Long-term evaluation of 'BARC 68Ge/68Ga generator' based on the nanoceria-polyacrylonitrile composite sorbent

Synthesis, Quality Control, and Bench-to-Bed Translation of a New [68Ga]Ga-Labeled NOTA-Conjugated Bisphosphonate for Imaging Skeletal Metastases by Positron Emission Tomography

Background: Early detection of skeletal metastasis is of great interest to determine the prognosis of cancer. Positron emission tomography-computed tomography (PET-CT) imaging provides a better temporal and spectral resolution than single photon emission computed tomography-computed tomography (SPECT-CT) imaging, and hence is more suitable to detect small metastatic lesions. Although [18F]NaF has been approved by U.S. FDA for a similar purpose, requirement of a medical cyclotron for its regular formulation restricts its extensive utilization. Efforts have been made to find suitable alternative molecules that can be labeled with 68Ga and used in PET-CT imaging. Objective: The main objective of this study is to synthesize and evaluate a new [68Ga]Ga-labeled NOTA-conjugated geminal bisphosphonate for its potential use in early detection of skeletal metastases using PET-CT. Methods: The authors performed a multistep synthesis of a new NOTA-conjugated bisphosphonic acid using thiourea linker and radiolabeled the molecule with 68Ga. The radiolabeled formulation was evaluated for its in vitro stability, affinity for hydroxyapatite (HA) particles, preclinical biodistribution in animal models, and PET-CT imaging in patients. Results: The bifunctional chelator (NOTA)-conjugated bisphosphonate was synthesized with 97.8% purity and radiolabeled with 68Ga in high yield (>98%). The radiolabeled formulation was found to retain its stability in vitro to the extent of >95% up to 4 h in physiological saline and human serum. The formulation also showed high affinity for HA particles in vitro with Kd = 907 ± 14 mL/g. Preclinical biodistribution studies in normal Wistar rats demonstrated rapid and almost exclusive skeletal accumulation of the complex. PET-CT imaging in a patient confirmed its ability to detect small metastatic skeletal lesions. Conclusions: The newly synthesized [68Ga]Ga-labeled NOTA-conjugated bisphosphonate is a promising radiotracer for PET-CT imaging for skeletal metastases.

Development and long-term evaluation of a new 68Ge/68Ga generator based on nano-SnO2 for PET imaging

Radionuclide generator systems can routinely provide radionuclides on demand such as ⁶⁸Ga produced by a ⁶⁸Ge/⁶⁸Ga generator without the availability of an on-site accelerator or a research reactor. Thus, in this work nano-SnO₂ was used to develop a new ⁶⁸Ge/⁶⁸Ga generator which was evaluated over a period of 17 months and 305 elution cycles. The elution yield was 91.1 ± 1.8% in the first 7 mL (1 M HCl as eluent) when the generator was new and then it decreased with time and use to 73.8 ± 1.9%. Around 80% of the elutable ⁶⁸Ga activity was obtained in 1 mL and the ⁶⁸Ge content in the eluate did not exceed 1 × 10^–4% over the investigation period when it was eluted regularly. The described generator provided adequate results for radiolabelling of DOTA-TOC with direct use of eluate. In addition, [⁶⁸Ga]Ga-DOTA-TOC was tested satisfactorily for in vivo tumor detection by microPET/CT imaging in a lung cancer mouse model.

Chitosan-TiO2 composite: A potential 68Ge/68Ga generator column material

A durable and ready to use ⁶⁸Ge-⁶⁸Ga generator column material is required for its routine use in radiopharmaceutical procedures. The present work comprises preliminary studies for development and evaluation of chitosan-TiO₂ based microsphere (C-TOM) composite towards its competence as a column material. The batch uptake studies showed higher distribution coefficients for ⁶⁸Ge vis-à-vis ⁶⁸Ga in the complete concentration range of HCl examined (0.01-1 mol.L^-1). Furthermore, C-TOM showed enduring physical and chemical stability in 0.01 mol.L^-1 HCl with persistent ⁶⁸Ga elution profiles (>95%) and negligible ⁶⁸Ge breakthrough (2 × 10^-4%) for the preliminary evaluation period of ∼2 months. Overall, the studies indicated that, ⁶⁸Ga with high radionuclidic purity (≥99.99%) can be eluted routinely in a small volume (∼1.5 mL) of 0.01 mol.L^-1 HCl proving its potentials as a novel solid phase extractant for ⁶⁸Ge/⁶⁸Ge generator system.

PET radiometals for antibody labeling

Recent advances in molecular characterization of tumors have made possible the emergence of new types of cancer therapies where traditional cytotoxic drugs and nonspecific chemotherapy can be complemented with targeted molecular therapies. One of the main revolutionary treatments is the use of monoclonal antibodies (mAbs) that selectively target the disseminated tumor cells while sparing normal tissues. mAbs and related therapeutics can be efficiently radiolabeled with a wide range of radionuclides to facilitate preclinical and clinical studies. Non-invasive molecular imaging techniques, such as Positron Emission Tomography (PET), using radiolabeled mAbs provide useful information on the whole-body distribution of the biomolecules, which may enable patient stratification, diagnosis, selection of targeted therapies, evaluation of treatment response, and prediction of dose limiting tissue and adverse effects. In addition, when mAbs are labeled with therapeutic radionuclides, the combination of immunological and radiobiological cytotoxicity may result in enhanced treatment efficacy. The pharmacokinetic profile of antibodies demands the use of long half-life isotopes for longitudinal scrutiny of mAb biodistribution and precludes the use of well-stablished short half-life isotopes. Herein, we review the most promising PET radiometals with chemical and physical characteristics that make the appealing for mAb labeling, highlighting those with theranostic radioisotopes.

Initial Clinical Experience with 68Ga-DOTA-NOC Prepared Using 68Ga from Nanoceria-polyacrylonitrile Composite Sorbent-based 68Ge/68Ga Generator and Freeze-dried DOTA-NOC Kits

Somatostatin receptor positron emission tomography–computed tomography (PET/CT) with ⁶⁸Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) peptides have become an indispensable part of disease assessment in patients with neuroendocrine tumors and forms the basis of personalized therapy with peptide receptor-based radionuclide therapy. With growing utilization of PET/CT in developing countries, availability of the indigenous GMP-certified ⁶⁸Ge/⁶⁸Ga generators is expected to further promote cost-effective molecular imaging service to the cancer patients. We present our initial clinical experience in 32 patients injected with ⁶⁸Ga-DOTA-NOC prepared using ⁶⁸Ga eluted from Bhabha Atomic Research Centre nanoceria-polyacrylonitrile sorbent-based ⁶⁸Ge/⁶⁸Ga generator and freeze-dried DOTA-NOC cold kits.

A simple method for preparation of pure 68 Ga-acetate precursor for formulation of radiopharmaceuticals: Physicochemical characteristics of the 68 Ga eluate of the SnO2 based-68 Ge/68 Ga column generator

Gallium-68 radioisotope is an excellent source in clinical positron emission tomography application due to its ease of availability from germanium-68 (⁶⁸ Ge)/gallium-68 (⁶⁸ Ga) generator having a shelf life of 1 year. In this paper, a modified method for purification of the primary eluate of ⁶⁸ Ge-⁶⁸ Ga generator by using a small cation exchange resin (Dowex-50) column has been described. The breakthrough of ⁶⁸ Ge before and after purification of ⁶⁸ Ga eluate was 0.014% and 0.00027%, respectively. The average recovery yield of ⁶⁸ Ga after purification was 84% ± 8.6% (SD, n = 335). The results of the physiochemical studies confirmed that the ⁶⁸ Ga-acetate obtained is suitable for labeling of radiopharmaceuticals.

Synthesis and evaluation of a (68)Ga labeled folic acid derivative for targeting folate receptors

Present work evaluates the potential of a newly synthesized (68)Ga-NOTA-folic acid conjugate for PET imaging of tumors over-expressing folate receptors (FRs). NOTA-folic acid conjugate was synthesized and characterized. It was radiolabeled with (68)Ga in ≥ 95% radiolabeling yields. In vitro cell binding studies showed a maximum cell uptake of 1.7±0.4% per million KB cells which was completely blocked on addition of cold folic acid showing specificity towards the FRs. However, further studies in tumor xenografts are warranted in order to assess the potential of (68)Ga-folic acid complex for imaging tumors over-expressing FRs.

68Ga-Based radiopharmaceuticals: production and application relationship

The contribution of ⁶⁸Ga to the promotion and expansion of clinical research and routine positron emission tomography (PET) for earlier better diagnostics and individualized medicine is considerable. The potential applications of ⁶⁸Ga-comprising imaging agents include targeted, pre-targeted and non-targeted imaging. This review discusses the key aspects of the production of ⁶⁸Ga and ⁶⁸Ga-based radiopharmaceuticals in the light of the impact of regulatory requirements and endpoint pre-clinical and clinical applications.

An overview of radioisotope separation technologies for development of 188W/188Re radionuclide generators providing 188Re to meet future research and clinical demands

Separation technologies for ¹⁸⁸W/¹⁸⁸Re radionuclide generators.

Intrinsically germanium-69-labeled iron oxide nanoparticles: synthesis and in-vivo dual-modality PET/MR imaging

Intrinsically germanium-69-labeled super-paramagnetic iron oxide nanoparticles are synthesized via a newly developed, fast and highly specific chelator-free approach. The biodistribution pattern and the feasibility of (69) Ge-SPION@PEG for in vivo dual-modality positron emission tomography/magnetic resonance (PET/MR) imaging and lymph-node mapping are investigated, which represents the first example of the successful utilization of a (69) Ge-based agent for PET/MR imaging.