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Radiosynthesis of [124I]Iodometomidate and Biological Evaluation Using Small-Animal PET

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Abstract

Purpose

The application of radiolabelled inhibitors of cytochrome P450 enzymes is a novel approach for molecular imaging of adrenocortical masses to detect adrenal tumours. One potential tracer is radiolabelled iodometomidate (IMTO) with a common option for scintigraphic diagnosis and therapeutic applications. The aim of this study was to radiolabel iodometomidate with the positron-emitting radionuclide iodine-124 (124I) for the investigation of the biological behaviour and pharmacokinetics with positron emission tomography (PET).

Procedures

[124I]IMTO has been synthesized by oxidative radioiodo-destannylation, purified via semi-preparative HPLC and formulated in acetate-buffered saline, which contained ascorbic acid and ethanol to avoid radiolytic decomposition. Biological evaluation was performed in rats which received 5.5 ± 0.7 MBq [124I]IMTO in vivo. The radioactivity distribution (n = 3) has been dynamically imaged from 0–120 min after intravenous (i.v.) injection by small-animal PET. Regions of interest have been defined manually in the reconstructed PET images, and the activity concentration was expressed as percent injected dose per gram tissue (%ID/g).

Results

[124I]IMTO was prepared with a radiochemical yield of 83 ± 5 % (n = 3) and a radiochemical purity of >97 %. The final formulation of [124I]IMTO was stable for up to 48 h at room temperature. Two hours after i.v. administration in rats, radioactivity concentration in the adrenal glands were 2.1 ± 0.3 %ID/g, which was sufficient to achieve highest-contrast adrenal PET images.

Conclusions

In the present study, the biological characteristics of radioiodinated metomidate were evaluated. [124I]IMTO appears as an attractive PET tracer for imaging of adrenals.

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Acknowledgments

The authors thank Thomas Filip and Maria Zsebedics for their skilful help with the laboratory animal handling and the staff of the radiochemistry laboratory (Seibersdorf Laboratories GmbH) for their continuous support.

Conflict of interest

The authors declare that they have no conflict of interest.

Author information

Authors and Affiliations

  1. Division of Nuclear Medicine, Medical University of Graz, Auenbruggerplatz 9, 8036, Graz, Austria

    Herbert Kvaternik & Reingard Aigner

  2. Health & Environment Department, AIT Austrian Institute of Technology GmbH, Vienna, Austria

    Thomas Wanek & Claudia Kuntner

  3. Institute of Organic Chemistry, University of Vienna, Vienna, Austria

    Friedrich Hammerschmidt

  4. Department of Medicinal/Pharmaceutical Chemistry, University of Vienna, Vienna, Austria

    Ilse Zolle

Authors
  1. Herbert Kvaternik
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  2. Thomas Wanek
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  3. Friedrich Hammerschmidt
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  4. Ilse Zolle
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  5. Reingard Aigner
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  6. Claudia Kuntner
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Corresponding author

Correspondence to Herbert Kvaternik.

Additional information

Ilse Zolle is deceased.

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Kvaternik, H., Wanek, T., Hammerschmidt, F. et al. Radiosynthesis of [124I]Iodometomidate and Biological Evaluation Using Small-Animal PET. Mol Imaging Biol 16, 317–321 (2014). https://doi.org/10.1007/s11307-013-0696-x

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  • DOI: https://doi.org/10.1007/s11307-013-0696-x

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