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Synthesis and Characterization of a High-Affinity NOTA-Conjugated Bombesin Antagonist for GRPR-Targeted Tumor Imaging
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Plattformen för preklinisk PET.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för radiologi, onkologi och strålningsvetenskap, Enheten för biomedicinsk strålningsvetenskap. Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Plattformen för preklinisk PET.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för radiologi, onkologi och strålningsvetenskap, Enheten för nuklearmedicin och PET.
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2013 (Engelska)Ingår i: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 24, nr 7, s. 1144-1153Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The gastrin-releasing peptide receptor (GRPR/BB2) is a molecular target for the visualization of prostate cancer. This work focused on the development of high-affinity, hydrophilic, antagonistic, bombesin-based imaging agents for PET and SPECT. The bombesin antagonist analog D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 ([D-Phe(6),Sta(13),Leu(14)]-bombesin[6-14]) was synthesized and conjugated to 1,4,7-triazacyclononane-N,N',N ''-triacetic acid (NOTA) via a diethylene glycol (PEG(2)) linker. The resulting conjugate, NOTA-PEG(2)-[D-Phe(6),Sta(13),Leu(14)]bombesin[6-14] (NOTA-P2-RM26), was labeled with Ga-68 (T-1/2 = 68 min, positron emitter) and In-111 (T-1/2 = 2.8 days, gamma emitter). The labeling stability, specificity, inhibition efficiency (IC50), and dissociation constant (K-D) of both labeled compounds as well as their cellular retention and internalization were investigated. The pharmacokinetics of the dual isotope) (In-111/Ga-68)-labeled peptide in both normal NMRI mice and PC-3 tumor-bearing Balb/c nu/nu mice was also studied. NOTA-P2-RM26 was labeled with In-111 and Ga-68 at a radiochemical yield of >98%. Both conjugates were shown to have high specificity and binding affinity for GRPR. The K-D value was determined to be 23 +/- 13 pM for the In-111-labeled compound in a saturation binding experiment. In addition, In-nat- and Ga-nat-NOTA-P2-RM26 showed low nanomolar binding inhibition concentrations (IC50 = 1.24 +/- 0.29 nM and 0.91 +/- 0.19 nM, respectively) in a competitive binding assay. The internalization rate of the radiolabeled conjugates was slow. The radiometal-labeled tracers demonstrated rapid blood clearance via the kidney and GRPR-specific uptake in the pancreas in normal mice. Tumor targeting and biodistribution studies in mice bearing PC-3 xenografts displayed high and specific uptake in tumors (8.1 +/- 0.4%ID/g for Ga-68 and 5.7 +/- 0.3%ID/g for In-111) and high tumor-to-background ratios (tumor/blood: 12 +/- 1 for Ga-68 and 10 +/- 1 for In-111) after only 1 h pi of 45 pmol of peptide. The xenografts were visualized by gamma and microPET cameras shortly after injection. In conclusion, the antagonistic bombesin analog NOTA-PEG(2)-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 (NOTA-P2-RM26) is a promisindg candidate for prostate cancer imaging using PET and SPECT/CT.

Ort, förlag, år, upplaga, sidor
2013. Vol. 24, nr 7, s. 1144-1153
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
URN: urn:nbn:se:uu:diva-207041DOI: 10.1021/bc300659kISI: 000322103200003OAI: oai:DiVA.org:uu-207041DiVA, id: diva2:646634
Forskningsfinansiär
CancerfondenVetenskapsrådetTillgänglig från: 2013-09-09 Skapad: 2013-09-09 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Ingår i avhandling
1. Bombesin Antagonists for Targeting Gastrin-Releasing Peptide Receptor-Positive Tumors: Design, Synthesis, Preclinical Evaluation and Optimization of Imaging Agents
Öppna denna publikation i ny flik eller fönster >>Bombesin Antagonists for Targeting Gastrin-Releasing Peptide Receptor-Positive Tumors: Design, Synthesis, Preclinical Evaluation and Optimization of Imaging Agents
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis is focused on the development, preclinical evaluation, and optimization of radiotracers for the detection of gastrin-releasing peptide receptor (GRPR)-expressing tumors. The work is divided into three distinct parts: (1) the development of bombesin (BN) antagonist (RM26)-based imaging radiotracers for the detection of GRPR-expressing tumors using different positron emission tomography (PET) and single photon emission computed tomography (SPECT) radionuclides (68Ga, 18F and 111In), (2) the establishment of a method to monitor the ligand-G protein-coupled receptor (GPCR) interaction in real time without requiring purification and stabilization of the receptors, and (3) the evaluation of radiopeptide structure-related factors (length of mini-PEG linker and composition of chelator for metal labeling) affecting the in vitro and in vivo characteristics of RM26-based tracers.

We demonstrated the possibility of high-contrast in vivo imaging of GRPR-expressing xenografts despite the physiological expression of GRPR in abdominal organs. Fast radioactivity clearance from the blood and healthy organs, including receptor-positive organs, and long retention in the tumors resulted in high tumor-to-background ratios. A novel real-time assay for measuring the kinetics of the radiotracers targeting GPCR was evaluated. Living cells were used instead of purified receptors in this technology, bringing the developmental work one step closer to the true target environment (imaging in living systems). The comparative study of 68Ga-labeled NOTA-PEGn-RM26 with di-, tri-, tetra- and hexaethylene glycol chains demonstrated that the addition of only a few units of ethylene glycol to the spacer is insufficient to appreciably affect the biodistribution of the radiopeptide. Finally, a comparative study of 68Ga-labeled PEG2-RM26 analogs N-terminally conjugated to NOTA, NODAGA, DOTA or DOTAGA highlighted the influence of the chelator on the targeting properties of the radiopeptide.

The main conclusion that can be drawn from this thesis is that 68Ga-NOTA-PEG2-RM26 has favorable biodistribution properties, such as rapid clearance from blood and tissues with physiological GRPR expression levels and long retention in GRPR-expressing tumors, and that this radiopeptide is potentially suitable for initial clinical investigation.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2014. s. 66
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 191
Nyckelord
Bombesin, Gastrin-releasing peptide receptor (GRPR), Antagonist, Radionuclide molecular imaging
Nationell ämneskategori
Farmaceutiska vetenskaper
Identifikatorer
urn:nbn:se:uu:diva-232123 (URN)978-91-554-9039-3 (ISBN)
Disputation
2014-10-31, Rudbecksalen, Dag Hammarskjölds väg 20, Uppsala, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-10-10 Skapad: 2014-09-12 Senast uppdaterad: 2018-01-11

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Varasteh, ZohrehVelikyan, IrinaLindeberg, GunnarSörensen, JensLarhed, MatsSandström, MattiasSelvaraju, Ram KumarMalmberg, JennieTolmachev, VladimirOrlova, Anna

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