Recombinant coagulation factor VIIa labelled with the fac-99 mTc(CO)3-core: synthesis and in vitro evaluation of a putative new radiopharmaceutical for imaging in acute bleeding lesion

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Jacob Madsen, Jesper B. Christensen, Ole H. Olsen, Carsten L. Christoffersen, Lars C. Petersen, Mikael Tranholm, Andreas Kjær, Birger Hesse

Coagulation in blood is initiated when coagulation factor VII (FVII) binds to exposed TF and is activated to FVIIa, and the TF/
FVIIa complex may therefore provide a marker of vascular injury potentially applicable in diagnostic imaging of acute
gastrointestinal (GI) bleeding. Methods: Recombinant FVIIa (rFVIIa) was radiolabeled with technetium-99m in a direct
labeling reaction using the ‘carbonyl approach’ using the IsoLink
carbonyl labeling agent. The properties of 99mTc(CO)3-
rFVIIa complex was analyzed by TCA precipitation, HPLC and FVIIa functional integrity was tested in in vitro assays.
Results: Labeling of rFVIIa was possible without tagging with a chelater. Incorporation of radioactivity depended strongly
on rFVIIa concentration and temperature. More than 95% incorporation was achieved after 30 min at 451C with 0.76 mg/ml
rFVIIa. 99mTc(CO)3-rFVIIa was obtained in 46% radiochemical yield and in 495% radiochemical purity. Pull down
experiments showed that the biological activity (binding to tissue factor and to anti-FVII antibody) of the radiolabelled
product remained intact in the formulation mixture as well as in human serum. By computer modeling analysis, two
candidate sites for stabilizing the 99mTc(CO)3
1-ligand structure in FVIIa were identified. Conclusion: Radiolabelled rFVIIa
derivatives may represent a novel tool for the diagnosis of acute gastrointestinal bleeding lesions.
Original languageEnglish
JournalJournal of Labelled Compounds and Radiopharmaceuticals
Issue number4
Pages (from-to)214-19
Number of pages6
Publication statusPublished - 2011

ID: 40215496