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Trastuzumab cotreatment improves survival of mice with PC-3 prostate cancer xenografts treated with the GRPR antagonist 177Lu-DOTAGA-PEG2-RM26
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Theranostics.ORCID iD: 0000-0001-7921-3268
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Theranostics.
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2019 (English)In: International Journal of Cancer, ISSN 0020-7136, E-ISSN 1097-0215Article in journal (Refereed) Published
Abstract [en]

Gastrin-releasing peptide receptors (GRPRs) are overexpressed in prostate cancer and are suitable for targeted radionuclidetherapy (TRT). We optimized the bombesin-derived GRPR-antagonist PEG2-RM26 for labeling with 177Lu and further determinedthe effect of treatment with 177Lu-labeled peptide alone or in combination with the anti-HER2 antibody trastuzumab in amurine model. The PEG2-RM26 analog was coupled to NOTA, NODAGA, DOTA and DOTAGA chelators. The peptide-chelatorconjugates were labeled with 177Lu and characterized in vitro and in vivo. A preclinical therapeutic study was performed in PC-3xenografted mice. Mice were treated with intravenous injections (6 cycles) of (A) PBS, (B) DOTAGA-PEG2-RM26, (C) 177LuDOTAGA-PEG2-RM26, (D) trastuzumab or (E) 177Lu-DOTAGA-PEG2-RM26 in combination with trastuzumab. 177Lu-DOTAGA-PEG2-RM26 demonstrated quantitative labeling yield at high molar activity (450 GBq/μmol), high in vivo stability (5 min pi >98% ofradioligand remained when coinjected with phosphoramidon), high affinity to GRPR (KD = 0.4 0.2 nM), and favorablebiodistribution (1 hr pi tumor uptake was higher than in healthy tissues, including the kidneys). Therapy with 177Lu-DOTAGAPEG2-RM26 induced a significant inhibition of tumor growth. The median survival for control groups was significantly shorterthan for treated groups (Group C 66 days, Group E 74 days). Trastuzumab together with radionuclide therapy significantlyimproved survival. No treatment-related toxicity was observed. In conclusion, based on in vitro and in vivo characterization ofthe four 177Lu-labeled PEG2-RM26 analogs, we concluded that 177Lu-DOTAGA-PEG2-RM26 was the most promising analog forTRT. Radiotherapy using 177Lu-DOTAGA-PEG2-RM26 effectively inhibited tumor growth in vivo in a murine prostate cancermodel. Anti-HER2 therapy additionally improved survival.

Place, publisher, year, edition, pages
2019.
Keywords [en]
radionuclide therapy, GRPR, HER2, prostate cancer, lutetium-177
National Category
Cancer and Oncology
Identifiers
URN: urn:nbn:se:uu:diva-389561DOI: 10.1002/ijc.32401OAI: oai:DiVA.org:uu-389561DiVA, id: diva2:1337863
Available from: 2019-07-17 Created: 2019-07-17 Last updated: 2019-08-16Bibliographically approved
In thesis
1. Prostate cancer theranostics using GRPR antagonist RM26
Open this publication in new window or tab >>Prostate cancer theranostics using GRPR antagonist RM26
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The malignant transformation of cells is often associated with an alteration of their molecular phenotype, resulting in overexpression of several cell surface proteins. Gastrin-releasing peptide receptor (GRPR) and prostate-specific membrane antigen (PSMA) are examples of such pro-teins that are expressed at a high density in prostate cancer. GRPR is primarily expressed in earlier stages of prostate cancer and tends to decrease with disease progression. This expression pattern indicates that GRPR could be a promising target for imaging and treatment of oligometa-static prostate cancer, an early step in prostate cancer progression characterized by limited meta-static spread. In contrast, the expression of PSMA increases with cancer progression and is significantly upregulated as tumors dedifferentiate into higher grade, in androgen-insensitive and metastatic lesions.

This thesis is based on five original articles (papers I-V) and focuses on the preclinical de-velopment of radiotracers for imaging and treatment of prostate cancer. The work can be divided into three distinct parts: (1) the development and optimization of GRPR-antagonist RM26 for high contrast PET and SPECT imaging of oligometastatic prostate cancer (papers I-III), (2) the preclinical evaluation of 177Lu-labeled RM26 as a potential candidate for peptide receptor radionuclide therapy (PRRT) in GRPR-expressing tumors, alone or in combination with anti-HER2 antibody trastuzumab (paper IV), and (3) the development of a bispecific heterodimer targeting both PSMA and GRPR in prostate cancer (paper V).

We have demonstrated that the in vitro and in vivo properties of GRPR antagonist RM26 are strongly influenced by the choice of chelator-radionuclide complex and that long-lived radionuclides are desirable for high-contrast imaging. Furthermore, our data indicate that 55Co-NOTA-PEG2-RM26 has remarkable potential for next-day high-contrast PET imaging of GRPR-expressing tumors. Experimental PRRT using 177Lu-DOTAGA-PEG2-RM26 resulted in a pronounced inhibition of tumor growth and a significantly longer median survival. Interestingly, survival was further improved when trastuzumab was co-injected with 177Lu-DOTAGA-PEG2-RM26. These data indicate that blocking HER2 with trastuzumab decreased the repairing ability of irradiated cells. Finally, we developed a heterodimer (NOTA-DUPA-RM26) for imaging GRPR and PSMA expression in prostate cancer shortly after administration.

In conclusion, we have successfully developed and preclinically evaluated radioconjugates for GRPR-directed theranostics in oligometastatic prostate cancer using the bombesin antagonistic analog RM26.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 80
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 274
Keywords
Gastrin-releasing peptide receptor (GRPR), Bombesin, Prostate-specific membrane antigen (PSMA), Antagonist, Radionuclide molecular imaging, Theranostics, Peptide receptor radionuclide therapy (PRRT).
National Category
Medicinal Chemistry
Identifiers
urn:nbn:se:uu:diva-389563 (URN)978-91-513-0695-7 (ISBN)
Public defence
2019-09-14, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 10:00 (English)
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Supervisors
Available from: 2019-08-23 Created: 2019-07-17 Last updated: 2019-09-17

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Mitran, BogdanRinne, Sara S.Larhed, MatsRosenström, UlrikaOrlova, Anna

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