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Pretze M, Michler E, Runge R, Wetzig K, Tietze K, Brandt F, Schultz MK, Kotzerke J. Influence of the Molar Activity of 203/212Pb-PSC-PEG 2-TOC on Somatostatin Receptor Type 2-Binding and Cell Uptake. Pharmaceuticals (Basel) 2023; 16:1605. [PMID: 38004470 PMCID: PMC10675797 DOI: 10.3390/ph16111605] [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: 10/10/2023] [Revised: 11/06/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
(1) Background: In neuroendocrine tumors (NETs), somatostatin receptor subtype 2 is highly expressed, which can be targeted by a radioactive ligand such as [177Lu]Lu-1,4,7,10-tetraazacyclododecane-N,N',N″,N‴,-tetraacetic acid-[Tyr3,Thr8]-octreotide (177Lu-DOTA-TOC) and, more recently, by a lead specific chelator (PSC) containing 203/212Pb-PSC-PEG2-TOC (PSC-TOC). The molar activity (AM) can play a crucial role in tumor uptake, especially in receptor-mediated uptake, such as in NETs. Therefore, an investigation of the influence of different molar activities of 203/212Pb-PSC-TOC on cell uptake was investigated. (2) Methods: Optimized radiolabeling of 203/212Pb-PSC-TOC was performed with 50 µg of precursor in a NaAc/AcOH buffer at pH 5.3-5.5 within 15-45 min at 95° C. Cell uptake was studied in AR42 J, HEK293 sst2, and ZR75-1 cells. (3) Results: 203/212Pb-PSC-TOC was radiolabeled with high radiochemical purity >95% and high radiochemical yield >95%, with AM ranging from 0.2 to 61.6 MBq/nmol. The cell uptake of 203Pb-PSC-TOC (AM = 38 MBq/nmol) was highest in AR42 J (17.9%), moderate in HEK293 sstr (9.1%) and lowest in ZR75-1 (0.6%). Cell uptake increased with the level of AM. (4) Conclusions: A moderate AM of 15-40 MBq/nmol showed the highest cell uptake. No uptake limitation was found in the first 24-48 h. Further escalation experiments with even higher AM should be performed in the future. It was shown that AM plays an important role because of its direct dependence on the cellular uptake levels, possibly due to less receptor saturation with non-radioactive ligands at higher AM.
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Affiliation(s)
- Marc Pretze
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Enrico Michler
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Roswitha Runge
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Kerstin Wetzig
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Katja Tietze
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Florian Brandt
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
| | - Michael K. Schultz
- Department of Radiology, University of Iowa, Iowa City, IA 52240, USA;
- Viewpoint Molecular Targeting, Inc. (DBA Perspective Therapeutics), Coralville, IA 52241, USA
- Department of Chemistry, University of Iowa, Iowa City, IA 52241, USA
- Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, USA
| | - Jörg Kotzerke
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (E.M.); (R.R.); (K.W.); (K.T.); (F.B.); (J.K.)
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Chapeau D, Koustoulidou S, Handula M, Beekman S, de Ridder C, Stuurman D, de Blois E, Buchatskaya Y, van der Schilden K, de Jong M, Konijnenberg MW, Seimbille Y. [ 212Pb]Pb-eSOMA-01: A Promising Radioligand for Targeted Alpha Therapy of Neuroendocrine Tumors. Pharmaceuticals (Basel) 2023; 16:985. [PMID: 37513897 PMCID: PMC10384862 DOI: 10.3390/ph16070985] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/03/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
Peptide receptor radionuclide therapy (PRRT) has been applied to the treatment of neuroendocrine tumors (NETs) for over two decades. However, improvement is still needed, and targeted alpha therapy (TAT) with alpha emitters such as lead-212 (212Pb) represents a promising avenue. A series of ligands based on octreotate was developed. Lead-203 was used as an imaging surrogate for the selection of the best candidate for the studies with lead-212. 203/212Pb radiolabeling and in vitro assays were carried out, followed by SPECT/CT imaging and ex vivo biodistribution in NCI-H69 tumor-bearing mice. High radiochemical yields (≥99%) and purity (≥96%) were obtained for all ligands. [203Pb]Pb-eSOMA-01 and [203Pb]Pb-eSOMA-02 showed high stability in PBS and mouse serum up to 24 h, whereas [203Pb]Pb-eSOMA-03 was unstable in those conditions. All compounds exhibited a nanomolar affinity (2.5-3.1 nM) for SSTR2. SPECT/CT images revealed high tumor uptake at 1, 4, and 24 h post-injection of [203Pb]Pb-eSOMA-01/02. Ex vivo biodistribution studies confirmed that the highest uptake in tumors was observed with [212Pb]Pb-eSOMA-01. [212Pb]Pb-eESOMA-01 displayed the highest absorbed dose in the tumor (35.49 Gy/MBq) and the lowest absorbed dose in the kidneys (121.73 Gy/MBq) among the three tested radioligands. [212Pb]Pb-eSOMA-01 is a promising candidate for targeted alpha therapy of NETs. Further investigations are required to confirm its potential.
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Affiliation(s)
- Dylan Chapeau
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Sofia Koustoulidou
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Maryana Handula
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Savanne Beekman
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Corrina de Ridder
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Debra Stuurman
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Erik de Blois
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Yulia Buchatskaya
- Nuclear Research & Consultancy Group, 1755 LE Petten, The Netherlands
| | | | - Marion de Jong
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Mark W Konijnenberg
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
| | - Yann Seimbille
- Erasmus MC, Department of Radiology and Nuclear Medicine, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands
- Erasmus MC Cancer Institute, 3015 GD Rotterdam, The Netherlands
- TRIUMF, Life Sciences Division, Vancouver, BC V6T 2A3, Canada
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Orcutt KD, Henry KE, Habjan C, Palmer K, Heimann J, Cupido JM, Gottumukkala V, Cissell DD, Lyon MC, Hussein AI, Liu D, Li M, Johnson FL, Schultz MK. Dosimetry of [ 212Pb]VMT01, a MC1R-Targeted Alpha Therapeutic Compound, and Effect of Free 208Tl on Tissue Absorbed Doses. Molecules 2022; 27:molecules27185831. [PMID: 36144563 PMCID: PMC9504749 DOI: 10.3390/molecules27185831] [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] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 08/26/2022] [Accepted: 08/27/2022] [Indexed: 01/28/2023]
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 [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 mGyRBE = 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.
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Affiliation(s)
- Kelly D. Orcutt
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA
| | | | | | | | | | | | | | | | | | | | - Dijie Liu
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA
| | - Mengshi Li
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA
| | | | - Michael K. Schultz
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA
- Department of Radiology, The University of Iowa, Iowa City, IA 52242, USA
- Department of Radiation Oncology, The University of Iowa, Iowa City, IA 52242, USA
- Departments of Radiology and Radiation Oncology, The University of Iowa, Iowa City, IA 52242, USA
- Correspondence: ; Tel.: +1-(319)-335-8017
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