Optimization, biological evaluation and microPET imaging of copper-64-labeled bombesin agonists, [64Cu-NO2A-(X)-BBN(7–14)NH2], in a prostate tumor xenografted mouse model

Introduction In the present study, we describe a 64Cu-radiolabeled heterodimeric peptide conjugate for dual αvβ3/GRPr (αvβ3 integrin/gastrin releasing peptide receptor) targeting of the form [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] (RGD: the amino acid sequence [Arg-Gly-Asp], a nonregulatory peptide used for αvβ3 integrin receptor targeting; Glu: glutamic acid; NO2A: 1,4,7-triazacyclononane-1,4-diacetic acid; 6-Ahx: 6-amino hexanoic acid; and RM2: (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2), an antagonist analogue of bombesin (BBN) peptide used for GRPr targeting). Methods [RGD-Glu-6Ahx-RM2] was conjugated to a NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid) complexing agent to produce [RGD-Glu-[NO2A]-6-Ahx-RM2], which was purified by reversed-phase high-performance liquid chromatography (RPHPLC) and characterized by electrospray ionization–mass spectrometry (ESI-MS). Radiolabeling of the conjugate with 64Cu produced [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] in high radiochemical yield (≥95%). In vivo behavior of the radiolabeled peptide conjugate was investigated in normal CF-1 mice and in the PC-3 human prostate cancer experimental model. Results A competitive displacement receptor binding assay in human prostate PC-3 cells using 125I-[Tyr4]BBN as the radioligand showed high binding affinity of [RGD-Glu-[natCu-NO2A]-6-Ahx-RM2] conjugate for the GRPr (3.09 ± 0.34 nM). A similar assay in human, glioblastoma U87-MG cells using 125I-Echistatin as the radioligand indicated a moderate receptor-binding affinity for the αvβ3 integrin (518 ± 37.5 nM). In vivo studies of [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] showed high accumulation (4.86 ± 1.01 %ID/g, 1 h post-intravenous injection (p.i.)) and prolonged retention(4.26 ± 1.23 %ID/g, 24 h p.i.) of tracer in PC-3 tumor-bearing mice. Micro-positron emission tomography (microPET) molecular imaging studies produced high-quality, high contrast images in PC-3 tumor-bearing mice at 4 h p.i. Conclusions The favorable pharmacokinetics and enhanced tumor uptake of 64Cu-NOTA-RGD-Glu-6Ahx-RM2 warrant further investigations for dual integrin and GRPr-positive tumor imaging and possible radiotherapy.

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“…(1.32±0.27% ID/g at 1 h p.i). This again suggests that the Cu(II)/NO2A metal complex was effectively stable under in vivo conditions [41]. …”

Section: Resultsmentioning

confidence: 99%

A heterodimeric [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] αvβ3/GRPr-targeting antagonist radiotracer for PET imaging of prostate tumors

Durkan

Jiang

Rold

et al. 2014

Nuclear Medicine and Biology

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“…These 2 peptides have been radiolabeled with radiometals ( 111 In, 68 Ga, and 64 Cu) for SPECT and PET imaging of PCa (24–27). AMBA has also been radiolabeled with 177 Lu for radionuclide therapy of PCa (23,28).…”

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confidence: 99%

A Comparative Study of Radiolabeled Bombesin Analogs for the PET Imaging of Prostate Cancer

Liu

et al. 2013

J Nucl Med

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Radiolabeled bombesin (BBN) analogs that bind to the gastrin-releasing peptide receptor (GRPR) represent a topic of active investigation for the development of molecular probes for PET or SPECT of prostate cancer (PCa). RM1 and AMBA have been identified as the 2 most promising BBN peptides for GRPR-targeted cancer imaging and therapy. In this study, to develop a clinically translatable BBN-based PET probe, we synthesized and evaluated 18F-AlF- (aluminum-fluoride) and 64Cu-radiolabeled RM1 and AMBA analogs for their potential application in PET imaging of PCa. Methods 1,4,7-triazacyclononane, 1-glutaric acid-4,7 acetic acid (NODAGA)–conjugated RM1 and AMBA were synthesized and tested for their GRPR-binding affinities. The NODAGA-RM1 and NODAGA-AMBA probes were further radiolabeled with 64Cu or 18F-AlF and then evaluated in a subcutaneous PCa xenograft model (PC3) by small-animal PET imaging and bio-distribution studies. Results NODAGA-RM1 and NODAGA-AMBA can be successfully synthesized and radiolabeled with 64Cu and 18F-AlF. 64Cu- and 18F-AlF-labeled NODAGA-RM1 demonstrated excellent serum stability and tumor-imaging properties in the in vitro stability assays and in vivo imaging studies. 64Cu-NODAGA-RM1 exhibited tumor uptake values of 3.3 ± 0.38, 3.0 ± 0.76, and 3.5 ± 1.0 percentage injected dose per gram of tissue (%ID/g) at 0.5, 1.5, and 4 h after injection, respectively. 18F-AlF-NODAGA-RM1 exhibited tumor uptake values of 4.6 ± 1.5, 4.0 ± 0.87, and 3.9 ± 0.48 %ID/g at 0.5, 1, and 2 h, respectively. Conclusion The high-stability, efficient tumor uptake and optimal pharmacokinetic properties highlight 18F-AlF-NODAGA-RM1 as a probe with great potential and clinical application for the PET imaging of prostate cancer.

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“…[31][32] Besides the previously tested linear carbon chain and polyethylene glycol, there are two other types of linkers, polyamino acid and the cationic 4-amino-(1-carboxymethyl)piperidine (Pip), that are also commonly used for the design of radio-peptides. [33][34][35][36][37][38] For comparison and in hopes to optimize the tumor-to-background contrast through the selection of linker, we synthesized two more analogs, 68 Ga-P04115 and 68 Ga-P04168 (Table 1 and Fig. 1), containing Gly-Gly and Pip, respectively as the linker.…”

Section: Biodistribution and Pet/ct Imagingmentioning

confidence: 99%

Imaging Bradykinin B1 Receptor with⁶⁸Ga-Labeled [des-Arg¹⁰]Kallidin Derivatives: Effect of the Linker on Biodistribution and Tumor Uptake

et al. 2015

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Bradykinin B1 receptor (B1R) that is overexpressed in cancers but minimally expressed in normal healthy tissues represents an attractive biomarker for the development of cancer imaging agents. The goal of this study was to evaluate the effect of different linkers on the pharmacokinetics and tumor uptake of a B1R-targeting radio-peptide sequence, 68Ga-DOTA-linker-Lys-Arg-Pro-Hyp-Gly-Cha-Ser-Pro-Leu. Four peptides, SH01078, P03034, P04115, and P04168, with 6-aminohexanoic acid, 9-amino-4,7-dioxanonanoic acid, Gly-Gly, and 4-amino-(1-carboxymethyl)piperidine, respectively, as the linker were synthesized and evaluated. In vitro competition binding assays showed that the Ki values of SH01078, P03034, P04115, and P04168 were 27.8±4.9, 16.0±1.9, 11.4±2.5, and 3.6±0.2 nM, respectively. Imaging and biodistribution studies were performed in mice bearing both B1R-positive HEK293T::hB1R and B1R-negative HEK293T tumors. All tracers showed mainly renal excretion with excellent tumor visualization and minimal background activity except for kidneys and bladder. The average uptake of 68Ga-labeled SH01078, P03034, and P04115 in HEK293T::hB1R tumor was similar (1.96-2.17%ID/g) at 1 h postinjection. 68Ga-P04168 generated higher HEK293T::hB1R tumor uptake (4.15±1.13%ID/g) and lower background activity, leading to a >2-fold improvement in HEK293T::hB1R tumor-to-background (HEK293T tumor, blood, muscle, and liver) contrasts over those of 68Ga-labeled SH01078, P03034, and P04115. Our results indicate that the choice of linker affects binding affinity, pharmacokinetics, and tumor targeting. The use of the cationic 4-amino-(1-carboxymethyl)piperidine linker improved tumor visualization, and the resulting 68Ga-P04168 might be promising for clinical application for imaging B1R-expressing tumors with positron emission tomography.

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Optimization, biological evaluation and microPET imaging of copper-64-labeled bombesin agonists, [64Cu-NO2A-(X)-BBN(7–14)NH2], in a prostate tumor xenografted mouse model

Cited by 65 publications

References 30 publications

A heterodimeric [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] αvβ3/GRPr-targeting antagonist radiotracer for PET imaging of prostate tumors

A heterodimeric [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] αvβ3/GRPr-targeting antagonist radiotracer for PET imaging of prostate tumors

A Comparative Study of Radiolabeled Bombesin Analogs for the PET Imaging of Prostate Cancer

Imaging Bradykinin B1 Receptor with⁶⁸Ga-Labeled [des-Arg¹⁰]Kallidin Derivatives: Effect of the Linker on Biodistribution and Tumor Uptake

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Optimization, biological evaluation and microPET imaging of copper-64-labeled bombesin agonists, [64Cu-NO2A-(X)-BBN(7–14)NH2], in a prostate tumor xenografted mouse model

Cited by 65 publications

References 30 publications

A heterodimeric [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] αvβ3/GRPr-targeting antagonist radiotracer for PET imaging of prostate tumors

A heterodimeric [RGD-Glu-[64Cu-NO2A]-6-Ahx-RM2] αvβ3/GRPr-targeting antagonist radiotracer for PET imaging of prostate tumors

A Comparative Study of Radiolabeled Bombesin Analogs for the PET Imaging of Prostate Cancer

Imaging Bradykinin B1 Receptor with68Ga-Labeled [des-Arg10]Kallidin Derivatives: Effect of the Linker on Biodistribution and Tumor Uptake

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Imaging Bradykinin B1 Receptor with⁶⁸Ga-Labeled [des-Arg¹⁰]Kallidin Derivatives: Effect of the Linker on Biodistribution and Tumor Uptake