A 99mTc-Labelled Tetrazine for Bioorthogonal Chemistry. Synthesis and Biodistribution Studies with Small Molecule trans-Cyclooctene Derivatives Academic Article uri icon

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abstract

  • A convenient strategy to radiolabel a hydrazinonicotonic acid (HYNIC)-derived tetrazine with 99mTc was developed, and its utility for creating probes to image bone metabolism and bacterial infection using both active and pretargeting strategies was demonstrated. The 99mTc-labelled HYNIC-tetrazine was synthesized in 75% yield and exhibited high stability in vitro and in vivo. A trans-cyclooctene (TCO)-labelled bisphosphonate (TCO-BP) that binds to regions of active calcium metabolism was used to evaluate the utility of the labelled tetrazine for bioorthogonal chemistry. The pretargeting approach, with 99mTc-HYNIC-tetrazine administered to mice one hour after TCO-BP, showed significant uptake of radioactivity in regions of active bone metabolism (knees and shoulders) at 6 hours post-injection. For comparison, TCO-BP was reacted with 99mTc-HYNIC-tetrazine before injection and this active targeting also showed high specific uptake in the knees and shoulders, whereas control 99mTc-HYNIC-tetrazine alone did not. A TCO-vancomycin derivative was similarly employed for targeting Staphylococcus aureus infection in vitro and in vivo. Pretargeting and active targeting strategies showed 2.5- and 3-fold uptake, respectively, at the sites of a calf-muscle infection in a murine model, compared to the contralateral control muscle. These results demonstrate the utility of the 99mTc-HYNIC-tetrazine for preparing new technetium radiopharmaceuticals, including those based on small molecule targeting constructs containing TCO, using either active or pretargeting strategies.

authors

  • Vito, Alyssa
  • Alarabi, Hussain
  • Czorny, Shannon
  • Beiraghi, Omid
  • Kent, Jeff
  • Janzen, Nancy
  • Genady, Afaf R
  • Alkarmi, Salma A
  • Rathmann, Stephanie
  • Naperstkow, Zoya
  • Blacker, Megan
  • Llano, Lisset
  • Berti, Paul
  • Valliant, John F

publication date

  • 2016