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11 pages, 218 KiB

Open AccessEditorial

Radioactive Molecules 2021–2022

by Svend Borup Jensen

Molecules 2024, 29(1), 265; https://doi.org/10.3390/molecules29010265 - 4 Jan 2024

Cited by 1 | Viewed by 1129

Abstract

In 2020 I was invited to write an editorial review on radioactive molecules published in Molecules in 2019 and 2020 [...] Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

Research

Jump to: Editorial, Review

14 pages, 4629 KiB

Open AccessArticle

Quality Assurance Investigations and Impurity Characterization during Upscaling of [¹⁷⁷Lu]Lu-PSMA^I&T

by Stefan Schmitl, Julia Raitanen, Stephan Witoszynskyj, Eva-Maria Patronas, Lukas Nics, Marius Ozenil, Victoria Weissenböck, Thomas L. Mindt, Marcus Hacker, Wolfgang Wadsak, Marie R. Brandt and Markus Mitterhauser

Molecules 2023, 28(23), 7696; https://doi.org/10.3390/molecules28237696 - 21 Nov 2023

Cited by 1 | Viewed by 1409

Abstract

[¹⁷⁷Lu]Lu-PSMA^I&T is widely used for the radioligand therapy of metastatic castration-resistant prostate cancer (mCRPC). Since this kind of therapy has gained a large momentum in recent years, an upscaled production process yielding multiple patient doses in one batch has been [...] Read more.

[¹⁷⁷Lu]Lu-PSMA^I&T is widely used for the radioligand therapy of metastatic castration-resistant prostate cancer (mCRPC). Since this kind of therapy has gained a large momentum in recent years, an upscaled production process yielding multiple patient doses in one batch has been developed. During upscaling, the established production method as well as the HPLC quality control were challenged. A major finding was a correlation between the specific activity and the formation of a pre-peak, presumably caused by radiolysis. Hence, nonradioactive reference standards were irradiated with an X-ray source and the formed pre-peak was subsequently identified as a deiodination product by UPLC-MS. To confirm the occurrence of the same deiodinated side product in the routine batch, a customized deiodinated precursor was radiolabeled and analyzed with the same HPLC setup, revealing an identical retention time to the pre-peak in the formerly synthesized routine batches. Additionally, further cyclization products of [¹⁷⁷Lu]Lu-PSMA^I&T were identified as major contributors to radiochemical impurities. The comparison of two HPLC methods showed the likelihood of the overestimation of the radiochemical purity during the synthesis of [¹⁷⁷Lu]Lu-PSMA^I&T. Finally, a prospective cost reduction through an optimization of the production process was shown. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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15 pages, 6998 KiB

Open AccessArticle

A Simple Kit for the Good-Manufacturing-Practice Production of [⁶⁸Ga]Ga-EDTA

by Monika Skulska and Lise Falborg

Molecules 2023, 28(16), 6131; https://doi.org/10.3390/molecules28166131 - 18 Aug 2023

Cited by 1 | Viewed by 1655

Abstract

Glomerular filtration rates for individual kidneys can be measured semi-quantitatively by a gamma camera using [^99mTc]Tc-DTPA, with limited diagnostic accuracy. A more precise measurement can be performed on a PET/CT scanner using the radiotracer [⁶⁸Ga]Ga-EDTA, which has been validated [...] Read more.

Glomerular filtration rates for individual kidneys can be measured semi-quantitatively by a gamma camera using [^99mTc]Tc-DTPA, with limited diagnostic accuracy. A more precise measurement can be performed on a PET/CT scanner using the radiotracer [⁶⁸Ga]Ga-EDTA, which has been validated in animal studies. The purpose of this study was to develop an easy kit-based synthesis of [⁶⁸Ga]Ga-EDTA that is compliant with good manufacturing practice (GMP) and applicable for human use. The production of the cold kit and its labeling were validated, as were the radiochemical purity measurement and analytical procedures for determining the Na₂EDTA dihydrate content in the kits. In this study, we validated a GMP kit for the simple production of [⁶⁸Ga]Ga-EDTA, with the intention of applicability for human use. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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22 pages, 6831 KiB

Open AccessArticle

Optimization of Deuteron Irradiation of ¹⁷⁶Yb for Producing ¹⁷⁷Lu of High Specific Activity Exceeding 3000 GBq/mg

by Lin Shao

Molecules 2023, 28(16), 6053; https://doi.org/10.3390/molecules28166053 - 14 Aug 2023

Cited by 2 | Viewed by 1306

Abstract

The irradiation of ¹⁷⁶Yb with deuterons offers a promising pathway for the production of the theranostic radionuclide ¹⁷⁷Lu. To optimize this process, calculations integrating deuteron transport, isotope production, and decay have been performed. In pure ¹⁷⁶Yb, the undesired production of [...] Read more.

The irradiation of ¹⁷⁶Yb with deuterons offers a promising pathway for the production of the theranostic radionuclide ¹⁷⁷Lu. To optimize this process, calculations integrating deuteron transport, isotope production, and decay have been performed. In pure ¹⁷⁶Yb, the undesired production of ^174g+mLu occurs at higher deuteron energies, corresponding to a distribution slightly shallower than that of ¹⁷⁷Lu. Hence, ^174g+mLu can be effectively filtered out by employing either a low-energy deuteron beam or stacked foils. The utilization of stacked foils enables the production of ¹⁷⁷Lu using a high-energy linear accelerator. Another unwanted isotope, ^176mLu, is produced roughly at the same depth as ¹⁷⁷Lu, but its concentration can be significantly reduced by selecting an appropriate post-irradiation processing time, owing to its relatively short half-life. The modeling approach extended to the mapping of yields as a function of irradiation time and post-irradiation processing time. An optimized processing time window was identified. The study demonstrates that a high-energy deuteron beam can be employed to produce ¹⁷⁷Lu with high specific activity exceeding 3000 GBq/mg. The effect of different purity levels (ranging from 98% to 100%) was also discussed. The impurity levels have a slight impact. The modeling demonstrates the feasibility of obtaining ¹⁷⁷Lu with a specific activity > 3000 GBq/mg and radionuclidic purity > 99.5% when using a commercially available ¹⁷⁶Yb target of 99.6% purity. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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11 pages, 1593 KiB

Open AccessArticle

A Reliable Production System of Large Quantities of [¹³N]Ammonia for Multiple Human Injections

by Luis Michel Alonso Martinez, Nabil Naim, Alejandro Hernandez Saiz, José-Mathieu Simard, Mehdi Boudjemeline, Daniel Juneau and Jean N. DaSilva

Molecules 2023, 28(11), 4517; https://doi.org/10.3390/molecules28114517 - 2 Jun 2023

Viewed by 2270

Abstract

[¹³N]Ammonia is one of the most commonly used Positron Emission Tomography (PET) radiotracers in humans to assess myocardial perfusion and measure myocardial blood flow. Here, we report a reliable semi-automated process to manufacture large quantities of [¹³N]ammonia in high [...] Read more.

[¹³N]Ammonia is one of the most commonly used Positron Emission Tomography (PET) radiotracers in humans to assess myocardial perfusion and measure myocardial blood flow. Here, we report a reliable semi-automated process to manufacture large quantities of [¹³N]ammonia in high purity by proton-irradiation of a 10 mM aqueous ethanol solution using an in-target process under aseptic conditions. Our simplified production system is based on two syringe driver units and an in-line anion-exchange purification for up to three consecutive productions of ~30 GBq (~800 mCi) (radiochemical yield = 69 ± 3% n.d.c) per day. The total manufacturing time, including purification, sterile filtration, reformulation, and quality control (QC) analyses performed before batch release, is approximately 11 min from the End of Bombardment (EOB). The drug product complies with FDA/USP specifications and is supplied in a multidose vial allowing for two doses per patient, two patients per batch (4 doses/batch) on two separate PET scanners simultaneously. After four years of use, this production system has proved to be easy to operate and maintain at low costs. Over the last four years, more than 1000 patients have been imaged using this simplified procedure, demonstrating its reliability for the routine production of large quantities of current Good Manufacturing Practices (cGMP)-compliant [¹³N]ammonia for human use. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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19 pages, 1902 KiB

Open AccessArticle

One-Pot Radiosynthesis of [¹⁸F]Anle138b—5-(3-Bromophenyl)-3-(6-[¹⁸F]fluorobenzo[d][1,3]dioxol-5-yl)-1H-pyrazole—A Potential PET Radiotracer Targeting α-Synuclein Aggregates

by Viktoriya V. Orlovskaya, Olga S. Fedorova, Nikolai B. Viktorov, Daria D. Vaulina and Raisa N. Krasikova

Molecules 2023, 28(6), 2732; https://doi.org/10.3390/molecules28062732 - 17 Mar 2023

Cited by 5 | Viewed by 1988

Abstract

Availability of PET imaging radiotracers targeting α-synuclein aggregates is important for early diagnosis of Parkinson’s disease and related α-synucleinopathies, as well as for the development of new therapeutics. Derived from a pyrazole backbone, ¹¹C-labelled derivatives of anle138b (3-(1,3-benzodioxol-5-yl)-5-(3-bromophenyl)-1H-pyrazole)—an inhibitor of [...] Read more.

Availability of PET imaging radiotracers targeting α-synuclein aggregates is important for early diagnosis of Parkinson’s disease and related α-synucleinopathies, as well as for the development of new therapeutics. Derived from a pyrazole backbone, ¹¹C-labelled derivatives of anle138b (3-(1,3-benzodioxol-5-yl)-5-(3-bromophenyl)-1H-pyrazole)—an inhibitor of α-synuclein and prion protein oligomerization—are currently in active development as the candidates for PET imaging α-syn aggregates. This work outlines the synthesis of a radiotracer based on the original structure of anle138b, labelled with fluorine-18 isotope, eminently suitable for PET imaging due to half-life and decay energy characteristics (97% β+ decay, 109.7 min half-life, and 635 keV positron energy). A three-step radiosynthesis was developed starting from 6-[¹⁸F]fluoropiperonal (6-[¹⁸F]FP) that was prepared using (piperonyl)(phenyl)iodonium bromide as a labelling precursor. The obtained 6-[¹⁸F]FP was used directly in the condensation reaction with tosylhydrazide followed by 1,3-cycloaddition of the intermediate with 3′-bromophenylacetylene eliminating any midway without any intermediate purifications. This one-pot approach allowed the complete synthesis of [¹⁸F]anle138b within 105 min with RCY of 15 ± 3% (n = 3) and A_m in the range of 32–78 GBq/µmol. The [¹⁸F]fluoride processing and synthesis were performed in a custom-built semi-automated module, but the method can be implemented in all the modern automated platforms. While there is definitely space for further optimization, the procedure developed is well suited for preclinical studies of this novel radiotracer in animal models and/or cell cultures. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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19 pages, 4357 KiB

Open AccessArticle

Dissolution of Molybdenum in Hydrogen Peroxide: A Thermodynamic, Kinetic and Microscopic Study of a Green Process for ^99mTc Production

by Flavio Cicconi, Alberto Ubaldini, Angela Fiore, Antonietta Rizzo, Sebastiano Cataldo, Pietro Agostini, Antonino Pietropaolo, Stefano Salvi, Vincenzo Cuzzola and on behalf of the SRF Collaboration

Molecules 2023, 28(5), 2090; https://doi.org/10.3390/molecules28052090 - 23 Feb 2023

Cited by 5 | Viewed by 3032

Abstract

^99mTc-based radiopharmaceuticals are the most commonly used medical radioactive tracers in nuclear medicine for diagnostic imaging. Due to the expected global shortage of ⁹⁹Mo, the parent radionuclide from which ^99mTc is produced, new production methods should be developed. The SORGENTINA-RF [...] Read more.

^99mTc-based radiopharmaceuticals are the most commonly used medical radioactive tracers in nuclear medicine for diagnostic imaging. Due to the expected global shortage of ⁹⁹Mo, the parent radionuclide from which ^99mTc is produced, new production methods should be developed. The SORGENTINA-RF (SRF) project aims at developing a prototypical medium-intensity D-T 14-MeV fusion neutron source specifically designed for production of medical radioisotopes with a focus on ⁹⁹Mo. The scope of this work was to develop an efficient, cost-effective and green procedure for dissolution of solid molybdenum in hydrogen peroxide solutions compatible for ^99mTc production via the SRF neutron source. The dissolution process was extensively studied for two different target geometries: pellets and powder. The first showed better characteristics and properties for the dissolution procedure, and up to 100 g of pellets were successfully dissolved in 250–280 min. The dissolution mechanism on the pellets was investigated by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. After the procedure, sodium molybdate crystals were characterized via X-ray diffraction, Raman and infrared spectroscopy and the high purity of the compound was established by means of inductively coupled plasma mass spectroscopy. The study confirmed the feasibility of the procedure for production of ^99mTc in SRF as it is very cost-effective, with minimal consumption of peroxide and controlled low temperature. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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9 pages, 1221 KiB

Open AccessArticle

Development of in-House Synthesis and Quality Control of [^99mTc]Tc-PSMA-I&S

by Elisabeth Plhak, Christopher Pichler, Edith Gößnitzer, Reingard M. Aigner and Herbert Kvaternik

Molecules 2023, 28(2), 577; https://doi.org/10.3390/molecules28020577 - 6 Jan 2023

Cited by 1 | Viewed by 2098

Abstract

Many radioactive PSMA inhibitory substances have already been developed for PET diagnostics and therapy of prostate cancer. Because PET radionuclides and instrumentation may not be available, technetium-99 m labelled tracers can be considered as a diagnostic alternative. A suitable tracer is [^99m [...] Read more.

Many radioactive PSMA inhibitory substances have already been developed for PET diagnostics and therapy of prostate cancer. Because PET radionuclides and instrumentation may not be available, technetium-99 m labelled tracers can be considered as a diagnostic alternative. A suitable tracer is [^99mTc]Tc-PSMA-I&S, primarily developed for radio-guided surgery, which has been identified for diagnostics of prostate cancer. However, there is no commercial kit approved for the preparation of [^99mTc]Tc-PSMA-I&S on the market. This work presents an automated process for the synthesis of [^99mTc]Tc-PSMA-I&S concerning good manufacturing practice (GMP). We used a Scintomics GRP 4 V module, with the SCC software package for programming sequences for this development. The optimum reaction conditions were evaluated in preliminary experiments. The pH of the reaction solution was found to be crucial for the radiochemical yield and radiochemical purity. The validation of [^99mTc]Tc-PSMA-I&S (n = 3) achieved a stable radiochemical yield of 58.7 ± 1.5% and stable radiochemical purities of 93.0 ± 0.3%. The amount of free [^99mTc]TcO₄⁻ in the solution and reduced hydrolysed [^99mTc]TcO₂ was <2%. Our automated preparation of [^99mTc]Tc-PSMA-I&S has shown reliability and applicability in the clinical setting. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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14 pages, 1758 KiB

Open AccessCommunication

PET Imaging of Fructose Metabolism in a Rodent Model of Neuroinflammation with 6-[¹⁸F]fluoro-6-deoxy-D-fructose

by Amanda J. Boyle, Emily Murrell, Junchao Tong, Christin Schifani, Andrea Narvaez, Melinda Wuest, Frederick West, Frank Wuest and Neil Vasdev

Molecules 2022, 27(23), 8529; https://doi.org/10.3390/molecules27238529 - 3 Dec 2022

Cited by 7 | Viewed by 2687

Abstract

Fluorine-18 labeled 6-fluoro-6-deoxy-D-fructose (6-[¹⁸F]FDF) targets the fructose-preferred facilitative hexose transporter GLUT5, which is expressed predominantly in brain microglia and activated in response to inflammatory stimuli. We hypothesize that 6-[¹⁸F]FDF will specifically image microglia following neuroinflammatory insult. 6-[¹⁸F]FDF [...] Read more.

Fluorine-18 labeled 6-fluoro-6-deoxy-D-fructose (6-[¹⁸F]FDF) targets the fructose-preferred facilitative hexose transporter GLUT5, which is expressed predominantly in brain microglia and activated in response to inflammatory stimuli. We hypothesize that 6-[¹⁸F]FDF will specifically image microglia following neuroinflammatory insult. 6-[¹⁸F]FDF and, for comparison, [¹⁸F]FDG were evaluated in unilateral intra-striatal lipopolysaccharide (LPS)-injected male and female rats (50 µg/animal) by longitudinal dynamic PET imaging in vivo. In LPS-injected rats, increased accumulation of 6-[¹⁸F]FDF was observed at 48 h post-LPS injection, with plateaued uptake (60–120 min) that was significantly higher in the ipsilateral vs. contralateral striatum (0.985 ± 0.047 and 0.819 ± 0.033 SUV, respectively; p = 0.002, n = 4M/3F). The ipsilateral–contralateral difference in striatal 6-[¹⁸F]FDF uptake expressed as binding potential (BP_SRTM) peaked at 48 h (0.19 ± 0.11) and was significantly decreased at one and two weeks. In contrast, increased [¹⁸F]FDG uptake in the ipsilateral striatum was highest at one week post-LPS injection (BP_SRTM = 0.25 ± 0.06, n = 4M). Iba-1 and GFAP immunohistochemistry confirmed LPS-induced activation of microglia and astrocytes, respectively, in ipsilateral striatum. This proof-of-concept study revealed an early response of 6-[¹⁸F]FDF to neuroinflammatory stimuli in rat brain. 6-[¹⁸F]FDF represents a potential PET radiotracer for imaging microglial GLUT5 density in brain with applications in neuroinflammatory and neurodegenerative diseases. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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14 pages, 3388 KiB

Open AccessArticle

Recovery of Gallium-68 and Zinc from HNO₃-Based Solution by Liquid–Liquid Extraction with Arylamino Phosphonates

by Fedor Zhuravlev, Arif Gulzar and Lise Falborg

Molecules 2022, 27(23), 8377; https://doi.org/10.3390/molecules27238377 - 1 Dec 2022

Cited by 5 | Viewed by 2187

Abstract

The cyclotron production of gallium-68 via the ⁶⁸Zn(p,n)⁶⁸Ga nuclear reaction in liquid targets is gaining significant traction in clinics. This work describes (1) the synthesis of new arylamino phosphonates via the Kabachnik–Fields reaction, (2) their use for liquid–liquid [...] Read more.

The cyclotron production of gallium-68 via the ⁶⁸Zn(p,n)⁶⁸Ga nuclear reaction in liquid targets is gaining significant traction in clinics. This work describes (1) the synthesis of new arylamino phosphonates via the Kabachnik–Fields reaction, (2) their use for liquid–liquid extraction of ⁶⁸Ga from 1 M Zn(NO₃)₂/0.01 M HNO₃ in batch and continuous flow, and (3) the use of Raman spectroscopy as a process analytical technology (PAT) tool for in-line measurement of ⁶⁸Zn. The highest extraction efficiencies were obtained with the extractants functionalized with trifluoromethyl substituents and ethylene glycol ponytails, which were able to extract up to 90% of gallium-68 in batch and 80% in flow. Only ppm amounts of zinc were co-extracted. The extraction efficiency was a function of pKa and the aqueous solubility of the extractant and showed marked concentration, solvent, and temperature dependence. Raman spectroscopy was found to be a promising PAT tool for the continuous production of gallium-68. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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16 pages, 2235 KiB

Open AccessArticle

Rapid Purification and Formulation of Radiopharmaceuticals via Thin-Layer Chromatography

by Travis S. Laferriere-Holloway, Alejandra Rios, Giuseppe Carlucci and R. Michael van Dam

Molecules 2022, 27(23), 8178; https://doi.org/10.3390/molecules27238178 - 24 Nov 2022

Cited by 2 | Viewed by 5736

Abstract

Before formulating radiopharmaceuticals for injection, it is necessary to remove various impurities via purification. Conventional synthesis methods involve relatively large quantities of reagents, requiring high-resolution and high-capacity chromatographic methods (e.g., semi-preparative radio-HPLC) to ensure adequate purity of the radiopharmaceutical. Due to the use [...] Read more.

Before formulating radiopharmaceuticals for injection, it is necessary to remove various impurities via purification. Conventional synthesis methods involve relatively large quantities of reagents, requiring high-resolution and high-capacity chromatographic methods (e.g., semi-preparative radio-HPLC) to ensure adequate purity of the radiopharmaceutical. Due to the use of organic solvents during purification, additional processing is needed to reformulate the radiopharmaceutical into an injectable buffer. Recent developments in microscale radiosynthesis have made it possible to synthesize radiopharmaceuticals with vastly reduced reagent masses, minimizing impurities. This enables purification with lower-capacity methods, such as analytical HPLC, with a reduction of purification time and volume (that shortens downstream re-formulation). Still, the need for a bulky and expensive HPLC system undermines many of the advantages of microfluidics. This study demonstrates the feasibility of using radio-TLC for the purification of radiopharmaceuticals. This technique combines high-performance (high-resolution, high-speed separation) with the advantages of a compact and low-cost setup. A further advantage is that no downstream re-formulation step is needed. Production and purification of clinical scale batches of [¹⁸F]PBR-06 and [¹⁸F]Fallypride are demonstrated with high yield, purity, and specific activity. Automating this radio-TLC method could provide an attractive solution for the purification step in microscale radiochemistry systems. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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25 pages, 4796 KiB

Open AccessArticle

Preparation, Optimisation, and In Vitro Evaluation of [¹⁸F]AlF-NOTA-Pamidronic Acid for Bone Imaging PET

by Hishar Hassan, Muhamad Faiz Othman, Hairil Rashmizal Abdul Razak, Zainul Amiruddin Zakaria, Fathinul Fikri Ahmad Saad, Mohd Azuraidi Osman, Loh Hui Yi, Zarif Ashhar, Jaleezah Idris, Mohd Hamdi Noor Abdul Hamid and Zaitulhusna M. Safee

Molecules 2022, 27(22), 7969; https://doi.org/10.3390/molecules27227969 - 17 Nov 2022

Cited by 2 | Viewed by 2278

Abstract

[¹⁸F]sodium fluoride ([¹⁸F]NaF) is recognised to be superior to [⁹⁹mTc]-methyl diphosphate ([^99mTc]Tc-MDP) and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in bone imaging. However, there is concern that [¹⁸F]NaF uptake is not cancer-specific, leading [...] Read more.

[¹⁸F]sodium fluoride ([¹⁸F]NaF) is recognised to be superior to [⁹⁹mTc]-methyl diphosphate ([^99mTc]Tc-MDP) and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in bone imaging. However, there is concern that [¹⁸F]NaF uptake is not cancer-specific, leading to a higher number of false-positive interpretations. Therefore, in this work, [¹⁸F]AlF-NOTA-pamidronic acid was prepared, optimised, and tested for its in vitro uptake. NOTA-pamidronic acid was prepared by an N-Hydroxysuccinimide (NHS) ester strategy and validated by liquid chromatography-mass spectrometry analysis (LC-MS/MS). Radiolabeling of [¹⁸F]AlF-NOTA-pamidronic acid was optimised, and it was ensured that all quality control analysis requirements for the radiopharmaceuticals were met prior to the in vitro cell uptake studies. NOTA-pamidronic acid was successfully prepared and radiolabeled with ¹⁸F. The radiolabel was prepared in a 1:1 molar ratio of aluminium chloride (AlCl₃) to NOTA-pamidronic acid and heated at 100 °C for 15 min in the presence of 50% ethanol (v/v), which proved to be optimal. The preliminary in vitro results of the binding of the hydroxyapatite showed that [¹⁸F]AlF-NOTA-pamidronic acid was as sensitive as [¹⁸F]sodium fluoride ([¹⁸F]NaF). Normal human osteoblast cell lines (hFOB 1.19) and human osteosarcoma cell lines (Saos-2) were used for the in vitro cellular uptake studies. It was found that [¹⁸F]NaF was higher in both cell lines, but [¹⁸F]AlF-NOTA-pamidronic acid showed promising cellular uptake in Saos-2. The preliminary results suggest that further preclinical studies of [¹⁸F]AlF-NOTA-pamidronic acid are needed before it is transferred to clinical research. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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9 pages, 876 KiB

Open AccessArticle

Preparation and Evaluation of [¹⁸F]AlF-NOTA-NOC for PET Imaging of Neuroendocrine Tumors: Comparison to [⁶⁸Ga]Ga-DOTA/NOTA-NOC

by Johan Hygum Dam, Niels Langkjær, Christina Baun, Birgitte Brinkmann Olsen, Aaraby Yoheswaran Nielsen and Helge Thisgaard

Molecules 2022, 27(20), 6818; https://doi.org/10.3390/molecules27206818 - 12 Oct 2022

Cited by 2 | Viewed by 2715

Abstract

Background: The somatostatin receptors 1–5 are overexpressed on neuroendocrine neoplasms and, as such, represent a favorable target for molecular imaging. This study investigates the potential of [¹⁸F]AlF-NOTA-[1-Nal³]-Octreotide and compares it in vivo to DOTA- and NOTA-[1-Nal³]-Octreotide radiolabeled [...] Read more.

Background: The somatostatin receptors 1–5 are overexpressed on neuroendocrine neoplasms and, as such, represent a favorable target for molecular imaging. This study investigates the potential of [¹⁸F]AlF-NOTA-[1-Nal³]-Octreotide and compares it in vivo to DOTA- and NOTA-[1-Nal³]-Octreotide radiolabeled with gallium-68. Methods: DOTA- and NOTA-NOC were radiolabeled with gallium-68 and NOTA-NOC with [¹⁸F]AlF. Biodistributions of the three radioligands were evaluated in AR42J xenografted mice at 1 h p.i and for [¹⁸F]AlF at 3 h p.i. Preclinical PET/CT was applied to confirm the general uptake pattern. Results: Gallium-68 was incorporated into DOTA- and NOTA-NOC in yields and radiochemical purities greater than 96.5%. NOTA-NOC was radiolabeled with [¹⁸F]AlF in yields of 38 ± 8% and radiochemical purity above 99% after purification. The biodistribution in tumor-bearing mice showed a high uptake in tumors of 26.4 ± 10.8 %ID/g for [⁶⁸Ga]Ga-DOTA-NOC and 25.7 ± 5.8 %ID/g for [⁶⁸Ga]Ga-NOTA-NOC. Additionally, [¹⁸F]AlF-NOTA-NOC exhibited a tumor uptake of 37.3 ± 10.5 %ID/g for [¹⁸F]AlF-NOTA-NOC, which further increased to 42.1 ± 5.3 %ID/g at 3 h p.i. Conclusions: The high tumor uptake of all radioligands was observed. However, [¹⁸F]AlF-NOTA-NOC surpassed the other clinically well-established radiotracers in vivo, especially at 3 h p.i. The tumor-to-blood and -liver ratios increased significantly over three hours for [¹⁸F]AlF-NOTA-NOC, making it possible to detect liver metastases. Therefore, [¹⁸F]AlF demonstrates promise as a surrogate pseudo-radiometal to gallium-68. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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12 pages, 1803 KiB

Open AccessArticle

Effective Preparation of [¹⁸F]Flumazenil Using Copper-Mediated Late-Stage Radiofluorination of a Stannyl Precursor

by Mohammad B. Haskali, Peter D. Roselt, Terence J. O’Brien, Craig A. Hutton, Idrish Ali, Lucy Vivash and Bianca Jupp

Molecules 2022, 27(18), 5931; https://doi.org/10.3390/molecules27185931 - 13 Sep 2022

Cited by 5 | Viewed by 2372

Abstract

(1) Background: [¹⁸F]Flumazenil 1 ([¹⁸F]FMZ) is an established positron emission tomography (PET) radiotracer for the imaging of the gamma-aminobutyric acid (GABA) receptor subtype, GABA_A in the brain. The production of [¹⁸F]FMZ 1 for its clinical use [...] Read more.

(1) Background: [¹⁸F]Flumazenil 1 ([¹⁸F]FMZ) is an established positron emission tomography (PET) radiotracer for the imaging of the gamma-aminobutyric acid (GABA) receptor subtype, GABA_A in the brain. The production of [¹⁸F]FMZ 1 for its clinical use has proven to be challenging, requiring harsh radiochemical conditions, while affording low radiochemical yields. Fully characterized, new methods for the improved production of [¹⁸F]FMZ 1 are needed. (2) Methods: We investigate the use of late-stage copper-mediated radiofluorination of aryl stannanes to improve the production of [¹⁸F]FMZ 1 that is suitable for clinical use. Mass spectrometry was used to identify the chemical by-products that were produced under the reaction conditions. (3) Results: The radiosynthesis of [¹⁸F]FMZ 1 was fully automated using the iPhase FlexLab radiochemistry module, affording a 22.2 ± 2.7% (n = 5) decay-corrected yield after 80 min. [¹⁸F]FMZ 1 was obtained with a high radiochemical purity (>98%) and molar activity (247.9 ± 25.9 GBq/µmol). (4) Conclusions: The copper-mediated radiofluorination of the stannyl precursor is an effective strategy for the production of clinically suitable [¹⁸F]FMZ 1. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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10 pages, 409 KiB

Open AccessArticle

Dosimetry of [²¹²Pb]VMT01, a MC1R-Targeted Alpha Therapeutic Compound, and Effect of Free ²⁰⁸Tl on Tissue Absorbed Doses

by Kelly D. Orcutt, Kelly E. Henry, Christine Habjan, Keryn Palmer, Jack Heimann, Julie M. Cupido, Vijay Gottumukkala, Derek D. Cissell, Morgan C. Lyon, Amira I. Hussein, Dijie Liu, Mengshi Li, Frances L. Johnson and Michael K. Schultz

Molecules 2022, 27(18), 5831; https://doi.org/10.3390/molecules27185831 - 8 Sep 2022

Cited by 3 | Viewed by 4554

Abstract

[²¹²Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. ²¹²Pb has an elementally matched gamma-emitting isotope ²⁰³Pb; thus, [²⁰³Pb]VMT01 can be used as an imaging surrogate for [...] Read more.

[²¹²Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. ²¹²Pb has an elementally matched gamma-emitting isotope ²⁰³Pb; thus, [²⁰³Pb]VMT01 can be used as an imaging surrogate for [²¹²Pb]VMT01. [²¹²Pb]VMT01 human serum stability studies have demonstrated retention of the ²¹²Bi daughter within the chelator following beta emission of parent ²¹²Pb. However, the subsequent alpha emission from the decay of ²¹²Bi into ²⁰⁸Tl results in the generation of free ²⁰⁸Tl. Due to the 10.64-hour half-life of ²¹²Pb, accumulation of free ²⁰⁸Tl in the injectate will occur. The goal of this work is to estimate the human dosimetry for [²¹²Pb]VMT01 and the impact of free ²⁰⁸Tl in the injectate on human tissue absorbed doses. Human [²¹²Pb]VMT01 tissue absorbed doses were estimated from murine [²⁰³Pb]VMT01 biodistribution data, and human biodistribution values for ²⁰¹Tl chloride (a cardiac imaging agent) from published data were used to estimate the dosimetry of free ²⁰⁸Tl. Results indicate that the dose-limiting tissues for [²¹²Pb]VMT01 are the red marrow and the kidneys, with estimated absorbed doses of 1.06 and 8.27 mGy_{RBE = 5}/MBq. The estimated percent increase in absorbed doses from free ²⁰⁸Tl in the injectate is 0.03% and 0.09% to the red marrow and the kidneys, respectively. Absorbed doses from free ²⁰⁸Tl result in a percent increase of no more than 1.2% over [²¹²Pb]VMT01 in any organ or tissue. This latter finding indicates that free ²⁰⁸Tl in the [²¹²Pb]VMT01 injectate will not substantially impact estimated tissue absorbed doses in humans. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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15 pages, 2252 KiB

Open AccessArticle

Production and Quality Control of [¹⁷⁷Lu]Lu-PSMA-I&T: Development of an Investigational Medicinal Product Dossier for Clinical Trials

by Valentina Di Iorio, Stefano Boschi, Cristina Cuni, Manuela Monti, Stefano Severi, Giovanni Paganelli and Carla Masini

Molecules 2022, 27(13), 4143; https://doi.org/10.3390/molecules27134143 - 28 Jun 2022

Cited by 8 | Viewed by 3213

Abstract

Since prostate cancer is the most commonly diagnosed malignancy in men, the theranostic approach has become very attractive since the discovery of urea-based PSMA inhibitors. Different molecules have been synthesized starting from the Glu-urea-Lys scaffold as the pharmacophore and then optimizing the linker [...] Read more.

Since prostate cancer is the most commonly diagnosed malignancy in men, the theranostic approach has become very attractive since the discovery of urea-based PSMA inhibitors. Different molecules have been synthesized starting from the Glu-urea-Lys scaffold as the pharmacophore and then optimizing the linker and the chelate to improve functional characteristics. This article aimed to highlight the quality aspects, which could have an impact on clinical practice, describing the development of an Investigational Medicinal Product Dossier (IMPD) for clinical trials with [¹⁷⁷Lu]Lu-PSMA-I&T in prostate cancer and other solid tumors expressing PSMA. The results highlighted some important quality issues of the final preparation: radiolabeling of PSMA-I&T with lutetium-177 needs a considerably longer time compared with the radiolabeling of the well-known [¹⁷⁷Lu]Lu-PSMA-617. When the final product was formulated in saline, the stability of [¹⁷⁷Lu]Lu-PSMA-I&T was reduced by radiolysis, showing a decrease in radiochemical purity (<95% in 24 h). Different formulations of the final product with increasing concentrations of ascorbic acid have been tested to counteract radiolysis and extend stability. A solution of 20 mg/mL of ascorbic acid in saline prevents radiolysis and ensures stability over 30 h. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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9 pages, 769 KiB

Open AccessArticle

Issues with the European Pharmacopoeia Quality Control Method for ^99mTc-Labelled Macroaggregated Albumin

by Svend Borup Jensen, Lotte Studsgaard Meyer, Nikolaj Schandorph Nielsen and Søren Steen Nielsen

Molecules 2022, 27(13), 3997; https://doi.org/10.3390/molecules27133997 - 22 Jun 2022

Cited by 1 | Viewed by 1985

Abstract

Technetium-99m macroaggregated albumin ([^99mTc]Tc-MAA) is an injectable radiopharmaceutical used in nuclear medicine for lung perfusion scintigraphy. After changing to a new batch of macroaggregated albumin (MAA), we saw unwanted uptake in the liver and spleen. The batch was therefore tested by [...] Read more.

Technetium-99m macroaggregated albumin ([^99mTc]Tc-MAA) is an injectable radiopharmaceutical used in nuclear medicine for lung perfusion scintigraphy. After changing to a new batch of macroaggregated albumin (MAA), we saw unwanted uptake in the liver and spleen. The batch was therefore tested by both the supplier and us and we found it to comply with the requirements of the European Pharmacopoeia (Ph. Eur.). However, a simple comparison between the problematic batch and a batch supplied by another manufacturer showed that there was a significant difference. The quality testing showed a higher number of small particles in the problem encumbered MAA batch with unwanted in vivo uptake. In this article we present a simple method of testing for particle size of [^99mTc]Tc-MAA, which gives a good indication of how the radioactive drug performs in vivo. We argue that the quality control method described in the Ph. Eur. should be changed. The changes will improve concordance between the laboratory analyzes and what is seen in vivo in human lung perfusion scintigraphy. Furthermore, we hope that the MAA suppliers without delay will replace their release procedure to be in accordance with the method described in this article. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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9 pages, 848 KiB

Open AccessArticle

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

by Costantina Maisto, Michela Aurilio, Anna Morisco, Roberta de Marino, Monica Josefa Buonanno Recchimuzzo, Luciano Carideo, Laura D’Ambrosio, Francesca Di Gennaro, Aureliana Esposito, Paolo Gaballo, Valentina Pirozzi Palmese, Valentina Porfidia, Marco Raddi, Alfredo Rossi, Elisabetta Squame and Secondo Lastoria

Molecules 2022, 27(12), 3862; https://doi.org/10.3390/molecules27123862 - 16 Jun 2022

Cited by 12 | Viewed by 3532

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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16 pages, 2393 KiB

Open AccessArticle

Synthesis and Evaluation of ¹¹C-Labeled Triazolones as Probes for Imaging Fatty Acid Synthase Expression by Positron Emission Tomography

by James M. Kelly, Thomas M. Jeitner, Nicole N. Waterhouse, Wenchao Qu, Ethan J. Linstad, Banafshe Samani, Clarence Williams, Jr., Anastasia Nikolopoulou, Alejandro Amor-Coarasa, Stephen G. DiMagno and John W. Babich

Molecules 2022, 27(5), 1552; https://doi.org/10.3390/molecules27051552 - 25 Feb 2022

Viewed by 2335

Abstract

Cancer cells require lipids to fulfill energetic, proliferative, and signaling requirements. Even though these cells can take up exogenous fatty acids, the majority exhibit a dependency on de novo fatty acid synthesis. Fatty acid synthase (FASN) is the rate-limiting enzyme in this process. [...] Read more.

Cancer cells require lipids to fulfill energetic, proliferative, and signaling requirements. Even though these cells can take up exogenous fatty acids, the majority exhibit a dependency on de novo fatty acid synthesis. Fatty acid synthase (FASN) is the rate-limiting enzyme in this process. Expression and activity of FASN is elevated in multiple cancers, where it correlates with disease progression and poor prognosis. These observations have sparked interest in developing methods of detecting FASN expression in vivo. One promising approach is the imaging of radiolabeled molecular probes targeting FASN by positron emission tomography (PET). However, although [¹¹C]acetate uptake by prostate cancer cells correlates with FASN expression, no FASN-specific PET probes currently exist. Our aim was to synthesize and evaluate a series of small molecule triazolones based on GSK2194069, an FASN inhibitor with IC₅₀ = 7.7 ± 4.1 nM, for PET imaging of FASN expression. These triazolones were labeled with carbon-11 in good yield and excellent radiochemical purity, and binding to FASN-positive LNCaP cells was significantly higher than FASN-negative PC3 cells. Despite these promising characteristics, however, these molecules exhibited poor in vivo pharmacokinetics and were predominantly retained in lymph nodes and the hepatobiliary system. Future studies will seek to identify structural modifications that improve tumor targeting while maintaining the excretion profile of these first-generation ¹¹C-methyltriazolones. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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Review

Jump to: Editorial, Research

16 pages, 2950 KiB

Open AccessReview

Bench to Bedside Development of [¹⁸F]Fluoromethyl-(1,2-²H₄)choline ([¹⁸F]D4-FCH)

by Amarnath Challapalli, Tara D. Barwick, Suraiya R. Dubash, Marianna Inglese, Matthew Grech-Sollars, Kasia Kozlowski, Henry Tam, Neva H. Patel, Mathias Winkler, Penny Flohr, Azeem Saleem, Amit Bahl, Alison Falconer, Johann S. De Bono, Eric O. Aboagye and Stephen Mangar

Molecules 2023, 28(24), 8018; https://doi.org/10.3390/molecules28248018 - 8 Dec 2023

Cited by 1 | Viewed by 1593

Abstract

Malignant transformation is characterised by aberrant phospholipid metabolism of cancers, associated with the upregulation of choline kinase alpha (CHKα). Due to the metabolic instability of choline radiotracers and the increasing use of late-imaging protocols, we developed a more stable choline radiotracer, [¹⁸ [...] Read more.

Malignant transformation is characterised by aberrant phospholipid metabolism of cancers, associated with the upregulation of choline kinase alpha (CHKα). Due to the metabolic instability of choline radiotracers and the increasing use of late-imaging protocols, we developed a more stable choline radiotracer, [¹⁸F]fluoromethyl-[1,2-²H₄]choline ([¹⁸F]D4-FCH). [¹⁸F]D4-FCH has improved protection against choline oxidase, the key choline catabolic enzyme, via a ¹H/²D isotope effect, together with fluorine substitution. Due to the promising mechanistic and safety profiles of [¹⁸F]D4-FCH in vitro and preclinically, the radiotracer has transitioned to clinical development. [¹⁸F]D4-FCH is a safe positron emission tomography (PET) tracer, with a favourable radiation dosimetry profile for clinical imaging. [¹⁸F]D4-FCH PET/CT in lung and prostate cancers has shown highly heterogeneous intratumoral distribution and large lesion variability. Treatment with abiraterone or enzalutamide in metastatic castrate-resistant prostate cancer patients elicited mixed responses on PET at 12–16 weeks despite predominantly stable radiological appearances. The sum of the weighted tumour-to-background ratios (TBRs-wsum) was associated with the duration of survival. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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21 pages, 3559 KiB

Open AccessReview

Recent Developments in Carbon-11 Chemistry and Applications for First-In-Human PET Studies

by Anna Pees, Melissa Chassé, Anton Lindberg and Neil Vasdev

Molecules 2023, 28(3), 931; https://doi.org/10.3390/molecules28030931 - 17 Jan 2023

Cited by 7 | Viewed by 3524

Abstract

Positron emission tomography (PET) is a molecular imaging technique that makes use of radiolabelled molecules for in vivo evaluation. Carbon-11 is a frequently used radionuclide for the labelling of small molecule PET tracers and can be incorporated into organic molecules without changing their [...] Read more.

Positron emission tomography (PET) is a molecular imaging technique that makes use of radiolabelled molecules for in vivo evaluation. Carbon-11 is a frequently used radionuclide for the labelling of small molecule PET tracers and can be incorporated into organic molecules without changing their physicochemical properties. While the short half-life of carbon-11 (¹¹C; t_½ = 20.4 min) offers other advantages for imaging including multiple PET scans in the same subject on the same day, its use is limited to facilities that have an on-site cyclotron, and the radiochemical transformations are consequently more restrictive. Many researchers have embraced this challenge by discovering novel carbon-11 radiolabelling methodologies to broaden the synthetic versatility of this radionuclide. This review presents new carbon-11 building blocks and radiochemical transformations as well as PET tracers that have advanced to first-in-human studies over the past five years. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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20 pages, 3915 KiB

Open AccessReview

Radionuclides for Targeted Therapy: Physical Properties

by Caroline Stokke, Monika Kvassheim and Johan Blakkisrud

Molecules 2022, 27(17), 5429; https://doi.org/10.3390/molecules27175429 - 25 Aug 2022

Cited by 27 | Viewed by 4466

Abstract

A search in PubMed revealed that 72 radionuclides have been considered for molecular or functional targeted radionuclide therapy. As radionuclide therapies increase in number and variations, it is important to understand the role of the radionuclide and the various characteristics that can render [...] Read more.

A search in PubMed revealed that 72 radionuclides have been considered for molecular or functional targeted radionuclide therapy. As radionuclide therapies increase in number and variations, it is important to understand the role of the radionuclide and the various characteristics that can render it either useful or useless. This review focuses on the physical characteristics of radionuclides that are relevant for radionuclide therapy, such as linear energy transfer, relative biological effectiveness, range, half-life, imaging properties, and radiation protection considerations. All these properties vary considerably between radionuclides and can be optimised for specific targets. Properties that are advantageous for some applications can sometimes be drawbacks for others; for instance, radionuclides that enable easy imaging can introduce more radiation protection concerns than others. Similarly, a long radiation range is beneficial in targets with heterogeneous uptake, but it also increases the radiation dose to tissues surrounding the target, and, hence, a shorter range is likely more beneficial with homogeneous uptake. While one cannot select a collection of characteristics as each radionuclide comes with an unchangeable set, all the 72 radionuclides investigated for therapy—and many more that have not yet been investigated—provide numerous sets to choose between. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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20 pages, 954 KiB

Open AccessReview

Production Review of Accelerator-Based Medical Isotopes

by Yiwei Wang, Daiyuan Chen, Ricardo dos Santos Augusto, Jixin Liang, Zhi Qin, Juntao Liu and Zhiyi Liu

Molecules 2022, 27(16), 5294; https://doi.org/10.3390/molecules27165294 - 19 Aug 2022

Cited by 13 | Viewed by 4852

Abstract

The production of reactor-based medical isotopes is fragile, which has meant supply shortages from time to time. This paper reviews alternative production methods in the form of cyclotrons, linear accelerators and neutron generators. Finally, the status of the production of medical isotopes in [...] Read more.

The production of reactor-based medical isotopes is fragile, which has meant supply shortages from time to time. This paper reviews alternative production methods in the form of cyclotrons, linear accelerators and neutron generators. Finally, the status of the production of medical isotopes in China is described. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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16 pages, 1105 KiB

Open AccessReview

Radiopharmaceutical Treatments for Cancer Therapy, Radionuclides Characteristics, Applications, and Challenges

by Suliman Salih, Ajnas Alkatheeri, Wijdan Alomaim and Aisyah Elliyanti

Molecules 2022, 27(16), 5231; https://doi.org/10.3390/molecules27165231 - 16 Aug 2022

Cited by 35 | Viewed by 6781

Abstract

Advances in the field of molecular biology have had an impact on biomedical applications, which provide greater hope for both imaging and therapeutics. Work has been intensified on the development of radionuclides and their application in radiopharmaceuticals (RP_S) which will certainly [...] Read more.

Advances in the field of molecular biology have had an impact on biomedical applications, which provide greater hope for both imaging and therapeutics. Work has been intensified on the development of radionuclides and their application in radiopharmaceuticals (RP_S) which will certainly influence and expand therapeutic approaches in the future treatment of patients. Alpha or beta particles and Auger electrons are used for therapy purposes, and each has advantages and disadvantages. The radionuclides labeled drug delivery system will deliver the particles to the specific targeting cell. Different radioligands can be chosen to uniquely target molecular receptors or intracellular components, making them suitable for personal patient-tailored therapy in modern cancer therapy management. Advances in nanotechnology have enabled nanoparticle drug delivery systems that can allow for specific multivalent attachment of targeted molecules of antibodies, peptides, or ligands to the surface of nanoparticles for therapy and imaging purposes. This review presents fundamental radionuclide properties with particular reference to tumor biology and receptor characteristic of radiopharmaceutical targeted therapy development. Full article

(This article belongs to the Special Issue Radiopharmaceuticals)

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