Dataset Information

Preclinical Evaluation of the Copper-64 Labeled GRPR-Antagonist RM26 in Comparison with the Cobalt-55 Labeled Counterpart for PET-Imaging of Prostate Cancer.

ABSTRACT: Gastrin-releasing peptide receptor (GRPR) is overexpressed in the majority of prostate cancers. This study aimed to investigate the potential of 64Cu (radionuclide for late time-point PET-imaging) for imaging of GRPR expression using NOTA-PEG2-RM26 and NODAGA-PEG2-RM26. Methods: NOTA/NODAGA-PEG2-RM26 were labeled with 64Cu and evaluated in GRPR-expressing PC-3 cells. Biodistribution of [64Cu]Cu-NOTA/NODAGA-PEG2-RM26 was studied in PC-3 xenografted mice and compared to the biodistribution of [57Co]Co-NOTA/NODAGA-PEG2-RM26 at 3 and 24 h p.i. Preclinical PET/CT imaging was performed in tumor-bearing mice. NOTA/NODAGA-PEG2-RM26 were stably labeled with 64Cu with quantitative yields. In vitro, binding of [64Cu]Cu-NOTA/NODAGA-PEG2-RM26 was rapid and GRPR-specific with slow internalization. In vivo, [64Cu]Cu-NOTA/NODAGA-PEG2-RM26 bound specifically to GRPR-expressing tumors with fast clearance from blood and normal organs and displayed generally comparable biodistribution profiles to [57Co]Co-NOTA/NODAGA-PEG2-RM26; tumor uptake exceeded normal tissue uptake 3 h p.i.. Tumor-to-organ ratios did not increase significantly with time. [64Cu]Cu-NOTA-PEG2-RM26 had a significantly higher liver and pancreas uptake compared to other agents. 57Co-labeled radioconjugates showed overall higher tumor-to-non-tumor ratios, compared to the 64Cu-labeled counterparts. [64Cu]Cu-NOTA/NODAGA-PEG2-RM26 was able to visualize GRPR-expression in a murine PC model using PET. However, [55/57Co]Co-NOTA/NODAGA-PEG2-RM26 provided better in vivo stability and overall higher tumor-to-non-tumor ratios compared with the 64Cu-labeled conjugates.

SUBMITTER: Baun C

PROVIDER: S-EPMC7766840 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Preclinical Evaluation of the Copper-64 Labeled GRPR-Antagonist RM26 in Comparison with the Cobalt-55 Labeled Counterpart for PET-Imaging of Prostate Cancer.

Baun Christina C Mitran Bogdan B Rinne Sara S SS Dam Johan H JH Olsen Birgitte B BB Tolmachev Vladimir V Orlova Anna A Thisgaard Helge H

Molecules (Basel, Switzerland) 20201218 24

Gastrin-releasing peptide receptor (GRPR) is overexpressed in the majority of prostate cancers. This study aimed to investigate the potential of 64Cu (radionuclide for late time-point PET-imaging) for imaging of GRPR expression using NOTA-PEG2-RM26 and NODAGA-PEG2-RM26. Methods: NOTA/NODAGA-PEG2-RM26 were labeled with 64Cu and evaluated in GRPR-expressing PC-3 cells. Biodistribution of [64Cu]Cu-NOTA/NODAGA-PEG2-RM26 was ...[more]

PMID: 33352838

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Project description:This study was designed to analyze the safety, biodistribution, and radiation dosimetry of a gastrin-releasing peptide receptor (GRPR) antagonist PET tracer, 68Ga-RM26; to assess its clinical diagnostic value in prostate cancer patients; and to perform a direct comparison between GRPR antagonist 68Ga-RM26 and agonist 68Ga-BBN. Methods: Five healthy volunteers were enrolled to validate the safety of 68Ga-RM26 and calculate dosimetry. A total of 28 patients with prostate cancer (17 newly diagnosed and 11 posttherapy) were recruited and provided written informed consent. All the cancer patients underwent PET/CT at 15-30 min after intravenous injection of 1.85 MBq (0.05 mCi) per kilogram of body weight of 68Ga-RM26. Among them, 22 patients (11 newly diagnosed and 11 posttherapy) underwent 68Ga-BBN PET/CT for comparison within 1 wk. 99mTc-MDP (methylene diphosphonate) bone scans were obtained within 2 wk for comparison. GRPR immunohistochemical staining of tumor samples was performed. Results: The administration of 68Ga-M26 was well tolerated by all subjects, with no adverse symptoms being noticed or reported during the procedure and at 2-wk follow-up. The total effective dose equivalent and effective dose were 0.0912 ± 0.0140 and 0.0657 ± 0.0124 mSv/MBq, respectively. In the 17 patients with newly diagnosed prostate cancer, 68Ga-RM26 PET/CT showed positive prostate-confined findings in 15 tumors with an SUVmax of 6.49 ± 2.37. In the 11 patients who underwent prostatectomy or brachytherapy with or without androgen deprivation therapy, 68Ga-RM26 PET/CT detected 8 metastatic lymph nodes in 3 patients with an SUVmax of 4.28 ± 1.25 and 21 bone lesions in 8 patients with an SUVmax of 3.90 ± 3.07. Compared with 68Ga-RM26 PET/CT, GRPR agonist 68Ga-BBN PET/CT detected fewer primary lesions and lymph node metastases as well as demonstrated lower tracer accumulation. There was a significant positive correlation between SUV derived from 68Ga-RM26 PET and the expression level of GRPR (P < 0.001). Conclusion: This study indicates the safety and significant efficiency of GRPR antagonist 68Ga-RM26. 68Ga-RM26 PET/CT would have remarkable value in detecting both primary prostate cancer and metastasis. 68Ga-RM26 is also expected to be better than GRPR agonist as an imaging marker to evaluate GRPR expression in prostate cancer.

Project description:Expression of the gastrin-releasing peptide receptor (GRPR) in prostate cancer suggests that this receptor can be used as a potential molecular target to visualize and treat these tumors. We have previously investigated an antagonist analog of bombesin (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2, RM26) conjugated to 1,4,7-triazacyclononane-N,N',N''-triacetic acid (NOTA) via a diethylene glycol (PEG2) spacer (NOTA-P2-RM26) labeled with (68)Ga and (111)In. We found that this conjugate has favorable properties for in vivo imaging of GRPR-expression. The focus of this study was to develop a (18)F-labelled PET agent to visualize GRPR. NOTA-P2-RM26 was labeled with (18)F using aluminum-fluoride chelation. Stability, in vitro binding specificity and cellular processing tests were performed. The inhibition efficiency (IC50) of the [(nat)F]AlF-NOTA-P2-RM26 was compared to that of the (nat)Ga-loaded peptide using (125)I-Tyr(4)-BBN as the displacement radioligand. The pharmacokinetics and in vivo binding specificity of the compound were studied. NOTA-P2-RM26 was labeled with (18)F within 1 h (60-65% decay corrected radiochemical yield, 55 GBq/µmol). The radiopeptide was stable in murine serum and showed high specific binding to PC-3 cells. [(nat)F]AlF-NOTA-P2-RM26 showed a low nanomolar inhibition efficiency (IC50=4.4±0.8 nM). The internalization rate of the tracer was low. Less than 14% of the cell-bound radioactivity was internalized after 4 h. The biodistribution of [(18)F]AlF-NOTA-P2-RM26 demonstrated rapid blood clearance, low liver uptake and low kidney retention. The tumor uptake at 3 h p.i. was 5.5±0.7 %ID/g, and the tumor-to-blood, -muscle and -bone ratios were 87±42, 159±47, 38±16, respectively. The uptake in tumors, pancreas and other GRPR-expressing organs was significantly reduced when excess amount of non-labeled peptide was co-injected. The low uptake in bone suggests a high in vivo stability of the Al-F bond. High contrast PET image was obtained 3 h p.i. The initial biological results suggest that [(18)F]AlF-NOTA-P2-RM26 is a promising candidate for PET imaging of GRPR in vivo.

Dataset Information

Preclinical Evaluation of the Copper-64 Labeled GRPR-Antagonist RM26 in Comparison with the Cobalt-55 Labeled Counterpart for PET-Imaging of Prostate Cancer.

Publications

Preclinical Evaluation of the Copper-64 Labeled GRPR-Antagonist RM26 in Comparison with the Cobalt-55 Labeled Counterpart for PET-Imaging of Prostate Cancer.

Similar Datasets

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