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. 2022 Dec 30;28(1):294.
doi: 10.3390/molecules28010294.

Radiochemical Synthesis of 4-[18F]FluorobenzylAzide and Its Conjugation with EGFR-Specific Aptamers

Viktor A Il'in  1 , Elena V Pyzhik  1 , Anton B Balakhonov  1 , Maksim A Kiryushin  1 , Evgeniya V Shcherbatova  1 , Andrey A Kuznetsov  1 , Pavel A Kostin  1 , Andrey V Golovin  2 , Vladimir A Korshun  3 , Vladimir A Brylev  3 , Kseniya A Sapozhnikova  3 , Alexey M Kopylov  2 , Galina V Pavlova  1   4   5 , Igor N Pronin  1
Affiliations

Radiochemical Synthesis of 4-[18F]FluorobenzylAzide and Its Conjugation with EGFR-Specific Aptamers

Viktor A Il'in et al. Molecules. .

Abstract

Central nervous system tumors related to gliomas are of neuroectodermal origin and cover about 30% of all primary brain tumors. Glioma is not susceptible to any therapy and surgical attack remains one of the main approaches to its treatment. Preoperative tumor imaging methods, such as positron emission tomography (PET), are currently used to distinguish malignant tissue to increase the accuracy of glioma removal. However, PET is lacking a specific visualization of cells possessing certain molecular markers. Here, we report an application of aptamers to enhancing specificity in imaging tumor cells bearing the epidermal growth factor receptor (EGFR). Glioblastoma is characterized by increased EGFR expression, as well as mutations of this receptor associated with active division, migration, and adhesion of tumor cells. Since 2021, EGFR has been included into the WHO classification of gliomas as a molecular genetic marker. To obtain conjugates of aptamers GR20 and GOL1-specific to EGFR, a 4-[18F]fluorobenzylazide radiotracer was used as a synthon. For the production of the synthon, a method of automatic synthesis on an Eckert & Ziegler research module was adapted and modified using spirocyclic iodonium ylide as a precursor. Conjugation of 4-[18F]fluorobenzylazide and alkyne-modified aptamers was carried out using Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) with/without the TBTA ligand. As a result, it was possible to obtain 18F-labelled conjugates with 97% radiochemical purity for [18F]FB-GR20 and 98% for [18F]FB-GOL1. The obtained conjugates can be used for further studies in PET analysis on model animals with grafted glioblastoma.

Keywords: CuAAC; EGFR; PET imaging; iodonium ylides; oligonucleotides.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chromatogram of 4-[18F]fluorobenzylazide after synthesis. Phenomenex Luna18 100 Å (5 µm, 4.6 × 250 mm) column; mobile phase: 55% acetonitrile and 45% 0.1 M ammonium formate; flow rate 1 mL/min.
Figure 2
Figure 2
Preparation of the aptamer conjugates using 4-[18F]fluorobenzylazide by the CuAAC method with/without TBTA (1-spyrocyclic iodonium ylide precursor, 2-4-[18F]fluorobenzylazide, 3-5′-alkyne-modified aptamer, 4-radioactive conjugate).
Figure 3
Figure 3
Click reaction without the TBTA ligand. HPLC profiles of the [18F]FB-GR20 conjugate ((A)—before and (C)—after purification on NAP-5) and the [18F]FB-GOL1 conjugate ((B)—before and (D)—after purification on NAP-5). Conditions: Phenomenex Luna C8 column (5 µm, 4.6 × 150 mm); mobile phase: linear gradient starting with 90% eluent A (0.1 M triethylammonium acetate in water) and 10% solvent B (acetonitrile) with replacement by 70% eluent A and 30% eluent B at 35 min; flow rate 1 mL/min.
Figure 4
Figure 4
Click reaction with the TBTA ligand. HPLC profiles of precipitated GOL1 conjugate ((A)—immediately after conjugation and (C)—after 2 h) and precipitated GR20 conjugate ((B)—immediately after conjugation and (D)—after 2 h). Conditions: Phenomenex Luna C18 column (5 µm, 4.6 × 250 mm); mobile phase: linear gradient: starting with 100% eluent A (0.1 M triethylammonium acetate in water) and 2% solvent B (acetonitrile) with replacement by 65% eluent A and 45% eluent B at 20 min, flow rate 1 mL/min.
Figure 5
Figure 5
Secondary structure of the GR20 aptamer.
Figure 6
Figure 6
Secondary structure of the GOL1 aptamer.
Figure 7
Figure 7
The synthesis scheme of 4-[18F]fluorobenzylazide.
See this image and copyright information in PMC

References

    1. Ostrom Q.T., Bauchet L., Davis F.G., Deltour I., Fisher J.L., Langer C.E., Pekmezci M., Schwartzbaum J.A., Turner M.C., Walsh K.M., et al. The epidemiology of glioma in adults: A “state of science” review. Neuro-Oncology. 2014;16:896–913. doi: 10.1093/neuonc/nou087. - DOI - PMC - PubMed
    1. Brown T.J., Brennan M.C., Li M., Church E.W., Brandmeir N.J., Rakszawski K.L., Patel A.S., Rizk E.B., Suki D., Sawaya R., et al. Association of the extent of resection with survival in glioblastoma: A systematic review and meta-analysis. JAMA Oncol. 2016;2:1460–1469. doi: 10.1001/jamaoncol.2016.1373. - DOI - PMC - PubMed
    1. Ostrom Q.T., Gittleman H., Liao P., Vecchione-Koval T., Wolinsky Y., Kruchko C., Barnholtz-Sloan J.S. CBTRUS Statistical report: Primary brain and other central nervous system tumors diagnosed in the United States in 2010–2014. Neuro-Oncology. 2017;19((Suppl. S5)):v1–v88. doi: 10.1093/neuonc/nox158. - DOI - PMC - PubMed
    1. Kopylov A.M., Zavyalova E.G., Pavlova G.V., Pronin I.N. Theranostics for glioblastoma with monoclonal antibodies to the epidermal growth factor receptor. Zh. Vopr. Neirokhir. Im. N. N. Burdenko. 2020;84:113–118. doi: 10.17116/neiro202084031113. - DOI - PubMed
    1. Louis D.N., Perry A., Wesseling P., Brat D.J., Cree I.A., Figarella-Branger D., Hawkins C., Ng H.K., Pfister S.M., Reifenberger G., et al. The 2021 WHO Classification of Tumors of the Central Nervous System: A summary. Neuro Oncol. 2021;23:1231–1251. doi: 10.1093/neuonc/noab106. - DOI - PMC - PubMed

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