Optimized production and quality control of 68Ga-EDTMP for small clinical trials

Evaluation of Safety and Dosimetry of 177Lu-DOTA-ZOL for Therapy of Bone Metastases

Palliative treatment of bone metastasis using radiolabeled bisphosphonates is a well-known concept proven to be safe and effective. A new therapeutic radiopharmaceutical for bone metastasis is 177Lu-DOTA-zoledronic acid (177Lu-DOTA-ZOL). In this study, the safety and dosimetry of a single therapeutic dose of 177Lu-DOTA-ZOL were evaluated on the basis of a series of SPECT/CT images and blood samples. Methods: Nine patients with exclusive bone metastases from metastatic castration-resistant prostate cancer (mCRPC) (70.8 ± 8.4 y) and progression under conventional therapies participated in this prospective study. After receiving 5,780 ± 329 MBq 177Lu-DOTA-ZOL, patients underwent 3-dimensional whole-body SPECT/CT imaging and venous blood sampling over 7 d. Dosimetric evaluation was performed for main organs and tumor lesions. Safety was assessed by blood biomarkers. Results:177Lu-DOTA-ZOL showed fast uptake and high retention in bone lesions and fast clearance from the bloodstream in all patients. The average retention in tumor lesions was 0.02% injected activity per gram at 6 h after injection and approximately 0.01% at 170 h after injection. In this cohort, the average absorbed doses in bone tumor lesions, kidneys, red bone marrow, and bone surfaces were 4.21, 0.17, 0.36, and 1.19 Gy/GBq, respectively. The red marrow was found to be the dose-limiting organ for all patients. A median maximum tolerated injected activity of 6.0 GBq may exceed the defined threshold of 2 Gy for the red bone marrow in individual patients (4/8). Conclusion:177Lu-DOTA-ZOL is safe and has a favorable therapeutic index compared with other radiopharmaceuticals used in the treatment of osteoblastic bone metastases. Personalized dosimetry, however, should be considered to avoid severe hematotoxicity for individual patients.

An Impressive Approach in Nuclear Medicine: Theranostics

Radiometal-based theranostics or theragnostics, first used in the early 2000s, is the combined application of diagnostic and therapeutic agents that target the same molecule, and represents a considerable advancement in nuclear medicine. One of the promising fields related to theranostics is radioligand therapy. For instance, the concepts of targeting the prostate-specific membrane antigen (PSMA) for imaging and therapy in prostate cancer, or somatostatin receptor targeted imaging and therapy in neuroendocrine tumors (NETs) are part of the field of theranostics. Combining targeted imaging and therapy can improve prognostication, therapeutic decision-making, and monitoring of the therapy.

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.

A brief overview of metal complexes as nuclear imaging agents

Metallic radionuclides have been instrumental in the field of nuclear imaging for over half a century. While recent years have played witness to a dramatic rise in the use of radiometals as labels for chelator-bearing biomolecules, imaging agents based solely on coordination compounds of radiometals have long played a critical role in the discipline as well. In this work, we seek to provide a brief overview of metal complex-based radiopharmaceuticals for positron emission tomography (PET) and single photon emission computed tomography (SPECT). More specifically, we have focused on imaging agents in which the metal complex itself rather than a pendant biomolecule or targeting moiety is responsible for the in vivo behavior of the tracer. This family of compounds contains metal complexes based on an array of different nuclides as well as probes that have been used for the imaging of a variety of pathologies, including infection, inflammation, cancer, and heart disease. Indeed, two of the defining traits of transition metal complexes-modularity and redox chemistry-have both been creatively leveraged in the development of imaging agents. In light of our audience, particular attention is paid to structure and mechanism, though clinical data is addressed as well. Ultimately, it is our hope that this review will not only educate readers about some of the seminal work performed in this space over the last 30 years but also spur renewed interest in the creation of radiopharmaceuticals based on small metal complexes.

Mucin-1 aptamer-armed superparamagnetic iron oxide nanoparticles for targeted delivery of doxorubicin to breast cancer cells

Introduction: Superparamagnetic iron oxide nanoparticles (SPIONs) can be functionalized with various agents (e.g., targeting and therapeutic agents) and used for targeted imaging/therapy of cancer. In the present study, we engineered doxorubicin (DOX)-conjugated anti-mucin -1 (MUC-1) aptamer (Ap)-armed PEGylated SPIONs for targeted delivery of DOX molecules to the breast cancer MCF-7 cells. Methods: The SPIONs were synthesized using the thermal decomposition method and modified by polyethylene glycol (PEG) to maximize their biocompatibility and minimize any undesired cytotoxicity effects. Subsequently, DOX molecules were loaded onto the SPIONs, which were further armed with amine-modified MUC-1 aptamer by EDC/NHS chemistry. Results: The morphologic and size analyses of nanoparticles (NPs) by transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed spherical and monodisperse MNPs with a size range of 5-64 nm. The FT-IR spectrophotometry and 1 HNMR analysis confirmed the surface modification of NPs. The cytotoxicity assay of the aptamer-armed MNPs exhibited a higher death rate in the MUC-1 over-expressing MCF-7 cells as compared to the MUC-1 under-expressing MDA-MB-231 cells. The flow cytometry analysis of the engineered Ap-armed SPIONs revealed a higher uptake as compared to the SPIONs alone. Conclusion: Based on our findings, the anti-MUC-1 Ap-armed PEGylated SPIONs loaded with DOX molecules could serve as an effective multifunctional theranostics for simultaneous detection and eradication of MUC-1-positive breast cancer cells.

Production and Clinical Applications of Radiopharmaceuticals and Medical Radioisotopes in Iran

During past 3 decades, nuclear medicine has flourished as vibrant and independent medical specialty in Iran. Since that time, more than 200 nuclear physicians have been trained and now practicing in nearly 158 centers throughout the country. In the same period, Tc-99m generators and variety of cold kits for conventional nuclear medicine were locally produced for the first time. Local production has continued to mature in robust manner while fulfilling international standards. To meet the ever-growing demand at the national level and with international achievements in mind, work for production of other Tc-99m-based peptides such as ubiquicidin, bombesin, octreotide, and more recently a kit formulation for Tc-99m TRODAT-1 for clinical use was introduced. Other than the Tehran Research Reactor, the oldest facility active in production of medical radioisotopes, there is one commercial and three hospital-based cyclotrons currently operational in the country. I-131 has been one of the oldest radioisotope produced in Iran and traditionally used for treatment of thyrotoxicosis and differentiated thyroid carcinoma. Since 2009, (131)I-meta-iodobenzylguanidine has been locally available for diagnostic applications. Gallium-67 citrate, thallium-201 thallous chloride, and Indium-111 in the form of DTPA and Oxine are among the early cyclotron-produced tracers available in Iran for about 2 decades. Rb-81/Kr-81m generator has been available for pulmonary ventilation studies since 1996. Experimental production of PET radiopharmaceuticals began in 1998. This work has culminated with development and optimization of the high-scale production line of (18)F-FDG shortly after installation of PET/CT scanner in 2012. In the field of therapy, other than the use of old timers such as I-131 and different forms of P-32, there has been quite a significant advancement in production and application of therapeutic radiopharmaceuticals in recent years. Application of (131)I-meta-iodobenzylguanidine for treatment of neuroblastoma, pheochromocytoma, and other neuroendocrine tumors has been steadily increasing in major academic university hospitals. Also (153)Sm-EDTMP, (177)Lu-EDTMP, (90)Y-citrate, (90)Y-hydroxyapatite colloid, (188/186)Re-sulfur colloid, and (188/186)Re-HEDP have been locally developed and now routinely available for bone pain palliation and radiosynovectomy. Cu-64 has been available to the nuclear medicine community for some time. With recent reports in diagnostic and therapeutic applications of this agent especially in the field of oncology, we anticipate an expansion in production and availability. The initiation of the production line for gallium-68 generator is one of the latest exciting developments. We are proud that Iran would be joining the club of few nations with production lines for this type of generator. There are also quite a number of SPECT and PET tracers at research and preclinical stage of development preliminarily introduced for possible future clinical applications. Availability of fluorine-18 tracers and gallium-68 generators would no doubt allow rapid dissemination of PET/CT practices in various parts of our large country even far from a cyclotron facility. Also, local production and availability of therapeutic radiopharmaceuticals are going to open exciting horizons in the field of nuclear medicine therapy. Given the available manpower, local infrastructure of SPECT imaging, and rapidly growing population, the production of Tc-99m generators and cold kit would continue to flourish in Iran.

Optimized production, quality control, biological evaluation and PET/CT imaging of 68Ga-PSMA-617 in breast adenocarcinoma model

Optimized production, quality control and preclinical evaluation of 68Ga-PSMA-617 as a PET radiotracer for PSMA-positive malignancies as well as successful application in imaging of breast adenocarcinomas are reported. 68Ga-PSMA-617 radiolabeling and QC optimization, stability, log P, biodistribution in breast adenocarcinomas-bearing mice (direct and blockade studies) and also PET/CT imaging was performed. 68Ga-PSMA-617 complex was prepared in high radiochemical purity (>96%, ITLC, HPLC) and specific activity of 300–310 GBq/mM at 95 °C using 2–4 micrograms of the peptide in 10 min followed by solid phase purification. The tracer was stable in serum and final formulation for at least 120 min. The log P was −1.98. Western blot test on the tumor cell homogenates demonstrated distinct existence of the PSMA on the surface. The biodistribution of the tracer demonstrated specific kidney and tumor significant uptake using blocking study. Significant tumor:blood and tumor:muscle ratio uptake observed at 30 min post-injection (2.69 and 19.1, respectively). A reduction of 40–80% off tumor uptake in the study time period observed using blocking test. 68Ga-PSMA-617 can be proposing a possible tracer for PET imaging of breast adenocarcinomas and other breast malignancies.

Preparation and preclinical evaluation of 68Ga-DOTA-amlodipine for L-type calcium channel imaging

Aim:

In order to develop a possible tracer for L-type calcium channel imaging, we here report the development of a Ga-68 amlodipine derivative for possible PET imaging.

Materials and Methods:

Amlodipine DOTA conjugate was synthesized, characterized and went through calcium channel blockade, toxicity, apoptosis/necrosis tests. [⁶⁸Ga] DOTA AMLO was prepared at optimized conditions followed by stability tests, partition coefficient determination and biodistribution studies using tissue counting and co incidence imaging up to 2 h.

Results:

[⁶⁸Ga] DOTA AMLO was prepared at pH 4–5 in 7–10 min at 95°C in high radiochemical purity (>99%, radio thin layer chromatography; specific activity: 1.9–2.1 GBq/mmol) and was stable up to 4 h with a log P of −0.94. Calcium channel rich tissues including myocardium, and tissues with smooth muscle cells such as colon, intestine, and lungs demonstrated significant uptake. Co incidence images supported the biodistribution data up to 2 h.

Conclusions:

The complex can be a candidate for further positron emission tomography imaging for L type calcium channels.

Preparation and Biological Study of (68)Ga-DOTA-alendronate

Objective(s):

In line with previous research on the development of conjugated bisphosphonate ligands as new bone-avid agents, in this study, DOTA-conjugated alendronate (DOTA-ALN) was synthesized and evaluated after labeling with gallium-68 (⁶⁸Ga).

Methods:

DOTA-ALN was synthesized and characterized, followed by ⁶⁸Ga-DOTA-ALN preparation, using DOTA-ALN and ⁶⁸GaCl₃ (pH: 4-5) at 92-95° C for 10 min. Stability tests, hydroxyapatite assay, partition coefficient calculation, biodistribution studies, and imaging were performed on the developed agent in normal rats.

Results:

The complex was prepared with high radiochemical purity (>99% as depicted by radio thin-layer chromatography; specific activity: 310-320 GBq/mmol) after solid phase purification and was stabilized for up to 90 min with a log P value of -2.91. Maximum ligand binding (65%) was observed in the presence of 50 mg of hydroxyapatite; a major portion of the activity was excreted through the kidneys. With the exception of excretory organs, gastrointestinal tract organs, including the liver, intestine, and colon, showed significant uptake; however, the bone uptake was low (<1%) at 30 min after the injection. The data were also confirmed by sequential imaging at 30-90 min following the intravenous injection.

Conclusion:

The high solubility and anionic properties of the complex led to major renal excretion and low hydroxyapatite uptake; therefore, the complex failed to demonstrate bone imaging behaviors.

Development of a (68)Ga-peptide tracer for PET GnRH1-imaging

OBJECTIVE

Total synthesis, quality control and preclinical evaluation of [(68)Ga]-DOTA-triptorelin ([(68)Ga]-DOTA-TRP) is reported as a possible PET radiotracer for GnRH receptor imaging.

METHODS

DOTA-TRP was totally synthesized in two steps and after characterization went through radiolabelling optimization studies followed by tracer stability. The biodistribution of the tracer in normal male rats and 4T1 tumour-bearing mice was performed in 120 min after i.v. injection.

RESULTS

The peptide and the conjugates were synthesized with >95 % chemical purity. [(68)Ga]-DOTA-TRP complex was prepared in high radiochemical purity (>99 %, ITLC, HPLC) and specific activity of 1400-2100 MBq/nM at 95 °C using 40-60 μg of the peptide in 5-7 min followed by solid phase purification. The IC50 [nM] DOTA-TRP was comparable to the intact peptide, 0.11 ± 0.01 and 0.22 ± 0.05, respectively. The biodistribution of the tracer demonstrated kidney, stomach, and testes significant uptake, all in accordance with GnRH receptor ligands. Significant tumour uptake was observed in 4T1 tumour-bearing female mice 30-120 min post-injection with tumour:blood and tumour:muscle ratios of 28 and >50 in 60 min, respectively. Kidney is rapidly washed from the tracer. [(68)Ga]-DOTA-TRP can be proposed as a possible tracer for GnRH-R imaging studies.