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Suzuki H, Kannaka K, Uehara T. Approaches to Reducing Normal Tissue Radiation from Radiolabeled Antibodies. Pharmaceuticals (Basel) 2024; 17:508. [PMID: 38675468 PMCID: PMC11053530 DOI: 10.3390/ph17040508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/02/2024] [Accepted: 04/12/2024] [Indexed: 04/28/2024] Open
Abstract
Radiolabeled antibodies are powerful tools for both imaging and therapy in the field of nuclear medicine. Radiolabeling methods that do not release radionuclides from parent antibodies are essential for radiolabeling antibodies, and practical radiolabeling protocols that provide high in vivo stability have been established for many radionuclides, with a few exceptions. However, several limitations remain, including undesirable side effects on the biodistribution profiles of antibodies. This review summarizes the numerous efforts made to tackle this problem and the recent advances, mainly in preclinical studies. These include pretargeting approaches, engineered antibody fragments and constructs, the secondary injection of clearing agents, and the insertion of metabolizable linkages. Finally, we discuss the potential of these approaches and their prospects for further clinical application.
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Affiliation(s)
- Hiroyuki Suzuki
- Laboratory of Molecular Imaging and Radiotherapy, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan; (K.K.); (T.U.)
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2
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Abstract
Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.
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Affiliation(s)
- Weijun Wei
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China.,Departments of Radiology and Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Room 7137, Madison, Wisconsin 53705, United States
| | - Zachary T Rosenkrans
- Department of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Jianjun Liu
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Gang Huang
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China.,Shanghai Key Laboratory of Molecular Imaging, Shanghai University of Medicine and Health Sciences, Shanghai 201318, China
| | - Quan-Yong Luo
- Department of Nuclear Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Weibo Cai
- Departments of Radiology and Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Room 7137, Madison, Wisconsin 53705, United States.,Department of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States.,University of Wisconsin Carbone Cancer Center, Madison, Wisconsin 53705, United States
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Höglund J, Tolmachev V, Orlova A, Lundqvist H, Sundin A. Cellular uptake and processing of directly and indirectly 125I-iodinated and 76BR-brominated monoclonal antibody A33. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.25804401251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Tolmachev V, Sjöberg S, Lundqvist H. Bromination of closo-dodecaborate (2-) anion in aqueous media using chloramine-T. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.25804401338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Lang L, Li W, Jia HM, Fang DC, Zhang S, Sun X, Zhu L, Ma Y, Shen B, Kiesewetter DO, Niu G, Chen X. New Methods for Labeling RGD Peptides with Bromine-76. Theranostics 2011; 1:341-53. [PMID: 21938262 PMCID: PMC3177243 DOI: 10.7150/thno/v01p0341] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 08/15/2011] [Indexed: 01/16/2023] Open
Abstract
Direct bromination of the tyrosine residues of peptides and antibodies with bromine-76, to create probes for PET imaging, has been reported. For peptides that do not contain tyrosine residues, however, a prosthetic group is required to achieve labeling via conjugation to other functional groups such as terminal α-amines or lysine ε-amines. The goal of this study was to develop new strategies for labeling small peptides with Br-76 using either a direct labeling method or a prosthetic group, depending on the available functional group on the peptides. A new labeling agent, N-succinimidyl-3-[(76)Br]bromo-2,6-dimethoxybenzoate ([(76)Br]SBDMB) was prepared for cyclic RGD peptide labeling. N-succinimidyl-2, 6-dimethoxybenzoate was also used to pre-attach a 2, 6-dimethoxybenzoyl (DMB) moiety to the peptide, which could then be labeled with Br-76. A competitive cell binding assay was performed to determine the binding affinity of the brominated peptides. PET imaging of U87MG human glioblastoma xenografted mice was performed using [(76)Br]-BrE[c(RGDyK)](2) and [(76)Br]-BrDMB-E[c(RGDyK)](2). An ex vivo biodistribution assay was performed to confirm PET quantification. The mechanisms of bromination reaction between DMB-c(RGDyK) and the brominating agent CH(3)COOBr were investigated with the SCRF-B3LYP/6-31G* method with the Gaussian 09 program package. The yield for direct labeling of c(RGDyK) and E[c(RGDyK)](2) using chloramine-T and peracetic acid at ambient temperature was greater than 50%. The yield for [(76)Br]SBDMB was over 60% using peracetic acid. The conjugation yields for labeling c(RGDfK) and c(RGDyK) were over 70% using the prosthetic group at room temperature. Labeling yield for pre-conjugated peptides was over 60%. SDMB conjugation and bromination did not affect the binding affinity of the peptides with integrin receptors. Both [(76)Br]Br-E[c(RGDyK)](2) and [(76)Br]BrDMB-E[c(RGDyK)](2) showed high tumor uptake in U87MG tumor bearing mice. The specificity of the imaging tracers was confirmed by decreased tumor uptake after co-administration of unlabeled dimeric RGD peptides. The energy barrier of the transition state of bromination for the dimethoxybenzoyl group was about 9 kcal/mol lower than that for the tyrosine residue. In conclusion, the newly developed N-succinimidyl-2, 6-dimethoxybenzoate molecule can be used either for one step labeling through pre-conjugation or as the precursor for a Br-76 labeled prosthetic group for indirect labeling. Radiobromination on a dimethoxybenzoyl group has selectivity over radiobromination on tyrosine. The energy barrier difference of the transition states of bromination between the dimethoxybenzoyl group and the tyrosine residue may account for the reaction selectivity when both groups are present in the same molecule.
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Affiliation(s)
- Lixin Lang
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
| | - Weihua Li
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
- 2. Department of Medical Imaging and Nuclear Medicine, the Fourth Affiliated Hospital, Harbin Medical University, Harbin 150001, China
| | - Hong-Mei Jia
- 3. Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - De-Cai Fang
- 3. Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Shushu Zhang
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
| | - Xilin Sun
- 2. Department of Medical Imaging and Nuclear Medicine, the Fourth Affiliated Hospital, Harbin Medical University, Harbin 150001, China
| | - Lei Zhu
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
| | - Ying Ma
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
| | - Baozhong Shen
- 2. Department of Medical Imaging and Nuclear Medicine, the Fourth Affiliated Hospital, Harbin Medical University, Harbin 150001, China
| | - Dale O. Kiesewetter
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
| | - Gang Niu
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
- 4. Imaging Sciences Training Program, Radiology and Imaging Sciences, Clinical Center and National Institute Biomedical Imaging and Bioengineering, NIH, Bethesda, Maryland, 20892, USA
| | - Xiaoyuan Chen
- 1. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA
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Aslam MN, Sudár S, Hussain M, Malik AA, Qaim SM. Evaluation of excitation functions of proton, ³He- and α-particle induced reactions for production of the medically interesting positron-emitter bromine-76. Appl Radiat Isot 2011; 69:1490-505. [PMID: 21723137 DOI: 10.1016/j.apradiso.2011.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 05/25/2011] [Accepted: 06/05/2011] [Indexed: 11/21/2022]
Abstract
Cross section data for production of the medically interesting radionuclide ⁷⁶Br (T(½)=16.2 h) via the proton induced reactions on ⁷⁶Se, ⁷⁷Se, ⁷⁸Se and ⁷⁹Br, and ³He- and α-particle induced reactions on ⁷⁵As were evaluated. The nuclear model codes STAPRE, EMPIRE and TALYS were used to check the consistency in the experimental data and a statistical procedure was applied to derive the recommended excitation functions. A comparison of various production routes of ⁷⁶Br (and of ⁷⁵Br) is presented.
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Abstract
Radioimmunoimaging and therapy has been an area of interest for several decades. Steady progress has been made toward clinical translation of radiolabeled monoclonal antibodies for diagnosis and treatment of diseases. Tremendous advances have been made in imaging technologies such as positron emission tomography (PET). However, these advances have so far eluded routine translation into clinical radioimmunoimaging applications due to the mismatch between the short half-lives of routinely used positron-emitting radionuclides such as (18)F versus the pharmacokinetics of most intact monoclonal antibodies of interest. The lack of suitable positron-emitting radionuclides that match the pharmacokinetics of intact antibodies has generated interest in exploring the use of longer-lived positron emitters that are more suitable for radioimmunoimaging and dosimetry applications with intact monoclonal antibodies. In this review, we examine the opportunities and challenges of radioimmunoimaging with select longer-lived positron-emitting radionuclides such as (124)I, (89)Zr, and (86)Y with respect to radionuclide production, ease of radiolabeling intact antibodies, imaging characteristics, radiation dosimetry, and clinical translation potential.
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Affiliation(s)
- Tapan K. Nayak
- Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institute of Health, Bethesda, MD-20892, USA
| | - Martin W. Brechbiel
- Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institute of Health, Bethesda, MD-20892, USA
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Almqvist Y, Steffen AC, Lundqvist H, Jensen H, Tolmachev V, Sundin A. Biodistribution of 211At-labeled humanized monoclonal antibody A33. Cancer Biother Radiopharm 2007; 22:480-7. [PMID: 17803442 DOI: 10.1089/cbr.2007.349a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Radioimmunotherapy (RIT) could be a possible adjuvant treatment method for patients with colorectal carcinoma. The A33 antigen is a promising RIT target, as it is highly and homogenously expressed in 95% of all colorectal carcinomas. In this study, the humanized monoclonal antibody A33 (huA33), targeting the A33 antigen, was labeled with the therapeutic nuclide 211At, and the biodistribution and in vivo targeting ability of the conjugate was investigated in an athymic mouse xenograft model. There was an accumulation of 211At in tumor tissue over time, but no substantial accumulation was seen in any organ apart from the skin and thyroid, indicating no major release of free 211At in vivo. At all time points, the uptake of 211At-huA33 was higher in tumor tissue than in most organs, and at 8 hours postinjection (p.i.), no organ had a higher uptake than tumor tissue. The tumor-to-blood ratio of 211At-huA33 increased with time, reaching 2.5 after 21 hours p.i. The highest absorbed dose was found in the blood, but the tumor received a higher dose than any organ other than the thyroid. An in vivo blocking experiment showed that 211At-huA33 binds specifically to human tumor xenografts in athymic mice. In conclusion, the favorable biodistribution and specific in vivo targeting ability of 211At-huA33 makes it a potential therapeutic agent for the RIT of metastatic colorectal carcinoma.
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Affiliation(s)
- Ylva Almqvist
- Unit of Radiology, Department of Oncology, Radiology, and Clinical Immunology, Uppsala University, Sweden, and Department of Clinical Physiology and Nuclear Medicine, PET and Cyclotron Unit, Rigshospitalet, Copenhagen, Denmark.
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9
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Mume E, Orlova A, Malmström PU, Lundqvist H, Sjöberg S, Tolmachev V. Radiobromination of humanized anti-HER2 monoclonal antibody trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate, a potential label for immunoPET. Nucl Med Biol 2006; 32:613-22. [PMID: 16026708 DOI: 10.1016/j.nucmedbio.2005.04.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Revised: 04/17/2005] [Accepted: 04/17/2005] [Indexed: 11/24/2022]
Abstract
Combining the specificity of radioimmunoscintigraphy and the high sensitivity of PET in an in vivo detection technique could improve the quality of nuclear diagnostics. Positron-emitting nuclide (76)Br (T(1/2)=16.2 h) might be a possible candidate for labeling monoclonal antibodies (mAbs) and their fragments, provided that the appropriate labeling chemistry has been established. For internalizing antibodies, such as the humanized anti-HER2 monoclonal antibody, trastuzumab, radiobromine label should be residualizing, i.e., ensuring that radiocatabolites are trapped intracellularly after the proteolytic degradation of antibody. This study evaluated the chemistry of indirect radiobromination of trastuzumab using N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate. Literature data indicated that the use of this method provided residualizing properties for iodine and astatine labels on some antibodies. An optimized "one-pot" procedure produced an overall labeling efficiency of 45.5+/-1.2% over 15 min. The bromine label was stable under physiological and denaturing conditions. The labeled trastuzumab retained its capacity to bind specifically to HER2-expressing SKOV-3 ovarian carcinoma cells in vitro (immunoreactivity more than 75%). However, in vitro cell test did not demonstrate that the radiobromination of trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate improves cellular retention of radioactivity in comparison with the use of N-succinimidyl 4-bromobenzoate.
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Affiliation(s)
- Eskender Mume
- Organic Chemistry, Department of Chemistry, Uppsala University, S-751 24 Uppsala, Sweden
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Abstract
Positron emission tomography (PET) is a medical imaging technique using compounds labelled with short-lived positron emitting radioisotopes to obtain functional information of physiological, biochemical and pharmacological processes in vivo. The need to understand the potential link between the ingestion of individual dietary agents and the effect of health promotion or health risk requires the exact metabolic characterization of food ingredients in vivo. This exciting but rather new research field of PET would provide new insights and perspectives on food chemistry by assessing quantitative information on pharmocokinetics and pharmacodynamics of food ingredients and dietary agents. To fully exploit PET technology in food chemistry appropriately radiolabelled compounds as relevant for food sciences are needed. The most widely used short-lived positron emitters are (11)C (t(1/2) = 20.4 min) and (18)F (t(1/2) = 109.8 min). Longer-lived radioisotopes are available by using (76)Br (t(1/2) = 16.2 h) and (124)I (t(1/2) = 4.12 d). The present review article tries to discuss some aspects for the radiolabelling of food ingredients and dietary agents either by means of isotopic labelling with (11)C or via prosthetic group labelling approaches using the positron emitting halogens (18)F, (76)Br and (124)I.
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Affiliation(s)
- F Wuest
- Positron Emission Tomography Center, Institute of Bioinorganic and Radiopharmaceutical Chemistry, Research Center Rossendorf, Dresden, Germany.
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Bruskin A, Sivaev I, Persson M, Lundqvist H, Carlsson J, Sjöberg S, Tolmachev V. Radiobromination of monoclonal antibody using potassium [76Br] (4 isothiocyanatobenzyl-ammonio)-bromo-decahydro-closo-dodecaborate (Bromo-DABI). Nucl Med Biol 2004; 31:205-11. [PMID: 15013486 DOI: 10.1016/j.nucmedbio.2003.08.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2003] [Revised: 06/18/2003] [Accepted: 08/23/2003] [Indexed: 11/23/2022]
Abstract
The use of charged linkers in attaching radiohalogens to tumor-seeking biomolecules may improve intracellular retention of the radioactive label after internalization and degradation of targeting proteins. Derivatives of polyhedral boron clusters, such as closo-dodecaborate (2-) anion, might be possible charged linkers. In this study, a bifunctional derivative of closo-dodecaborate, (4-isothiocyanatobenzyl-ammonio)-undecahydro-closo-dodecaborate (DABI) was labeled with positron-emitting nuclide (76)Br (T 1/2 = 16.2 h) and coupled to anti-HER2/neu humanized antibody Trastuzumab. The overall labeling yield at optimized conditions was 80.7 +/- 0.6%. The label was proven to be stable in vitro in physiological and a set of denaturing conditions. The labeled antibody retained its capacity to bind to HER-2/neu antigen expressing cells. The results of the study demonstrated feasibility for using derivatives of closo-dodecaborate in indirect labeling of antibodies for radioimmunoPET.
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Affiliation(s)
- Alexander Bruskin
- Unit of Biomedical Radiation Sciences, Rudbecklaboratoriet, Uppsala University, S-751 85, Uppsala, Sweden
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Winberg KJ, Persson M, Malmström PU, Sjöberg S, Tolmachev V. Radiobromination of anti-HER2/neu/ErbB-2 monoclonal antibody using the p-isothiocyanatobenzene derivative of the [76Br]undecahydro-bromo-7,8-dicarba-nido-undecaborate(1-) ion. Nucl Med Biol 2004; 31:425-33. [PMID: 15093812 DOI: 10.1016/j.nucmedbio.2003.11.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2003] [Revised: 10/18/2003] [Accepted: 11/27/2003] [Indexed: 11/28/2022]
Abstract
The monoclonal humanized anti-HER2 antibody trastuzumab was radiolabeled with the positron emitter (76)Br (T(1/2) =16.2 h). Indirect labeling was performed using the p-isothiocyanatobenzene derivative of the [(76)Br]undecahydro-bromo-7,8-dicarba-nido-undecaborate(1-) ((76)Br-NBI) as a precursor molecule. (76)Br-NBI was prepared by bromination of the 7-(p-isothiocyanato-phenyl)dodecahydro-7,8-dicarba-nido-undecaborate(1-) ion (NBI) with a yield of 93-95% using Chloramine-T (CAT) as an oxidant. Coupling of radiobrominated NBI to antibody was performed without intermediate purification, in an "one pot" reaction. An overall labeling yield of 55.7 +/- 4.8% (mean +/- maximum error) was achieved when 300 microg of antibody was labeled. The label was stable in vitro in physiological and denaturing conditions. In a cell binding test, trastuzumab remained immunoreactive after labeling.
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Affiliation(s)
- Karl Johan Winberg
- Institute of Chemistry, Department of Organic Chemistry, Uppsala University, Sweden
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Beattie BJ, Finn RD, Rowland DJ, Pentlow KS. Quantitative imaging of bromine‐76 and yttrium‐86 with PET: A method for the removal of spurious activity introduced by cascade gamma rays. Med Phys 2003; 30:2410-23. [PMID: 14528963 DOI: 10.1118/1.1595599] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Positron Emission Tomography of bromine-76 and yttrium-86 results in the detection of coincident events that are not strictly associated with annihilation photon pairs. Instead, these coincidences occur because prompt gamma rays emitted by these nuclides result in cascades of photons that are emitted within the timing window of the PET scanner. Pairs of detected photons from these cascades are not angularly correlated and therefore contain little information regarding the location of their source. Furthermore, these coincidences are not removed by correction procedures (e.g., randoms, scatter) routinely applied to PET data. If left uncorrected, the cascade coincidences will result in spurious apparent activity within the PET images. A correction, applied within projection space, that removes the cascade coincidence signal from septa-in (i.e., two-dimensional) datasets is proposed and tested on phantom data.
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Affiliation(s)
- Bradley J Beattie
- Department of Neurology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
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