which gave 1.52 GBq of [68Ga]Ga-PSMA-11. Formulated products passed package insert quality control (QC) requirements. When dual target irradiations were performed, 2.84 GBq was delivered to an external vial and used to label 1 NetSpot and 2 Illuccix kits simultaneously, and each kit also met or exceeded established QC criteria.

CONCLUSION

Methods are reported for using cyclotron-produced 68Ga from a liquid target in conjunction with FDA-approved NetSpot and Illucix kits. By employing a 2 mL ZR Load resin with a 4 mL ZR CG resin, adequate resolution between residual 68Zn and desired 68Ga was achieved. By modifying the FASTLab procedure to retain the final 2.5 mL of eluate from the ZR CG resin, [68Ga]GaCl3 equivalent to a new 1.85 GBq generator was obtained. This was suitable for labeling NetSpot and Illucix kits, resulting in high incorporation of 68Ga (RCP >95 %), which has not previously been demonstrated. Delivering [68Ga]GaCl3 into an external vial and diluting with 0.1 M HCl makes it possible to prepare multiple kits simultaneously. These new procedures should facilitate use of cyclotron-produced [68Ga]GaCl3 for clinical production going.

Development of a high-performance liquid chromatography method for rapid radiochemical purity measurement of [18 F]PSMA-1007, a PET radiopharmaceutical for detection of prostate cancer

Since first becoming commercially available in 2018, the PET radiopharmaceutical [¹⁸ F]PSMA-1007 has been used widely for the diagnosis and staging of prostate cancer. A pharmacopoeia monograph first became available in 2021, prescribing a radiochemical purity specification of >91%, based on analytical results from both TLC (for [¹⁸ F]fluoride impurity alone) and HPLC (for all other ¹⁸ F-impurities). Though this monograph has provided clarity for the quality control testing of [¹⁸ F]PSMA-1007, it prescribes a HPLC method using phosphate buffer mobile phase that may present a risk of precipitation of phosphate salts in the HPLC system. The method also requires specialised hardware not immediately available to all laboratories. This work describes the development of a simple, rapid reversed-phase HPLC method utilising 0.1 M ammonium formate mobile phase for the accurate assessment of both [¹⁸ F]fluoride impurity and overall radiochemical purity in a single test. This method is especially useful for assessment of product stability over time. A more accurate TLC method for [¹⁸ F]fluoride impurity is also described.

68Ga-DOTATATE Prepared from Cyclotron-Produced 68Ga: An Integrated Solution from Cyclotron Vault to Safety Assessment and Diagnostic Efficacy in Neuroendocrine Cancer Patients

Cyclotron production of ⁶⁸Ga is a promising approach to supply ⁶⁸Ga radiopharmaceuticals. To validate this capability, an integrated solution for a robust synthesis of ⁶⁸Ga-DOTATATE prepared from cyclotron-produced ⁶⁸Ga was achieved. A retrospective comparison analysis was performed on patients who underwent PET/CT imaging after injection of DOTATATE labeled with ⁶⁸Ga produced by a cyclotron or eluted from a generator to demonstrate the clinical safety and diagnostic efficacy of the radiopharmaceutical as a routine standard-of-care diagnostic tool in the clinic. Methods: An enriched pressed ⁶⁸Zn target was irradiated by a cyclotron with a proton beam set at 12.7 MeV for 100 min. The fully automated process uses an in-vault dissolution system in which a liquid distribution system transfers the dissolved target to a dedicated hot cell for the purification of ⁶⁸GaCl₃ and radiolabeling of DOTATATE using a cassette-based automated module. Quality control tests were performed on the resulting tracer solution. The internal radiation dose for ⁶⁸Ga-DOTATATE was based on extrapolation from rat biodistribution experiments. A retrospective comparison analysis was performed on patients who underwent PET/CT imaging after injection of DOTATATE labeled with cyclotron- or generator-produced ⁶⁸Ga. Results: The synthesis of ⁶⁸Ga-DOTATATE (20.7 ± 1.3 GBq) with high apparent molar activity (518 ± 32 GBq/μmol at the end of synthesis) was completed in 65 min, and the radiopharmaceutical met the requirements specified in the European Pharmacopoeia monograph on ⁶⁸Ga-chloride (accelerator-produced) solution for radiolabeling. ⁶⁸Ga-DOTATATE was stable for at least 5 h after formulation. The dosimetry calculated with OLINDA for cyclotron- and generator-produced ⁶⁸Ga-DOTATATE was roughly equivalent. The SUV_mean or SUV_max of tumoral lesions with cyclotron-produced ⁶⁸Ga-DOTATATE was equivalent to that with generator-produced ⁶⁸Ga. Among physiologic uptake levels, a significant difference was found in kidneys, spleen, and stomach wall, with lower values in cyclotron-produced ⁶⁸Ga-DOTATATE in all cases. Conclusion: Integrated cyclotron production achieves reliable high yields of clinical-grade ⁶⁸Ga-DOTATATE. The clinical safety and imaging efficacy of cyclotron-produced ⁶⁸Ga-DOTATATE in humans provide supporting evidence for its use in routine clinical practice.

Cyclotron vs generator-produced 68Ga PSMA: a single-institution, prospective clinical trial

The clinical utility of gallium 68 (⁶⁸Ga)-PSMA PET for the diagnosis and management of prostate cancer is driven in part by radioisotope availability and production costs. This study evaluates the equivalence between the two manufacturing processes for ⁶⁸Ga-PSMA: ⁶⁸Ga-PSMA-cyclotron (from a solid target) and ⁶⁸Ga-PSMA-generator. A prospective, single-arm, single-institution non-randomized study was conducted where 16 patients with prostate adenocarcinoma underwent PET/CTs consecutively within 12 to 48 hours with each type of manufactured ⁶⁸Ga-PSMA between December 2020 and June 2021. The intraclass correlation coefficients suggested acceptable reliability in all lesion parameters (ICC > 0.70). Bland-Altman analysis demonstrated acceptable bias levels for all lesion parameters. Thereby ⁶⁸Ga-cyclotron (solid target) and ⁶⁸Ga-generator production methods tagged to the same PSMA ligand resulted in scans which were deemed to be equivalent in detecting PSMA+ lesions in our study. As cyclotron-produced, solid- target ⁶⁸Ga can be made in large (Ci) quantities, it is a promising tool for future application in ⁶⁸Ga-PSMA PET scans with the potential to decrease radiotracer production costs and increase isotope availability.

Cyclotron Production of Gallium-68 Radiopharmaceuticals Using the 68Zn(p,n)68Ga Reaction and Their Regulatory Aspects

Designing and implementing various radionuclide production methods guarantees a sustainable supply, which is important for medical use. The use of medical cyclotrons for radiometal production can increase the availability of gallium-68 (⁶⁸Ga) radiopharmaceuticals. Although generators have greatly influenced the demand for ⁶⁸Ga radiopharmaceuticals, the use of medical cyclotrons is currently being explored. The resulting ⁶⁸Ga production is several times higher than obtained from a generator. Moreover, the use of solid targets yields end of purification and end of synthesis (EOS) of up to 194 GBq and 72 GBq, respectively. Furthermore, experiments employing liquid targets have provided promising results, with an EOS of 3 GBq for [⁶⁸Ga]Ga-PSMA-11. However, some processes can be further optimized, specifically purification, to achieve high ⁶⁸Ga recovery and apparent molar activity. In the future, ⁶⁸Ga will probably remain one of the most in-demand radionuclides; however, careful consideration is needed regarding how to reduce the production costs. Thus, this review aimed to discuss the production of ⁶⁸Ga radiopharmaceuticals using Advanced Cyclotron Systems, Inc. (ACSI, Richmond, BC, Canada) Richmond, Canada and GE Healthcare, Wisconsin, USA cyclotrons, its related factors, and regulatory concerns.

A digital twin for 64Cu production with cyclotron and solid target system

One method for finding reliable and cost-effective solutions for designing radioisotope production systems is represented by the “digital twin” philosophy of design. Looking at cyclotron solid targets, uncertainties of the particle beam, material composition and geometry play a crucial role in determining the results. The difference between what has been designed and what can be effectively manufactured, where processes such as electroplating are poorly controllable and generate large non-uniformities in deposition, must also be considered. A digital twin, where the target geometry is 3D scanned from real models, can represent a good compromise for connecting “ideal” and “real” worlds. Looking at the 64Ni(p,n)64Cu reaction, different Unstructured-Mesh MCNP6 models have been built starting from the 3D solid target system designed and put into operation by COMECER. A characterization has been performed considering the designed ideal target and a 3D scan of a real manufactured target measured with a ZEISS contact probe. Libraries and physics models have been also tested due to limited cross-section data. Proton spectra in the target volume, 3D proton-neutron-photon flux maps, average energies, power to be dissipated, shut-down dose-rate, 64Cu yield compared with various sources of experimental data and beam axial shifting impact, have been estimated. A digital twin of the 64Ni(p,n)64Cu production device has been characterized, considering the real measured target geometry, paving the way for a fully integrated model suitable also for thermal, structural or fluid-dynamic analyses.

Good practices for 68Ga radiopharmaceutical production

Background

The radiometal gallium-68 (⁶⁸Ga) is increasingly used in diagnostic positron emission tomography (PET), with ⁶⁸Ga-labeled radiopharmaceuticals developed as potential higher-resolution imaging alternatives to traditional ^99mTc agents. In precision medicine, PET applications of ⁶⁸Ga are widespread, with ⁶⁸Ga radiolabeled to a variety of radiotracers that evaluate perfusion and organ function, and target specific biomarkers found on tumor lesions such as prostate-specific membrane antigen, somatostatin, fibroblast activation protein, bombesin, and melanocortin.

Main body

These ⁶⁸Ga radiopharmaceuticals include agents such as [⁶⁸Ga]Ga-macroaggregated albumin for myocardial perfusion evaluation, [⁶⁸Ga]Ga-PLED for assessing renal function, [⁶⁸Ga]Ga-t-butyl-HBED for assessing liver function, and [⁶⁸Ga]Ga-PSMA for tumor imaging. The short half-life, favourable nuclear decay properties, ease of radiolabeling, and convenient availability through germanium-68 (⁶⁸Ge) generators and cyclotron production routes strongly positions ⁶⁸Ga for continued growth in clinical deployment. This progress motivates the development of a set of common guidelines and standards for the ⁶⁸Ga radiopharmaceutical community, and recommendations for centers interested in establishing ⁶⁸Ga radiopharmaceutical production.

Conclusion

This review outlines important aspects of ⁶⁸Ga radiopharmacy, including ⁶⁸Ga production routes using a ⁶⁸Ge/⁶⁸Ga generator or medical cyclotron, standardized ⁶⁸Ga radiolabeling methods, quality control procedures for clinical ⁶⁸Ga radiopharmaceuticals, and suggested best practices for centers with established or upcoming ⁶⁸Ga radiopharmaceutical production. Finally, an outlook on ⁶⁸Ga radiopharmaceuticals is presented to highlight potential challenges and opportunities facing the community.

Analysis of Pros and Cons in Using [68Ga]Ga-PSMA-11 and [18F]PSMA-1007: Production, Costs, and PET/CT Applications in Patients with Prostate Cancer

The aim of this work is to compare [⁶⁸Ga]Ga-PSMA-11 and [¹⁸F]PSMA-1007 PET/CT as imaging agents in patients with prostate cancer (PCa). Comparisons were made by evaluating times and costs of the radiolabeling process, imaging features including pharmacokinetics, and impact on patient management. The analysis of advantages and drawbacks of both radioligands might help to make a better choice based on firm data. For [⁶⁸Ga]Ga-PSMA-11, the radiochemical yield (RCY) using a low starting activity (L, average activity of 596.55 ± 37.97 MBq) was of 80.98 ± 0.05%, while using a high one (H, average activity of 1436.27 ± 68.68 MBq), the RCY was 71.48 ± 0.04%. Thus, increased starting activities of [⁶⁸Ga]-chloride negatively influenced the RCY. A similar scenario occurred for [¹⁸F]PSMA-1007. The rate of detection of PCa lesions by Positron Emission Tomography/Computed Tomography (PET/CT) was similar for both radioligands, while their distribution in normal organs significantly differed. Furthermore, similar patterns of biodistribution were found among [¹⁸F]PSMA-1007, [⁶⁸Ga]Ga-PSMA-11, and [¹⁷⁷Lu]Lu-PSMA-617, the most used agent for RLT. Moreover, the analysis of economical aspects for each single batch of production corrected for the number of allowed PET/CT examinations suggested major advantages of [¹⁸F]PSMA-1007 compared with [⁶⁸Ga]Ga-PSMA-11. Data from this study should support the proper choice in the selection of the PSMA PET radioligand to use on the basis of the cases to study.

Rapid Flow-Based System for Separation of Radioactive Metals by Selective Complex Formation

Short-lived radioactive metals are important tracers in clinical diagnosis. Radioactive metals for clinical use are produced from suitable target metals in cyclotrons. The trace amount of radioactive metal produced is contained in a relatively large amount of target metal. A rapid and effective method is required to isolate the radioactive metal. In the present study, selective complex formation followed by cation-exchange adsorption was performed in a continuous flow-based system. Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) was selected as the ligand after simulation of the separation of radioactive Ga from the target (Zn). Selectively, the Ga-EDTA complex passed through the cation trap, while Zn²⁺ was trapped. This separation principle is opposite to that of typical solid-phase extraction, which captures the target ion. The proposed separation was performed in a flow-based system with a parallel, open-channel ion trap. The performance was optimized by altering the channel dimensions, channel-filling mesh, and flow rate. Finally, the target radioactive metal, Ga, was selectively and effectively (>99%) separated from a mixture of 50 fg Ga/L and 100 mg Zn/L. The concentration of Zn remaining in the Ga solution was 2.3 μg/L. The complexed Ga was converted to free Ga³⁺ by a simple UV irradiation method. The proposed method effectively and rapidly separates trace amounts of radioactive metals contained in larger amounts of target metals using a simple flow system that can be operated on site.

Demystifying solid targets: Simple and rapid distribution-scale production of [68Ga]GaCl3 and [68Ga]Ga-PSMA-11

BACKGROUND

As the demand for ⁶⁸Ga continues to grow, there is increasing interest in single-to-multi-Curie production quantities of both [⁶⁸Ga]GaCl₃ and tracers such as [⁶⁸Ga]Ga-PSMA-11. While such quantities are possible with solid targets, this implementation is often challenging as it typically requires significant site expertise for solid target processing and careful operator-dependent synchronization of multiple independent time-sensitive chemistry steps. Herein we focus on a fully automated solid target production and purification process whereby we avoid the need for tongs/tele-pliers, and have simplified the chemistry by implementing a single sequence (i.e. "time-list") to execute cassette-based dissolution, purification, and labeling.

METHODS

Electroplated ⁶⁸Zn was irradiated in a PETtrace prototype automated solid target system. Following irradiation, and using a single FASTlab time-list, the ⁶⁸Zn was automatically dissolved with HCl/H₂O₂ and purified as [⁶⁸Ga]GaCl₃ using a combination of resins (ZR/TK400, A8, TK200: Triskem). For select experiments, [⁶⁸Ga]Ga-PSMA-11 was also produced on the same cassette/single time-list (N = 4), or, by kit labeling (N = 1). Efforts focused towards on-cassette production of [⁶⁸Ga]GaCl₃ strived to maximize activity and quality, whereas efforts focused towards on-cassette production of [⁶⁸Ga]Ga-PSMA-11 aimed at limiting the entire production cycle to 1 h including the irradiation time (i.e. start-of-bombardment ➔ end-of-synthesis [EOS]).

RESULTS

For the high activity triplicate [⁶⁸Ga]GaCl₃ productions (i.e. 80 μA, 102 min, 216 ± 10 mg), [⁶⁸Ga]GaCl₃ was purified (end-of-bombardment ➔ end-of-purification [EOP]) in ~28 min with activity yields of 181 ± 8 GBq at EOP and average radiochemical yields of 66 ± 5%. Average AMAs of 2.26 ± 0.16 TBq/μmol using DOTA (N = 3) and 12.00 TBq/μmol using HBED (PSMA-11) (N = 1) at EOP were measured. For the single kit test, (80 μA, 120 min, 263 mg ⁶⁸Zn) for which 18 mg ascorbic acid was added to the buffer, 199 GBq of [⁶⁸Ga]Ga-PSMA-11 was successfully produced (thin layer chromatography-based radiochemical purity >99% at 6 h EOS). Finally, for efforts focused at expedient [⁶⁸Ga]Ga-PSMA-11, up to 42 GBq [⁶⁸Ga]Ga-PSMA-11 with a radiochemical yield of 51.2% was produced in 63 min, including beamtime, using 220 mg of ⁶⁸Zn as target material.

CONCLUSION

With the goal of simplifying solid target production and purification efforts, automated methods using single-use, cassette-based approaches for rapid, large-scale, single time-list production of [⁶⁸Ga]GaCl₃ and [⁶⁸Ga]Ga-PSMA-11 were developed. These methods were simple to execute and yielded high quality multi-Curie levels of both [⁶⁸Ga]GaCl₃ and [⁶⁸Ga]Ga-PSMA-11.

Clinically Applicable Cyclotron-Produced Gallium-68 Gives High-Yield Radiolabeling of DOTA-Based Tracers

By using solid targets in medical cyclotrons, it is possible to produce large amounts of ⁶⁸GaCl₃. Purification of Ga³⁺ from metal ion impurities is a critical step, as these metals compete with Ga³⁺ in the complexation with different chelators, which negatively affects the radiolabeling yields. In this work, we significantly lowered the level of iron (Fe) impurities by adding ascorbate in the purification, and the resulting ⁶⁸GaCl₃ could be utilized for high-yield radiolabeling of clinically relevant DOTA-based tracers. ⁶⁸GaCl₃ was cyclotron-produced and purified with ascorbate added in the wash solutions through the UTEVA resins. The ⁶⁸Ga eluate was analyzed for radionuclidic purity (RNP) by gamma spectroscopy, metal content by ICP-MS, and by titrations with the chelators DOTA, NOTA, and HBED. The ⁶⁸GaCl₃ eluate was utilized for GMP-radiolabeling of the DOTA-based tracers DOTATOC and FAPI-46 using an automated synthesis module. DOTA chelator titrations gave an apparent molar activity (AMA) of 491 ± 204 GBq/µmol. GMP-compliant syntheses yielded up to 7 GBq/batch [⁶⁸Ga]Ga-DOTATOC and [⁶⁸Ga]Ga-FAPI-46 (radiochemical yield, RCY ~ 60%, corresponding to ten times higher compared to generator-based productions). Full quality control (QC) of ⁶⁸Ga-labelled tracers showed radiochemically pure and stable products at least four hours from end-of-synthesis.

Recent Advances in the Clinical Translation of Silicon Fluoride Acceptor (SiFA) 18F-Radiopharmaceuticals

The incorporation of silicon fluoride acceptor (SiFA) moieties into a variety of molecules, such as peptides, proteins and biologically relevant small molecules, has improved the generation of ¹⁸F-radiopharmaceuticals for medical imaging. The efficient isotopic exchange radiofluorination process, in combination with the enhanced [¹⁸F]SiFA in vivo stability, make it a suitable strategy for fluorine-18 incorporation. This review will highlight the clinical applicability of [¹⁸F]SiFA-labeled compounds and discuss the significant radiotracers currently in clinical use.

Is Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography Imaging Cost-effective in Prostate Cancer: An Analysis Informed by the proPSMA Trial

BACKGROUND

Before integrating prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) into routine care, it is important to assess if the benefits justify the differences in resource use.

OBJECTIVE

To determine the cost-effectiveness of PSMA-PET/CT when compared with conventional imaging.

DESIGN, SETTING, AND PARTICIPANTS

A cost-effectiveness analysis was developed using data from the proPSMA study. proPSMA included patients with high-risk prostate cancer assigned to conventional imaging or 68Ga-PSMA-11 PET/CT with planned health economics data collected. The cost-effectiveness analysis was conducted from an Australian societal perspective.

INTERVENTION

68Ga-PSMA-11 PET/CT compared with conventional imaging (CT and bone scan).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary outcome from proPSMA was diagnostic accuracy (nodal and distant metastases). This informed a decision tree analysis of the cost per accurate diagnosis.

RESULTS AND LIMITATIONS

The estimated cost per scan for PSMA PET/CT was AUD$1203, which was less than the conventional imaging cost at AUD$1412. PSMA PET/CT was thus dominant, having both better accuracy and a lower cost. This resulted in a cost of AUD$959 saved per additional accurate detection of nodal disease, and AUD$1412 saved for additional accurate detection of distant metastases. The results were most sensitive to variations in the number of men scanned for each 68Ga-PSMA-11 production run. Subsequent research is required to assess the long-term costs and benefits of PSMA PET/CT-directed care.

CONCLUSIONS

PSMA PET/CT has lower direct comparative costs and greater accuracy compared to conventional imaging for initial staging of men with high-risk prostate cancer. This provides a compelling case for adopting PSMA PET/CT into clinical practice.

PATIENT SUMMARY

The proPSMA study demonstrated that prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) better detects disease that has spread beyond the prostate compared with conventional imaging. Our analysis shows that PSMA PET/CT is also less costly than conventional imaging for the detection of disease spread. This research was presented at the European Association of Nuclear Medicine Scientific Meeting in October 2020.

Automated production of [18F]SiTATE on a Scintomics GRP™ platform for PET/CT imaging of neuroendocrine tumors

INTRODUCTION

[¹⁸F]SiTATE (formerly known as [¹⁸F]SiFAlin-TATE) was recently introduced as a highly promising imaging agent for the diagnosis of well-differentiated neuroendocrine tumors (NET) using positron emission tomography/computed tomography (PET/CT). A high tumor uptake and excellent image quality, the straightforward labeling approach, as well as the economic and logistic advantages of ¹⁸F- over ⁶⁸Ga-labeled compounds predestinate [¹⁸F]SiTATE to become a potential new clinical reference standard. A novel state-of-the-art methodology of automated radiopharmaceutical production is required to establish [¹⁸F]SiTATE in clinical routine. This work illustrates the development of a novel synthesis procedure of [¹⁸F]SiTATE on an automated synthesis unit (ASU) and the clinical applicability of the tracer in human NET imaging.

METHODS

A new synthesis protocol was generated for the production of [¹⁸F]SiTATE on the Scintomics GRP™ platform for clinical NET imaging. The synthesis was carried out according to common Good Manufacturing Practice (GMP) guidelines including all quality control measurements. To confirm utility, clinical batches (n = 3) were produced and applied to six patients diagnosed with NET.

RESULTS

[¹⁸F]SiTATE was obtained in 54 ± 4% (n = 3) non-decay corrected radiochemical yield (RCY), with a radiochemical purity of 96.3 ± 0.1% and a molar activity (A_m) of 472 ± 45 GBq/μmol (n = 3). Quality control measurements always met the local release criteria. All specifications were taken or adapted from the Ph.Eur. regulations. PET/CT imaging with [¹⁸F]SiTATE produced on the GRP™ module confirmed the expected high image quality. The in vivo distribution pattern and excellent tumor to non-tumor contrast observed, matched the quality of the manually prepared [¹⁸F]SiTATE batches.

CONCLUSIONS

The automated manufacture of [¹⁸F]SiTATE was developed using the Scintomics GRP™ platform. The high quality of the radiotracer matched stringent quality control requirements adhering to common GMP guidelines, and its clinical applicability was confirmed by human PET/CT investigations.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

The automated process for the manufacture of [¹⁸F]SiTATE described herein represents an important contribution to make [¹⁸F]SiTATE routinely accessible for its use in clinical NET diagnosis.

Total Body PET: Why, How, What for?

PET instruments are now available with a long axial field-of-view (LAFOV) to enable imaging the total-body, or at least head and torso, simultaneously and without bed translation. This has two major benefits, a dramatic increase in system sensitivity and the ability to measure kinetics with wider axial coverage so as to include multiple organs. This manuscript presents a review of the technology leading up to the introduction of these new instruments, and explains the benefits of a LAFOV PET-CT instrument. To date there are two platforms developed for TB-PET, an outcome of the EXPLORER Consortium of the University of California at Davis (UC Davis) and the University of Pennsylvania (Penn). The uEXPLORER at UC Davis has an AFOV of 194 cm and was developed by United Imaging Healthcare. The PennPET EXPLORER was developed at Penn and is based on the digital detector from Philips Healthcare. This multi-ring system is scalable and has been tested with 3 rings but is now being expanded to 6 rings for 140 cm. Initial human studies with both EXPLORER systems have demonstrated the successful implementation and benefits of LAFOV scanners for both clinical and research applications. Examples of such studies are described in this manuscript.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

Fully automated preparation of 68Ga-PSMA-11 at curie level quantity using cyclotron-produced 68Ga for clinical applications

⁶⁸Ga-PSMA-11 is currently one of the most investigated PET agents for imaging both recurrent prostate cancer and relevant metastases; however, the production and distribution of ⁶⁸Ga-PSMA-11 is limited to a supply of only a few daily doses when using a commercially available ⁶⁸Ge/⁶⁸Ga generator. ⁶⁸Ge/⁶⁸Ga generators deliver only a modest amount of activity, up to 1850 MBq (50 mCi), when new, but it decreases with time. Additionally, the production of ⁶⁸Ga/⁶⁸Ge generators has not been able to meet the increasing demand of ⁶⁸Ga radiotracers. In response to the need for a more economically viable alternative, the focus of this study was to provide a simple and efficient method for producing ⁶⁸Ga-PSMA-11, using cyclotron-produced ⁶⁸Ga that is ready for routine clinical practice.