Synthesis and characterization of 18F-labeled active site inhibited factor VII (ASIS)

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Maria Erlandsson, Carsten Haagen Nielsen, Troels Elmer Jeppesen, Jesper B. Kristensen, Lars C. Petersen, Jacob Madsen, Andreas Kjaer

Activated factor VII blocked in the active site with Phe-Phe-Arg-chloromethyl ketone (active site inhibited factor VII (ASIS)) is a 50-kDa protein that binds with high affinity to its receptor, tissue factor (TF). TF is a transmembrane glycoprotein that plays an important role in, for example, thrombosis, metastasis, tumor growth, and tumor angiogenesis. The aim of this study was to develop an 18F-labeled ASIS derivative to assess TF expression in tumors. Active site inhibited factor VII was labeled using N-succinimidyl-4-[18F]fluorobenzoate, and the [18F]ASIS was purified on a PD-10 desalting column. The radiochemical yield was 25 ± 6%, the radiochemical purity was >97%, and the pseudospecific radioactivity was 35 ± 9 GBq/µmol. The binding efficacy was evaluated in pull-down experiments, which monitored the binding of unlabeled ASIS and [18F]ASIS to TF and to a specific anti-factor VII antibody (F1A2-mAb). No significant difference in binding efficacy between [18F]ASIS and ASIS could be detected. Furthermore, [18F]ASIS was relatively stable in vitro and in vivo in mice. In conclusion, [18F]ASIS has for the first time been successfully synthesized as a possible positron emission tomography tracer to image TF expression levels. In vivo positron emission tomography studies to evaluate the full potential of [18F]ASIS are in progress.

Original languageEnglish
JournalJournal of Labelled Compounds and Radiopharmaceuticals
Issue number5
Pages (from-to)196-201
Number of pages6
Publication statusPublished - May 2015

ID: 134952913