1
|
Munekane M, Fuchigami T, Ogawa K. Recent advances in the development of 225Ac- and 211At-labeled radioligands for radiotheranostics. ANAL SCI 2024; 40:803-826. [PMID: 38564087 PMCID: PMC11035452 DOI: 10.1007/s44211-024-00514-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 01/16/2024] [Indexed: 04/04/2024]
Abstract
Radiotheranostics utilizes a set of radioligands incorporating diagnostic or therapeutic radionuclides to achieve both diagnosis and therapy. Imaging probes using diagnostic radionuclides have been used for systemic cancer imaging. Integration of therapeutic radionuclides into the imaging probes serves as potent agents for radionuclide therapy. Among them, targeted alpha therapy (TAT) is a promising next-generation cancer therapy. The α-particles emitted by the radioligands used in TAT result in a high linear energy transfer over a short range, inducing substantial damage to nearby cells surrounding the binding site. Therefore, the key to successful cancer treatment with minimal side effects by TAT depends on the selective delivery of radioligands to their targets. Recently, TAT agents targeting biomolecules highly expressed in various cancer cells, such as sodium/iodide symporter, norepinephrine transporter, somatostatin receptor, αvβ3 integrin, prostate-specific membrane antigen, fibroblast-activation protein, and human epidermal growth factor receptor 2 have been developed and have made remarkable progress toward clinical application. In this review, we focus on two radionuclides, 225Ac and 211At, which are expected to have a wide range of applications in TAT. We also introduce recent fundamental and clinical studies of radiopharmaceuticals labeled with these radionuclides.
Collapse
Affiliation(s)
- Masayuki Munekane
- Graduate School of Medical Sciences, Kanazawa University, Kakuma-Machi, Kanazawa, Ishikawa, 920-1192, Japan
| | - Takeshi Fuchigami
- Graduate School of Medical Sciences, Kanazawa University, Kakuma-Machi, Kanazawa, Ishikawa, 920-1192, Japan.
| | - Kazuma Ogawa
- Graduate School of Medical Sciences, Kanazawa University, Kakuma-Machi, Kanazawa, Ishikawa, 920-1192, Japan.
- Institute for Frontier Science Initiative, Kanazawa University, Kakuma-Machi, Kanazawa, Ishikawa, 920-1192, Japan.
| |
Collapse
|
2
|
Albertsson P, Bäck T, Bergmark K, Hallqvist A, Johansson M, Aneheim E, Lindegren S, Timperanza C, Smerud K, Palm S. Astatine-211 based radionuclide therapy: Current clinical trial landscape. Front Med (Lausanne) 2023; 9:1076210. [PMID: 36687417 PMCID: PMC9859440 DOI: 10.3389/fmed.2022.1076210] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 12/06/2022] [Indexed: 01/09/2023] Open
Abstract
Astatine-211 (211At) has physical properties that make it one of the top candidates for use as a radiation source for alpha particle-based radionuclide therapy, also referred to as targeted alpha therapy (TAT). Here, we summarize the main results of the completed clinical trials, further describe ongoing trials, and discuss future prospects.
Collapse
Affiliation(s)
- Per Albertsson
- Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden,Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden,*Correspondence: Per Albertsson ✉
| | - Tom Bäck
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Karin Bergmark
- Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden,Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Andreas Hallqvist
- Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden,Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Mia Johansson
- Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden,Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emma Aneheim
- Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden,Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Sture Lindegren
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Chiara Timperanza
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Knut Smerud
- Smerud Medical Research International AS, Oslo, Norway
| | - Stig Palm
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| |
Collapse
|
3
|
Batra V, Samanta M, Makvandi M, Groff D, Martorano P, Elias J, Ranieri P, Tsang M, Hou C, Li Y, Pawel B, Martinez D, Vaidyanathan G, Carlin S, Pryma DA, Maris JM. Preclinical Development of [211At]meta- astatobenzylguanidine ([211At]MABG) as an Alpha Particle Radiopharmaceutical Therapy for Neuroblastoma. Clin Cancer Res 2022; 28:4146-4157. [PMID: 35861867 PMCID: PMC9475242 DOI: 10.1158/1078-0432.ccr-22-0400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 06/09/2022] [Accepted: 07/19/2022] [Indexed: 01/07/2023]
Abstract
PURPOSE [131I]meta-iodobenzylguanidine ([131I]MIBG) is a targeted radiotherapeutic administered systemically to deliver beta particle radiation in neuroblastoma. However, relapses in the bone marrow are common. [211At]meta-astatobenzylguanidine ([211At] MABG) is an alpha particle emitter with higher biological effectiveness and short path length which effectively sterilizes microscopic residual disease. Here we investigated the safety and antitumor activity [211At]MABG in preclinical models of neuroblastoma. EXPERIMENTAL DESIGN We defined the maximum tolerated dose (MTD), biodistribution, and toxicity of [211At]MABG in immunodeficient mice in comparison with [131I]MIBG. We compared the antitumor efficacy of [211At]MABG with [131I]MIBG in three murine xenograft models. Finally, we explored the efficacy of [211At]MABG after tail vein xenografting designed to model disseminated neuroblastoma. RESULTS The MTD of [211At]MABG was 66.7 MBq/kg (1.8 mCi/kg) in CB17SC scid-/- mice and 51.8 MBq/kg (1.4 mCi/kg) in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice. Biodistribution of [211At]MABG was similar to [131I]MIBG. Long-term toxicity studies on mice administered with doses up to 41.5 MBq/kg (1.12 mCi/kg) showed the radiotherapeutic to be well tolerated. Both 66.7 MBq/kg (1.8 mCi/kg) single dose and fractionated dosing 16.6 MBq/kg/fraction (0.45 mCi/kg) × 4 over 11 days induced marked tumor regression in two of the three models studied. Survival was significantly prolonged for mice treated with 12.9 MBq/kg/fraction (0.35 mCi/kg) × 4 doses over 11 days [211At]MABG in the disseminated disease (IMR-05NET/GFP/LUC) model (P = 0.003) suggesting eradication of microscopic disease. CONCLUSIONS [211At]MABG has significant survival advantage in disseminated models of neuroblastoma. An alpha particle emitting radiopharmaceutical may be effective against microscopic disseminated disease, warranting clinical development.
Collapse
Affiliation(s)
- Vandana Batra
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Minu Samanta
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Mehran Makvandi
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - David Groff
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Paul Martorano
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jimmy Elias
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Pietro Ranieri
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Matthew Tsang
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Catherine Hou
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yimei Li
- Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Bruce Pawel
- Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles and Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Daniel Martinez
- Division of Anatomic Pathology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | | | - Sean Carlin
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Daniel A. Pryma
- Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - John M. Maris
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.,Corresponding Author: John M. Maris, Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, 3501 Civic Center Boulevard, Philadelphia, PA 19104. Phone: 215-590-5242; E-mail:
| |
Collapse
|
4
|
Oxidation of p-[125I]Iodobenzoic Acid and p-[211At]Astatobenzoic Acid Derivatives and Evaluation In Vivo. Int J Mol Sci 2022; 23:ijms231810655. [PMID: 36142567 PMCID: PMC9506049 DOI: 10.3390/ijms231810655] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 08/17/2022] [Accepted: 08/24/2022] [Indexed: 11/23/2022] Open
Abstract
The alpha particle-emitting radionuclide astatine-211 (211At) is of interest for targeted radiotherapy; however, low in vivo stability of many 211At-labeled cancer-targeting molecules has limited its potential. As an alternative labeling method, we evaluated whether a specific type of astatinated aryl compound that has the At atom in a higher oxidation state might be stable to in vivo deastatination. In the research effort, para-iodobenzoic acid methyl ester and dPEG4-amino acid methyl ester derivatives were prepared as HPLC standards. The corresponding para-stannylbenzoic acid derivatives were also prepared and labeled with 125I and 211At. Oxidization of the [125I]iodo- and [211At]astato-benzamidyl-dPEG4-acid methyl ester derivatives provided materials for in vivo evaluation. A biodistribution was conducted in mice with coinjected oxidized 125I- and 211At-labeled compounds. The oxidized radioiodinated derivative was stable to in vivo deiodination, but unfortunately the oxidized [211At]astatinated benzamide derivative was found to be unstable under the conditions of isolation by radio-HPLC (post animal injection). Another biodistribution study in mice evaluated the tissue concentrations of coinjected [211At]NaAtO3 and [125I]NaIO3. Comparison of the tissue concentrations of the isolated material from the oxidized [211At]benzamide derivative with those of [211At]astatate indicated the species obtained after isolation was likely [211At]astatate.
Collapse
|
5
|
Ohshima Y, Sasaki I, Watanabe S, Sakashita T, Higashi T, Ishioka NS. Organic cation transporter 3 mediates the non-norepinephrine transporter driven uptake of meta-[211At]astato-benzylguanidine. Nucl Med Biol 2022; 112-113:44-51. [DOI: 10.1016/j.nucmedbio.2022.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 05/28/2022] [Accepted: 06/16/2022] [Indexed: 10/17/2022]
|
6
|
Recent progress of astatine-211 in endoradiotherapy: Great advances from fundamental properties to targeted radiopharmaceuticals. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.03.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
7
|
Sakashita T, Matsumoto S, Watanabe S, Hanaoka H, Ohshima Y, Ikoma Y, Ukon N, Sasaki I, Higashi T, Higuchi T, Tsushima Y, Ishioka NS. Nonclinical study and applicability of the absorbed dose conversion method with a single biodistribution measurement for targeted alpha-nuclide therapy. EJNMMI Phys 2021; 8:80. [PMID: 34897556 PMCID: PMC8665908 DOI: 10.1186/s40658-021-00425-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 11/19/2021] [Indexed: 11/15/2022] Open
Abstract
Background We recently reported a new absorbed dose conversion method, RAP (RAtio of Pharmacokinetics), for 211At-meta-astatobenzylguanidine (211At-MABG) using a single biodistribution measurement, the percent injected dose/g. However, there were some mathematical ambiguities in determining the optimal timing of a single measurement of the percent injected dose/g. Thus, we aimed to mathematically reconstruct the RAP method and to examine the optimal timing of a single measurement. Methods We derived a new formalism of the RAP dose conversion method at time t. In addition, we acquired a formula to determine the optimal timing of a single measurement of the percent injected dose/g, assuming the one-compartment model for biological clearance. Results We investigated the new formalism’s performance using a representative RAP coefficient with radioactive decay weighting. Dose conversions by representative RAP coefficients predicted the true [211At]MABG absorbed doses with an error of 10% or less. The inverses of the representative RAP coefficients plotted at 4 h post-injection, which was the optimal timing reported in the previous work, were very close to the new inverses of the RAP coefficients 4 h post-injection. Next, the behavior of the optimal timing was analyzed by radiolabeled compounds with physical half-lives of 7.2 h and 10 d on various biological clearance half-lives. Behavior maps of optimal timing showed a tendency to converge to a constant value as the biological clearance half-life of a target increased. The areas of optimal timing for both compounds within a 5% or 10% prediction error were distributed around the optimal timing when the biological clearance half-life of a target was equal to that of the reference. Finally, an example of RAP dose conversion was demonstrated for [211At]MABG. Conclusions The RAP dose conversion method renovated by the new formalism was able to estimate the [211At]MABG absorbed dose using a similar pharmacokinetics, such as [131I]MIBG. The present formalism revealed optimizing imaging time points on absorbed dose conversion between two radiopharmaceuticals. Further analysis and clinical data will be needed to elucidate the validity of a behavior map of the optimal timing of a single measurement for targeted alpha-nuclide therapy. Supplementary Information The online version contains supplementary material available at 10.1186/s40658-021-00425-z.
Collapse
Affiliation(s)
- Tetsuya Sakashita
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan.
| | - Shojiro Matsumoto
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Shigeki Watanabe
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Hirofumi Hanaoka
- Department of Bioimaging Information Analysis, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Yasuhiro Ohshima
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Yoko Ikoma
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Naoyuki Ukon
- Advanced Clinical Research Center, Fukushima Medical University, 1 Hikariga-oka, Fukushima, 960-1295, Japan
| | - Ichiro Sasaki
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Tetsuya Higuchi
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Yoshito Tsushima
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Noriko S Ishioka
- Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| |
Collapse
|
8
|
Sakashita T, Watanabe S, Hanaoka H, Ohshima Y, Ikoma Y, Ukon N, Sasaki I, Higashi T, Higuchi T, Tsushima Y, Ishioka NS. Absorbed dose simulation of meta- 211At-astato-benzylguanidine using pharmacokinetics of 131I-MIBG and a novel dose conversion method, RAP. Ann Nucl Med 2021; 35:121-131. [PMID: 33222123 DOI: 10.1007/s12149-020-01548-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 11/02/2020] [Indexed: 11/28/2022]
Abstract
OBJECTIVE We aimed to estimate in vivo 211At-labeled meta-benzylguanidine (211At-MABG) absorbed doses by the two dose conversion methods, using 131I-MIBG biodistribution data from a previously reported neuroblastoma xenograft model. In addition, we examined the effects of different cell lines and time limitations using data from two other works. METHODS We used the framework of the Monte Carlo method to create 3200 virtual experimental data sets of activity concentrations (kBq/g) to get the statistical information. Time activity concentration curves were produced using the fitting method of a genetic algorithm. The basic method was that absorbed doses of 211At-MABG were calculated based on the medical internal radiation dose formalism with the conversion of the physical half-life time of 131I to that of 211At. We have further improved the basic method; that is, a novel dose conversion method, RAP (Ratio of Pharmacokinetics), using percent injected dose/g. RESULTS Virtual experiments showed that 211At-MABG and 131I-MIBG had similar properties of initial activity concentrations and biological components, but the basic method did not simulate the 211At-MABG dose. Simulated 211At-MABG doses from 131I-MIBG using the RAP method were in agreement with those from 211At-MABG, so that their boxes overlapped in the box plots. The RAP method showed applicability to the different cell lines, but it was difficult to predict long-term doses from short-term experimental data. CONCLUSIONS The present RAP dose conversion method could estimate 211At-MABG absorbed doses from the pharmacokinetics of 131I-MIBG with some limitations. The RAP method would be applicable to a large number of subjects for targeted nuclide therapy.
Collapse
Affiliation(s)
- Tetsuya Sakashita
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan.
| | - Shigeki Watanabe
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Hirofumi Hanaoka
- Department of Bioimaging Information Analysis, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Yasuhiro Ohshima
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Yoko Ikoma
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Naoyuki Ukon
- Advanced Clinical Research Center, Fukushima Medical University, 1 Hikariga-oka, Fukushima, 960-1295, Japan
| | - Ichiro Sasaki
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Tetsuya Higuchi
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Yoshito Tsushima
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, 371-8511, Japan
| | - Noriko S Ishioka
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, 370-1292, Japan
| |
Collapse
|
9
|
Sudo H, Tsuji AB, Sugyo A, Nagatsu K, Minegishi K, Ishioka NS, Ito H, Yoshinaga K, Higashi T. Preclinical Evaluation of the Acute Radiotoxicity of the α-Emitting Molecular-Targeted Therapeutic Agent 211At-MABG for the Treatment of Malignant Pheochromocytoma in Normal Mice. Transl Oncol 2019; 12:879-888. [PMID: 31078058 PMCID: PMC6514325 DOI: 10.1016/j.tranon.2019.04.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/03/2019] [Accepted: 04/10/2019] [Indexed: 12/23/2022] Open
Abstract
The α-emitter 211At-labeled meta-astatobenzylguanidine (211At-MABG) has a strong antitumor effect on pheochromocytoma xenograft tumors and holds great promise as a new therapeutic option for malignant pheochromocytoma. To evaluate the acute radiation-related toxicity of 211At-MABG, we conducted biodistribution and dosimetry studies of 211At-MABG in ICR mice to estimate the doses absorbed by organs. We determined the maximum tolerated doses (MTD) of 211At-MABG on the basis of body weight loss and assessed the acute radiation-related toxicity induced by MTD administration on the basis of organ weights, histologic features, hematologic indices, and biochemical indices. The biodistribution and dosimetry studies of α-emitting 211At-MABG revealed high doses absorbed by most organs except the brain in ICR mice. The administration of 1.1, 2.2, and 3.3 MBq of 211At-MABG induced transient body weight loss, and 4.4 MBq of 211At-MABG induced unrecoverable body weight loss; thus, the MTD was 3.3 MBq for ICR mice. Although by day 5 the administration of 3.3 MBq had induced some radiation-related toxicity symptoms—such as body weight loss and leucopenia, which are generally observed in radiation therapy including β−-emitting radiopharmaceuticals—the mice had recovered by day 28. We observed no unexpected severe toxicity in ICR mice despite the high absorbed doses in most organs, especially the thyroid, heart, stomach, and adrenal glands. Our findings suggest that therapeutic treatments with appropriate doses of 211At-MABG estimated by dosimetry in each patient could be tolerated, although lower doses may initially be necessary to ensure patient safety in the first-in-human study.
Collapse
Affiliation(s)
- Hitomi Sudo
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan
| | - Atsushi B Tsuji
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan.
| | - Aya Sugyo
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan
| | - Kotaro Nagatsu
- Department of Radiopharmaceuticals, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan
| | - Katsuyuki Minegishi
- Department of Radiopharmaceuticals, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan
| | - Noriko S Ishioka
- Department of Radiation-Applied Biology Research, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Takasaki, Japan
| | - Hiroshi Ito
- Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima 960-1295, Japan
| | - Keiichiro Yoshinaga
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan.
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (QST-NIRS), Inage, Chiba 263-8555, Japan
| |
Collapse
|
10
|
Ohshima Y, Sudo H, Watanabe S, Nagatsu K, Tsuji AB, Sakashita T, Ito YM, Yoshinaga K, Higashi T, Ishioka NS. Antitumor effects of radionuclide treatment using α-emitting meta- 211At-astato-benzylguanidine in a PC12 pheochromocytoma model. Eur J Nucl Med Mol Imaging 2018; 45:999-1010. [PMID: 29350258 PMCID: PMC5915519 DOI: 10.1007/s00259-017-3919-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 12/20/2017] [Indexed: 11/29/2022]
Abstract
PURPOSE Therapeutic options for patients with malignant pheochromocytoma are currently limited, and therefore new treatment approaches are being sought. Targeted radionuclide therapy provides tumor-specific systemic treatments. The β-emitting radiopharmaceutical meta-131I-iodo-benzylguanidine (131I-MIBG) provides limited survival benefits and has adverse effects. A new generation of radionuclides for therapy using α-particles including meta-211At-astato-benzylguanidine (211At-MABG) are expected to have strong therapeutic effects with minimal side effects. However, this possibility has not been evaluated in an animal model of pheochromocytoma. We aimed to evaluate the therapeutic effects of the α-emitter 211At-MABG in a pheochromocytoma model. METHODS We evaluated tumor volume-reducing effects of 211At-MABG using rat pheochromocytoma cell line PC12 tumor-bearing mice. PC12 tumor-bearing mice received intravenous injections of 211At-MABG (0.28, 0.56, 1.11, 1.85, 3.70 and 5.55 MBq; five mice per group). Tumor volumes were evaluated for 8 weeks after 211At-MABG administration. The control group of ten mice received phosphate-buffered saline. RESULTS The 211At-MABG-treated mice showed significantly lower relative tumor growth during the first 38 days than the control mice. The relative tumor volumes on day 21 were 509.2% ± 169.1% in the control mice and 9.6% ± 5.5% in the mice receiving 0.56 MBq (p < 0.01). In addition, the mice treated with 0.28, 0.56 and 1.11 MBq of 211At-MABG showed only a temporary weight reduction, with recovery in weight by day 10. CONCLUSION 211At-MABG exhibited a strong tumor volume-reducing effect in a mouse model of pheochromocytoma without weight reduction. Therefore, 211At-MABG might be an effective therapeutic agent for the treatment of malignant pheochromocytoma.
Collapse
Affiliation(s)
- Yasuhiro Ohshima
- Department of Radiation-Applied Biology Research, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanukimachi, Takasaki-shi, Gunma, 370-1292, Japan
| | - Hitomi Sudo
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Shigeki Watanabe
- Department of Radiation-Applied Biology Research, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanukimachi, Takasaki-shi, Gunma, 370-1292, Japan
| | - Kotaro Nagatsu
- Department of Radiopharmaceuticals Development, National Institutes for Quantum and Radiological Science and Technology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Atsushi B Tsuji
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Tetsuya Sakashita
- Department of Radiation-Applied Biology Research, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanukimachi, Takasaki-shi, Gunma, 370-1292, Japan
| | - Yoichi M Ito
- Department of Biostatistics, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan
| | - Keiichiro Yoshinaga
- Diagnostic and Therapeutic Nuclear Medicine, National Institutes for Quantum and Radiological Science and Technology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Noriko S Ishioka
- Department of Radiation-Applied Biology Research, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanukimachi, Takasaki-shi, Gunma, 370-1292, Japan
| |
Collapse
|
11
|
Pandit-Taskar N, Modak S. Norepinephrine Transporter as a Target for Imaging and Therapy. J Nucl Med 2017; 58:39S-53S. [PMID: 28864611 DOI: 10.2967/jnumed.116.186833] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 07/19/2017] [Indexed: 01/01/2023] Open
Abstract
The norepinephrine transporter (NET) is essential for norepinephrine uptake at the synaptic terminals and adrenal chromaffin cells. In neuroendocrine tumors, NET can be targeted for imaging as well as therapy. One of the most widely used theranostic agents targeting NET is metaiodobenzylguanidine (MIBG), a guanethidine analog of norepinephrine. 123I/131I-MIBG theranostics have been applied in the clinical evaluation and management of neuroendocrine tumors, especially in neuroblastoma, paraganglioma, and pheochromocytoma. 123I-MIBG imaging is a mainstay in the evaluation of neuroblastoma, and 131I-MIBG has been used for the treatment of relapsed high-risk neuroblastoma for several years, however, the outcome remains suboptimal. 131I-MIBG has essentially been only palliative in paraganglioma/pheochromocytoma patients. Various techniques of improving therapeutic outcomes, such as dosimetric estimations, high-dose therapies, multiple fractionated administration and combination therapy with radiation sensitizers, chemotherapy, and other radionuclide therapies, are being evaluated. PET tracers targeting NET appear promising and may be more convenient options for the imaging and assessment after treatment. Here, we present an overview of NET as a target for theranostics; review its current role in some neuroendocrine tumors, such as neuroblastoma, paraganglioma/pheochromocytoma, and carcinoids; and discuss approaches to improving targeting and theranostic outcomes.
Collapse
Affiliation(s)
| | - Shakeel Modak
- Memorial Sloan Kettering Cancer Center, New York, New York
| |
Collapse
|
12
|
Vaidyanathan G, Zalutsky MR. Applications of 211At and 223Ra in targeted alpha-particle radiotherapy. Curr Radiopharm 2012; 4:283-94. [PMID: 22202151 DOI: 10.2174/1874471011104040283] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 03/08/2011] [Accepted: 03/10/2011] [Indexed: 11/22/2022]
Abstract
Targeted radiotherapy using agents tagged with α-emitting radionuclides is gaining traction with several clinical trials already undertaken or ongoing, and others in the advanced planning stage. The most commonly used α-emitting radionuclides are 213Bi, 211At, 223Ra and 225Ac. While each one of these has pros and cons, it can be argued that 211At probably is the most versatile based on its half life, decay scheme and chemistry. On the other hand, for targeting bone metastases, 223Ra is the ideal radionuclide because simple cationic radium can be used for this purpose. In this review, we will discuss the recent developments taken place in the application of 211At-labeled radiopharmaceuticals and give an overview of the current status of 223Ra for targeted α-particle radiotherapy.
Collapse
Affiliation(s)
- Ganesan Vaidyanathan
- Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
| | | |
Collapse
|
13
|
Yang Y, Lin R, Liu N, Liao J, Wei M, Jin J. Astatine-211 labeling of protein using TCP as a bi-functional linker: synthesis and preliminary evaluation in vivo and in vitro. J Radioanal Nucl Chem 2010. [DOI: 10.1007/s10967-010-0872-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
14
|
Bauwens M, Wimana L, Keyaerts M, Peleman C, Lahoutte T, Kersemans K, Snykers S, Vinken M, Mertens J, Bossuyt A. Preliminary In Vivo Evaluation of [131I]-2-Iodo-D-Phenylalanine as a Potential Radionuclide Therapeutic Agent in R1M-Fluc Rhabdomyosarcoma Tumor-Bearing NuNu Mice Using Bioluminescent Imaging. Cancer Biother Radiopharm 2010; 25:225-31. [DOI: 10.1089/cbr.2009.0705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Lena Wimana
- BEFY, Vrije Universitet Brussel, Brussels, Belgium
| | | | | | | | | | | | | | - John Mertens
- BEFY, Vrije Universitet Brussel, Brussels, Belgium
| | - Axel Bossuyt
- NUGE, Vrije Universitet Brussel, Brussels, Belgium
| |
Collapse
|
15
|
Montaldo PG, Pagnan G, Raffaghello L, Pastorino F, Allen TM, Kirchmeier M, Ponzoni M. Anti Gd2-Immunoliposome-Mediated Targeting of [125I] Metaiodobenzylguanidine to Neuroblastoma and Melanoma Cells in Vitro. J Liposome Res 2008. [DOI: 10.3109/08982109909018657] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
16
|
Abstract
For the treatment of minimum residual diseases such micrometastases and residual tumor margins that remain after debulking of the primary tumor, targeted radiotherapy using radiopharmaceuticals tagged with alpha-particle-emitting radionuclides is very attractive. In addition to the their short range in tissue, which helps minimize harmful effects on adjacent normal tissues, alpha-particles, being high LET radiation, have several radiobiological advantages. The heavy halogen, astatine-211 is one of the prominent alpha-particle-emitting radionuclides in practice. Being a halogen, it can often be incorporated into biomolecules of interest by adapting radioiodination chemistry. A wide spectrum of compounds from the simple [(211)At]astatide ion to small organic molecules, peptides, and large proteins labeled with (211)At have been investigated with at least two reaching the stage of clinical evaluation. The chemistry, cytotoxic advantages, biodistribution studies, and microdosimetry/pharmacokinetic modeling of some of these agents will be reviewed. In addition, potential problems such as the harmful effect of radiolysis on the synthesis, lack of sufficient in vivo stability of astatinated compounds, and possible adverse effects when they are systemically administered will be discussed.
Collapse
Affiliation(s)
- Ganesan Vaidyanathan
- Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Michael R. Zalutsky
- Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA
| |
Collapse
|
17
|
Optimizing MIBG therapy of neuroendocrine tumors: preclinical evidence of dose maximization and synergy. Nucl Med Biol 2008; 35 Suppl 1:S9-20. [DOI: 10.1016/j.nucmedbio.2008.04.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Revised: 04/09/2008] [Accepted: 04/23/2008] [Indexed: 11/19/2022]
|
18
|
Eisenhofer G, Siegert G, Kotzerke J, Bornstein SR, Pacak K. Current progress and future challenges in the biochemical diagnosis and treatment of pheochromocytomas and paragangliomas. Horm Metab Res 2008; 40:329-37. [PMID: 18491252 PMCID: PMC4714589 DOI: 10.1055/s-2008-1073156] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Findings from five independent studies - with close to 350 patients with pheochromocytoma and more than 2,500 in whom the tumor was excluded - indicate that measurements of plasma free metanephrines provide an overall diagnostic sensitivity of 98% and specificity of 92%. The recommendation that initial testing for the tumor should always include measurements of either plasma or urinary fractionated metanephrines results from recognition of the high diagnostic sensitivity of measurements of plasma metanephrines. The few patients with pheochromocytoma in whom the test may not yield a positive result include those with very small tumors or microscopic disease and others with tumors that do not produce norepinephrine and epinephrine. Such patients are typically normotensive and do not exhibit symptoms of catecholamine excess. Additional measurements of methoxytyramine can be useful for detecting those tumors that produce only dopamine. Suboptimal diagnostic specificity and difficulties in distinguishing true- from false-positive elevations of plasma metanephrines remain challenges for diagnosis. Improvements in analytical technology (e.g., liquid chromatography with tandem mass spectrometry) and new strategies for follow-up testing provide possible solutions to these problems. The single most important remaining clinical care challenge is the development of effective cures for patients with malignant disease. Current treatments, none of which are truly satisfactory, include chemotherapy and radiopharmaceutical therapy with (131)I-labelled M-iodobenzylguanidine or radioactive somatostatin analogues. Improvements in treatment may in the future come from several fronts, but proof of efficacy ideally will require well-coordinated multicenter prospective trials in larger numbers of patients than in previous studies.
Collapse
Affiliation(s)
- G Eisenhofer
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus Dresden, Germany.
| | | | | | | | | |
Collapse
|
19
|
Vaidyanathan G, Affleck DJ, Alston KL, Zhao XG, Hens M, Hunter DH, Babich J, Zalutsky MR. A kit method for the high level synthesis of [211At]MABG. Bioorg Med Chem 2007; 15:3430-6. [PMID: 17387017 PMCID: PMC1885228 DOI: 10.1016/j.bmc.2007.03.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 03/07/2007] [Accepted: 03/08/2007] [Indexed: 10/23/2022]
Abstract
meta-[(211)At]Astatobenzylguanidine ([(211)At]MABG), an analogue of meta-iodobenzylguanidine (MIBG) labeled with the alpha-emitter (211)At, targets the norepinephrine transporter. Because MABG has been shown to have excellent characteristics in preclinical studies, it has been considered to be a promising targeted radiotherapeutic for the treatment of tumors such as micrometastatic neuroblastoma that overexpress the norepinephrine transporter. To facilitate clinical evaluation of this agent, a convenient method for the high level synthesis of [(211)At]MABG that is adaptable for kit formulation has been developed. A tin precursor anchored to a solid-support was treated with a methanolic solution of (211)At in the presence of a mixture of H(2)O(2)/HOAc as the oxidant; [(211)At]MABG was isolated by simple solid-phase extraction. By using C-18 solid-phase extraction, the radiochemical yield from 25 batches was 63+/-13%; however, loss of radioactivity during evaporation of the methanolic solution was a problem. This difficulty was avoided by use of a cation exchange resin cartridge for isolation of [(211)At]MABG, which resulted in radiochemical yields of 63+/-9% in a shorter duration of synthesis. The radiochemical purity was more than 90% and no chemical impurity has been detected. The final doses were sterile and apyrogenic. These results demonstrate that [(211)At]MABG can be prepared via a kit method at radioactivity levels anticipated for initiation of clinical studies.
Collapse
|
20
|
Liu N, Yang Y, Zan L, Liao J, Jin J. Astatine-211 labeling of insulin: Synthesis and preliminary evaluation in vivo and in vitro. J Radioanal Nucl Chem 2007. [DOI: 10.1007/s10967-006-6781-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
21
|
Lindencrona U, Nilsson M, Forssell-Aronsson E. Similarities and differences between free 211At and 125I- transport in porcine thyroid epithelial cells cultured in bicameral chambers. Nucl Med Biol 2001; 28:41-50. [PMID: 11182563 DOI: 10.1016/s0969-8051(00)00179-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The transport and accumulation of free 211At and 125I- were investigated in thyrocytes cultured as monolayers in bicameral chambers under the influence of thyroid-stimulating hormone, stable iodide, ouabain and perchlorate. The results indicate that there are similarities and differences in the transport mechanisms of free 211At and 125I-. These results will be valuable in the development of radiation protection when handling and using 211At-labeled radiopharmaceuticals, and for the potential use of free 211At in radiation therapy of poorly differentiated thyroid cancer.
Collapse
Affiliation(s)
- U Lindencrona
- Department of Radiation Physics, Göteborg University, Sahlgrenska University Hospital, SE-413 45, Göteborg, Sweden.
| | | | | |
Collapse
|
22
|
Rutgers M, Buitenhuis CK, Hoefnagel CA, Voûte PA, Smets LA. Targeting of meta-iodobenzylguanidine to SK-N-SH human neuroblastoma xenografts: tissue distribution, metabolism and therapeutic efficacy. Int J Cancer 2000; 87:412-22. [PMID: 10897048 DOI: 10.1002/1097-0215(20000801)87:3<412::aid-ijc16>3.0.co;2-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The clinical results of [(131)I]meta-iodobenzylguanidine (MIBG)-targeted radiotherapy in neuroblastoma patients is highly variable. To assess the therapeutic potential of [(131)I]MIBG, we used the SK-N-SH human neuroblastoma, xenografted in nude mice. The model was first characterized for basic parameters of MIBG handling in the host species. This demonstrated the presence of both strain- and nu/nu mutation-related differences in [(131)I]MIBG biodistribution. Fecal and urinary clearance rates of [(131)I]MIBG in mice roughly resemble those in humans, but mice metabolize MIBG more extensively. In both species, enzymatic deiodination in vivo was not an important metabolic route. Therapy with increasing [(131)I]MIBG doses (25-92 MBq) given as single i.v. injections resulted in proportionally increasing specific growth delay values (tumor regrowth delay/doubling time) of 1 to 5. Using gamma-camera scintigraphy for non-invasive dosimetry, the corresponding calculated absorbed tumor radiation doses ranged from 2 to 11 Gy. We also compared the therapeutic effects of a single [(131)I]MIBG administration with those resulting from a more protracted exposure by fractionating the dose in 2 to 6 injections or with high dose rate external-beam irradiation. No therapeutic advantage of a fractionated schedule was observed, and 5.5 Gy delivered by low dose-rate [(131)I]MIBG endo-irradiation was equi-effective with 5.0 Gy X-rays. The SK-N-SH neuroblastoma xenograft model thus appears suitable to evaluate possible treatment improvements to reach full potential of MIBG radiotherapy.
Collapse
Affiliation(s)
- M Rutgers
- Department of Experimental Therapy, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | | | | | | | | |
Collapse
|
23
|
Abstract
Radionuclides such as 211At and 212Bi which decay by the emission of alpha-particles are attractive for certain applications of targeted radiotherapy. The tissue penetration of 212Bi and 211At alpha-particles is equivalent to only a few cell diameters, offering the possibility of combining cell-specific targeting with radiation of similar range. Unlike the beta-particles emitted by radionuclides such as 131I and 90Y, alpha-particles are radiation of high linear energy transfer and thus greater biological effectiveness. Several approaches have been explored for targeted radiotherapy with 212Bi- and 211At-labelled substances including colloids, monoclonal antibodies, metabolic precursors, receptor-avid ligands and other lower molecular weight molecules. An additional agent which exemplifies the promise of alpha-emitting radiopharmaceuticals is meta-[211At]astatobenzylguanidine. The toxicity of this compound under single-cell conditions, determined both by [3H]thymidine incorporation and by limiting dilution clonogenic assays, for human neuroblastoma cells is of the order of 1000 times higher than that of meta-[131I] iodobenzylguanidine. For meta-[211At] astatobenzylguanidine, the Do value was equivalent to only 6-7 211At atoms bound per cell. These results suggest that meta-[211At] astatobenzylguanidine might be valuable for the targeted radiotherapy of micrometastatic neuroblastomas.
Collapse
Affiliation(s)
- G Vaidyanathan
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA
| | | |
Collapse
|