In vitro and in vivo evaluation of a 64Cu-labeled NOTA-Bn-SCN-Aoc-bombesin analogue in gastrin-releasing peptide receptor expressing prostate cancer

Background: [68Ga]Ga-RM2 is a potent Gastrin-Releasing Peptide-receptor (GRP-R) antagonist for imaging prostate cancer and breast cancer, currently under clinical evaluation in several specialized centers around the world. Targeted radionuclide therapy of GRP-R-expressing tumors is also being investigated. We here report the characteristics of a kit-based formulation of RM2 that should ease the development of GRP-R imaging and make it available to more institutions and patients. Methods: Stability of the investigated kits over one year was determined using LC/MS/MS and UV-HPLC. Direct 68Ga-radiolabeling was optimized with respect to buffer (pH), temperature, reaction time and shaking time. Conventionally prepared [68Ga]Ga-RM2 using an automated synthesizer was used as a comparator. Finally, the [68Ga]Ga-RM2 product was assessed with regards to hydrophilicity, affinity, internalization, membrane bound fraction, calcium mobilization assay and efflux, which is a valuable addition to the in vivo literature. Results: The kit-based formulation, kept between 2 °C and 8 °C, was stable for over one year. Using acetate buffer pH 3.0 in 2.5–5.1 mL total volume, heating at 100 °C during 10 min and cooling down for 5 min, the [68Ga]Ga-RM2 produced by kit complies with the requirements of the European Pharmacopoeia. Compared with the module production route, the [68Ga]Ga-RM2 produced by kit was faster, displayed higher yields, higher volumetric activity and was devoid of ethanol. In in vitro evaluations, the [68Ga]Ga-RM2 displayed sub-nanomolar affinity (Kd = 0.25 ± 0.19 nM), receptor specific and time dependent membrane-bound fraction of 42.0 ± 5.1% at 60 min and GRP-R mediated internalization of 24.4 ± 4.3% at 30 min. The [natGa]Ga-RM2 was ineffective in stimulating intracellular calcium mobilization. Finally, the efflux of the internalized activity was 64.3 ± 6.5% at 5 min. Conclusion: The kit-based formulation of RM2 is suitable to disseminate GRP-R imaging and therapy to distant hospitals without complex radiochemistry equipment.

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[99mTc]Tc-DB15 in GRPR-Targeted Tumor Imaging with SPECT: From Preclinical Evaluation to the First Clinical Outcomes

Cancers ◽

10.3390/cancers13205093 ◽

2021 ◽

Vol 13 (20) ◽

pp. 5093

Author(s):

Berthold A. Nock ◽

Aikaterini Kaloudi ◽

Panagiotis Kanellopoulos ◽

Barbara Janota ◽

Barbara Bromińska ◽

...

Keyword(s):

Tumor Imaging ◽

Pharmacokinetic Profile ◽

Diglycolic Acid ◽

Preclinical Evaluation ◽

Peptide Receptor ◽

Gastrin Releasing Peptide ◽

Specific Uptake ◽

Grpr Antagonist

Diagnostic imaging and radionuclide therapy of prostate (PC) and breast cancer (BC) using radiolabeled gastrin-releasing peptide receptor (GRPR)-antagonists represents a promising approach. We herein propose the GRPR-antagonist based radiotracer [99mTc]Tc-DB15 ([99mTc]Tc-N4-AMA-DGA-DPhe6,Sar11,LeuNHEt13]BBN(6-13); N4: 6-carboxy-1,4,8,11-tetraazaundecane, AMA: aminomethyl-aniline, DGA: diglycolic acid) as a new diagnostic tool for GRPR-positive tumors applying SPECT/CT. The uptake of [99mTc]Tc-DB15 was tested in vitro in mammary (T-47D) and prostate cancer (PC-3) cells and in vivo in T-47D or PC-3 xenograft-bearing mice as well as in BC patients. DB15 showed high GRPR-affinity (IC50 = 0.37 ± 0.03 nM) and [99mTc]Tc-DB15 strongly bound to the cell-membrane of T-47D and PC-3 cells, according to a radiolabeled antagonist profile. In mice, the radiotracer showed high and prolonged GRPR-specific uptake in PC-3 (e.g., 25.56 ± 2.78 %IA/g vs. 0.72 ± 0.12 %IA/g in block; 4 h pi) and T-47D (e.g., 15.82 ± 3.20 %IA/g vs. 3.82 ± 0.30 %IA/g in block; 4 h pi) tumors, while rapidly clearing from background. In patients with advanced BC, the tracer could reveal several bone and soft tissue metastases on SPECT/CT. The attractive pharmacokinetic profile of [99mTc]DB15 in mice and its capability to target GRPR-positive BC lesions in patients highlight its prospects for a broader clinical use, an option currently being explored by ongoing clinical studies.

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In Vivo Stabilization of a Gastrin-Releasing Peptide Receptor Antagonist Enhances PET Imaging and Radionuclide Therapy of Prostate Cancer in Preclinical Studies

Theranostics ◽

10.7150/thno.13580 ◽

2016 ◽

Vol 6 (1) ◽

pp. 104-117 ◽

Cited By ~ 24

Author(s):

Kristell L.S. Chatalic ◽

Mark Konijnenberg ◽

Julie Nonnekens ◽

Erik de Blois ◽

Sander Hoeben ◽

...

Keyword(s):

Prostate Cancer ◽

Receptor Antagonist ◽

Pet Imaging ◽

Radionuclide Therapy ◽

Preclinical Studies ◽

Peptide Receptor ◽

Gastrin Releasing Peptide

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In vitro and in vivo evaluation of first-generation carbosilane arene Ru(II)-metallodendrimers in advanced prostate cancer

European Polymer Journal ◽

10.1016/j.eurpolymj.2019.01.047 ◽

2019 ◽

Vol 113 ◽

pp. 229-235 ◽

Cited By ~ 7

Author(s):

Marta Maroto-Diaz ◽

Natalia Sanz del Olmo ◽

Laura Muñoz-Moreno ◽

Ana M. Bajo ◽

M. José Carmena ◽

...

Keyword(s):

Prostate Cancer ◽

Advanced Prostate Cancer ◽

First Generation ◽

In Vivo Evaluation

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In Vitro and In Vivo Application of Radiolabeled Gastrin-Releasing Peptide Receptor Ligands in Breast Cancer

Journal of Nuclear Medicine ◽

10.2967/jnumed.114.153023 ◽

2015 ◽

Vol 56 (5) ◽

pp. 752-757 ◽

Cited By ~ 24

Author(s):

S. U. Dalm ◽

J. W. M. Martens ◽

A. M. Sieuwerts ◽

C. H. M. van Deurzen ◽

S. J. Koelewijn ◽

...

Keyword(s):

Breast Cancer ◽

Receptor Ligands ◽

Peptide Receptor ◽

Gastrin Releasing Peptide

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In Vitro Evaluation and Biodistribution Studies of HPMA Copolymers Targeting the Gastrin Releasing Peptide Receptor in Prostate Cancer

Pharmaceutical Research ◽

10.1007/s11095-020-02952-3 ◽

2020 ◽

Vol 37 (11) ◽

Author(s):

Sameer Alshehri ◽

Wei Fan ◽

Wenting Zhang ◽

Jered C. Garrison

Keyword(s):

Prostate Cancer ◽

In Vitro Evaluation ◽

Peptide Receptor ◽

Gastrin Releasing Peptide ◽

Biodistribution Studies ◽

Hpma Copolymers

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Stability Evaluation and Stabilization of a Gastrin-Releasing Peptide Receptor (GRPR) Targeting Imaging Pharmaceutical

Molecules ◽

10.3390/molecules24162878 ◽

2019 ◽

Vol 24 (16) ◽

pp. 2878 ◽

Cited By ~ 2

Author(s):

Arijit Ghosh ◽

Karen Woolum ◽

Shankaran Kothandaraman ◽

Michael F. Tweedle ◽

Krishan Kumar

Keyword(s):

Prostate Cancer ◽

Ascorbic Acid ◽

Animal Models ◽

Acetate Buffer ◽

Tumor Uptake ◽

Gentisic Acid ◽

Peptide Receptor ◽

Gastrin Releasing Peptide ◽

Human Sera

The prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR) are identified as important targets on prostate cancer. Receptor-targeting radiolabeled imaging pharmaceuticals with high affinity and specificity are useful in studying and monitoring biological processes and responses. Two potential imaging pharmaceuticals, AMBA agonist (where AMBA = DO3A-CH2CO-G-[4-aminobenzyl]- Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH2) and RM1 antagonist (where RM1 = DO3A-CH2CO-G-[4-aminobenzyl]-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2), have demonstrated high binding affinity (IC50) to GRP receptors and high tumor uptake. Antagonists, despite the poor tumor cell internalization properties, can show clearer images and pharmacokinetic profiles by virtue of their higher tumor uptake in animal models compared to agonists. For characterization, development, and translation of a potential imaging pharmaceutical into the clinic, it must be evaluated in a series of tests, including in vitro cell binding assays, in vitro buffer and serum stability studies, the biodistribution of the radiolabeled material, and finally imaging studies in preclinical animal models. Data related to acetate buffer, mouse, canine, and human sera stability of 177Lu-labeled RM1 are presented here and compared with the acetate buffer and sera stability data of AMBA agonist. The samples of 177Lu-labeled RM1 with a high radioconcentration degrade faster than low-radioconcentration samples upon storage at 2–8 °C. Addition of stabilizers, ascorbic acid and gentisic acid, improve the stability of 177Lu-labeled RM1 significantly with gentisic acid being more efficient than ascorbic acid as a stabilizer. The degradation kinetics of 177Lu-labeled AMBA and RM1 in sera follow the order (fastest to slowest): mouse > canine > human sera. Finally, 177Lu-labeled RM1 antagonist is slower to degrade in mouse, canine, and human sera than 177Lu-labeled AMBA agonist, further suggesting that an antagonist is a more promising candidate than agonist for the positron emission tomography (PET) imaging and therapy of prostate cancer patients.

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