Pre-clinical evaluation of eight DOTA coupled gastrin-releasing peptide receptor (GRP-R) ligands for in vivo targeting of receptor-expressing tumors (original) (raw)
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Gastrin-Releasing Peptide (GRP) Analogues for Cancer Imaging
Cancer Biotherapy and Radiopharmaceuticals, 2004
Small neuropeptides, labeled with gamma-and/or beta-emitting radionuclides, are currently being investigated for their ability to bind to cell-surface receptors, overexpressed in a wide variety of malignant tissues being, thus, potentially useful for radionuclide detection and/or therapy for tumors. Particular attention has been focused on the amphibian peptide, bombesin (BN), and the molecularly related gastrin-releasing peptide (GRP). These peptides act as neurotransmitters and endocrine cancer cell-growth factors on normal tissues as well as on neoplastic cells of various origin. In recent investigations, modification of the native peptide structure has been attempted in order to obtain derivatives, which might easily be labeled with radionuclides. Thus, iodinated (I-125) BN derivatives, as well as Indium (In-111) labeled BN analogs are currently being investigated, presenting satisfactory tumor localization. Also, some new BN analogs containing a 6-carbon linker have been prepared and labeled with Rhenium-188, resulting in positive in vitro binding to prostate cancer cells. More recent studies refer to the Technetium-99m labeling of BN, performed either directly, after attaching proper technetium-chelating groups onto the BN sequence, or indirectly, by coupling BN to a preformed 99m Tc-tagging ligand. Both types of conjugates were found to have a high in vitro affinity for cells with BN receptors, also presenting satisfactory in vivo uptake in experimental tumor models. Pilot clinical studies of a new BN-derived, 99m Tclabeled pentadecapeptide indicated significant uptake by breast cancer and invaded lymph nodes, as well as by prostate cancer, small-cell lung carcinoma, gastro-entero-pancreatic tumors, and others, Further studies of this new GRP derivative, as well as of other new BN-like peptides, are intensively performed internationally today.
Journal of Nuclear Medicine, 2014
Gastrin-releasing peptide receptors (GRPrs) are overexpressed on a variety of human cancers, providing the opportunity for peptide receptor targeting via radiolabeled bombesin-based peptides. As part of our ongoing investigations into the development of improved GRPr antagonists, this study aimed at verifying whether and how Nterminal modulations improve the affinity and pharmacokinetics of radiolabeled GRPr antagonists. Methods: The potent GRPr antagonist MJ9, Pip-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 (Pip, 4-amino-1-carboxymethyl-piperidine), was conjugated to 1,4,7triazacyclononane, 1-glutaric acid-4,7 acetic acid (NODAGA), and 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and radiolabeled with 68 Ga and 64 Cu. The GRPr affinity of the corresponding metalloconjugates was determined using 125 I-Tyr 4-BN as a radioligand. The labeling efficiency of 68 Ga 31 was compared between NODAGA-MJ9 and NOTA-MJ9 in acetate buffer, at room temperature and at 95°C. The 68 Ga and 64 Cu conjugates were further evaluated in vivo in PC3 tumor xenografts by biodistribution and PET imaging studies. Results: The half maximum inhibitory concentrations of all the metalloconjugates are in the high picomolar-low nanomolar range, and these are the most affine-radiolabeled GRPr antagonists we have studied so far in our laboratory. NODAGA-MJ9 incorporates 68 Ga 31 nearly quantitatively (.98%) at room temperature within 10 min and at much lower peptide concentrations (1.4 • 10 −6 M) than NOTA-MJ9, for which the labeling yield was approximately 45% under the same conditions and increased to 75% at 95°C for 5 min. Biodistribution studies showed high and specific tumor uptake, with a maximum of 23.3 ± 2.0 percentage injected activity per gram of tissue (%IA/g) for 68 Ga-NOTA-MJ9 and 16.7 ± 2.0 %IA/g for 68 Ga-NODAGA-MJ9 at 1 h after injection. The acquisition of PET images with the 64 Cu-MJ9 conjugates at later time points clearly showed the efficient clearance of the accumulated activity from the background already at 4 h after injection, whereas tumor uptake still remained high. The high pancreas uptake for all radiotracers at 1 h after injection was rapidly washed out, resulting in an increased tumor-to-pancreas ratio at later time points. Conclusion: We have developed 2 GRPr antagonistic radioligands, which are improved in terms of binding affinity and overall biodistribution profile. Their promising in vivo pharmacokinetic performance may contribute to the improvement of the diagnostic imaging of tumors overexpressing GRPr.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2015
Breast cancer (BC) consists of multiple subtypes defined by various molecular characteristics, for instance estrogen receptor (ER) expression. Methods for visualizing BC include mammography, magnetic resonance imaging, ultrasound and nuclear medicine based methods such as (99m)Tc-sestamibi and (18)F-FDG PET, unfortunately all lacking specificity. Peptide receptor scintigraphy (PRS) and radionuclide therapy (PRRT) are successfully applied for imaging and therapy of somatostatin receptor (SSTR)-expressing neuroendocrine tumors using SSTR radioligands. Based on a similar rationale, radioligands targeting the gastrin releasing peptide receptor (GRP-R) might offer a specific method for imaging and therapy of BC. The aim of this study was to explore the application of GRP-R radioligands for imaging and therapy of BC by introducing valid preclinical in-vitro and in-vivo models. GRP-R expression of 50 clinical BC specimens and the correlation with ER-expression was studied by in-vitro autor...
The Journal of Nuclear Medicine, 2014
Gastrin-releasing peptide receptor (GRPR) is overexpressed in human prostate cancer and is being used as a target for molecular imaging. In this study, we report on the direct comparison of 3 novel GRPR-targeted radiolabeled tracers: Al 18 F-JMV5132, 68 Ga-JMV5132, and 68 Ga-JMV4168 (JMV5132 is NODA-MPAA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 ], JMV4168 is DOTA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 ], and NODA-MPAA is 2-[4-(carboxymethyl)-7-{[4-(carboxymethyl) phenyl]methyl}-1,4,7-triazacyclononan-1-yl]acetic acid). Methods: The GRPR antagonist JMV594 (H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2) was conjugated to NODA-MPAA for labeling with Al 18 F. JMV5132 was radiolabeled with 68 Ga and 18 F, and JMV4168 was labeled with 68 Ga for comparison. The inhibitory concentration of 50% values for binding GRPR of JMV4168, JMV5132, nat Ga-JMV4168, and nat Ga-JMV5132 were determined in a competition-binding assay using GRPR-overexpressing PC-3 tumors. The tumor-targeting characteristics of the compounds were assessed in mice bearing subcutaneous PC-3 xenografts. Small-animal PET/CT images were acquired, and tracer biodistribution was determined by ex vivo measurements. Results: JMV5132 was labeled with 18 F in a novel 1-pot, 1-step procedure within 20 min, without need for further purification and resulting in a specific activity of 35 MBq/nmol. Inhibitory concentration of 50% values (in nM) for GRPR binding of JMV5132, JMV4168, nat Ga-JMV5132, nat Ga-JMV4168, and Al nat F-JMV5132 were 6.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2014
Gastrin-releasing peptide receptor (GRPR) is overexpressed in human prostate cancer and is being used as a target for molecular imaging. In this study, we report on the direct comparison of 3 novel GRPR-targeted radiolabeled tracers: Al(18)F-JMV5132, (68)Ga-JMV5132, and (68)Ga-JMV4168 (JMV5132 is NODA-MPAA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2], JMV4168 is DOTA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2], and NODA-MPAA is 2-[4-(carboxymethyl)-7-{[4-(carboxymethyl)phenyl]methyl}-1,4,7-triazacyclononan-1-yl]acetic acid). The GRPR antagonist JMV594 (H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) was conjugated to NODA-MPAA for labeling with Al(18)F. JMV5132 was radiolabeled with (68)Ga and (18)F, and JMV4168 was labeled with (68)Ga for comparison. The inhibitory concentration of 50% values for binding GRPR of JMV4168, JMV5132, (nat)Ga-JMV4168, and (nat)Ga-JMV5132 were determined in a competition-binding assay using GRPR-overexpressing PC-3 tumors. The tumor-t...
Pharmaceutics, 2021
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 th...
Nuclear Medicine and Biology, 2012
Introduction: Bombesin (BN) is an amphibian peptide that binds to the gastrin-releasing peptide receptor (GRPR). It has been demonstrated that BN analogues can be radiolabeled for potential diagnosis and treatment of GRPR-expressing malignancies. Previous studies have conjugated various chelators to the eight C-terminal amino acids of ] for radiolabeling with 64 Cu. Recently, (1,4,7triazacyclononane-1,4,7-triacetic acid) (NOTA) has been evaluated as the five-coordinate 64 Cu complex, with results indicating GRPRspecific tumor uptake. This study aimed to conjugate S-2-(4-isothiocyanatobenzyl)-NOTA (p-SCN-Bn-NOTA) to BN(7-14) such that it could form a six-coordinate complex with 64 Cu and to evaluate the resulting peptide. Methods: p-SCN-NOTA was conjugated to 8-aminooctanoic acid (Aoc)-BN(7-14) in solution to yield NOTA-Bn-SCN-Aoc-BN(7-14). The unlabeled peptide was evaluated in a cell binding assay using PC-3 prostate cancer cells and 125 I-Tyr 4 -BN to determine the IC 50 value. The peptide was radiolabeled with 64 Cu and evaluated for internalization into PC-3 cells and for tumor uptake in mice bearing PC-3 xenografts using biodistribution and micro-positron emission tomography imaging studies.
PLOS ONE
The Gastrin-Releasing Peptide Receptor (GRPR) is over-expressed in estrogen receptor (ER) positive breast tumors and related metastatic lymph nodes offering the opportunity of imaging and therapy of luminal tumors. 68 Ga-RM2 binding and 18 F-FDG binding in tumoral zones were measured and compared using tissue micro-imaging with a beta imager on 14 breast cancer samples (10 primaries and 4 associated metastatic lymph nodes). Results were then assessed against ER expression, progesterone receptor (PR) expression, HER2 over-expression or not and Ki-67 expression. GRPR immunohistochemistry (IHC) was also performed on all samples. We also retrospectively compared 68 Ga-RM2 and 18 F-FDG bindings to 18 F-FDG SUV max on the pre-therapeutic PET/CT examination, if available. 68 Ga-RM2 binding was significantly higher in tumors expressing GRPR on IHC than in GRPRnegative tumors (P = 0.022). In ER + tumors, binding of 68 Ga-RM2 was significantly higher than 18 F-FDG (P = 0.015). In tumors with low Ki-67, 68 Ga-RM2 binding was also significantly increased compared to 18 F-FDG (P = 0.029). Overall, the binding of 68 Ga-RM2 and 18 F-FDG displayed an opposite pattern in tumor samples and 68 Ga-RM2 binding was significantly higher in tumors that had low 18 F-FDG binding (P = 0.021). This inverse correlation was also documented in the few patients in whom a 18 F-FDG PET/CT examination before surgery was available. Findings from this in vitro study suggest that GRPR targeting can be an alternative to 18 F-FDG imaging in ER + breast tumors. Moreover, because GRPR antagonists can also be labeled with lutetium-177 this opens new avenues for targeted radionuclide therapy in the subset of patients with progressive metastatic disease following conventional treatments.
The aim of this study was to determine the human biodistribution and radiation dosimetry of 99m Tc-RP527, a promising radioligand for the visualization of gastrin-releasing peptide (GRP) receptor-expressing human malignancies. Methods: Wholebody scans were obtained up to 48 h after intravenous injection of 555 MBq 99m Tc-RP527 in each of 6 subjects. Blood samples were taken at various times up to 48 h after injection. Urine was collected up to 48 h after injection for calculation of renal clearance and whole-body clearance. Time-activity curves were generated for the thyroid, heart, breasts in women, testes in men, and liver by fitting the organ-specific geometric mean counts, obtained from regions of interest, on the respective images as a function of the time after injection. The MIRD formulation was applied to calculate the absorbed radiation dose for various organs. Results: The serial whole-body images showed rapid hepatobiliary excretion, resulting in low background and potentially high-contrast imaging of the thoracic region. Imaging of abdominal tumors may prove problematic, however, because of the extensive bowel activity. 99m Tc-RP527 was predominantly cleared by the kidneys and to a lesser extent by the gastrointestinal tract. The mean excretion in the urine (ϮSD) at 48 h after injection was 58.3 Ϯ 5.4 percentage of the injected activity corrected for decay to the time of injection. The highest absorbed doses were received by the excretory organs (i.e., the urinary bladder and gallbladder wall). The average effective dose of 99m Tc-RP527 was estimated to be 0.0095 mSv/MBq. Conclusion: The biodistribution of 99m Tc-RP527 revealed low lung, myocardial, and liver uptake, which allowed early imaging of the supradiaphragmatic region with a favorable dosimetry (including effective dose) for administered activities required for SPECT imaging.